FACTOEY LIGHTING McGraw-Hill BookCompany Electrical World TTie Engineering and Mining Journal Engineering Record Engineering News Railway Age G azett. * . ... . -. 65 General items General requirements based on the foregoing con- vii viii CONTENTS siderations A typical office investigated Simple rules Design factors High ceilings Offices of odd dimensions Narrow office, 15 by 35 ft. Small office, 10 ft. by 12 ft. 6 in. Rectangular office, 15 by 20 ft. CHAPTER VI DRAFTING ROOM LIGHTING 85 Difficult conditions General requirements Eliminating shadows A practical investigation Combined direct and indirect light Illumination features Various fixture combinations Other conditions. CHAPTER VII FACTORY LIGHTING 98 New ideas regarding factory conditions Various items concerning the work and surroundings General requirements Method of light- ing by over-head lamps The field of various types of lamps Glass and metal reflectors compared Side lighting The lighting circuits A practical case in a location with moderate ceiling height A practical case in a location where the lamps must be mounted very high Other items Cost factors. CHAPTER VIII POWER HOUSE LIGHTING 115 Relations of lighting to operation General requirements Econ- omy afforded by good lighting The modern viewpoint Various locations involved A practical case where medium-sized lamps are used Arc and mercury vapor lamps Simple principles im- portant Definite rules are apt to mislead Maintenance Gen- eral hints Summary. CHAPTER IX IRON AND STEEL MILL LIGHTING 125 General items Electrical considerations The various buildings involved General requirements Peculiar importance of over-head lighting Adaptation of the various types of lamps Specific loca- tions involved Other items Economy of superior lighting facilities. CHAPTER X MACHINE TOOL LIGHTING 144 Importance of adequate light on the machine tool Cases provided for by over-head lamps Points on the mounting of individual lamps Cost relations of artificial light and machine tool operation Physical size of the individual lamp Extension lines Shadow contrasts Candle-power of individual lamps Concluding items. INDEX .57 FACTORY LIGHTING CHAPTER I GENERAL ITEMS AND REQUIREMENTS 1. New Ideas Regarding Factory Lighting. The inadequate means available for illumination in the past has contributed to the slowness of an appreciation of the features of artificial light which influence the working efficiency of the eye. Gas, carbon incandescent, and arc lamps, practically the only illumi- nants available ten years ago, play but a small part in the pres- ent approved methods of factory lighting. The large variety of comparatively new electric lamps in- cludes the Nernst, mercury vapor, metallized filament, tanta- lum, tungsten, Moore tube, metallic flame or magnetite arc, the flame carbon arc and the quartz lamp. Possibilities in factory lighting are now attainable which, before the introduction of these new lamps, were either unthought of, or impossible. Con- sideration of the eye as a delicate organ, together with the new ideas of the items which affect its comfort and efficiency, have resulted in establishing certain principles in illumination work, and have directed attention naturally and in a growing manner to the proper use and application of these new lamps. Another item has been the increased attention to the general betterment of shop conditions. Besides many other things con- nected with the factory equipment, one of the major studies has been that of artificial illumination for the attainment of several well defined objects, as follows: (1) Increased production for the same labor cost. (2) Greater accuracy in workmanship. (3) Reduced number of accidents. (4) Less eye strain. (5) More cheerful surroundings. (6) Greater comfort for the workmen. (7) More order and neatness in the shop. 1 FACTORY LIGHTING (8) Supervision of the men made easier on dark days and at night. The term light in the past has been used to designate the effect from the lamp as well as the effect on the work. This term is now used by common acceptance in relation to the lamp alone, while the effect in rendering objects visible is called the illumi- nation. This latter term will be used, therefore, in reference to the result produced by the lamp or lamps of a system. The term system is employed because in the typical shop, office or drafting room the floor space is often used entirely for working operations. Artificial light in such cases is sometimes provided over the entire area of floor space by lamps mounted near the ceiling, so that a given object receives light from several lamps, hence the term system. 2. Practical Features. The following specific requirements should be secured in factory lighting systems: (1) Sufficient illumination should be provided for each person. (2) Uniform illumination should in most cases be secured so that it may be satisfactory without regard to the location of the work; that is, the entire working surface should be illuminated. (3) Hand lamps, as distinguished from those which afford general illumination, should be eliminated where it is possible to make the general illumination sufficient without their use. (4) The blinding effect of bright rays, commonly called glare, should be reduced to a minimum through a proper arrangement of the lamps, and by the use of a suitable size of lamp and a suitable reflector. (5) Steadiness of the light should be secured by constant voltage; that is, the lamps should not flicker with the varying demands on lighting circuits. (6) Adaptation to Conditions. The type of lamp should be selected in reference to the foregoing requirements and to the particular class of work to be served; also to the limitations of mounting height, and the general physical surroundings, such as the clearance between cranes and ceiling. 3. Classification. Factory lighting may be classified into two general divisions: first, general illumination provided by lamps mounted over-head; and second, specific illumination provided by individual lamps located close to the work. For practical purposes this classification is sufficient. In numerous GENERAL ITEMS AND REQUIREMENTS 3 cases a combination of these two methods must be used, but further subdivision is hardly necessary. General Lighting. Where the lamps are high enough to be out of the line of ordinary vision, and are of a size and are so spaced as to furnish illumination at any position of the floor where work may be placed, the system is referred to as the over- head method of lighting. This method has many advantages which will be subsequently outlined. Its general adoption, which has been somewhat slow, has increased with the intro- duction of the many new types of lamps. Specific Lighting. Where a small amount of general illu- mination from over-head lamps is coupled with specific illumina- tion from individual lamps, a large part of the floor space in many shops is in relative darkness, and much dependence must be placed on the hand lamps close to the work. The small number of over-head lamps generally used in such cases pro- vides merely a small amount of additional illumination over the floor space. Locations with low ceilings, until recently, have been lighted by the individual hand lamp method, because the carbon-fila- ment lamp, being of low candle-power, could not well be used close to the ceiling, while the old type of arc lamp was often impractical, due to its large physical size, as well as its relatively high candle-power. This statement must be slightly modified as carbon-filament lamps have sometimes been used in clusters for low ceilings, this scheme being, however, inefficient and un- satisfactory in comparison with modern methods of lighting. In a particular manner, therefore, suitable illumination has been difficult with low ceilings. New types of lamps have a range of candle-power from very low to very high values, and the over-head system with the elimination of hand lamps is thus possible; that is, a size of lamp may now be selected for nearly every factory condition. 4. The Influence of Candle-power and Physical Dimensions of Modern Lamps. The development of electric lamps has con- sisted, first, in increased candle-power for given power consumed; and second, in the tendency toward a reduction in physical di- mensions for given candle-power values. Notable results have been attained in these directions. The illumination in previous years, mainly by the carbon-filament lamp and the arc lamp, is now produced by a diversity of lamp sizes. The old carbon- 4 FACTORY LIGHTING filament lamp as one extreme has been followed by the metallized filament, the tantalum and the tungsten lamp; and the old open arc lamp as the other extreme, by the enclosed carbon arc, the open flame carbon arc, the metallic flame or magnetite arc, and the long-burning flame carbon arc lamp. In addition, other lamps, as previously intimated, are now available, namely, the Nernst, the mercury vapor, the quartz mercury vapor, and the Moore tube lamps. The limitations in candle-power of old as compared to new lamps are shown in Fig. 1. The average mean spherical candle- power values of old as well as new types are taken from various Carbon Filament Enclosed Carbon Arc Open Carbon Arc New Types Tungsten Nernst Mercury Vapor Quartz Mercury Vapor Metallic Flame Arc Flame Carbon Arc 8 | ~ w< ::: :.-'.' - w w ".'.' : : \ w ~W. x?j P M ::- : " M : ' . : < : : : : : : : ; ; :;v: : :xXv>} '.'.'.'.' VT-T- - rV-'-'. v.v.. $?TW 200 400 600 800 1000 1200 1400 1600 Mean Spherical Candle- Power Ranges FIG. 1. Candle-power ranges of relatively old and new lamps. authorities. The chart shows further that the new lamps not only have candle-power values between those of former years, but also far greater values than were available in the past. The physical dimensions of lamps are important in factory work owing to the difficulty in the installing of lamps in many locations. The small clearance between cranes and ceiling, and other limiting conditions, often make the over-all dimensions a determining factor. The relative over-all dimensions of va- rious old and new types are shown in Fig. 2. 5. Effective Illumination. High candle-power per watt power input is but one method of obtaining effectiveness from electric lamps. Many lamps would be very inefficient in the illumi- GENERAL ITEMS AND REQUIREMENTS 5 nation they furnish were it not for reflectors. The rays of light otherwise dissipated in horizontal or upward directions are thus sent mainly in useful downward directions. Electric lighting systems are now rated according to the effective intensity of illumination on the work rather than the FIG. 2. Over-all dimension shown in comparative manner of relatively old and new lamps. quantity of light produced by the lamps, the question now being that of illumination as well as light efficiency. 6. Quality of Light and Illumination. Electric lamps are made to-day not only in a large variety of sizes but also with various qualities of light. The criterion of good light has usually, in the past, been quantity; quality is now almost on a par with quantity. The quality of the light includes principally its color value, while the quality of the illumination relates to such items as uni- formity over the working area, diffusion, adequate intensities on the sides of the work, absence of glare, and the like. These items are of equal, or greater importance than the securing of a definite downward intensity of the illumination. Refine- ments in the quality of illumination, as well as certain standards with reference to quantity in relation to factory conditions, and the significance of these factors in manufacturing efficiency will be indicated under appropriate heads. CHAPTER II ILLUMINATION DESIGN 7. Scope of Illumination Design. Illumination design refers to the preparation of plans and specifications for lighting sys- tems, in the determination of the best available type of lamp for the location it is to serve, and in the indication of how such lamps are to be placed. This work obviously covers a large variety of problems and the steps for a given case may be stated as follows: (1) The determination, through a study of the requirements and the surroundings, of the quantity and quality of light necessary. (2) The study of how the light can best be provided. Under the latter head a selection is made in a scientific and practical manner of (a) the type; (b) the size; and (c) the number of lamps required; together with (d) their spacing; and (e) their mounting. From these items proper plans may be provided for attaining desired results. 8. Inspection of the Location. The first step in the design is to ascertain, by inspection or otherwise, the class of work in- volved. This largely determines the intensity of illumination necessary for satisfactory conditions, and also, in a measure, the number of lamps to be used. The dimensions of the location should be measured, since the width, length and height determine in general the total num- ber of lamps necessary, as well as the character of the area over which the lamps are to be distributed. The location and size of columns, when present, dividing as they do the floor space into bays of a certain number and size, should be noted; the class of ceiling, whether plain or set with deep girders, in their relation to symmetry and convenience of the wiring; and the color of ceiling and walls, whether light or dark, in its effect as an aid to the rays of light transmitted directly to the work, as the extra light from the reflection of rays trans- mitted directly to the ceiling and walls and thence reflected to the floor, is often a large factor. 6 ILLUMINATION DESIGN 7 The girders, when present, should further be observed, both regarding height and location, in that very deep girders may cause appreciable shadow effects where the lamps must be mounted near the ceiling. The type of wall has a bearing, first, on the locating of the control circuits and switches, and second, in the matter of color in its reflecting power, either as an aid to the net illumination, or perhaps in the blinding effect or glare sometimes caused when looking at brightly lighted walls, a fea- ture most noticeable, of course, in the case of glossy light colors, and where too much light shines on the walls. Where the space to be lighted is merely a portion of a large floor area divided from the other portions of the building by columns, the switches must in general be mounted on the columns, and the surroundings treated as dark walls as far as reflection is concerned, unless the lamps in the surrounding floor space contribute light to the space in question. The Supply Circuits. The electric circuits contemplated in the case of new plants, or those available in old plants, must be noted as to capacity of the wires; the voltage and its variation dependent upon variable power requirements; and whether direct or alternating current is to be used for lighting. The importance of these items will be apparent when it is considered that the type of lamp is thus largely influenced. Table I indicates the classes of circuits commonly used in indus- trial plants and the types of lamps which are available for each. The Space between Floor and Ceiling. The conditions of the free space between the work and the ceiling should be noted. Under this head is included open locations free from belting; spaces filled with many belts; and those in which much dust and dirt is present in large quantities, as for example in the foundry. Daylight Conditions. The natural lighting facilities should be observed in that the switch control of lamps, generally ar- ranged in rows or groups parallel to the windows, is thus largely dependent on the location of windows. It should also be stated that the required intensity of artificial light when necessary at certain portions of the day due to clouds or smoke, is some- what dependent in such cases on the amount of natural light present. Under mixed conditions of natural and artificial light, the artificial light, to be satisfactory, must usually have a higher intensity than would be the case if its use was limited to the hours of total darkness. FACTORY LIGHTING TABLE I. ELECTRIC CIRCUITS ORDINARILY FOUND IN PRACTICE AND TYPES OF LAMPS OPERATIVE THEREON Direct-current circuits Series Multiple or multiple series 110 volts 220 volts 550 volts Carbon filament. Gem. Tungsten. Enclosed carbon Carbon filament. Gem. Tungsten. Enclosed carbon Carbon filament. Gem. Tungsten. Enclosed carbon Carbon filament. Gem. Tungsten. Enclosed carbon arc. Metallic flame arc. Metallic flame arc. Metallic flame arc. Metallic flame arc. Flame carbon arc. Flame carbon arc. Flame carbon arc. Flame carbon arc. arc. Nernst. Cooper-Hewitt. arc. Nernst. Cooper-Hewitt. arc. Cooper-Hewitt. Alternating-current circuits Series Multiple 110 volts 220 volts 25 cycles 60 cycles 25 cycles 60 cycles Carbon fila- Carbon fila- Carbon fila- Carbon fila- Carbon fila- ment. ment. ment. ment. ment. Gem. Gem. Gem. Gem. Gem. Tungsten. Tungsten. Tungsten. Tungsten. Tungsten. Enclosed car- Flame carbon Enclosed car- Flame car- Enclosed bon arc. arc (long bon arc. bon arc (long carbon arc. burning) . burning). Flame carbon Flame carbon Flame carbon arc. arc. arc. Nernst. Nernst. Nernst. Nernst. Cooper- Cooper- Hewitt. Hewitt. Thus on a cloudy day, when natural illumination is insufficient, a greater intensity of the added artificial light is necessary to produce satisfaction for the eye than on the same work at night. This is probably best explained by considering that the eye is contracted during the day on account of the relatively great intensities of daylight as compared to artificial light. In this contracted state the eye is not as sensitive to changes in illumi- nation intensity as at night when relaxed under the relatively low intensities of artificial light. If, therefore, the lighting system has been designed for an intensity suitable at night, it is possible that the intensity of this same system may not be adequate at those times during ILLUMINATION DESIGN 9 the day when required. Hence an allowance is sometimes made in the design for the difference between day and night requirements. 9. Reflectors and Globes. A reflector is used in conjunction with a lamp for the purpose of reducing the glare otherwise caused by looking directly into a bare lamp, as well as for the purpose of redirecting the light most effectively to the work. Uniformity of Illumination. Reflectors are now obtainable which are designed for specific sizes of lamps, and hence care should be used to be sure that both reflectors and lamps are of the correct size in their relation to each other. This is of the utmost importance in securing uniform illumination for a given spacing distance and mounting height of the lamps. For a certain ratio between the spacing and height of lamps, a reflector can nearly always be secured which will furnish uniform il- lumination on the working plane. 1 Redirection of Light. Owing to the direction of the light rays from the lamp, nearly all types of lamps, in addition to down- ward light, furnish some rays which go upward or away from the objects to be illuminated, and are therefore relatively not useful. The function of a reflector is to intercept these other- wise useless or comparatively useless rays and reflect them in a useful direction. In performing this function there is a choice, through the design of the reflector, in the manner of distributing the light so as to make the illumination on the floor space prac- tically uniform with certain spacing distances and mounting heights. With the use of lamps, like the tungsten type, for which a large variety of reflectors is available, the proper reflector for the given spacing distance and mounting height must be selected if uniform illumination on the floor is to be obtained. In other cases, as in the use of the arc lamp, where the globe or reflector is usually a fixed part of the lamp, care must be exercised to space the lamps at sufficiently close intervals to insure uniformity of the illumination, that is, a freedom from the relatively dark spaces which exist between lamps when spaced too far apart. 2 1 This statement applies more especially to tungsten lamps than to other types. 2 The Holophane Company (now known as the Holophane Works of the General Electric Company, Cleveland, Ohio) has designed and placed on the 10 FACTORY LIGHTING 10. Type of Lamp. The choice of type of lamp is dependent upon several items, chief of which are the electric supply avail- able, space conditions, to some extent on the element of color of the light produced, the surroundings, the limits of candle- power values of the different lamps of a given type, and upon the cost of operation. The surroundings have a considerable influence on the type of lamp to be used. Obviously arc lamps would not be used in a small office, nor would it be advantageous to use small tungsten lamps in very high factory spaces. The condition of the space between floor and ceiling, that is, whether or not there is much belting, will also often determine the type of lamp, for it has been found by experience that where much belting exists, lamps of the mercury vapor type, for example, are more advantageous than those units which furnish the light from a point rather than from a long tube. Often the size of lamp desired is either of a very small or a very large candle-power, and this leads to the choice of that type of lamp, which possesses the required volume of light. Again, some lamps are best adapted to alternating current and others to direct-current circuits; some must be operated in series and others in multiple; hence the characteristics of the circuit on which the lamps are to be operated will largely determine the choice, although 110-volt direct-current or alternating-current circuits cover practically all cases. The relative first cost and operation cost of the various lamps are items of considerable weight in the choice between one or another type, and these items will be discussed in connection with the specific lighting appropriate to various departments of the factory. 11. Size of Lamp. The proper size of lamp for a given loca- market a standard line of reflectors for tungsten lamps calculated to furnish uniform illumination on the working surface provided the ratio between spacing distance and mounting height is in accord with the conditions for which the reflector was designed. This standard line consists of the focus- ing type, concentrating; the intensive type, moderately distributing; and the extensive type, broadly distributing. The focusing type is intended for use where the ratio of spacing to mounting height is about 0.7; the intensive type where this ratio is about 1.25; and the extensive type where this ratio is about 2.0. Reflectors of other manufacturers may be used to furnish similar results provided their distribution conforms in a general way to the distribution of the reflectors referred to. ILLUMINATION DESIGN 11 tion is dependent on the spacing decided upon. The size of lamp for a system should, however, primarily be based on the height of mounting. Fig. 3 shows that for a given shadow effect, the lower the ceiling the smaller may be the size of lamp because of the closer spacing. In like manner, for high ceilings,, larger lamps with wider spacing may be used. Furthermore, the fatigue of the eyes is less with small lamps, if they must be mounted low. FIG. 3. Relation of shadow effect to average spacing and mounting height of lamps. Experiment and experience determine the relation between mounting height and candle-power, and this solution can hardly be realized through any "other channel. Table II has been prepared to show candle-power sizes which have been used in a variety of factory locations for various mounting heights, and a reference to this table will indicate that for low ceilings small lamps are generally selected in well designed installations, the sizes increasing with the height. 12 FACTORY LIGHTING TABLE II. CANDLE-POWER OF LAMPS CORRESPONDING TO MOUNTING HEIGHT AS RECOMMENDED FROM THE EXPERIENCE OF THE AUTHOR FOR DISTRIBUTED LIGHTING SYSTEMS This table is suggestive only, as fixed rules may mislead Mounting height in feet Candle-power of lamp Corresponding lamp type or types 9 to 12 48 to 80 Tungsten 60 and 100 watt. 12 to 16 80 to 300 Tungsten 100, 150 and 250 watt; mer- cury vapor and in certain cases arc lamps. 16 to 25 200 to 500 Tungsten 250, 400 and 500 watt; mer- cury vapor and arc lamps. 25 to 50 300 to 3,000 Tungsten 400 and 500 watt; mercury vapor; quartz and arc lamps. Note. Small lamps are in general preferable to large ones, and when there is a range to choose from, it is advisable to lean to the smaller rather than the larger from the illumination standpoint. 12. Spacing of Lamps. The spacing distances will largely depend on the condition of the work, whether crowded or scat- tered over a given floor area, and also to some extent on whether the work must be viewed from the side as well as from above. Further, the spacing is naturally dependent on the size of the TABLE III. SPACING DISTANCES FOR TUNGSTEN LAMPS, OR LAMPS EQUIVALENT CANDLE-POWER, RECOMMENDED FROM THE EXPERI- ENCE OF THE AUTHOR FOR DISTRIBUTED LIGHTING SYSTEMS This table is suggestive only, as fixed rules may mislead OF Ceiling height in feet Location Spacing distance 9 to 12 Office. 6ft. in. to 7ft. 6 in. 12 to 16 Office. 7ft. 6 in. to 9ft. in. 9 to 16 Drafting rooms. 1 8 ft. in. to 9 ft. 6 in. 9 to 12 Factory, power-house and steel 8 ft. in. to 10 ft. in. mills. 12 to 16 Factory, power-house and steel 10ft. in. to 12ft. in. mills. 16 to 25 Factory, power-house and steel 12 ft. in. to 15 ft. in. mills. 25 to 50 Factory, power-house and steel (Spacing depends large- mills. ly on circumstances.) Note. Tables II, III and IV are intended for use together. Obviously the size of lamp cannot be determined from this table, but must be selected from Table II. Table IV is a check on the selection of size and spacing distance. 1 The spacing here given refers to the inverted fixture or semi-direct light- ing scheme as shown in Fig. 62. ILLUMINATION DESIGN 13 lamp, that is, for a given size of lamp, a given spacing is necessary in order to produce the required amount of illumination. Hav- ing determined the approximate size of lamp for the height of the location, the advisable spacing distance may in turn be determined independently, based on the nature of the work and its disposition over the floor space. The size of lamp and the spacing distance for the system should then be brought together, that is, adjusted to each other, to produce the desired intensity. Table III shows average spacing distances for a variety of in- dustrial conditions, referring mainly to tungsten lamps or other types of equal candle-power. 13. Mounting Height of Lamps. The mounting height of lamps is often limited by the details of building construction or by the interference of cranes. In general, the lamps should be mounted at such a height as to be out of the line of vision, thus preventing that glare, or blinding effect, which results from look- ing directly into lamps mounted too low/ Where, however, the ceiling itself is low, ,thus limiting the available mounting height, small lamps properly equipped with reflectors should be used. Thus the system is not as likely to produce fatiguing effect on the eye as if large lamps are in- stalled. The glare and resulting eye fatigue and even strain from lamps mounted low enough to be in the line of vision is extremely harmful, and in addition to the evil effect on the eye, it renders the resulting illumination less effective. The contraction of the pupil under the stimulus of the bright lamp causes the eye to be less responsive than otherwise. Sometimes it is necessary that the light from over-head lamps shall fall upon the work at an angle, as in the case of work in a vise or in a milling machine. In such cases it may be necessary to mount the lamps lower than would be advisable were glare the only consideration. In the production of a greater side component of the light it is usually better, however, to keep the lamps high and to provide them with broader distributing reflectors than would be called for by rules looking merely to uniform downward illumination, thus securing sufficient side ilght without the objectionable glare. The mounting height, although partially fixing the size of the lamp to be used, should be determined with exactness after the spacing has been fixed. The determination of mounting height should be such as to secure uniformity of the resulting 14 FACTORY LIGHTING illumination, provided glare is not incurred by too low a mount- ing as an extreme case. With Holophane prismatic reflectors the proper height is determined by the ratio of spacing distance to mounting, for which a given type of reflector has been designed so as to furnish uniform results as already described in Art. 9. The proper mounting height for uniform or nearly uniform dis- tribution may be determined for all types of lamps, provided the distribution curve of the particular type of lamp in question is available. This calculation, although somewhat tedious, may be made as described under the subject of point addition in Art. 17. 14. Switch Control. The control of lamps in industrial lighting systems is important in all cases, but more especially where a large number is used in preference to a small number of lamps for given factory spaces. For example, where tungsten lamps of small size are used, a large number will of course be necessary for given floor areas, and in such cases the number of control circuits may at times seem excessive. Such circuits, however, in rendering the system more flexible, will be more than paid for by the saving in energy and maintenance due to turning out lamps not needed in certain sections of the fac- tory, provided the number of hours per day the lamps are used on the average is relatively large. The lamps most distant from the windows will usually be re- quired at times when the natural light near the windows is en- tirely adequate, thus making it an advantage to arrange the groups of lamps in circuits parallel to the windows. This scheme is shown in Fig. 4. The advantage of this method is further apparent when it is considered that if lamps are controlled in rows perpendicular to the windows, all lamps in a row will necessarily be on at one time, while a portion only may be required. The foregoing statement may be developed into a simple proposition. To install a single switch may involve say $5.00 as the first cost. If ten 60-watt tungsten lamps are to be con- trolled from a single switch, these ten lamps must obviously either all be turned on or off. An additional switch at a cost of $5.00 will permit either half of these ten lamps being turned off, if not required, while the remaining five are needed. This extra switch may or may not be an economy. Consider, for example, the case where these five 60-watt tungsten lamps are turned off by the extra switch on an average of one-half hour ILLUMINATION DESIGN 15 per day while the others are needed, or vice versa. In a year's time the energy saved at 1 cent per kilowatt-hour will amount to perhaps 50 cents. At this rate it will require ten years for the energy saved to pay for the first cost of the extra switch. Natur- ally this would not be a distinct economy. If the energy cost be greater, or if the number of hours per day during which a portion only of the lamps will not be used be greater, these values will of course be correspondingly modified. ^$$$} K$$$ ssssi R$$$ J$$$$j ^$$$^$$$$$1 R$$$ :; $$$^ ^ $$$$$^ $$$$: 'K-4>! Ki [K "~K] [k kl TO rji i tf XC i TK kl -44^8^4-4- ^ ft- ~^TJ 1 [3 t"" J E [K Kj i i j [K KJ Kj ^,.J fk ! i i i i !K _K] I F ["K KI i"i ta | J=T-=-J P 3 L j ' [ J L J L r ,- - ., i Pf 1 ! ? 4 ' i L^T ^ |K KJ KJ 1 u K KJ i F K Kj i K Kj , &* , XC K 1 i i j , Is-d f w] 1 1 1 i j i L *=# J JK k 1 | !K K i i i [K_ _K ] T 1 J L J L jW^ K ! "p lK-f- K 1 Kj i j A A| 1 i i i i )^( KI K Kj i i i i !K KJ IK K] ! ! !K Kj JK ! KJ ^ [K-pN Kj fa kl [K W^ [k KJ iW X(j L K] k^i t^mi i^^ {^ ^^ K^ ^a fe^ ^a (^ Plan * I;;: ! : ^^W^ : ^ : > : SN^^ Elevation FIG. 4. Switch control shown parallel to windows. (See also Fig. 24.) 15. The Working Drawing. After the spacing of the lamps has been decided upon, the next step will be to indicate the ar- rangement on a diagram drawing of the floor space as shown in Fig. 4. This plan should contain an elevation, where such an addition to the drawing will make it more intelligible. The drawing, to be of practical service, should contain the floor 16 FACTORY LIGHTING space outline drawn accurately to scale with the columns located in such a manner as to be easily identified. In the case of new buildings the framing plan showing the exact location of the iron work is useful. Further, the lamps should be located to scale and all spacing distances given, the dimensions to be referred to some point on structural columns or other boundary locations. The scale of the drawing is of some importance, due to the fact that too small a scale may make an interpretation of the design difficult for the wiremen when making the installation. In general, 1/4 or 1/8 in. to the foot will be found convenient. On the drawing the arrangement of switch circuits may be shown by placing a numeral adjacent to each lamp. Thus, if four given lamps are to be controlled from one switch, the nu- meral (l) adjacent to each of these four lamps will indicate the fact. This feature is shown in Fig. 24. Another simple method is to surround all lamps to be controlled from one switch by a dotted line, as shown in Fig. 4. The drawing should also contain or be accompanied by specifi- cations, including the type of lamp, reflector and reflector holder, the mounting height of the lamps and such other details as may be necessary for the one who is to order the supplies, or for the wiremen who have the installation in hand. 16. Lighting System Efficiency. The ratio of the actual light which is received by the work to the total light given out by the lamps is here defined as the efficiency of the lighting system. This ratio must be obtained by the use of the proper units of light, usually expressed in terms of the light flux furnished to the work, divided by the total light flux from the lamps. 1 The calculation of the total number of lamps necessary for lighting a location could be based on the efficiency predicted for the conditions of the given location. Thus, based on tests 1 The term flux is used to express the total quantity of light either given by the lamp, or incident to a given surface. For example, a 60-watt tungsten lamp at a certain rating develops say 500 lumens or in other words 500 units of light flux. Thus, if out of a total of 500 lumens but 100 are effective on the working surfaces, the other 400 being wasted in directions not useful to the work and absorbed by dark surroundings, the system is said to have an efficiency of 100 divided by 500, or 20 per cent. This method of calculating efficiency obviously takes into account the condition of surroundings as well as the lighting units. The lumen value here taken for a 60-watt tungsten lamp is not a fixed quantity, but depends altogether on the watts consump- tion per candle-power at which the lamp is operated. ILLUMINATION DESIGN 17 in other similar locations, the illumination efficiency in a typical factory location might be predicted to equal 25 per cent. If an illumination intensity of three foot-candles 1 on the work is desired, the total light flux in lumens is found by the product of the floor space in square feet and the intensity of the illu- mination in foot-candles. This result divided by the predicted efficiency is equal to the total light flux which must be furnished by the entire number of lamps in the proposed system. On the other hand, the importance of choosing the proper size of lamp and the proper spacing, in the relation of these two factors to the success or failure of the resulting illumination, both as regards directional features of the light and the reduc- tion of eye fatigue, is such as to make these two items of the utmost importance. Therefore, the efficiency of a system should be used as a check on the total number of lamps only after the size of the lamps and their spacing have previously and carefully been determined. Table IV shows a number of efficiency values obtained for tungsten lamps under actual factory condi- tions. It must be remembered that these values are modified by the condition of ceiling and wall reflection, together with the effect of dirt and dust on the reflectors or globes. TABLE IV. AVERAGE EFFICIENCY VALUES OF TUNGSTEN LIGHTING SYSTEMS TESTED UNDER THE SUPERVISION OF THE AUTHOR* Average efficiency of system Low office 27 . 1 per cent. Fairly high factory office 27 . 4 per cent. Low factory space 27 per cent. Medium high factory space 30 . 8 per cent. Fairly high factory space 29. 1 per cent. All efficiency values corrected for normal lamp voltage. "These tests were taken throughout the time between cleaning intervals, and are therefore averages of illumination intensity values found under the systems when both clean and soiled. 17. Point Addition of Intensity Values. By the term point addition for a distributed system of lamps is meant the calcula- tion of the intensity of light at a given point on the working 1 The foot-candle is the unit of illumination intensity, and may be defined as the illumination produced at a point one foot distant from a source of one candle-power. The foot-candle intensity on a surface multiplied by the. area of the surface in square feet gives a product which is called lumens of light flux. 2 18 FACTORY LIGHTING surface produced by all the lamps which are effective in illumi- nating that point. This may be done by the aid of- the distribu- tion curve of the lamps in question. Fig. 5 shows a simple diagram which may be used in making this calculation. It will be seen from this diagram that the candle-power in certain directions is divided by the square of the distance between the lamp and the point at which it is desired to add together the light from the various lamps, the result being the intensity in foot-candles at the point but in a direction parallel to the ray of .P.= Candle Power Direction of P .. F Reference Planet v i n Di ------------ } ------ A p I < Distance from Point Directly > | below Lamp to Point P K Vertically Downward Height of [ ^Intensity at Point P Reference Plane \ j r p V _ T = ~V Cos 3 A Floor FIG. 5. Diagram for illumination calculations. light from the lamp. This intensity of illumination is then cor- rected so as to secure the component of the resultant illumi- nation in a direction perpendicular to the working surface. It is evident that this calculation must be made for each lamp and for each different direction in which the light rays from the various lamps strike the point under consideration. It is therefore a problem of some length to calculate the illumination at a given point on the floor space in those cases where a consid- erable number of lamps is used to illuminate the point. A simple method has been devised, however, which enables this calculation to be made conveniently by the use of a rule, as shown in Fig. 6. In Fig. 7, for example, a diagram shows the ILLUMINATION DESIGN 19 location of the lamps on a given floor space to scale. It is assumed that the lamps are mounted 10 ft. above the surface of the work. If it is desired to calculate the total intensity of the illumination at the point " A" produced by all the lamps which contribute light to that point it is only necessary to pre- pare a simple card-board rule, as shown in Fig. 6, on which the intensities of illumination on a plane 10 ft. below the lamp at different dis- tances from a point perpendicularly beneath the lamp are indicated. The markings on this rule are made to the same scale as the drawing, while the values on the rule are calculated by the method indicated by Fig. 5. It is convenient to place this rule on the draw- ing as shown in Fig. 7, the illumination at the point "A" due to each lamp being read directly from the rule. Turn the rule about the point "A" until it intercepts another lamp, and the resultant illumination can be read from the rule. After proceeding with this method until all the lamps have been intercepted and their values ob- served, the values as a whole for the point "A" are added together numerically, giving the re- sulting vertical illumination at the point "A." The term vertical as here used refers to the ver- tically downward component of the illumination produced by each lamp which contributes to the intensity at the point " A" on the working plane. By this means the intensities at a sufficient number of points on the working plane may be determined in a short time to indicate the ap- proximate intensity of the illumination due to certain spacing distances, mounting heights, types and sizes of lamps. This will further in- dicate whether the illumination will probably be uniform over the working surface. The point addition method has been suggested as a means for calculating the arrangement of lamps for new lighting systems. Thus, the lamps are located on the floor plan outline drawing in a more or less arbitrary manner m 1 +3 -a >t Candlei Directly 1 '1 I Ip 5 ^j a fl 3 .S l " -^ Intensi stance f roi 'So Q <3 JH -60'0 S 3 O d -^ * a g -w-o ** f -H)'I CO i_ -II 'I CI 1 -LI'T - - 20 FACTORY LIGHTING and the illumination at the various points over the floor space calculated. If the intensity is not sufficient, another arrange- ment is given trial on the drawing, and the lamps either shifted back and forth, or changed in number or size until the intensity seems to be sufficient on the working surface. This, however, is open to the objection that it eliminates the question of size of lamp and the spacing as distinct considerations. These two items are in a manner quite separate from the uniformity or intensity of the light, particularly as regards the directional qualities of the illumination effective on the work. Therefore, the method of K K K & K ! K K K K | Reading? U^ | K K K H H Jf ^W | o 8 M X ' K XA< 'jr* K tt | K K Observa K ion Points H H K H K H | K K K H K K W | K K H H K K H W K | FIG. 7. Diagram to illustrate application of illumination rule. point addition just described, as well as the method of efficiency as described in Art. 16, should be used as checks only after the size of lamp and spacing have been independently determined. It should be kept in mind that the point addition method of calculating intensity under a lighting system does not take into account reflection from walls and ceiling, which are items that may materially affect the results. 18. Problem Illustrating Steps in Typical Design. The follow- ing case is given in detail to make plain the various steps in working out a typical lighting problem. Proposition. Given a low factory space with ceiling height of 12 ft. 6 in., and columns and girders so arranged that the bays have dimensions of 16 by 40 ft. Clearance between crane and ceiling is 12 in. and the ceiling is of wood with a very dark surface. There are no walls to this space, as it is simply divided ILLUMINATION DESIGN 21 from the other adjacent shop sections by columns. The work is on lathes, together with some assembly, all the work possessing very dark surfaces. The circuits available are 25-cycle 110-volt alternating current. Required. A lighting system is to be planned which will furnish adequate illumination on the working surface approxi- mately 3 ft. above the floor. Individual lamps are to be elimi- nated if possible, and a control arrangement of the lamps provided which is flexible enough to permit of turning off the lamps where not required. The total number of lamps for twenty bays are to be specified as well as their spacing and mounting height. Type and Size of Lamp. Referring to Table II it will be found that for a 12-ft. ceiling, lamps of approximately 80 candle- power are used in well designed systems. The surroundings being dark, a unit which transmits some of the light to the ceiling and in horizontal directions seems advisable on account of the added cheerfulness thus given the factory space. 1 Owing to the circuits available as well as to the ceiling height we conclude from Table I, and from a knowledge of the candle- power ranges of the various available lamps, that the tungsten type seems most desirable. This conclusion is emphasized by the very small clearance between the crane and ceiling, which will accommodate a tungsten lamp, but not an arc lamp. The 100-watt tungsten lamp has a candle-power of 80 and is therefore chosen. Spacing the Lamps. A diagram of one of the bays of this location 16 by 40 ft. should now be drawn and the lamps located tentatively to scale as shown in Fig. 8, according to Table III. From this table we note that an average spacing distance for a 12-ft. ceiling ranges from 8 to 10 ft. Hence in a direction parallel to the length of the aisle an 8-ft. spacing of lamp rows conforms to the table, and at the same time makes the lamps sym- metrical with respect to the cross girders, while a 10-ft. spacing across the aisle makes the lamps symmetrical to the width. 1 This statement seems to violate the idea that all of the light should be transmitted in useful downward directions to secure the highest efficiency, because obviously the light transmitted upward in a proposed system like the one under discussion will be mostly absorbed by the dark ceiling. In gloomy factory spaces, however, it may be an advantage to sacrifice some- what in efficiency, if, by using glass reflectors which transmit some of the light in upward and horizontal directions, the location is rendered more pleasing in appearance. 22 FACTORY LIGHTING These spacing distances, conforming to the averages from Table III and giving a symmetrical arrangement, are chosen. We should now check the chosen size and the spacing dis- tances which have been determined separately, in order to ascer- tain if the resulting illumination will probably be uniferm over the floor area, and of sufficient intensity. The spacing of 8 by 10 ft. results in one 100-watt tungsten lamp for each 80 FIG. 8.- Elevation -Diagram of typical factory bay showing lamp locations. sq. ft. In Art. 16, under the subject of lighting system efficiency, we find in Table IV efficiency values of about 30 per cent, through- out the interval between cleanings for factory conditions. The 100-watt lamps in say two bays furnish 16 X 830, or about 13,280 lumens of light flux. 1 With an efficiency of 30 per 1 There are 16 lamps in two bays and each lamp furnishes about 830 lumens at a given rating. Two bays are taken merely to give an average effect, as the illumination at any point on the floor is made up of the light received from all the lamps moderately near the point, and also because in some systems the edge lamps are not one-half the spacing distance between lamps, from the walls. ILLUMINATION DESIGN 23 cent., the total number of lumens on the 1,280 sq. ft. lighted by the 16 lamps would approximate 4,000, that is 30 per cent, of 13,280. Dividing the available lumens on the working surface by the area over which they are distributed we have 4,000 divided by 1,280 or 3.1 foot-candles as the intensity on the working surface. Table V shows this to be adequate for factory work of the kind described. It must be remembered that the intensity* as just calculated is an average between cleanings of lamps and reflectors, and its value will therefore be less than calculated values based on clean lamps and reflectors. TABLE. V. ILLUMINATION INTENSITIES RECOMMENDED FBOM THE EXPE- RIENCE OF THE AUTHOR FOR CERTAIN CONDITIONS This table is suggestive only, as fixed rules may mislead Class of work Foot-candle intensity Office 3.0 Drafting 7 Factory storage 0.5 Factory rough manufacturing work 3 Factory, fine manufacturing work 5.0 Power-house . . 3.5 Note. These values indicate good working intensities. While consider- ably higher than found in a large number of existing lighting systems, they are reasonable for each class of work involved, always assuming that engin- eering judgment will be used in applying such information. Mounting Height. The clearance between crane and ceiling determines in this case the mounting height, which is approxi- mately 12 ft. The average spacing being 9 ft., we divide this by 9, the mounting height above the machines, and find the ratio between spacing and mounting to be 1, which according to Art. 9, footnote, is nearest to the intensive type of reflector. For the conditions, this arrangement should provide practically uniform illumination over the working surface. 1 Point Addition. Making a diagrammatic sketch of six bays as shown in Fig. 9, drawn to a scale of 1/8 in. to the foot, and by the use of an illumination rule as shown in Figs. 6 and 7, adapted to an intensive type reflector for the height in question, the illu- 1 The calculations up to this point are usually sufficient to give a general idea of the lay-out of a proposed system, and especially so where rules governing the ratio of spacing to mounting are available. Often, however, it is necessary to check the preliminary lay-out as to uniformity and intensity as in the case of arc lamps or other types with which such ratio constants may not be furnished, and the subsequent paragraphs on point addition then become important. 24 FACTORY LIGHTING mination may now be integrated at each of several points as furnished by all the lamps contributing light to each point, in order to check the value of the resulting illumination from the method worked out under the efficiency scheme. Taking the point "A" and placing the end of the rule at this point, the illumination at the point " A" produced by lamp (1) is found to be 0.20 foot-candle; that produced by lamp (2) at the point " A" is 0.95 foot-candle; by lamp (3) is 0.95 foot-candle; by lamp (4) is 0.20; by lamp (5) 0.20; by lamp (6) 0.95; by lamp NM-i-s'-h* 4 - H \-ffi V. 1 1 -' H H H H H H f H H -Hj- Hi H H ? Ao oH H H He H? H" H H H K H H H *H H H H H H H H H Plan FIG. 9. Diagram of six factory bays with points for illumination rule addition. (7) 0.95; and by lamp (8) 0.20 foot-candle. Hence the total illumination intensity at the point "A" produced by the eight lamps which mainly affect this point, is about 4.60 foot-candles. In like manner it is found that the illumination at the point "B" is 4.84 foot-candles; at point "C" 4.60; at point "D" 4.34; at point "E" 3.93; at point "F" 4.94; at point "G" 4.52; and at point "H" 4.94 foot-candles. Hence the average inten- sity which may be expected over this factory bay based on the eight points, and with clean lamps operated at normal voltage is about 4.6 foot-candles. 1 Allowing say 30 per cent, for deteri- oration between cleanings due to accumulations of dust and dirt on reflectors and lamps, this results in a minimum of say 3.0 1 These values indicate that the illumination should be fairly uniform on a plane say 3 ft. above the floor, but since the calculations are often based on an uncertain distribution curve of the reflector and do not take into account the effect of surroundings, they should not be relied upon further than as a guide to the probable uniformity of the resulting illumination, unless the distribution curve of the reflector is reliable and surroundings be given due weight in the conclusions. ILLUMINATION DESIGN 25 foot-candles, and hence checks in a close manner with the intensity thought available from the efficiency method, further verifying the conclusions as to size of lamp and the spacing. Switch Control and Number of Lamps. A flexible and practical method of controlling the lamps in each bay is shown in Fig. 8, the lamps controlled from each switch being indicated by the same numeral. According to the calculations as just described, eight lamps are required in each bay, making a total of 160 lamps for the 20 bays to be lighted. FIG. 10. Reproduced from a photograph taken at night under the arti- ficial light in the factory space discussed. The Actual Results of this Installation as Made. It is of interest to note that the location corresponding to this example was equipped with 100- watt tungsten lamps mounted 11 ft. 6 in. above the floor, with a spacing of 8 by 10 ft. as shown in Fig. 9 and in Fig. 10. The intensity, as recorded from test measure- ments, was about 3.1 foot-candles with fairly clean lamps and reflectors, and the efficiency about 30 per cent. The actual conditions thus found are somewhat lower than might have been expected from the point addition calculations, probably because the lamps were operated a trifle below their normal voltage at the time of making the test, or the distribution curve of the suauirq duii3[ j^o^ A"q paptA -ip Qutsid aupjJOM no euara -nq; uia^sA's jo Xouaionjg MUM jad suaumrj sajpueo-^ooj m A^ISUS^UJ 3{JOAV joog iiii lili.il . .. 3 M3JSS .-3 .as: +3 -^ c3 += J2 o3 on* c3 e3 liSS * rf 13^** .^H ^3 a-* 3 ^* ^ ^ ^ > ^> -^ . l || "TiTfTT Ml M b> T -o !3 * > ^ ^ O5O5 .OT:OOOO OOOOOOOao M ' 02 CO ^ ^3 LL. rt< COlOOOCCKNiM rH CD O5 CO CO (N NO5'*C'C5 IN CO rH CD M< (N C CO Tt< CO CO Tj* CO +3 +3 03 03 o3 c3 o3 03 = = = s s s .2.2.2 0.2.2.2 sssss 2 ro ^ ^ 'C'E'C'E'C assa aa III 2 j||l -sggggg g a a a a a 03^3 c3 . OOOOOO OOOOOOOO __ ______^__ 'S5S 0000000 oooooo oooooooo CO CO CO CO CD CO CO CO CO CO CO "C CO CDOO>COOOC ddddd dddddd dddddddd NCO^H OCOO505OO COOOOOOOCO O5OOOOO>-iCl OOOOOCO-<*iO t^ i-l (N O> CO CO CO 1-1 OOOOOOCOiC 00 O5 rH CO CO CO 00 rH (N CO CO CO CO 26 ILLUMINATION DESIGN 27 reflector from which the illumination rule was made, may have indicated candle-power values higher than the actual. It is instructive to note that the actual illumination produced where the surroundings are bright may be appreciably higher than indicated by preliminary point addition calculations, on account of reflection from walls and ceilings. Further, the efficiency of a system may be appreciably lower than the pre- liminary efficiency calculations would indicate, if the surroundings are darker than assumed, and vice versa. Note. From what has been set forth in the foregoing discussion it may be thought that illumination calculations are not only complex but without system. In this connection it should be clearly stated that the object of the discussion on illumination design has been to describe the practical reasoning which should be followed in work of this kind. It has not been the intention to formulate a set of definite rules, but rather to get away from the idea of constants and formulae, and instead to describe the methods which are used in the practical planning of lighting systems. As illuminating engineering work advances and accurate data accumulates, it is reasonable to suppose that the design of lighting sys- tems will become more the result of engineering judgment .than is now the case. Until then, such work should be conducted in the careful and painstaking manner described in the preceding paragraphs. In numerous cases where the refinements as here discussed cannot, through a lack of working knowledge on the part of the designer, be con- sidered, there will be found on the market a limited number of groups of reflectors that may be used for tungsten lamps. If, therefore, tungs- ten lamps are to be used, the determination of that group of reflectors adapted to given conditions may be made in a fairly simple manner, either by securing this information from the reflector companies, or through the medium of published information relating to various reflectors. The illumination resulting from the selection of a given type of reflector for a given type of lamp, based on the data furnished by the reflector manufacturers, is apt to produce a fairly satisfactory result, even without any considerable amount of calculation. Where extensive work is to be undertaken, however, it is very desirable to do away as much as possible with rules and formulae as generalized information, and to use them, if at all, only in conjunction with the methods herein set forth. The information furnished in rule books or in tables such as Table VI will then be merely a guide to an intelligent application of engineering methods. It should always be kept in mind, however, that even the most care- fully prepared plans for lighting may produce results far different than anticipated if due allowance is not made for reflection from or absorption by walls, ceilings, and surrounding objects. CHAPTER III LIGHTING INSTALLATION WORK 19. The installation of a lighting system includes the wiring and the placing of switches, lamps and reflectors according to pre-arranged plans. In the preceding chapter it was shown that illumination design fundamentally considers the proper location of lighting units to secure a definite and advantageous result. It is obvious that in planning new lighting systems the details of the building construction should be taken into account, and that lamps should preferably not be placed where it is incon- venient to mount them. From the standpoint of the designing engineer, the wire- men should be posted in this work concerning the importance of accurately locating the lamps according to the plan. It will thus be apparent that there are two viewpoints, the one that of the designer, and the other that of the wiremen. Hence the need for a co-operative spirit between illuminating engineers and wiring foremen or contractors, without which such work is apt to be less successful than otherwise. 20. Theory and Practice. The illuminating engineer should consider at the outset the object of adapting certain lamps to specific purposes, and should determine the locations for these lamps in a manner to produce the most effective result. In following this plan of procedure, however, he should keep in mind that slight changes in lamp locations often reduce the cost of wiring to such an extent that the differences in the illumi- nation are small compared to the greater ease in mounting the lamps according to the modified plan. The first duty of the designer, however, is to distribute the outlets for the lamps in such a way that the illumination shall be satisfactory for the conditions in question, and after this determination has been made, an inspection should follow to ascertain whether or not certain small changes may be an advantage in order to accommodate wiring conditions. This is a factor of importance, perhaps, more in the case of buildings 28 LIGHTING INSTALLATION WORK 29 already constructed than where the wiring is to be installed during the process of construction. A careful balance between engineering accuracy and the practical application of the plans, is apt to result most success- fully for all concerned. 25K.W Service Supply x 50 Circuit Panel Box 1 -Locate 2 Pole Switch here FIG. 11. Wiring plan showing conduit. 21. Installing Lamps According to a Fixed Plan. The work- ing plans, to be most easily interpreted by the wiring foreman, should define all items of information necessary to permit the installing of the lamps in accordance with the same. The drawing, as explained in Art. 15, should indicate the location of the lamps to scale, and a list of materials should 30 FACTORY LIGHTING either be placed on the drawing or on accompanying specifications. Fig. 11 represents a wiring arrangement and the various sizes of conduit together with panel box, transformer and the control arrangement, the latter by means of dotted lines which enclose the lamps controlled from a single switch. In wiring work the conditions are likely to be trying, and, especially in factories where production must not be delayed by wiring work, it is necessary in as far as possible to facilitate the wiring by complete information. Toggle Bolt _^__ Metal Moulding Conductors FIG. 12. Toggle bolt used for holding moulding to tile ceilings. 22. Estimating the Cost of the Work. After the completion of a drawing, it is advisable to make an estimate of the expense connected with the installation of the system. The estimate is comparatively simple if the drawing contains the necessary circuits and control features. A practical form is shown in Table VII, which may be followed approximately in estimating on such work. TABLE VII. SHOWING ITEMS INVOLVED IN A TYPICAL LIGHTING ESTI- MATE. THE COSTS ARE TO BE ADDED AFTER EACH ITEM AND THE TOTAL THEN INDICATES THE ENTIRE ESTIMATED COST OF MAKING THE INSTALLATION Amt. Item 268 100-watt, 112-volt clear Tungs- ten lamps. 268 Type "1-9" Holophane reflect- ors. 268 Form "H" holders. 268 Keyless sockets. 268 Fused rosettes. 268 Wood socket bushings. 67 10-amp. snap switches. 17 Fuse blocks. 34 Fuse plugs. 34 Fuses. Amt. . Item 134 ft. No. 16 lamp cord. 40 Conduit boxes. 400 ft. 1/2 in. Loricated conduit. 1500 ft. 2-wire moulding and cap. 2 gro. 1 1/4-in. No. 8 F. H, wood screws. 5000 ft. No. 12 R. C. wire. 4 rolls Friction tape. 5 Ib. Solder. Labor. Over-head charges. Total. LIGHTING INSTALLATION WORK 31 The cost per outlet is of particular importance and may be used as a unit of comparison between the cost of the proposed system and that of other systems previously installed, to deter- mine whether or not the plans proposed are either extravagant, on account of certain arrangements which may be modified, or as showing the wiremen what is expected of them in the economy of making the installation, a valuable item where the work is under the supervision of the electrical department of a plant. "It is highly desirable in large plants to keep a record of all such estimates until the work of a given installation is complete, and then to follow up the original estimate by checking the actual costs with the same. These exact costs can then be filed for future reference when additional work is considered. FIG. 13. Plain wood ceiling, no under beams. 23. Relation of Ceiling Construction to Wiring Expense. The nature oi the ceiling obviously has a large influence on the expense of installation. Industrial buildings present a large va- riety of ceiling construction, some of which may be indicated as follows : (1) Wood ceilings with no under beams or joists. (2) Wood ceilings with under beams or joists. (3) Plaster ceilings or concrete construction. 32 FACTORY LIGHTING (4) Tile ceilings covered with plaster. (5) Brick ceilings arched, with iron girder supports. (6) Open-girder construction where the only support for the lamps and wiring is either on the trusses or on stringer boards located between the same, unless the .wiring and lamps are attached directly to the roof of the building and the lamps suspended in such a way as to avoid shadows which result on the work if they are located above and too nearly in line with the iron work. FIG. 14. Wood ceiling with under beams. The simplest wiring problems are associated with wood ceilings in those buildings where the lamps are to be installed after the construction of the plant. Here the wires may be attached directly by means of porcelain knobs or cleats, by ..wood moulding, or in some cases conduit may be attached directly to the ceiling. Where the wood ceiling is divided into sections by under beams or joists it is usually best to arrange the various circuits to be self-contained in each bay, thus avoiding the necessity of extending the control circuits either through or beneath the beams. With plaster or tile ceilings, the problems of attaching the LIGHTING INSTALLATION WORK 33 wires in old buildings is complicated by the finding of lodgment for screws or bolts. A toggle bolt may be used by drilling the tile, forcing the toggle bolt into place, which when pulled down is anchored on the inner side of the tile as shown in Fig. 12. Knobs, cleats or any of the various types of moulding may then be attached to these toggle bolts. To arched brick ceilings small boards may be attached either directly or preferably through the medium of drilling the iron FIG. 15. Tile ceiling covered with plaster. work at the bay intersections. The wiring may conveniently be mounted on these boards. With open-girder construction several methods maybe adopted. One scheme is to attach the wires to the roof and to drop the lamps by means of cord or supporting wires to a level or directly below the iron work. Another scheme is to attach stringer boards to the under side of the horizontal iron work and to support wires and lamps on these boards. The foregoing statements apply in general to those cases where the wiring is put in immediately after the building has been 34 FACTORY LIGHTING constructed or in old buildings as open work. Some of the types of ceiling described are shown in Figs. 13, 14, 15, 16, and 17. 24. Following up the Work. After turning over the plans to the wiring foreman, it is an advantage to the engineer in charge to visit the location during the course of the installation in order that he may determine the accuracy with which the plans are being followed. A word of explanation to the wiremen now and then, before the work is well under way, may avoid serious errors in the location of lamps through a possible .misunder- FIG. 16. Brick ceiling with iron girder supports. standing of certain items on the drawing, although this possibility is reduced where the plans contain full information. In some cases it may be best to locate the lamps as originally planned, irrespective of the difficulty or expense. Judgment, however, should be exercised in this connection and wherever an obstacle seems to be serious enough to warrant, a modification in the original plans should be made to accommodate the difficulty. 25. Underwriters' Rules. All wiring should be installed in a correct and permanent manner, not only to insure reliable service LIGHTING INSTALLATION WORK 35 but also to adhere to the Rules of the National Board of Fire Underwriters. 26. Supporting the Lamps Securely. In view of the tendency to use a large number of lamps for given areas, positively secure fittings should always be employed. In some cases there is no direct means of support above the location of the lamp and in some of these cases special stretched wire supports have been used for high mounting as shown in Fig. 18. The lamps are run out on the wires from a point at the center of the aisle to a posi- tion toward the side of the building and here it is of the utmost importance to anchor the ends of such supports securely. FIG. 17. Open girder construction. Simple brackets may be used in some instances where a vertical roof support serves also to support the lamp in order to bring the lower portion of the lamp on a level with the over-head* horizontal iron work. This is shown in Fig. 19. Large tungsten lamps which have a flexible cord connection between the rosette at the ceiling and the socket should be rein- forced by means of small chains which may be attached to the shade holder on the one hand and to the ceiling on the other, as shown in Fig. 20. 36 FACTORY LIGHTING Glass globes and reflectors should be enclosed with a fine- mesh screen to prevent accidental falling of the reflector in case it becomes detached from the holder, or if broken, to prevent small pieces of glass from falling. Such a mesh screen is shown for an arc lamp globe in Fig. 21, and for a glass reflector in Fig. 22. The foregoing items are of much importance on account of the danger to employes when constantly moving under large numbers of over-head lamps as suggested by Fig. 23. Some reflectors are very heavy and the danger should they become FIG. 18. Stretched-wire supports for arc lamps. % detached through the result of insecure fittings is apparent. With glass reflectors the holder by which the reflector is attached to the socket should be securely fastened. The so- called spring type holder has been used to great advantage, and the flexibility of its fitting is such as to make it particularly well adapted to glass reflectors for tungsten lamps. 27. Control Circuits. Wall switches should be placed on similar portions of the wall or on relatively the same column locations throughout the building, that is, on the same side of each column and on the same side of the aisle. This will avoid confusion when lamps are turned on or off in large numbers a few at a time. LIGHTING INSTALLATION WORK 37 Such control circuits are largely run from the lamps to a point within reach of the floor, the wires being run down either the walls or the columns. The expense of these circuits will depend to a great extent on the ease or difficulty with which the wires can be attached to walls or columns, and also on the distance between the switch and the lamps it is to control. In many cases the extension of elaborate control circuits may almost entirely be eliminated by the use of the pendant or pull switch. By this means the circuits are controlled through the medium of switch connections at the ceiling directly in line with FIG. 19. Bracket for supporting arc lamps. the wires which feed each circuit. In ordinary factory sections there is a slight disadvantage connected with the use of pendant switches. They are often hung in such a way that workmen walking up and down the aisles may thoughtlessly strike or tamper with the switch, thus causing excessive maintenance and a continual annoyance from having the control apparatus out of order. The use of the pull switch practically eliminates this difficulty in that it makes possible the mounting of the switch itself at the ceiling, and the control is effected by a cord and a small handle attached to the same. This class of switch is particularly adapted to fairly low ceilings and also where com- 38 FACTORY LIGHTING paratively large numbers of small or medium sized lamps are used with a relatively large number of switches. Where the factory sections are fairly wide and where windows are located at one side of the aisle only, the floor space at the center of the building in the early morning and the late afternoon hours may be practically without natural light in comparison with the floor space near the windows. As stated in Art. 14, if all the lamps across the floor are controlled from one switch in Ceiling Chain attached to Shade Holder and Anchored to Ceiling FlG. 20.- -Small chains for supporting glass reflectors used with tungsten lamps. rows, the floor space at the center of building will often be supplied with artificial light when the workmen immediately adjoining the windows will still be supplied with adequate natural light. Hence the lamps near the windows should be on a separate circuit from the 'lamps near the central portion of the aisles. This is indicated in Figs. 4 and 24 which show the lamps controlled in rows parallel to windows. While somewhat more expensive as to first cost than where a large number of lamps is controlled from one switch, this method is usually an economy in the long run due to the flexible control arrangement. Thus, lamps not required near the windows may be turned out without LIGHTING INSTALLATION WORK 39 interfering with the illumination at the more central portions of the building. 28. Series and Multiple Systems. The series system of lighting, which is so well adapted to exterior service on account of its simplicity and comparatively low cost for wiring installa- tion, is very poorly adapted either as a constant current or a constant voltage system for interior industrial purposes. The disadvantages of the series system for interior work are, first, the large number of lamps controlled from a single switch, which implies that a large floor area is apt to be lighted by one circuit of lamps. It is not always convenient nor economical to use all the lamps on a single series circuit at one time. A multiple FIG. 21. Mesh screen used with arc-lamp globes to prevent falling of glass in case of breakage. arrangement of lamps where each lamp or small group of lamps may be controlled from one switch permits a disposition of the circuits to far greater advantage than in the case' of series systems. A second disadvantage of the series system is the high voltage usually associated with its use. This entails a greater risk to the wiremen when working on such circuits, and largely on ac- count of this risk the series system is not recommended for interior work. In those instances where series circuits are already in use, or where they have been made necessary by other special circumstances, care should be taken to provide a switch at each end of the circuit and these switches should both be open when wiremen are at work on the circuits. 40 FACTORY LIGHTING 29. Supply Circuits. With the prevailing tendency toward large increases in the illumination in factory buildings, the in- stallation of new in place of older systems calls for special attention to the supply circuits on account of the large amount of energy usually required even with higher efficiency lamps when a more liberal number of lamps is substituted for what has previously been inadequate illumination. There is a tendency to make use of old circuits for supplying new arrangements of lamps, but this should be done only after a study has been made of the new power requirements, and after it has been determined that the old circuits are adequate in capacity for the new conditions. FIG. 22. Mesh screen used with glass reflectors for tungsten lamps to prevent falling in case of breakage. Electric lamps in factory work should always be supplied from circuits of constant voltage to secure the advantages of steady light, and also from the standpoint of irriproved operating conditions where the voltage is uniform in value. When new circuits are provided, the mains should be made sufficiently large to permit of extensions as new buildings or new additions are made to the equipment. Power and lighting circuits should be separate, on account of varying demands placed on combined circuits by motor loads. There is a tendency to tap in a motor circuit here and there on lighting mains where they are conveniently located with respect to the machines, but a rigid adherence to the separation of motor and lighting mains is best. LIGHTING INSTALLATION WORK 41 An accurate diagram or map of the wiring in the factory should be on file so that changes or modifications in the wiring may be made without the necessity of tracing out the mains and circuits on the floor. The difficulty connected with obtaining such a wiring map in an old plant, as well as the work of keeping it up to date, is small in comparison to the convenience it affords for wiring changes, while in a new plant it is a simple matter to secure such a map when the lighting equipment is installed. Fig. 25 indicates a wiring map of an actual installation in part and from this an idea may be gained as to one method of re- ducing the wiring conditions to an exact diagram. 30. Methods of Installation in Relation to Maintenance. The maintenance cost of lighting systems is largely influenced by the accessibility of the lamps. With moderate ceiling heights up to 14 or 16 ft. the lamps may be reached from a step ladder. For ceiling heights. above 16 ft. it is hardly practical to use a step ladder and where it is impossible to reach the lamps from the top of a crane, it is sometimes necessary to mount the lamps suffi- ciently below the ceiling to make them accessible from a ladder on the floor. Where the lamps are maintained from the top of a crane care must be exercised to avoid accidents to the lamp or repair men through carelessness in getting on or off the crane, or through the movement of the crane while the lamp man is at work. A rigid rule should be enforced that in no case shall the crane be moved while a man is at work on the same. In some instances where the lamps are mounted very high, small wood walkways have been provided up^ and down the aisles and above the crane. This walkway is attached directly to the roof trusses in such a manner that the lamps may readily be renewed or trimmed. While the first cost for such a walkway may not seem warranted, such an addition in large factories forms a ready access to the lamps without interfering with the crane service and this in the end will usually save considerable time in the operation of the shop. Automatic cutouts may be employed where it is possible to lower lamps from high positions. The lamps when lowered by this means are disconnected from the supply circuits, and, besides facilitating the maintenance work, added safety is thus insured the lamp men. 31. Economy in Using Wiring Material. In turning a light- 42 FACTORY LIGHTING ing plan over to the wiring foreman where no indication is made as to the amount of wiring material required, undue amounts of material may be wasted in cutting wire or conduit lengths, with- out regard to the limits of spacing between lamps. For this reason it may be desirable to show the fittings and dimensons in such a way that the lengths of wire and other material may be made up in an accurate manner. In large installations the por- tions of moulding or conduit cut off the ends of poorly matched pieces of material may run into a relatively large expense. FIG. 23. Typical factory lighting system showing the large number of glass reflectors over the workmen. These reflectors are supported by small chains to the ceiling and covered with wire mesh screens. 32. Tungsten Lamps Under Shop Conditions. The growing use of tungsten lamps for moderate ceiling heights in many factory buildings has in the past been somewhat hindered by the objection of filament breakage from vibration of the lamps. Many devices have been suggested for reducing the shock or vibration under rough shop conditions. These so-called shock absorbers are, however, unnecessary in general if a small piece of flexible cord from one to two or more inches long is connected between the rosette at the ceiling and the socket. This small LIGHTING INSTALLATION WORK 43 length of cord is sufficient to absorb practically all shock. Furthermore, the recent developments of the drawn-wire tungsten filaments under the trade name of Mazda lamps, have greatly reduced the breakage due to vibration, so that at the present time tungsten lamps are used very generally in many factory buildings even under very rough service. Where, however, the lamps must be supported among line shafting and belting, it is advisable to eliminate flexible cord in mounting the lamps on account of the danger from the accidental flying off of belts. In such cases the lamps may be mounted rigidly to the ceiling by means of gas pipe or conduit. r 6 7 # 7 6 # 7 # 7 7 9 10 10 10 9 io K> ft 10 ^11 ^11 ^12 ^12 ;c(i2 )^11 ^11 )^12 )^12 FIG. 24. Control of lamps parallel to windows. (See also Fig. 4.) 33. Installing Small Numbers of Lamps at a Time. The necessity for a revision of old lighting systems sometimes calls for extensive improvements. In such cases factory managers are apt to be confronted with an expense which they may not be able to bear at any one time. A method which has been employed in some instances is to draw up complete plans for one section of the factory after another, and to extend the installation period over a comparatively long time. A small portion of the new system may then be installed one month, another portion the following month, and so on. In such cases the system as a whole, if possible, should be 44 FACTORY LIGHTING planned before beginning the work, at least as regards given de- partments of the factory, so that the final arrangement of lamps may conform to a systematic plan. An additional advantage of this scheme, especially where experiments are contemplated for ascertaining the best method of illumination for given purposes, is the ability it gives, after the installation of the first small Column Numbers 7 18 a a o> 2C d 0> ^MoJ 2 1 22 2} g 1 ^.1 5 24 25 26 2J Aj 29 C? |> , 3( i ) 8 | iJ &j S| II 1 Hi II 11 a 3 i \ \ ^ 1 ^ 1 2 HJ Hh^ LH.J 1 ^ E-I j r H 1 IfH 1 o Q I Q ^ Q 1 ' | | H .H | H H OJVolt A.C. CO C ycles, -Main s ^ 1 1 1 1 /\ I 1 tn 3 Volt D.O. CKI no, -Mains - d 1 1 1 >, Volt A.C. 25 ( 3yc)es -Mai ns<^ 3 2 P^ase< 1 1 d 3 Volt A.C. 25 C jdles,- Mai CQ | 1 d 1 1 a D Volt D. C.- M insx -^ 1 1 o i 1 Volt A.C. GO C y( lies , Ma r is "*~To Tungsten Lamps il II CQ To Tungsten Lamps FIG. 25. Portion of typical wiring map for a factory aisle. section, to observe the illumination effect. If unsatisfactory, or if any modifications are required, they may more easily be made than if the lamps are installed as a whole at the start. 34. Locating the Outlets on the Ceiling. Before installing the wires and hanging the lamps it is well to chalk out the loca- tion of the outlets on the ceiling according to the working draw- ing. At this juncture the engineer will find 'a good opportunity for checking over the drawing in terms of the building details. It is recommended as a general rule that all locations of outlets in new, or in old buildings where revisions in lighting are to be made, be thus chalked out prior to the placing of wires, in order that the designer may have a chance to inspect the outlet loca- tions in relation to the ceiling construction and objects to be lighted. LIGHTING INSTALLATION WORK 45 Where stringer boards take the place of a ceiling in the over- head open factory girder construction for supporting the lamps, these boards should be supported rigidly and positively to the iron work. Lamp trimmers and maintenance men will support their ladders against these stringer boards, if say 16 ft. or less above the floor, and the physical strength of these boards ought to be sufficient to permit the placing of a ladder against them without the accidents which have occurred now and then from the giving way of boards fastened insecurely. 35. Concluding Items. From the foregoing an idea may be gained of the refinements of installing lamps systematically. Much may be said in favor of instructing the wiring foreman beforehand as to the importance of following the plans accurately in every detail, and as previously intimated, co-operation be- tween the wiring foreman and the designer will be productive of the best results. Factory buildings equipped with lighting systems based on careful plans, and where the installation has been made in accord with the principles just explained, present not only a pleasing appearance, but what is more important, they furnish to the plant equipment a distinct asset in lower maintenance and improved illumination conditions, which are valuable in their relation to the general efficiency of the factory. CHAPTER IV LIGHTING MAINTENANCE AND MAINTENANCE RECORDS 36. Deterioration of Lighting Equipment Every lighting system suffers deterioration as the time of service goes on, and unless careful attention is given to renewal and repair, and to other features involved in maintaining highly efficient service, the lighting equipment will decrease in effectiveness. Systematic maintenance involves attention to many simple items. In fact one reason for the gross neglect of well installed lighting systems in some instances is the overlooking of these very simple features. For example, the accumulation of dirt on the surface of reflectors or globes is frequently left from month to month simply because the deterioration of light which the dirt produces may be so gradual as to be scarcely noticeable to the untrained eye. Where lighting systems consist of a number of small or medium sized lamps, those which become dim with age or even lamps which have burned out are often unnoticed by the maintenance department unless regular attention is directed to items of this kind. TABLE VIII. TEST RESULTS OBTAINED UNDER THE SUPERVISION OF THE AUTHOR TO SHOW LOSSES DUE TO SOILED LAMPS AND REFLECTORS Conditions of test Low office Fairly high factory office Low factory space Medium high factory space Fairly high factory space Ceiling Light. Light. Dark. Light. None. Walls Light. Light. None. Light. Dark. Lamps 60-W. Cl. 60-W. Cl. 100-W. Cl. 100-W. Cl. 100-W. Cl. Reflectors 1-60 SF. 1-60 Cl. 1-100 Cl. 1-100 Cl. F-100 Cl. Class of work Desk. Desk. Machines. Esnca. Bench. Time between washings 14 weeks. 17 weeks. 9 weeks. 11 weeks. 13 weeks. Results Efficiency in per cent. Soiled lamps 19.7 24.2 22.4 25 20.1 Soiled reflectors. Clean lamps 20.7 24.9 22.5 27 23.6 Soiled reflectors. Clean lamps 34. 1 29.3 31.2 35.3 33.6 Clean reflectors. New lamps 34.1, 31.2 31.9 36.1 39.1 Clean reflectors. All efficiency values corrected for normal lamp voltage. 46 LIGHTING MAINTENANCE AND RECORDS 47 37. Importance of Systematic Maintenance. The necessity for such work is shown by the large losses of light produced by dirt on lamps and reflectors, which may amount to as much as 50 per cent, in extreme cases. Its importance is further shown by the results of an experiment conducted to ascertain how bad this deterioration effect may be in a practical case, as shown in Table VIII, the results of this test corresponding to a certain de- gree of neglect in the proper upkeep of the systems investigated. In Fig. 26, the effect is shown of not renewing the burned-out lamps in a large tungsten lighting system on certain days. In 5 6 t S *4 9 10 11 12 .' ~ B 14 15 16 17 18 19 20 21 i I FIG. 26. Curve showing effect on number of lamps to be renewed when renewals are not made on Saturday and Sunday of each week. Note the peak on Monday in each case indicating the additional lamps burned out since the last renewal. This shows that lighting conditions become very poor if the lamps are not renewed regularly. the short interval between Friday and Monday mornings the number of lamps burned out has been such that on the Monday mornings following these intervals, an appreciably larger num- ber of lamps must be renewed than when the various systems are inspected and the renewals made day by day. If therefore the renewal of burned-out lamps is neglected for weeks at a time, such systems will soon be practically worthless as efficient light producers, and where large sums of money are expended for the best practical illumination, it is correspondingly important for those in charge of the general building equipment to properly and promptly take care of items which have so large an influence on the working efficiency of the employes. In another instance several tungsten lighting installations equipped with glass reflectors were allowed to be in service for 48 FACTORY LIGHTING an interval of several weeks, during which tests were made. The results of these tests for an office and for an average factory space are shown in Figs. 27 and 28. The office in question was about 20 by 50 ft. with a 11-ft. ceiling and walls and ceiling of light color. The factory space was made up of 16 by 40 ft. bays with horizontal roof iron work 16 ft. above the floor, and with no ceiling, the lamps being suspended from stringer boards and the surroundings very dark, although with not a great deal of dust and dirt in the air. It should be stated that the intervals between cleanings, as carried out by the maintenance department, were 14 weeks in the office and 13 weeks in the factory space. 5.6 4.8- | 4.0 2 3.2 I 2 ' 4 1 1.6 0.8 12 18 24 30 36 Elapsed Time in Days 42 48 54 FIG. 27. Deterioration curve showing effect of dust and dirt accumula- tions on glass reflectors. (Office.) Calculations of the losses in light at a fixed cost per kilowatt- hour show in Fig. 29 that the system in the office might have been thoroughly* cleaned at intervals of 4 weeks instead of 14, and the system in the factory space might have been cleaned at intervals of less than 2 weeks instead of 13, at an expense equal to the integrated loss of light between cleaning intervals of 4 and 2 weeks respectively. The foregoing tests were conducted on a large number of lamps in practical service. Another evidence of the losses of light is indicated in Fig. 30, which shows the light distribution from a tungsten lamp and glass reflector before and after cleaning, the unit having been in LIGHTING MAINTENANCE AND RECORDS 49 service for 14 weeks between the times of cleaning. The loss of light from dirt accumulations in this case amounted to 40 per cent. In this last case if we interpret into cash values the loss of light by the gradual deterioration of the reflector and lamp throughout the 14 weeks, it will be found on certain practical assumptions that the part of the energy supplied to this lamp which was wasted, due to absorption of the dirt on the lamp and reflector, amounted throughout this interval to 27 cents, while the taking down, washing and replacing of the reflector amounted 5.6 4.8 0.8 \ 12 18 24 30 36 Elapsed Time in Days 42 48 54 FIG. 28. Deterioration curve showing effect of dust and dirt accumula- tions on glass reflectors. (Factory.) in this particular location to but 3 cents. Therefore, if the illum- ination had been considered sufficient throughout this interval under the soiled conditions, it is obvious that considerably smaller lamps might have been used had a more frequent clean- ing interval been employed. 38. Cost Relations between Maintenance and Losses from Lack of Maintenance. It is possible to use a larger lamp than necessary at the start provided one decides that the lamps will not be cleaned for a very long interval; or a smaller lamp may be used if the intervals for cleaning are sufficiently short. Based on the experiences of some very large tungsten installations, it may be stated as an illustration that in planning for a system of 50 FACTORY LIGHTING one thousand 100- watt tungsten lamps with glass reflectors, the first cost will amount to say $4,000 on certain assumptions regarding wiring and installation expenses. If the lamps and accessories are cleaned at intervals of one month, the average intensity of the illumination on the work throughout the interval between cleanings will, under certain conditions, be about 3 foot-candles. If, on the other hand, the "system were not cleaned more often than once every three months, the average intensity will be about 2.5 foot-candles in certain locations. The use of the shorter cleaning interval tt Cents for each Jten Lamp co ,u ** ci to o co c- Er era vat 2C< Jilts pci Ki o\va tt-i :ou: / / / / / Av Jl'Ut C C 3St < f C eaii ing: z 3Cc nts J / Losses Due to Dirt i 100 -Watt Tung f N> bo * / / V / 1 / ,- / 7 2 y z ^ s / ^ /S J / ji( sS S ' sS / *a> ? 1 5 9 13 17 21 25 29 33 37 Elapsed Time in Days FIG. 29. Curves showing the losses as indicated in Figs. 27 and 28, inter- preted into kilowatt-hour cost equivalent. insures, therefore, in this case a resulting average intensity equal to 20 per cent, more than where the longer cleaning inter- val is employed. Taking up the matter in further detail, it is apparent that if the shorter time interval is decided upon, thus producing an average intensity as shown of 20 per cent, more than with the longer cleaning interval, the number of lamps in the original installation might have been cut down almost 16 per cent., or by an amount equal to about $700 in $4,000, provided the lower average intensity was considered satisfactory. In other words, to the factory where the cleaning of extensive lighting systems is given no attention for three months at a time, it may be stated LIGHTING MAINTENANCE AND RECORDS 51 that by cleaning the system once a month, if the conditions are the same as assumed in the foregoing illustration, work can be performed equally well either with lamps approximately 16 per cent, smaller in size, or with a system composed of say 16 per cent, less lamps than the system in question, with the correspond- ing lower first cost and the decrease in energy consumption where a smaller number of lamps is employed. The percentages just given will obviously be larger or smaller depending on the nature of the location, but considerations of this kind, although hypothetical in a degree, are instructive in emphasizing the necessity for careful attention to such work. 1 90i JJ-^ on AH/-I 90' 15 FIG. 30. Distribution curves of tungsten lamp and reflector before and after washing. The curve obtained after washing shows that 40 per cent, of the available light was lost by absorption when the reflector was soiled. 39. Items Connected with the Maintenance. The term main- tenance as used in connection with lighting is employed in a somewhat liberal sense. It is intended to cover the general work of maintaining highly efficient illumination and therefore com- prehends all items bearing on efficient lighting service. Tungsten Lamps. In the case of tungsten lamps, for example, it is necessary after the system has been installed to renew all burned out, broken or missing lamps; to renew broken or damaged reflectors; and to clean the lamps when soiled and to remove and wash thoroughly the reflectors when the accumulations of dust and dirt warrant. The items mentioned include both labor and material costs and are summarized in Table IX, which indicates 1 See paper by the author on "Industrial Illumination and the Average Performance of Lighting Systems," Transactions American Institute of Electrical Engineers, Vol. XXXI, June, 1912. 52 FACTORY LIGHTING * the components of tungsten maintenance. The costs connected with wiring repair are not included since they fall naturally under the head of wiring upkeep. 1 TABLE IX. TABLE OF MAINTENANCE ITEMS FOR TUNGSTEN LAMPS Item Item Cost of power for month. Labor on reflector washing. Cost of renewal of lamps. Labor on reflector screening. Cost of reflectors broken. Over-head expense. Labor on lamp and reflector renewals. Total. Arc Lamps. In like manner, the various items connected with the upkeep of arc lamps include the labor and material for trim- ming the lamps, renewing globes and reflectors, incidental repairs on the lamps, and washing the globes and reflectors. These items are shown in Table X. TABLE X. TABLE OF MAINTENANCE ITEMS FOR ARC LAMPS Item Item Cost of power for month. Labor on lamp repairs. Cost of carbons. Labor on lamp trimming. Cost of globes broken. Labor on globe washing and screening Cost of repair parts. Overhead expense. Total. Other Lamps. In a similar manner, the items connected with the maintenance of other types of lamps may be enumerated and in a subsequent article, under the head of maintenance records, they will be considered more at length. 40. Inspecting Lighting Systems. Formerly the matter of looking after lamps and accessories was usually delegated to the repair man, who was sent out from the repair room from time to time to investigate wiring difficulties. In fact, it has not been a matter of such great importance regularly to inspect lamps and auxiliaries in the past as is the case to-day for two reasons. First, a larger variety of lamps is in use now than formerly and often a large number of medium-sized lamps is in service; second, the greater appreciation for efficient illumi- nation has caused a great demand for a more liberal use of lamps than formerly. 1 See paper by the author on " Report Submitted by the Illuminating Engineering Department of the Westinghouse Electric and Manufacturing Company," Transactions National Electric Light Association, May 29 to June 2, 1911. LIGHTING MAINTENANCE AND RECORDS 53 Experiences in the immediate past in the formation of an inspection division have shown that in the average factory a distinctly new division in the organization of the lamp depart- ment is required to include regular inspections of the lighting equipment. The development of the inspection division in a typical factory has shown several interesting features which are subsequently described with particular reference to installations of small or medium-sized over-head lamps. The floor space of the factory in question was divided into sections, each of which is covered by an inspector early on each morning and according to a definite route as shown in Fig. 31. 200 Feet FIG. 31. Typical inspection route in a factory. It is the duty of the inspector to follow this route and to indi- cate as he proceeds the location of burned-out lamps, as well as the lamps which have deteriorated due to life limit or to dirt accumulations, also lamps which have been removed from the sockets, loose or broken switches, imperfect fuse connections, and similar items. If the lamps are not burning, it is his duty to turn them on and to make sure that all are in good working order. Judgment must be exercised by such an inspector to detect accumulations of dirt and dust which may be such as to cause the lamps on a given day to have reached a" condition of unsatis- factory service. One of the most difficult things in the main- 54 FACTORY LIGHTING tenance and inspection work is to appreciate fully the degree of dirt deterioration of lamps and their auxiliaries. Thus, reflectors in the factory or in the office which may appear clean when not compared with other reflectors which are clean, may be soiled in a degree which is difficult to realize until the dirt has been removed. It is a common occurrence in passing under a large number of over-head lamps after a casual observa- tion, to feel that they are in good shape. After turning off the lamps, however, and cleaning one lamp and its reflector, the comparison between the clean lamp and the others will often show remarkable differences, which sometimes aggregate 40 and even 50 per cent, in light. As the inspection is made, a record must be prepared which indicates the locations at which the burned out or otherwise defective lamps are to be found. Upon the completion of the inspection the report is made up into concise form and turned over to the maintenance division after which the necessary renewals and repairs are made, preferably on the same day. In following such a course it should be kept in mind that one lamp out may affect the work of a man to a degree far in excess of the cost of quickly and effectively remedying the bad lamp. When looked at from the standpoint of production working results as affected by the lighting, the labor and effort both of the inspection and the prompt action following the inspection become insignificant in the matter of relative cost. A common form of inspection report is shown in Fig. 32, where the first portion of the figure indicates the inspector's report made up immediately after the completion of the rounds. The second portion indicates the carbon copy of the original report, which is returned to the inspection division after all the lamps reported have been renewed. When the renewal man ascertains that a certain lamp reported as burned out is not a defective lamp but is perhaps loose in the socket, he checks off the item on the report after placing the lamp in service. The inspection division is furnished in this way with an accurate record of the number of lamps renewed and this record may be used at the end of each month to form a complete report on maintenance costs. In some instances it is possible with the force available to complete the inspection by ten or eleven o'clock in the morning, and by a short time after the noon hour to have all lamps in working order. LIGHTING MAINTENANCE AND RECORDS 55 One of the important points connected with such inspection work is to indicate in a clear manner for the renewal man, the location of the defective lamps so as to avoid delays in finding the same. This is done to the best advantage by specifying Or/g/naf Copy Date 6-/9-S2.. LOCATION STYLE OUT BLK FUSE MISS NOTES 6-7 /7 46-17 Carbon Copy Date 6- LOCATION ~tft fkre ") (Shop ) STYLE OUT BLK FUSE MISS NOTES . - I/ 6-7 I/ / 7 -^ 7 ff-/ z-/ FIG. 32. Inspection reports before and after the day's work in the main- tenance department. the exact location between column numbers, and to this end the various columns or bays throughout the factory should be numbered to facilitate work of this kind as well as many other branches of the general upkeep work. 56 FACTORY LIGHTING 41. Cleaning Reflectors and Globes. It should be the duty of inspectors to report promptly all lighting equipment in need of cleaning. In some instances it may be practicable for the lamp renewal man himself to undertake the cleaning of glassware or reflectors. For example, the arc lamp trimmer can brush out the globes from time to time when renewing the carbons or electrodes. In many cases, however, as with the glass reflectors for tung- sten lamps, it is necessary to make the cleaning of reflectors FIG. 33. Truck used for maintenance of reflectors in tungsten systems. a distinctly separate part of the work. It is a good thing to have a regular schedule for cleaning the various lamp auxiliaries, but such a schedule must often necessarily be supplemented by a regular inspection. At first thought it may appear an almost impossible problem to handle thousands of glass reflectors used with tungsten lamps, but this work like all other maintenance work can be reduced to a systematic basis. In some large factories a special washing division has been located in the lamp department, to which point all the dirty reflectors are removed for cleaning. In factories where the floor space is under one roof, the reflectors may be removed LIGHTING MAINTENANCE AND RECORDS 57 from the various installations to this central washing point on a specially prepared truck as shown in Fig. 33. In this case, when an installation requires washing, the reflectors are taken down one at a time and clean reflectors which have been hauled out on the truck are at once installed. The dirty reflectors being loaded in turn on the truck are returned to the washing station, where they are washed, dried and returned to stock ready for future use. Difficulties are sometimes en- countered in removing reflectors. In some cases the lamps are ac- cessible only from the top of a crane or from the sides of galler- ies, and hence two men are gen- erally needed to carry on the work successfully. One of these men removes the reflector while the other receives the dirty unit and hands up a clean one thus facilitating the handling of the glassware. If the lighting installations are small, the renewal reflectors may be carried from place to place on small hand racks as shown in Fig. 34, this obviating the necessity of a truck. Here the reflectors are placed over the rod after the removal of the handle at the top of the rack, after which the handle is inserted and the rack is ready for use. Fig. 35 shows a simple washing trough with supporting surfaces for dirty reflectors and drain boards for those which have been washed. 42. Maintenance Records. The need is keenly felt for a standard scheme which will make possible the accurate account- ing of the costs of factory lighting systems. On the one hand, the operating man desires to know definitely how much the operation and maintenance cost of every part of his factory equipment amounts to, and also how it compares with similar FIG. 34. Hand rack for carry- ing glass reflectors. 58 FACTORY LIGHTING costs in other plants; on the other hand, the man who contem- plates the purchase of new lighting apparatus desires a standard basis on which to compare the many types of lamps now avail- able. Simple as these two viewpoints may appear, they include probably the most discussed items connected with the whole practical lighting field. For the purpose of laying stress on the importance of system- atically recording lighting maintenance items, and also for advancing general interest and adherence to certain set forms for such records, the subsequent paragraphs are presented. FIG. 35. Washing trough used for cleaning glass reflectors and globes. 43. Items Included in the Lighting System. A definite record of each group of lamps throughout the factory should be on file. This record should contain the boundaries of each location, the type of lamp and its auxiliary reflector or globe, the type of holder which supports the reflector, or globe, the spacing distance and mounting height of the lamps, and the height of the ceiling or iron work of the building. This information may be tabulated on a chart as shown in Fig. 36, and it should be kept up to date for use. as a ready reference by lamp trimmers and main- tenance men. LIGHTING MAINTENANCE AND RECORDS 59 The preparation and maintaining of a record of this kind is a valuable item in every factory whether small or large, but its importance increases with the size of the factory. This rec- ord will indicate first the exact nature of the lighting equipment when taking stock of the various kinds of apparatus in the plant ; second, it serves as a basis for maintenance records from month to month; and third, it is a guide to inspectors in keeping their rounds up to date when needed revisions are necessary to accom- modate additions to the factory. A record as just described is comparatively simple if one type of lamp only is in service. Where many types of lamps are used in a great variety of groups throughout the buildings, the Location Lamp Reflector koideij Ceiling Height Mounting Height Spacing Distance Watts per Square Ft. No. Type Size Volts Bize T,p _ FIG. 36. Table of information of tungsten systems in a factory used by maintenance department for ready reference. records become somewhat more difficult, but they are of greater importance in the latter case than in the former. Although a large chart has been suggested by Fig. 36, the records may also be kept to advantage in a blank book, at the top of the pages of which the various types of lamps are indicated, and the spaces below these headings may be used for recording the maintenance items from time to time. 44. Record Charts. It is highly desirable to make use of regularly prepared charts for recording the various maintenance items from month to month. Charts for the tungsten, arc and mercury vapor lamps are shown in Figs. 37, 38, and 39. It is advisable at the end of each month to incorporate on these charts the tabulated items in all the divisions of the lighting service for each type of lamp. At the end of a year a comparison of the monthly values indicates in a certain manner whether some of the items are running higher than normal, and shows the differ- ence between winter and summer conditions. Such records are valuable to the operating man in connection with his plant at any given time, and they form a practical 60 FACTORY LIGHTING Monthly Tungsten Lamp Maintenance 1912. 5 Number of Lamps Installed Kilowatt Hours for Entire Month Assuming 9 Hours per Day Service 1 Total Lamps Burned out Total Lamps Blackened r Total Lamps Missing Total Renewals: all Sizes Material Labor Over Head Expense D I 3g c3 S Maintenance Cost per Kilowatt Hour Maintenance per Month per 1000 Sq. Ft. per 2U.8U F.O. ^ Vfc 1*1 fi st . j K g Plan FIG. 52. Lighting arrangement in a typical office 15X20 ft., using two rows of lamps 2 ft. 6 in. from the upper and lower walls in the figure. These edge lamps furnish adequate light to desks against and facing these two walls, but the spacing of 10 ft. is too great ordinarily. Compare with Fig. 51. ued service due, first, to the natural deterioration of the lamps, and, second, to the accumulation of dust and dirt on the surfaces of lamps and reflectors. Hence, what may at first appear to be a rather expensive installation, may on the average be just satisfactory. 57. Rectangular Office 15 by 20 ft. Figs. 51, 52, and 53 show another limiting case where from the table and chart it is found that the office is somewhat too small for three rows and 82 FACTORY LIGHTING somewhat too large for two rows. Two rows may be used as shown in Fig. 51 and the recommended spacing of 7 ft. 6 in. com- plied with, but here the lamps are too far from two of the walls to produce satisfactory results on the outside wall desks. In like manner, two rows might be used as in Fig. 52, with the lamps properly located for taking care of wall desks, that is, 2 ft. 6 in. from the walls, but with the result that the interior portion of the 1 4 6 5 H ^ . Elevation i on' i ZU ' -2'6^-^ r'Q'l ^_._ 7 ' 6 ^ -.^.^g: &T k A lo 3 f X la 1 )*t > X w Plan FIG. 53. Lighting arrangement in a typical office 15X20 ft., using three rows of lamps between upper and lower walls in the figure. This arrangement is superior to the schemes shown in Figs. 51 and 52, but may be criticized as using too many lamps for the area involved. office where the spacing is 10 ft., is poorly lighted. In Fig. 53, however, an arrangement of three rows is shown where the wall desks as well as those at the central portion of the office are ade- quately lighted. The spacing distance between lamps along the direction of the narrow portion of the office is, however, now 5 ft., which is considerably smaller than the recommended spacing of 7 ft. 6 in. for office practice. The usual safe policy in a case of this kind should be to lean to the higher number of lamps for reasons stated in a previous article. OFFICE LIGHTING 83 In a large number of cases possessing these limiting conditions lamps have been installed with the higher rather than the lower number, and the average performance has indicated that the resulting intensity is not too high for the conditions involved. Figs. 54 and 55 indicate typical offices with lamps arranged according to the rules just given. 1 FIG. 54. Reproduced from a photograph taken at night under arti- ficial light in a typical office lighted according to the suggestions in Chapter V. 60-watt (48 candle-power) tungsten lamps are used equipped with Holophane "Intensive" type reflectors. Indirect and Semi-indirect Lighting. Considerable emphasis in the preceding paragraphs has been placed on the arrangement in offices of relatively small lamps. Where the office has a suitable ceiling, that is, light in color, a smaller number of outlets with larger lamps so arranged as to send much of the light to the ceiling and thence to the desks by reflection, may prove as satisfactory as with the larger number of lamps furnishing light ^ee articles by the author on "Notes on Office Lighting," Electric Journal, VoL VII, pp. 352-358, May, 1910; and on "Lighting of Small Offices," Electric Journal, Vol. VIII, pp. 537-546, June, 1911. 84 FACTORY LIGHTING directly to the desks from reflectors. While the energy required for indirect and semi-indirect lighting is often higher for a given intensity than where direct lighting is employed, the advantages gained by the former sometimes entirely offset the increased cost for energy and maintenance if these items happen to be slightly higher than for the direct system. FIG. 55. Reproduced from a photograph taken at night under the arti- ficial light in a typical office lighted according to the suggestions in Chapter V. 60-watt (48 candle-power) tungsten lamps are used equipped with Holophane "Focusing" type reflectors. CHAPTER VI DRAFTING-ROOM LIGHTING 58. Difficult Conditions. Of the various problems in indus- trial lighting, that of the drafting room is difficult in a peculiar manner. The constant use of the eye in the distinction of fine lines and much detail requires illumination of exceptional qualities. In addition to work on the drawings, various instruments and scales must continually be handled, all of which places a demand on the eye equalled in but few other classes of work. A slight shadow is often noticeable along the edge of ruling devices as with the triangle and the T-square. Shadows are also objectionable when handling dividers, bow-pens and other similar instruments. A peculiar feature connected with- the shadows is that the draftsman in an effort to do accurate work often overlooks these shadows, but the constant strain thus produced is apt to result in early fatigue of the eyes and the general physical system, to a considerably greater extent than if the shadows were not present. The shadows depend of course on the direction in which the natural or artificial light reaches the drawing. In tracing, the light must be sufficiently intense to penetrate the tracing cloth, and in practically all work of the draftsman the light should be strong enough for his needs and yet not so strong as to cause a blinding or partly blinding effect from the drawing paper or from instruments on the table. 59. General Requirements. The requirements for drafting- room lighting conform in a general way to those of other forms of industrial lighting, but should include the following items which differ slightly from those of office lighting: (1) Sufficient illumination for each person in the drafting room. (2) An arrangement of lamps which produces a satisfactory illumination effect without regard to the location of desks. This is a requirement specially applicable to large drafting rooms, where the desks may be shifted now and then due to changing conditions in the conduct of the work. 85 86 FACTORY LIGHTING In a small room containing one or two drawing boards it is not particularly difficult to have a lamp located directly above each desk and to move the desk lamp in case it is found necessary to shift the desk, but in a large number of factories rearrangements of desks are necessary now and then and if the lamp over each desk must be shifted with the desk the expense of wiring is essen- tially increased. (3) An installation of lamps which will avoid eye strain. (4) A type of lamp and an arrangement which will fur- nish illumination on the drawing boards with the least possible shadow effect in the use of instruments and ruling devices. (5) Illumination with an intensity which permits of ready discernment of fine lines and details, and sufficient for tracing work. 60. Eliminating Shadows. The most intense shadow is cast by an object that intercepts the light from a single lamp. A single lamp, however, located properly with respect to a drawing board can, by the continual changing of its position, be made to throw the light in a direction so as almost entirely to prevent objectionable shadows. Where there are two drawing boards, each with its own lamp, and where the light from one lamp partly illuminates the neighboring board, this interaction of the light complicates the problem, and this complication is found in many drafting offices due to the large number of lamps made necessary by crowded desk conditions. It consumes time to adjust a lamp for each position of a triangle or T-square, and in general, lamps close to the work not only require a certain amount of time in such adjustment, but are also to some extent in the way of the draftsman in the performance of his work. An engineering investigation con- ducted to ascertain the best means for securing convenience and avoiding shadows in these cases has, through a number of ex- periments, shown that probably the best method for illuminating the desk surfaces in the drafting room is by means of over-head lamps arranged for the elimination of shadows. 61. A Practical Investigation. For the purpose of finding some standard scheme for lighting the drafting room, an investi- gation covering a considerable length of time was undertaken somewhat as follows: A given bay in a large room was taken as the basis for the study. The size of the bay was 16 by 20 ft. and the ceiling DRAFTING-ROOM LIGHTING 87 height 11 ft. 6 in. This bay contained a number of lamps approximately as shown in Fig. 56, the size of the lamps being rather large and the mounting height relatively low. The arrangement of lamps was equivalent to 2.5 watts per square foot. The original scheme for lighting in this room is a good illustration of the interaction between a number of large lamps in producing shadows, because quite a number of the lamps contribute to the illumination of a single desk. Elevation 20' - 5 -co 10 Plan FIG. 56. Plan and elevation of bay in a typical drafting room showing original lighting arrangement. 300 candle-power lamps were used, shadows were intense, and the glare very objectionable. This scheme was the source of numerous complaints, and the objectionable features may be enumerated as follows: (1) The illumination was poorly distributed, that is, some desks received a higher intensity of illumination than others. (2) The lamps being mounted fairly close to the desks resulted in glare which was disagreeable and harmful to those persons who in certain positions received the direct light from the large 88 FACTORY LIGHTING lamps whenever looking up from their work, and who were also subject to the glare from papers and instruments. (3) The shadows cast by the relatively small number of large lamps were dense, and required a constant shifting of ruling devices so that the light might be received on the work at the proper angles, and this task was difficult even with shifting the work because of the trouble to get the light from suitable directions. I N 1 4 Elevation 20' T i. ** - 6- - XX a 'H Plan FIG. 57. Plan and elevation of bay in typical drafting room showing first trial for improvement of the lighting. 100-watt (80 candle-power) tungsten lamps were used. After an analysis of the conditions which were the cause of the complaints, the work of solving the difficulties was under- taken in a systematic manner and at the outset an endeavor was made to secure the five requirements for good drafting- room lighting as stated in a previous paragraph. As a first step, nine lamps somewhat smaller in size than originally used were installed in a single bay as shown in Fig. 57. This sample installation resulted in a sufficiently intense light DRAFTING-ROOM LIGHTING 89 and was more uniform than the original system with less glare. It will be noted, however, that the shadows cast by the larger number of relatively small lamps were nine per bay instead of four as formerly, and while each shadow was somewhat less intense because offset to some extent by the light of neighboring lamps, the excessive shadows were found to be a decided objec- tion. When drawing a circle with a bow-pen, nine shadows T i V-i T I T Elevation 20- 1 10' 4- 5 - x*f Plan FIG. 58. Plan and elevation of bay in typical drafting room showing second trial for improvement of the lighting. The larger lamps are 100- watt (80 candle-power) and the smaller 40-watt (32 candle-power) tungsten lamps, grouped as indicated. stood out in all directions from the instrument and rotated with relative motion when a circle was described, thus adding a con- fusing and annoying element. Considerable complaint resulted from this first trial. It was then suggested that a still larger number of lamps per bay might reduce the shadow effect, particularly if the lamps were arranged in groups instead of being installed as single units. 90 FACTORY LIGHTING As a second step, therefore, twelve units arranged in groups were placed in service as shown in Fig. 58, the system being made up of four groups, each containing one 100-watt and two 40-watt tungsten lamps. Draftsmen who worked under this scheme for some days soon experienced the same trouble as before from shadows, and the effect was even more noticeable on account of the four groups of lamps in a single bay instead of nine single units. It will also be noted that although the number of lamps per bay was larger in this trial, the uniformity of the light was less satisfactory than with nine distributed lamps. The single group of lamps in the last scheme served to take the place of a single unit in the first trial in its relation to the illumination distribution over the desks. The last scheme did not, therefore, conform in a satisfactory manner to the needs of the case. The next step was the extreme use of twenty-one lamps in a single bay, the idea here being to have the entire ceiling a mass of light in the hope of eliminating the shadows. The effect was somewhat novel in that the bay appeared intensely and very brightly lighted. The shadows seemed somewhat offset by the high intensity, that is, the eye did not respond to the spaces which were ordinarily in shadow, but the idea of using such a scheme was entirely out of the question on account of the expense of lamps in such numbers for a given floor area. A fourth scheme was the installation of four 250-watt tungsten lamps per bay, each lamp being equipped with a broadly distribut- ing reflector. It was suggested that the high intensities of light at small angles below the horizontal might be such as to build up the intensity at various points on the drawing boards where shadows previously existed. Under good conditions where there are no obstacles as is the case with drawing boards rather than machinery, the illumination in this scheme might, under favorable circumstances, be built up at given points otherwise in shadow, by the light from lamps at some distance from the worker. This theoretical consideration, however, is offset to some extent by practical conditions in the average drafting room, and also by the fact that lamps of this high candle-power are too large for relatively low ceilings. The engineering features of the building up of the light from lamps with broadly distributing reflectors is at least interesting even if of no particular help in this case. A fifth scheme, and the one finally chosen, was based on the principle that light furnished from a source of large area practi- DRAFTING-ROOM LIGHTING 91 cally eliminates shadows. It is possible to secure a very large area of light source where individual lamps are mounted so as to throw their light directly upon the work in case of the tungsten type only where the lamp is surrounded by a large globe, and even this is limited. By inverting the lamps, however, and using a reflector which not only transmits but diffuses some of the light from the lamp the area of light source is increased, and this is still further increased if the lamps are mounted in the inverted position close enough to the ceiling to permit the reflection from the ceiling of whatever light reaches it. FIG. 59. Four-lamp fixture designed for drafting room lighting. 60-watt (48 candle-power) tungsten lamps and "Alba" glass reflectors are used. In the chosen arrangement, a trial of opaque reflectors was made. Here no light is transmitted directly to the work but the ceiling is used to reflect the bulk of the light to the work. This scheme while providing practically uniform and shadowless illumination, did not seem adequate unless rather large lamps were used. Various methods of mounting the lamps for the inverted arrangement were given trial, one of which was the use of a three light fixture with the lamps in a vertical position and also when in an angular position directed toward the ceiling but somewhat away from the fixture. Later a four-light fixture 92 FACTORY LIGHTING as shown in Fig. 59 was tried, and with reflectors capable of diffusing the light and which at the same time directed some of the light to the ceiling, this scheme seemed to fulfil the various requirements. 62. Combined Direct and Indirect Light. The foregoing investigation with the accompanying results shows some of the refinements of the principles of illumination which may be utilized in securing definite results. The method finally chosen makes use of direct light in as far as the reflectors transmit a certain part of the light directly to the drawing boards, and of 1 |H H K H H s s s 1 is K s ^K K ^ | -3-4-8-' 8- 5 $ VY ^ ^ (T-S 4w W w t /^N /""N S**\ K 8 S 8 \i/ V.LX M M 1 w |s s Column )-( )-( n H ^ J w te s s )-( )-( K K K ^^ >'4-- FIG. 60. Plan of typical drafting room showing fifth trial and final ar- rangement for improvement of the lighting. Note spacing as compared to Figs. 5Q, 57 and 58. Each outlet shown in this diagram is equipped with a four-lamp fixture as shown in Fig. 59. indirect light as regards that part of the light which is trans- mitted to the ceiling and in turn reflected to the boards. The reflectors best adapted to this work were not chosen primarily for their reflecting efficiency, but for the diffusion quality pre- viously mentioned. A reflector of the Alba type 1 gave an ex- cellent result. In Fig. 60 the general arrangement of fixtures is shown, which produces illumination at once uniform, free from objectionable glare, and softened by the quality of the glass which gives the light a pleasing yellow tone. 1 Manufactured by the Macbeth-Evans Glass Company of Pittsburgh. DRAFTING-ROOM LIGHTING 93 Shadows were almost entirely eliminated and by the choice of a suitable size of lamp, the intensity was made adequate through- out the room. Considerable emphasis must be placed on the spacing distance between fixtures and the distance from lamps to the ceiling, also the distance from the floor to ceiling. Various installations of drafting-room lighting have been made, based on the foregoing investigation, some of which have been entirely successful, but in some cases where the spacing has been changed from that originally found desirable, the shadows have been somewhat increased. Thus with a slightly larger spacing dis- tance than that shown in the illustration, the shadow effect has been found large enough to make the illumination rather unsatisfactory. A number of experiments were made by raising and lowering the fixtures in order to determine the relation between the direct light from the reflector and the reflected rays from the ceiling. The distance of 2 ft. 6 in. between lamps and ceiling seemed to furnish the best relation, that is, the net efficiency of the two components seemed greatest with this mounting condition. 63. Illumination Features. The average intensity for draft- ing work may be placed at 7 foot-candles. Higher intensities are recorded, even up to 10 foot-candles, and lower values down to 5 foot-candles, although much deviation from the average given is apt to produce poor results. With the combination of direct and indirect lighting as just explained, and where the ceiling and wall conditions are such as to aid the lamps by their light-colored surfaces, an average of three watts per square foot for tungsten lamps rated at 1.25 watts per candle, produces a satisfactory result. This value of watts per square foot is practically the same as was the case in the original installation where the foregoing experiments were made, but the illumination is so much superior with the new arrange- ment that there is no comparison between the illumination of the two extremes. It should be remembered that as the rating of tungsten lamps changes these values of watts per square foot likewise change. The installation expense of fixtures for inverted lamps is slightly higher than for a system of direct lighting. When, however, consideration is given to the small percentage of the labor cost of the average drafting room which is equivalent to the cost for artificial lighting, the difference between one and 94 FACTORY LIGHTING : another scheme of lighting is small indeed, as far as the resulting advantages to the draftsmen from the superior illumination are concerned. It is interesting when drafting rooms are presented for light- ing equipment, to ascertain the total wages per day in the entire room and to equate the entire cost of lighting per day in the room to the wages for the number of minutes which are equivalent to the lighting cost. It may be found, for example, that in a large drafting room the inverted system of tungsten lamps can be paid for by the wages of five or six minutes per day. It is rather surprising to compare this cost relation with the similar relation between the wages and the cost of an inferior lighting system, which may be found to equal the wages of four or five minutes per day. The difference therefore between a good and a poor lighting system often amounts thus to but one or two minutes per day. Considerations of this kind are most convincing in establishing the warrant for the superior arrangement of lamps. In short, if the better scheme insures a net saving of but one or two minutes per day by increasing the facilities for superior and more rapid work, there is no economy whatever, but an actual loss to the efficiency of the entire drafting room, by using the inferior system because it may be a little cheaper. In a certain case when two rooms were in use, one with individual units and the other with the semi-indirect lighting, the chief said he would prefer men to work seven hours per day with the good lighting than seven and one- half hours with the light from individual lamps. 64. Various Fixture Combinations. It has been found that four units per fixture, although selected somewhat at random at the outset, have, after a trial of other schemes, seemed best suited to this class of work. Formerly a single large unit had been tried in the place of the four-lamp arrangement, the single unit being enclosed by a large reflector. Apparently the single unit somewhat reduces the advantage gained by the large area from the four- unit scheme, and although one larger lamp at each outlet may appeal somewhat from the standpoint of appearance, the shadow effect seems to be greater than in the case of the four units per fixture. Various devices are on the market for securing or approximately securing the results of this combination of direct and indirect lighting, but for average factory drafting conditions the fixture shown in Fig. 59 can readily be made up of ordinary DRAFTING-ROOM LIGHTING 95 conduit and elbows, with a reducer at the point where the socket is attached to the fixture. Such improvised fixtures are relatively inexpensive and serve every purpose as far as excellence of the illumination is concerned, although there is a great variety of fixtures available on the market from which' a selection may be made to suit practically any case. 65. Other Conditions. Some cases are apt to arise where there is no ceiling from which to derive the advantages of ceiling reflection. Fig. 61 shows a scheme that has been devised to take care of such conditions. The plates supported directly above the lamps serve the purpose of a ceiling. This plan is fairly simple and may be installed where the requirements of Reflecting surface, which can be folded during the day, preventing any obstruction to the daylight. FIG. 61. Plates designed as substitute for ceiling thus making possible semi-indirect lighting over the drawing tables beneath. the work seem to warrant the expense thus incurred for securing the results of the inverted or semi-indirect arrangement. Fig. 62 is reproduced from a photograph of such an installation and shows the lamps mounted directly below the iron plates, these plates taking the place of the ceiling in the office shown. 1 Attention should be given the choice of reflector for this method of lighting and the bowl shape as shown in the illustration is preferable to a flat type with which a portion of the lamp is exposed when the fixtures are viewed at some distance. Further, the efficiency of the reflector is not the largest item, because what is desirable is that quite a proportion of the light be trans- mitted through the glass. For this reason the prismatic glass, although more efficient, does not seem so well adapted for inverted use as a reflector of the opalescent type. 1 See article by the Author on "Drafting Room Lighting Problems," American Machinist, Vol. XXXIV, pp. 686-689, April 13, 1911. 96 FACTORY LIGHTING It is essential also to have the ceiling and the upper part of walls fairly light, and the retinting of the walls and ceiling from time to time is an actual economy in the maintaining of illumina- tion facilities through the medium of the inverted lamps. The principles just enumerated are found to apply in a number of cases other than drafting rooms, as, for example, in the com- posing rooms of printing houses. Type forms, when resting on horizontal table surfaces, must be read with the eye of the ob- FIG. 62. Reproduced from a photograph taken at night under the arti- ficial light in a drafting room equipped with a substitute ceiling as shown in Fig. 61. 100-watt (80 candle-power) tungsten lamps and "Alba" glass reflectors are used. server fairly close to the type. It has been suggested that shadowless illumination in such cases will be somewhat of an objection due to an absence of relief on the edges of the type. From observation it has seemed that the minute shadows evident even with the inverted system, are sufficient to give the needed relief to the type, and it is quite possible that a very small shadow effect, which is practically not noticeable in this system, may in reality be an advantage in a case of this kind. DRAFTING-ROOM LIGHTING 97 As shown in the various diagrams, an average spacing distance of no more than 8 to 10 ft. is necessary with average ceiling heights from 12 to 16 ft. in large drafting rooms, in order to secure the best results with the four-light fixture. These fixtures may then be equipped with 60- watt tungsten lamps, enclosed in some type of opalescent bowl- shaped reflector as shown in Fig. 63, and the result will in most cases be found to justify the care and ex- pense connected with the trial and installation of the system. FIG. 63. Reproduced from a photograph taken at night under the artificial light in a drafting room equipped with four-light fixtures as shown in Figs. 59 and 60. While much has been said regarding the advantages of the inverted or semi-indirect tungsten lighting scheme for the draft- ing room, it should be noted that the mercury vapor lamp pos- sesses many points favorable for this purpose. The length of the tube, which is the light source, is such as to greatly reduce shad- ows, and in many instances this type of lamp is in service for drafting work with excellent results. CHAPTER VII FACTORY LIGHTING 66. New Ideas Regarding Factory Conditions. A marked change has become evident toward factory environment during recent years. This change in attitude has resulted in a great deal of attention to the improvement of such items as that of factory lighting. The basis for this change in attitude as regards light- ing may be included under the following heads: Economic Relations. Factory managers have come to realize the importance of suitable surroundings in their relation to sat- isfied workmen and to greater output. The old ideas of having the work done without regard to surroundings has given way to a study of environment in its relation to improved efficiency in shop operations. Adequate light increases output and it has been found that a saving of four or five minutes per day for the average workman actually pays for the entire cost of operat- ing a modern equipment of factory lighting. This relation is shown in Fig. 64. There are other features which promote efficiency in the plant such as adequate ventilation, an efficient heating system, the maintaining of cleanliness and neatness, and other items all of which have an indirect influence on the out- put and which improve the living conditions in the factory. In early morning and late afternoon hours and on the cloudy days throughout the year, many factory locations are in practical darkness as far as natural light is concerned. A good system of artificial light aids production at these times and thus tends to maintain efficient workmanship throughout the work- ing day. In like manner, the night turn in many shops must depend altogether on artificial light so that lighting as an eco- nomic factor is here apparent. The importance of factory lighting can thus scarcely be overestimated and attention to those items which affect the excellence of the light is of much weight both as regards the economy of the plant and the comfort of the employee. New Lamps Available. A decade ago factory lighting was practically limited to the carbon filament lamp on the one hand, 98 FACTORY LIGHTING 99 Energy at 1 Cent per Kilowatt-Hour 10 Men 1000 Square Ft. Tungsten Lighting Watts per Sq. Ft. Assumed ..amps Burning 5 Hours per Day All Lamps Burning 4 HOUTS per Day~ All Lamps Burning 3 Hours per Da All Lamps Burning 2 Hours per Day All Lamps Burning 1 Hours per Day 34567 Working Periods in Minutes Energy at 2 Cents per Kilowatt-Hour Lamps Burning 2 Hours per Day Lamps Burning 1 Hours 45678 Working Periods in Minutes Energy at 3 Cen per Kilowatt-Hour All| Lamps Burning 2 Hours per Day Lamps Burning 1 Hours per Day FIG. 64. Diagram showing relation of average wages to lighting costs. 100 FACTORY LIGHTING and the arc lamp on the other. Both of these types are still used but numerous cases arise in almost every factory which come under the head of intermediate conditions. These inter- mediate locations are made up of floor areas with ceiling heights ranging from 12 to 18 ft. With these moderate ceiling heights the carbon filament lamp cannot be used economically unless placed close to the work or possibly in clusters near the ceiling. Both of these schemes are expensive in maintenance and energy consumption, as well as unsatisfactory from the illumination standpoint. Arc lamps in these cases require a considerable separation and on this account provide a poor distribution of the light and to some extent are in the line of vision which causes glare. As explained in a former chapter, the introduction of the new types of lamps with candle-power values intermediate between those of the carbon filament and the arc lamp, has made possible the solution of many problems related to these inter- mediate conditions in a way not possible by either of the older types. A brief review of the influence of these new types of lamps shows that a new era in factory lighting has been reached, and an important feature of this new era is the scientific planning and installing of lamps in a manner which adapts the most economic size of lamp to each location and class of work, and the giving of due weight to the indirect gains x>f good light all of which piomote a better as well as a larger output. Popular Ideas. Numerous articles dealing with popular opinion regarding the subject of factory environment have referred to lighting as well as other conditions throughout the country. This indicates a growing attention of the public to these conditions and shows that the American people is becom- ing alive to the necessity for improved factory surroundings. This popular interest has resulted in legislative measures in some of the states where certain standards of environment have been adopted, and it is also of interest to note that in a recent message to Congress a President of the United States called attention to the surroundings in the government build- ings throughout the United States. It is believed, however, that one of the strongest features as far as the factory owner is concerned, is the economic rela- tions of improved factory conditions to the production and gen- eral workmanship, and for this reason greater emphasis is placed FACTORY LIGHTING r l6l on the economic side of the subject than on the popular or legis- lative side, in the subsequent pages. 67. Various Items Concerning the Work and Surroundings. It is not the intention to attempt a classification of factory work to cover all cases, the diversity of buildings and classes of work making this impracticable. Some of the important items as related to the artificial light will, however, be discussed in the following paragraphs. Ceiling Height. From the viewpoint of the lighting, one of the most satisfactory divisions of factory buildings- is under the head of ceiling height or the mounting height of lamps which is possible under given conditions. As previously explained, the size of the lamp and the spacing depend on this height, and for this reason the various locations naturally group themselves into spaces with varying ceiling heights. Nature of Factory Work. The various factory operations com- monly found may be divided into two main groups as regards the illumination required. First, those cases where the work is mostly on horizontal surfaces, as in bench work of some kinds and in some assembly work, where practically only downward illumi- nation in a vertical direction is required; and second, those eases as in some machine tool operations, foundry moulds, punch presses, and assembly work where in addition to the vertically downward light it is necessary to have the sides of the work ade- quately illuminated by means of side components of the light thrown from the lamps in angular directions, a feature which is dependent on the size of the room and somewhat on the reflec- tion from walls with the over-head system of lighting. It is important in each of these cases to have a low shadow effect. In that class where the surfaces are mostly horizontal the problems are usually the most simple, while in the other class where the sides of the work and openings must be cared for, added refinements are sometimes necessary to produce a satisfactory result. Space between Floor and Ceiling. Belting and other obstacles may exist between floor and ceiling or the space may be entirely free from obstruction. Again, there may be much dust and dirt in the air as in the foundry or blacksmith shop, and here special types of lamps are required for each case. The open spaces sim- plify the problems and make possible the use of lamps spaced comparatively far apart, while in the midst of belting the type of 102 FACTORY LIGHTING lamp and the spacing must be such as to reduce the shadows other- wise cast by the belts. In dusty spaces, a penetrating light must be employed in order to insure adequate illumination on the working surfaces. Ceiling Conditions. The installation of lamps is affected by the ceiling construction both in the cost of wiring and in the reflection of that portion of the light which may reach the ceiling. As shown in a previous chapter the ceilings in factory buildings may roughly be divided into those of wood, concrete, metal and the like, a distinction being made between plain ceilings and those below which iron work projects thus dividing the ceilings into sections or bays. Surroundings. In its relation to the net illumination on the work, the color and condition of walls and the work has a consid- erable bearing. With dark surroundings a larger number of lamps, or lamps of greater candle-power than otherwise are neces- sary to produce satisfactory results. With very large machines of a dark nature, the effect is to dampen out the resulting illumina- tion in such a way as to call for very much higher intensities than would be the case with lighter surfaces. 68. General Requirements. The following requirements for factory lighting are made all the more important by the peculiar limitations and conditions in factory buildings and in factory work: (1) Sufficient illumination should usually be provided for each workman irrespective of his position on the floor space. (2) The lamps should be installed and selected so as to avoid eye strain to the workmen. (3) The lamps should be operated from circuits which will in- sure reliable illumination facilities, particularly on account of the demoralizing effect produced by intermittent service just when the light is most needed. (4) Adequate illumination should be provided from over- head lamps in such measure that individual carbon filament lamps close to the work may be unnecessary except in special cases. (5) The type and size of lamp should be adapted to the particu- lar ceiling height and class of work in question. (6) In addition to the illumination provided by over-head lamps, individual lamps of the carbon filament type should be placed close to the work if they are absolutely necessary, and in FACTORY LIGHTING 103 such cases the lamp should be provided with a suitable opaque reflector. These requirements may now be met by means of the new types of lamps, one type of which can usually be found for practically every factory location and adapted to general physical conditions typified by clearance between cranes and ceiling and other similar items. 69. Method of Lighting by Over -head Lamps. The mounting of lamps over-head in such numbers as to eliminate the need for individual lamps, is referred to as the over-head method of light- ing. This system possesses many features which make is particu- larly well adapted to factory conditions, and by the proper choice of the size of the lamp and its mounting, results can be secured which will conform to the requirements just enumerated. The many advantages of this over-head method when compared to the use of individual lamps close to the work, commend it for general adoption. Its superior features may be stated as follows: The over-head lamps may be made to furnish adequate ilumi- nation in a general manner over the entire working surface, thus permitting work to be done at every portion of the floor space, rather than to limit the work to certain specific points under in- dividual lamps. The glare of the lamp if too close to the work, is practically eliminated by mounting the lamps well above the heads of the workmen. Further, this glare from lamps close to the work is accentuated by the fact that the light is usually on a small por- tion of the work only. Comparative darkness in the neighboring space about this bright spot makes it difficult to find tools and material, and in addition to reducing the efficiency of the work- man to this extent, there is a strain on the eye which is largely avoided if the entire working surface is liberally illuminated. The maintenance of over-head lamps is definite and clear cut as compared to the individual lamp method, and may be con- ducted by a central maintenance division, generally with better results and at a lower cost per man, taking into account the improved condition of the lighting from over-head lamps in making such a comparison. The appearance of the factory where all drop cords are removed is incidentally greatly improved, and the illumination furnished from lamps near the ceiling gives to the entire space a neat and pleasing appearance, in 104 FACTORY LIGHTING marked contrast to locations equipped with many drop cords each of which is covered with a metal shade. Finally, tests have shown that the eyes are in a better condi- tion for vision with a given illumination intensity when general illumination is provided by over-head lamps than when indi- vidual lamps are placed close to the object, with the surround- ings comparatively dark. 70. The Field of Various Types of Lamps. Very low ceilings require small lamps, while high ceilings require correspondingly larger lamps. The tungsten lamp is a good example of the me- dium-sized lamp which has done so much for the intermediate ceiling heights. The mercury vapor lamp in like manner is well adapted to moderate ceiling heights, while lamps of the flaming carbon arc type serve in those locations where the ceiling height is 20 ft. and higher. There is a wrong tendency to generalize conclusions regarding the use of one type of lamp for all factory conditions, whereas too much emphasis cannot be placed on the fact that each type of lamp has in a general way a field of its own, and the best results are secured by the selection of the proper type of lamp for a given location without prejudice. 71. Glass and Metal Reflectors Compared. The question is sometimes raised as to the use of glass reflectors in connection with tungsten lamps for factory lighting. The question is one largely of economy and maintenance, and in the prevention of glare from tungsten lamps when not provided with some shielding reflector. The answer to such a question may either be from a theoretical standpoint or as the result of practical experience with both types. In large installations of tungsten lamps there has been an effort to establish the merits for both glass and metal reflectors by equipping lamps in adjacent bays with glass reflectors in one case and metal reflectors in the other. It has been found almost invariably that if the choice is left to the workmen and super- intendents, glass reflectors will be given preference over the metal mainly on account of the added cheerfulness they produce. If, therefore, the first cost and maintenance cost of the glass reflectors is practically the same as with the metal, then glass should be employed. Glass reflectors on the market are capable of producing an amount of illumination equal and even greater in some cases than that produced by the best metal reflectors, and even if the first cost is somewhat higher, the added advantage FACTORY LIGHTING 105 of glass as opposed to metal is usually sufficient to make the small difference in cost a negligible item. This factor is all the more noticeable when one considers that the reflector itself is a small part of the total cost connected with the wiring, the lamp and its reflector. As regards maintenance with glass reflectors it may be stated that under rough factory conditions, glass reflectors are to-day used by the thousands with but a small increase in maintenance due to breakage. Thus, out of the total maintenance cost in one large installation it has been found that the charges may be proportioned as follows: Renewals, cost of lamps 75 per cent. Renewals, broken reflectors 3 per cent. Labor, making renewals and changing re- flectors for washing 16 per cent. ' Labor, reflector washing 2 per cent. Additional indirect charges 4 per cent. Total 100 per cent. Reflectors will not be classified from the commercial stand- point, but the following items should be considered in the selec- tion of every type of reflector for factory use: (1) Utilization efficiency; how much does the reflector con- tribute to the effective illumination on the work? (2) The effect in reducing glare. (3) Natural deterioration with age through accumulations of dust and dirt. (4) Ease in handling and uniformity of manufacture. (5) Physical strength and the absence of projections which may increase the breakage. A study of the various reflectors on the market with the aid of the foregoing items, will determine what reflectors are best adapted to given conditions. Regarding the third item in the foregoing list, it may be stated that under comparative tests in service the accumulations of dust and dirt on glass reflectors does not seem to be any greater than the coating of dirt which accumulates on the inside of a metal reflector in the same length of time. 72. Side Lighting. It has been customary in the past to meas- ure effectiveness of illumination in terms of the vertically down- ward component of the light. This method has ignored the value 106 FACTORY LIGHTING of side components in their relation to vertical surfaces and open- ings in the side of the work. It is sometimes more necessary to light the side of a machine or the side of a piece of work than the horizontal surface. If, then, when designing a factory lighting system, the prime object is the production of the greatest amount of downward illumination, it may happen that the side compo- nent is so small that the sides of machines and of the work are inadequately lighted. Experience indicates that there are two general ways in which to secure adequate side lighting. One of these methods is to lower the lamps, and the other is to use a broader distributing re- flector than is called for by the rules which consider uniformity of the downward illumination only. Side walls or other reflecting surfaces will of course modify the results. Thus, after the de- termination of a certain type of reflector for producing uniform vertically downward illumination, it may be found that more side light is necessary, and this extra side component may, as stated, usually be secured by selecting a somewhat more dis- tributing reflector. Broader reflectors are apt to result in less downward illumination, and will sometimes call for larger lamps than found necessary by preliminary calculations. As an illustration, in a certain lighting system a vertically downward intensity of 3 foot-candles was deemed sufficient for the work involved. Measurements and observations showed that the side light was not sufficient. In this particular installa- tion it was found necessary to produce a vertically downward in- tensity of 5 foot-candles on the average in order to secure an intensity of 2 foot-candles on the sides of the work, and also to use a somewhat broader distributing reflector than at first chosen. Two foot-candles on the sides of the work was sufficient in this case where bench work and work in the vise on small machine parts was conducted. It is recommended that the lamps be mounted near the ceiling in all reasonable cases where side light is necessary, and that the side light be increased, not by lowering the lamps, but through the medium of broader distributing reflectors and larger lamps if required. This stand is taken on account of the glare which results when the lamps are mounted too close to the work, a fea- ture most noticeable by the absence of a reflector or where glass reflectors are used. 73. The Lighting Circuits. The question of lighting circuits FACTORY LIGHTING 107 has already been discussed but is here mentioned with particular reference to factory conditions where motor loads are apt to be large in comparison to the energy consumption for electric lamps. In some cases the proportion of motor load to lighting load is in the ratio of 10 to 1, in others 7 to 1, and so on, and the varying demands on the circuits by motors may greatly affect the lamps. Hence it is important to maintain strictly separate supply circuits for the lamps in order to avoid the varying voltage apt to result if the motors are connected to the same circuits. In addition to the superior illumination resulting from lamps supplied from constant voltage mains, some types operate with longer life or very much better mechanically when supplied with constant voltage than otherwise. These features will therefore generally more than offset the somewhat greater cost of maintain- ing separate circuits for each class of service. 74. A Practical Case in a Location with Moderate Ceiling Height. As a typical example of factory lighting, a moderate ceiling height of 13 ft. 6 in. is considered. The building is divided into bays 16 by 23 ft. and one of these typical bays is shown in Fig. 65. The walls and ceilings are light in color, thus aiding the net illumination. The work may be classed as bench work where adequate side light is required; also machine work, where some line shafting and belting form an obstruction to the illumina- tion; and some assembly work where side light is required. The ceilings are of wood, and hence wood moulding may be used, while the switches may be located on central columns in easy reach of the workman from the floor. The various switches are wired through the medium of conduit running down the con- crete columns, and iron outlet boxes serve the double purpose of supporting the snap switch, and supplying a wall receptacle at each column as an outlet for extension lines when necessary. After numerous experiments, an arrangement of tungsten lamps as shown in Fig. 65 was found to supply the required vertically downward intensity of illumination. The relation of the spac- ing distance to the mounting height called for a concentrating reflector in order to produce uniform downward illumination as previously explained, but the requirements of side light for many of the kinds of work made it necessary to use a somewhat more distributing reflector than called for by rules of the reflector com- panies, that is, an intensive type instead of a focusing type in this case. Glass reflectors are also used to give a cheerful appearance 108 FACTORY LIGHTING to the factory spaces as an incidental advantage, and where the ceiling is light in color that portion of the light which is transmitted through the glass to the ceiling is in turn reflected to the work thus adding to the resulting illumination. On account of the various requirements throughout this factory higher intensities of illumination are required in some parts than II. FIG. 65. Plan and elevation of bay in a typical factory location showing arrangement of the 100- watt tungsten lamps over-head. in others, and the arrangement of lamps is well adapted to this end, for by using smaller lamps in the outlets the intensity is re- duced without in any way affecting the uniformity provided the size of the reflector always corresponds to the size of the lamp. The lamps are mounted at the ceiling to avoid glare and the appearance in this particular location is thus greatly benefited. Fig. 65 shows that the lamps are distributed in a symmetrical manner with respect to the bays, and the wiring was thus sim- FACTORY LIGHTING 109 plified because the circuits could be confined to the separate bays, that is, one circuit per bay. This makes it unnecessary to extend the wires under girders in order to feed the lamps in adjacent bays. The size of the bays seemed to favor the control of six lamps per switch, but the requirements of the workmen near the center of the building made artificial lighting necessary so often when the men near the windows were still supplied with sufficient light, that the two lamps in each bay nearest the window were FIG. 66. Reproduced from a photograph taken at night under the arti- ficial light from 100-watt tungsten in a typical factory location. controlled from one switch, while the four remaining lamps in the outside bays were controlled from a second switch and the six lamps in the central bay were each controlled from a third switch, and so on. The intensity of both vertically downward and side compo- nents of the illumination is such that practically no individual lamps are necessary even for the machine work, thus removing the necessity for the maintenance of drop cords and sockets near the machinery. Fig. 66 shows a view of a factory location where the lighting has been installed according to the foregoing 110 FACTORY LIGHTING description, and some idea of the uniformity of the illumination is given by the illustration, also the neat appearance of the over- head system and the added cheerfulness produced by the reflec- tion from walls, columns and ceilings. Figs. 67 and 68 show other typical factory lighting systems where modern illumina- tion design has been applied. 75. A Practical Case in a Location Where the Lamps Must be Mounted Very High. As an illustration of a case where the mounting height of the lamps is determined by the crane near FIG. 67. Reproduced from a photograph taken at night under the arti- ficial from 300 candle-power mercury vapor lamps in a typical factory location. the over-head iron work of the building, a factory space is taken where the distance from floor to girder line is 50 ft. The loca- tion is divided into bays 16 by 70 ft., several of these bays being shown in Fig. 69. There is no regular ceiling because of the open girder construction, and the walls and surroundings are dark. The work consists of large machine tool operations and heavy assembly, and here the vertically downward as well as the side light must be adequate. The absence of a ceiling from which to support the lamps and the small clearance between the crane FACTORY LIGHTING 111 and the iron work makes it necessary to mount the lamps on specially constructed wire supports. The latter scheme was used on account of the advantage to be derived in pulling the lamps into a central point for trimming. The control circuits are run down the structural columns to a point accessible from the floor, the switch loops being run in iron conduit which is attached to the columns. On account of the mounting height, a large lamp is necessary because of the volume of light needed to produce the required FIG. 68. Reproduced from a photograph taken at night under the artificial light from 100 watt tungsten lamps in a typical factory location. effect on the work, and also to reduce the maintenance which may be somewhat high if a large number of small, lamps are distributed at such heights. Two rows of arc lamps of the flame carbon type are arranged in alternate bays so as to be staggered, and the control circuits include the lamps on one side only in each case, so that the operation of the lamps in either row is independent of the other. This scheme has the advantage of steadying the illumination, when a momentary failure of the lamps on one circuit might otherwise greatly reduce the net lighting effect. Fig. 69 shows the arrangement in several bays, and also 112 FACTORY LIGHTING the mounting by means of the wire supports, which extend from the center of aisle to the walls on either side. This arrangement and the size of lamps produce a good illumi- nation on the work nearly 50 ft. below the lamps, and the qual- ity of the light is such as to penetrate the large distance in an exceptional manner. The low maintenance of the long burning Elevation Girder Line ' Plan FIG. 69. Plan and elevation of several bays in a typical factory where high mounting of lamps is necessary. Flame carbon arc lamps used. flame carbon arc lamp makes it an economical unit and its use in cases of this kind is apt to be quite satisfactory. 76. Other Items. The items connected with the selection of the type of lamp, the mounting height and the spacing distance have been described in a previous chapter, and a reference to FACTORY LIGHTING 113 that treatment should be made in the design of factory lighting systems. All the points brought out in that chapter are appli- cable to factory lighting, and possibly greater emphasis should be placed on the following of the principles of illumination design for factory lighting than for other classes of lighting. The maintenance items discussed in a previous chapter apply also in an exceptional manner to the conditions in factory build- ings, and so great is the importance of these problems in connec- tion with lighting systems in the factory that they may be said to form one of the major items in the furnishing of adequate light. The installation of the system according to a scientific design is naturally most important, but the maintenance of the lamps so as to keep the system up to the same excellence from month to month is equally important. 77. Cost Factors. The shop manager is concerned with the value of the artificial light in relation .to the factory output, and hence looks for a return both in quantity and quality of work as a direct result from the expense of a modern system of illumination. The value of adequate light can easily be reduced to the time saved by employees in the performance of given work, in im- proved accuracy of workmanship, in the protection afforded the eyes of the workmen, and in the beneficial effect on tempera- ment produced by brighter and more cheerful surroundings as well as in the decrease in accidents and greater safety. If, therefore, improved light is interpreted into the equivalent time saved by employees in the various shop operations due to all these elements, the equivalent wages or the larger and better output as the case may be, can then be classed as a distinct asset to the plant through the medium of improved illumination. Fig. 64 shows graphically these relations between wages and lighting costs. As a starting point, therefore, in the economy of factory light- ing, a proper attitude should be taken to the accompanying improvement in quality and quantity of workmanship through the usefulness of the light, to the exclusion in a degree of emphasis on the relative cost values of the light itself. If the entire light- ing question can be viewed rather as an asset to the output of the plant in the study of the merits of various types of illumina- tion, than in the directing of all attention to minor differences in first cost and operation expense, the needs for legislative insistence 114 FACTORY LIGHTING on improvements of lighting conditions will become a secondary influence. As a matter of fact, many of the present conditions are so changed over former factory surroundings that the idea of light- ing as an asset to production has begun to be taken as a definite working basis. The factory manager, whose buildings are equipped with modern lighting, prides himself on the improved appearance, while he gains in the improved workmanship and the greater contentment among employes, all directly resulting from a higher standard of environment. CHAPTER VIII POWER-HOUSE LIGHTING 78. Relations of Lighting to Operation. Reliable operation in power plants demands the use of every available resource to that end. Investments in switchboard appliances for the control of circuits are considered an asset to the station equipment, and so great is the importance of continuity of service that central stations spare no reasonable expense for maintaining continuous operation. Throughout the day and night there are many intervals during which artificial light is required. Repairs to broken down machines must usually be made with the utmost dispatch and every facility should be provided to aid the rapidity with which such work is accomplished. This feature is emphasized by the tendency to broaden the responsibility of each employe to include a large amount of expensive apparatus in the station service. To permit each man to fulfil his duties makes it there- fore all the more necessary that the best artificial light available be provided. 79. General Requirements. In the lighting of the power house several requirements should be made the object of study: (1) Sufficient illumination at all points of the floor space for general operation, inspection and repairs to machines. (2) An arrangement of lamps which will distribute the light to the various parts of the machines making them readily visible at all times. (3) The elimination of dense shadows by a sufficient number of lamps properly mounted. (4) Absolute reliability even when the station is temporarily disabled. (5) An arrangement of individual lamps which will furnish suitable light to valves, gauges, and switchboard instruments. In overhauling steam and electrical equipment it is desirable that the various openings in and about the machinery be suitably lighted, and the sides of apparatus must be given due weight in 115 116 FACTORY LIGHTING properly directing the light, because these parts, with ordinary methods of lighting, are often in comparative darkness, either on account of a lack of side light, or due to excessive shadows, which amounts to the same result. 80. Economy Afforded by Good Lighting. As previously implied, the successful operation of central stations and other power houses is promoted by adequate and reliable types of steam and electrical equipment, by a suitable arrangement of machinery, the coal and water facilities, ventilation, and artificial light of an intensity, quality, and distribution to serve as an aid in the operation of the plant during dark days and at night and thus facilitate repairs and emergency work in the continuous operation of the plant. The central station is looked upon as the source from which energy for light and power is to be derived for the public, and a fact which has to some extent been overlooked in the past is that the station itself requires light of suitable quality and relia- bility in the economy of its own operation. A shut down in the power station connected with a factory, due to an accident or to other causes, involves considerably more inconvenience and greater losses of time and money than perhaps any other similar auxiliary to the factory operation. No element of the equip- ment, therefore, should be overlooked in the attempt to secure that continuity of service which aids reliability of operation. Again, the power plants connected with the factory -provide not only the artificial light but usually all the motive power for machine tools and other purposes, and a shut down of several minutes often involves losses of hundreds of dollars in output which must obviously be charged to the power house. The avoidance of such difficulties is a problem met by every station superintendent connected with industrial plants. 81. The Modern Viewpoint. In the past power-house lighting has been neglected to some extent due to a lack of appreciation of the effect of sufficient artificial light on the operation, but due also in large measure to the absence of suitable lamps for the conditions in such buildings. As already stated, both of these causes are now giving way to conditions which are pro- ducing many improvements in the station lighting equipment. There t is^ certainly a deeper appreciation of the necessity for adequate light, and types of lamps are now available for practi- cally every condition to be solved. POWER-HOUSE LIGHTING 117 A recent editorial in one of the technical journals referred to the question of power house lighting as an old and threadbare topic. Neither of these words is quite in place because while the problems in one sense may be looked upon as old and threadbare, they deal directly with economy and reliability of operation and they can be solved in new ways by new lamps. A commendable feature in the editorial is the emphasis placed on the neglect of many lighting companies to look to their own lighting while being most progressive in other lines of their equipment as well as in the scientific installation of lamps in establishments of their customers. It is believed that with the many improvements in modern lighting apparatus, power station men are now coming to a posses- sion of distinctly new ideas regarding efficiency of operation, and that these ideas are beginning to include not only the generating apparatus itself, but all of those features which contribute to its maintenance and operation in the best possible manner. 82. Various Locations Involved. The Engine Room A typ- ical engine room consists of a rather long and relatively narrow building with high roof trusses, and as a consequence these buildings lend themselves to the over-head method of lighting. Difficulties in the past have usually been an insufficiency of light and poor distribution. Fig. 70 indicates an efficient method of distributing the lamps for securing sufficient general light for attendance and repairs. The switch control used in this in- stallation makes possible the control of lamps in alternate groups so that for ordinary purposes a moderate intensity is available with half of the lamps, and a higher intensity with all the lamps turned on at times of emergency and repairs. This arrangement of lamps insures adequate side light by the use of a relatively large number of medium-sized units, and also that the light at any one point on the floor space is derived from numerous sources, coming in many directions and thus reducing marked shadows. By mounting the lamps at the girder line glare is avoided. Probably, the most important item is absolute reliability of the illumination at all times. To secure this end, the lighting circuit is fed from a source entirely separate from the outgoing feeders. In some cases storage batteries are installed with a switch in the lighting circuit so that the lamps may be connected to this emer- gency supply when required. In other cases a small number of auxiliary lamps are connected to the exciter circuit as a further 118 FACTORY LIGHTING safeguard, although the use of the exciter circuit is not generally recommended. The Boiler Room. Boiler rooms usually consist of a narrow passage way faced either on one or both sides by the boilers, on which are located the gauges. The piping, stoking apparatus and valves require moderate light, and the lamps used for this pur- pose are often controlled by conveniently located switches so that they may be turned on when necessary. Sufficient light is required over the main passage, but the requirements of the boiler room are sometimes offset by the firing and general care of fur- naces, which are usually in themselves sufficiently lighted by the fires. Some side light on the front of boilers and furnaces is necessary, however, and it is desirable to eliminate the glare which is particularly objectionable with the dark surroundings if the lamps are mounted too low. Coal Bins and Conveyors. In those boiler rooms equipped with stoking apparatus, the coal bins are ordinarily above the boiler room and must be accessible for some attendance and in- spection. Here an adequate number of lamps should be provided, but by controlling them from convenient switches they need be turned on only during the times of actual attendance and in- spection. Passages through which the coal conveyors run must be judiciously lighted for preventing accidents, and to facilitate access to the various parts of the equipment. The lamps should be so located as to be safe from accidental breakage. Basement. The basement usually has a fairly low ceiling and is apt to be crowded with pumps and condensers. This apparatus sometimes extends from the floor to the ceiling, making the lighting difficult. In fact, general lighting is in many cases out of the question, and individual lamps must then be located at those points where they will be the most useful. The installation of wiring and lamps must be made to with- stand the dampness and conduit work is possibly the best means for running the wires. On account of the low head room and the usual crowded conditions, small lamps in large numbers are preferable. Transformer, Oil Switch and Bus-bar Compartments. The loca- tion of this apparatus is often in compartments separated from the main engine room by concrete or brick walls, and only a meager quantity of artificial light is required for the ordinary purposes. However, a sufficient number of lamps should be in- POWER-HOUSE LIGHTING 119 stalled to permit of fairly high illumination at those times when the compartments are inspected or when repairs are necessary. Carbon filament lamps may be used, although tungsten lamps may also be employed to advantage. 83. A Practical Case where Medium-sized Lamps are Used. To illustrate the items involved, a typical power house as shown in Fig. 70 is selected. The floor dimensions are 75 by 128 ft. and Elevation 128- 16---H & Switch board./ Plan FIG. 70. Plan and elevation of typical power house showing arrangement of 250-watt (200 candle-power) tungsten lamps equipped with Holophane " Focusing" type glass reflectors. the ceiling height is 21 ft. This ceiling height may be classed as moderate and medium-sized lamps are, for this reason, the best. This station was poorly lighted formerly by six rather large lamps spaced about 32 ft. apart and mounted at the ceiling. This original arrangement is shown in Fig. 71, and the complaints from the lighting were somewhat as follows: (1) The illumination was so inadequate as to cause much difficulty in the routine work of attendance and in emergency work on dark days and at night. 120 FACTORY LIGHTING (2) As usual in such cases, the very small number of large lamps with the large spacing distances produced excessive shadows. Extension lines were required, therefore, when making repairs on the apparatus, involving losses of time through the handling of individual lamps. (3) The service was unreliable and somewhat intermittent due to voltage conditions because the lamps were fed from the regular service mains. j "5 x r 1 r W L. Elevation 12S >] || j H H H 3 5 ft tt H Plan FIG. 71. Plan and elevation of the typical power house shown in Fig. 70 indicating here the old arrangement of lamps. Compare with Fig. 70. In the installation shown above enclosed carbon arc lamps were used. The Improved Arrangement. In Fig. 70 is shown the improved arrangement where 250-watt tungsten lamps are used. A com- parison with Fig. 71 shows that the spacing of the lamps is greatly reduced, thus improving the directional features of the light. The service from this new scheme resulted in the following advantages : (1) Uniform illumination over the entire station with adequate side light on vertical surfaces of the machines. POWER-HOUSE LIGHTING 121 (2) The large number of lamps eliminates marked shadows and facilitates the work in and about tall machines. (3) The control arrangement is flexible, and alternate rows of lamps may be turned on for general purposes, while for emergency all of the lamps may be used. It will be noted that even with half of the lamps turned on in alternate rows, the intensity of the illumination is fairly uniform. FIG. 72. Reproduced from a photograph taken at night under the arti- ficial light from 250-watt (200 candle-power) tungsten lamps and Holo- phane "Focusing" type glass reflectors as shown in Fig. 70. (4) By mounting the lamps near the ceiling, glare is avoided because the lamps are well above the line of vision. All wiring is placed in conduit and by the use of waterproof sockets the wires are protected from bad effects due to dampness. In this case the supply circuit for the station lamps is fed from a separate lighting transformer, and a special switch is provided for throwing the lamps to a steam-driven exciter. For reasons already stated, the rule has been followed of keeping the lighting circuits entirely separate from the station switchboard. A remarkable difference was noted in this particular case between the appearance of the old and the new lighting schemes. 122 FACTORY LIGHTING Elevation A view of the station at night taken under the artificial light is shown in Fig. 72, which shows to some extent the absence of marked shadows and the uniformly distributed lighting effect. 84. Arc Lamps and Mercury Vapor Lamps. A power house with a ceiling height of 40 ^ ft. and floor area of 63 by 168 ft. is shown in Fig. 73. As previously explained, the need for a large number of lamps decreases some- what as the ceiling height increases, and hence for a mounting height of 40 ft., lamps of large size are permissable and may be arranged to produce results comparable with those pro- duced by smaller lamps when mounted lower. Here it is planned to use lamps of the long-burning flame carbon arc type as shown in the illustration. These lamps are to be supplied from a separate lighting circuit and the control by the alternate scheme permits the use of a portion of the lamps only, or all as the needs require. Mercury vapor lamps are also particularly well adapted to many cases of power-house lighting, and numerous instances are to be found where this type of lamp is in service for power-house lighting purposes. 85. Simple Principles Important. From the foregoing illustrations the station superin- tendent will realize that the expense for suffi- cient artificial light is a small item when com- pared with the saving in labor and the avoid- ance of losses in time in the general operation and upkeep of the station. It is also apparent that the choice of lamp is largely dependent on the surroundings and on the ceiling height. Where incandescent lamps are mounted low they should always be provided with suitable shielding reflectors so as to reduce glare, but the most advantageous way to overcome glare is to mount the lamps sufficiently near the ceiling to place them above the line of vision. n H H B n B lis *v Plan FIG. 73. Plan and arrangement of a typical power house showing ar- rangement for the use of flame car- bon arc lamps (long burning) . This represents the use which may be made advantage- ously of large lamps for high ceilings. POWER-HOUSE LIGHTING 123 Flexibility of control is an item to incorporate in the original plans, but if the lamps are to be installed without set plans, care must be taken to arrange the circuits so that the lamps may be controlled in a flexible manner, and that for low intensities, that is, where a portion only of the lamps is used, the light may be uniformly distributed. It is specially important to control a few lamps from a single switch so that lamps not required may be turned out without affecting too large a portion of the floor space. 86. Definite Rules are Apt to Mislead. The practical operator naturally looks for definite rules on which to base the plans for new lighting. This is not only difficult in lighting work on account of the many factors involved, but may even be objection- able on account of the tendency to use such rules without due regard to the obtaining of the best results. If the ceilings and walls are dark, either more or larger lamps are required than if these parts of the building are painted white. The foregoing general items are intended to give an idea of the requirements and should enable the station superintendent to plan for the new lighting system or will show the importance of obtaining expert advice for securing desired results. Intensity Required. The simplest test of any lighting instal- lation is the answer to the question "how well can the objects be seen?" but a safe conclusion can be reached only after the illum- ination has been worked under for a considerable time. Con- clusions reached after a casual glance should never be depended upon. Another objection to using this common sense test is that practically every individual has his own idea of the amount of light required for given purposes, and what may be adequate in the estimation of one person may seem inadequate to another. The solution of the problem must then be in obtaining an average which is satisfactory to the normal eye. Based on tests conducted in various power houses, it may be stated that for average conditions from 2 to 3 foot-candles are adequate. In some cases, however, power houses are operated with an intensity but slightly over 1 foot-candle. This latter value under average conditions is somewhat low, particularly when the artificial light must be used at various times on dark days as well as at night. The point cannot be too strongly empha- sized that the walls and ceilings should be a light color so as to augment the artificial light by their reflecting surfaces. 124 FACTORY LIGHTING 87. Maintenance. As explained in a previous chapter the maintenance work is as important in the lighting equipment of the power house as elsewhere. Reflectors used with tungsten lamps should be cleaned at fairly frequent intervals, and burned out or otherwise defective lamps renewed or repaired systematic- ally. The various details of this work have, however, been explained at length in the chapter under that subject. 88. General Hints. In order to aid the practical station man it may be stated that the size of lamps should always be adapted to the ceiling or mounting height. It is best to space the lamps symmetrically, that is, in squares or in rectangles, depending on the length and width of each bay. As before in- dicated, mount the lamps sufficiently high to avoid glare, and if tungsten lamps are employed always use a reflector and compen- sate for the increased height with high ceilings by the use of a concentrating reflector. Water gauges have been the subject of some attention in con- nection with their proper lighting, and several devices have been suggested for taking care of this unique case. Dirt accumulations on the glass often make the water level difficult to see, and for this reason the lighting may be intensified to some extent by suspend- ing a piece of white cardboard or a white-painted metal shield behind the glass so that the water level may be read by the con- trast thus afforded. 89. Summary. The foregoing instances are given as examples. Before attempting to utilize the results as here described, par- ticular attention should be given to the items involved in the problem and due allowance made for varying conditions between these examples and a case under consideration. A study of the surroundings and the general building construc- tion should be made in connection with these notes and after realizing the significance of the features which contribute to a successful lighting arrangement, it is quite possible that plans drawn up with slight modifications from these illustrations and notes, will insure far better results than would be the case were the question approached in a more or less haphazard manner. CHAPTER IX IRON AND STEEL MILL LIGHTING 90. General Items. The various classes of work throughout the buildings of iron and steel mills cover a large number of differ- ent operations. Some of these operations and locations may be classed under general heads as follows: (1) The foundry. (2) Open hearth furnaces. (3) Machine shops. (4) Erecting shops. . (5) Flanging shops. (6) Cooling tables and laying out floors. (7) Blooming mills. (8) Loading sheds. (9) Carpenter and pattern shops. (10) Yards. The work in each of these divisions is characterized by certain set forms, and the problems connected with the lighting may be taken up perhaps to the best advantage if grouped under these divisions of the plant. Although practically every iron and steel mill has its own power house, the lighting in these buildings has been discussed in a chapter under that subject, and is therefore not treated in the following pages. There are also numerous other varieties of build- ings and work not mentioned in the foregoing list, most of which, however, can be included under one or another of the locations mentioned. 91. Electrical Considerations. A peculiar feature of the elec- trical equipment throughout iron and steel mills is the fact that the first application of electrical energy took place years before the refinements of illuminating engineering became recog- nized, and was originally connected with arc and incandescent lamps for lighting. This was followed by the introduction of electric motors in steel mill work, and in this latter connection the use of the variable speed motor in the past led to an extended 125 126 FACTORY LIGHTING use of 220-volt direct- current circuits in many of the mills. This condition is somewhat unique and has produced certain peculiar features in the light of modern practice. We find, for example, that as the mills have increased in size thus making larger yards necessary, the lighting of what have now be- come immense yard spaces is by means of 220-volt direct-cur- rent circuits, with the accompanying excessive copper for feeders. Other difficulties in the selection of types of lamps are brought into evidence by the limitations of supply circuits in many plants of this kind. It is necessary to use the 1'10-volt tungsten lamp in a multiple series arrangement, that is, two lamps in series across 220-volt lines, in some of the mills, and all lamps of the arc or mercury vapor types which possess, mechanism must in general fulfil the conditions for operation on 220-volt circuits, wherever the plant is limited to this one class of circuit. Recently, however, alternating current with a frequency of 25 cycles has been introduced in steel mill work, and many of the larger plants are installing alternating current, and are con- verting only a portion of the total power for direct- current use. This is an aid to the lighting problems, for by a reference to Table I of Chapter II it will be found that a large number of the lamps now available may be operated on one or another of the circuits just mentioned. It should be kept in mind when con- sulting Table I that, while many of the lamps are operative on perhaps all of the commercial circuits, it may be far better to operate them on some of these than on others. The table is intended to show what lamps are available for the commercial circuits found in practice, but it does not show on what circuits a given type of lamp is most advantageously operated. 92. The Various Buildings Involved. The typical iron and steel mill building consists of a large high-roofed area with dark surroundings. The areas to be lighted in most of the buildings are very large when compared to average factory conditions, and the lamps must usually be in large numbers and often in large sizes so that the required illumination may be effective on the work sometimes 50 ft. or more below the lamps. The dark surroundings have a decided influence on the amount of light which is effective on the work, and in numerous cases vari- ous buildings connected with the steel plant will be found where the walls and under side of the roof are maintained a light color. Thus, the reflection from walls and roof not only aids the general IRON AND STEEL MILL LIGHTING 127 lighting effect but adds cheerfulness to an otherwise gloomy interior. Nearly all steel mill buildings are of the open-girder con- struction with no ceiling, and hence the lamps must be supported either directly to the roof iron work, or to the under side of the roof itself, if they are to be mounted over-head. The buildings 12 g/ Elevation - "i H Plan FIG. 74. Plan and elevation of a typical foundry showing arrangement of flame carbon arc lamps for adequate lighting effect. are also nearly always equipped with a crane so that the lamps must usually be mounted directly above the crane. 93. General Requirements. It is difficult to outline specific requirements to cover all cases, but the following items are of importance in practically all the buildings involved: (1) For many of the operations a small amount of illumination is sufficient to enable the workmen to get around the building 128 FACTORY LIGHTING without accident risk. In general, however, a higher amount of illumination is warranted than is found in a majority of cases. (2) Eye strain should be avoided by mounting the lamps sufficiently high to be above the ordinary line of vision. (3) The lamps should be operated from circuits which are separate from the motor circuits, to insure reliable and steady operation. (4) In many cases the illumination must be adequate without the use of individual hand lamps, because of the nature of the work which may prohibit the handling of an incandescent lamp. Here the illumination must be sufficient from over-head lamps. (5) The type of lamps and its size should conform to the mounting height and to the nature of the work. (6) The yards should be provided with fairly low uniform illumination in order to aid in the handling and transporting of material by the yardmen. (7) Passages and walkways should be provided with guide posts supporting lamps, and the many gauges connected with steel mill operations require small lamps for specific illumination on the dials. Available lamps may now be used for the attainment of these features, but for its fullest usefulness, the illumination in steel mills should be of a somewhat higher standard than is found at present in a large number of the cases. The problems in these mills are often so great as regards the lighting, that it is some- times difficult to convince those responsible for the expenditures of the economy of such outlays. 94. Peculiar Importance of Over -head Lighting. An observa- tion of conditions shows that much of the work is of large pro- portions thus requiring continual crane service in the handling of heavy materials. Largely for this reason, in much of the work either individual hand lamps must be used, or the illumination must be sufficient from lamps over-head. Hence, it is well to make the over-head lighting sufficient even for the large proc- esses and thus to remove the need for individual lamps close to the work. The comparative cost of the two methods is relatively small in difference when the relative advantages are given due weight in the case of lamps well over-head. Considerable work has been done in the immediate past toward the introduction of this scheme in steel mill work, but the most important step has been IRON AND STEEL MILL LIGHTING 129 the partial raising of the standard of illumination as regards quantity. Before the conditions can be pronounced entirely satisfactory, a further step must be taken in still higher standards of the quantity of light provided for given classes of service. For example, in some of the large machine shops heavy expendi- tures have been made to install over-head lamps, and the results Elevation T w Pit 51- Elevation Pit ? a Plan Plan FIG. 75. FIG. 76. FIG. 75. Plan and elevation of a typical foundry showing arrangement of 500-watt tungsten lamps for a fairly good lighting effect. FIG. 76. Plan and elevation of a typical open-hearth furnace building showing a poor lighting arrangement, with enclosed carbon arc lamps. are superior to former conditions, but still inadequate to permit of accurate work without the use of individual lamps close to the work. Another point of importance is in the providing of some stand- ard of illumination intensity for given classes of work. In 130 FACTORY LIGHTING passing through the various buildings of such plants, it will sometimes be noticed that two similar classes of work are fur- nished with entirely different intensities. It is recommended, therefore, that in studying the improvements required in these buildings, attention be devoted to standards of illumination which will fill the requirements of each given case. 95. Adaptation of the Various Types of Lamps. The variety of the buildings and the diverse nature of the operations, require attention in the selection of the best type of lamp for the purpose it is to serve. The features to be considered in this connection are discussed in Chapter II and are for use in cases of this kind where it is desired to adapt the lamp scientifically to the building conditions and to the nature of the work. 96. Specific Locations Involved. The Foundry. Due to the dark surroundings and the presence of dust and dirt in the average foundry, the lighting of these departments is typical of the problem in the iron and steel plant. For this reason, it will be given somewhat more space than would otherwise be warranted. Not only must adequate light be furnished to the moulds, but the purpose of the light is also to prevent stumbling over hot metal or other accidents which may result when the air is filled with steam and smoke at the time of pouring. The surfaces of the moulds are dark, and the dark walls and ceilings make it necessary to provide more light than would be required if the surroundings were light. It is further important to reduce shadows so that uneven places may be detected on the moulds when finishing the surfaces before pouring, and to have the light sufficiently intense for the general routine of foundry work. The dust, dirt and steam in the air form an obstruction which must be penetrated by the light in passing from the lamps to the work, and a deposit of dirt is apt to be coated on the lamps which causes the deterioration of the lamps in effectiveness. This makes it desirable to provide for the deterioration which will result between cleaning intervals by the providing of a higher intensity of light at the start than would otherwise be thought necessary. It also makes it desirable to use a type of lamp which will not be rapidly affected by the dirt deposits. Fig. 74 shows the design for a foundry where lamps of the flame carbon arc type are indicated. The yellow light from these lamps as well as the light of the mercury vapor lamp is pene- IRON AND STEEL MILL LIGHTING 131 trating in an exceptional degree and thus tends to illuminate the dark surfaces sufficiently. The diagram shows that the lamps are mounted rather close to the moulds because of the low-roof supports, but this is rather an advantage in the foundry if not | ! i * P. V [A ^^^^ jrnace^ ^^^ Elevation | !J p \ -)12 ^- 5 "<: $ t * 1 * 'urnace Girder Line/ - | 1 5 t - I, $ ** Elevation 131-30' 4- * Girder Line' K H Plan Plan FIG. 77. FIG. 78. FIG. 77. Plan and elevation of a typical open-hearth furnace building showing an improved lighting arrangement. Compare with Fig. 76. This system designed for use of long burning flame carbon arc lamps. FIG. 78. Plan and elevation of typical steel mill machine shop showing arrangement of enclosed carbon arc lamps. carried to an extreme by mounting them so low as to produce glare. Fig. 75 shows an installation of smaller lamps, namely, the 500-watt tungsten type. Although the dust and dirt are apt to cause a more rapid deterioration with this type of lamp, it 132 FACTORY LIGHTING may be used in some cases where the dust does not occur in such large quantities. It will be noted that the size of lamp in the preceding case is somewhat larger than would be thought desira- ble from the tables in Chapter II. This exception to the general standard is perhaps warranted, however, due to the extreme con- ditions of the surroundings which are usually darker than in most of the other buildings. Open-hearth Furnaces. The amount of light required for these buildings is small in comparison to other locations as the light from the furnaces aids the workmen in getting about. A small amount of general lighting is warranted, how- ever, and is necessary for safety and for effective work. Fig. 76 shows a typical installa- tion where the light is inadequate, while in Fig. 77 another plan for lighting such a building is shown. In the second illustration the num- ber and type of lamps is calculated to give the desirable quantity of light to facilitate the work about the furnaces. The light from the furnaces is intermittent and hence should not be relied upon as the main source of illumination, and further the spaces back of the fur- naces require light specially when loading is carried on there. Machine Shops. The questions of machine-shop lighting have been covered in a former chapter. Some of the shops about steel mills, how- ever, are unusually large and Fig. 78 gives some idea of such a space with a fairly low ceiling where enclosed carbon arc lamps are used to advantage. Fig. 79 shows a shop with high ceiling or girder line where large lamps are indicated. The arrangement of lamps in the latter illustration apparently Elevation X 56'6 -- - Girder Line / Plan FIG. 79. Plan and eleva- tion of typical steel mill machine shop showing ar- rangement of 700 candle-power mercury vapor lamps for high mounting. IRON AND STEEL MILL LIGHTING 133 was calculated to furnish enough light from over-head to make individual lamps unnecessary, the intensity on the work being about 2 foot-candles, although with an intensity of this value individual lamps are actually required for many machining operations. Machine shops about steel mills are to be found where intensi- ties as low as 8/10 foot-candle are erroneously considered sufficient for general lighting purposes, but in practically all such cases FIG. 80. Reproduced from a photograph taken at night under the arti- ficial light in a typical steel mill machine shop. Note the excellent dis- tribution of the light produced by 700 candle-power mercury vapor lamps in this location. individual lamps are placed close to the work. If the individual lamps are to be eliminated, therefore, it is necessary to provide higher intensities from the over-head lamps. Fig. 80 illustrates the excellence which may be attained by a well-designed installa- tion of shop lighting in a steel mill. Erecting Shops. The buildings used for erecting large machines are often of very large proportions with high roof clearance. Distances of 70 ft. between floor and girder line are to be found, 134 FACTORY LIGHTING Elevation and the supplying of sufficient illumination to the work from lamps at this height is difficult. Fig. 81 shows such a space where mercury vapor lamps of about 700 candle-power each are employed. These lamps are mounted 70 ft. above the floor and furnish an intensity of about 8/10 foot-candle on the work near the floor. This quantity of illumination is fairly adequate but hardly sufficient for contin- uous work and close application. Somewhat higher intensities are therefore recommended for this class of work as an economy to the operations. Flanging Shops. The work of flanging boiler heads and other shapes is carried on while the metal is at a red heat, and the artificial light required is there- fore correspondingly reduced. In handling this material, however, after it has cooled, a low amount of general illumination is re- quired at night, somewhat higher than is to be found in the average building of this kind. Fig. 82 shows a diagram of a typical building where the lamps are in- dicated. The average intensity in this location was found by measurement to be very low and entirely inadequate for the quick handling of the cold metal at night. Fig. 83 shows an ar- rangement of lamps calculated to be sufficient for the work, the intensity in the latter case amounting to between 1 and 2 foot-candles. Cooling Tables and Laying out Floors. The cooling tables for large metal plates are generally used for laying out the work as well. As the metal cools the plates are tipped on edge for inspection and it is at this point that artificial light is most impor- Girder Line' Plan FIG. 81. Plan and elevation of typical erecting shop in a steel mill showing arrangement of 700 candle-power mercury vapor lamps for very high mounting. IRON AND STEEL MILL LIGHTING 135 tant. It has been found that the mercury vapor lamp is well suited for this inspection work with some classes of material. In other cases where the material is different the opinion of some operators is that the light from the mercury vapor lamp does not bring out certain defects in the metal as well as a more yel- low light. For these reasons no definite rules can be stated Elevation K Plan FIG. 82. Plan and elevation of typical steel mill flanging shop showing very poor arrangement of lamps. The lamps of 700 candle-power are much too far apart. as to the quality of light best suited for the inspection of all sheet metal, but the intensity of the light for this operation should equal from 1 to 2 foot-candles to facilitate accurate inspection. After the plates have been inspected, the various shapes are chalked out while the metal is in a horizontal position, and at 136 FACTORY LIGHTING this time the lighting must be fairly intense, both on dark days and at night. Fig. 84 shows one location where the lamps are indicated. In this particular case the lighting shown is very much superior to the former conditions with an older system, but observation and test seem to indicate that the light is still inadequate for rapid, accurate and continuous work. The Girder Line - B Plan FIG. 83. Plan and elevation of typical steel mill flanging shop showing improved arrangement of 700 candle-power lamps. Compare with Fig. 82 and note the closer spacing in this improved scheme. intensity found here amounts to about 1 foot-candle, while about 1 1/2 foot-candles should be the average with the mercury vapor lamps here used. Blooming Mills. The work in the blooming mill is usually carried on with the metal at a red heat, and while the metal is passing through the rolls, practically no artificial light is required. IRON AND STEEL MILL LIGHTING 137 Since the work is intermittent, however, the illumination avail- able from the lamps should be sufficient not only for the regular work but for repairs. Fig. 85 shows a portion of a blooming mill where the lamps are located near the walls, hence the light is very poor in the central portions of the building. An improved scheme is shown in Fig. 86 where the light by a higher mount- FIG. 84. Plan and elevation of typical steel mill cooling tables and laying out floor showing arrangement of 800 candle-power mercury vapor lamps. The work of marking the plates is carried on directly below the lamps shown in this diagram. . ing is distributed more uniformly over the floor space. If the control circuits are arranged properly the lamps in this latter plan may be used economically by turning off the units not required. Loading Sheds. Here the metal is handled in a cold state, and the work must usually be done with dispatch in loading cars. 138 FACTORY LIGHTING The entire floor space should thus be lighted by lamps so con- trolled that when the work is grouped at one portion of the build- ing only, those units not required may be turned off. It is better to have the spaces in use lighted adequately when required, than to have all the lamps turned on at all times and have so few installed that the lighting at no point is sufficient. Fig. 87 f Elevation Elevation ~? -81 Girder Line- X X Incandescent' Cluster X X Plan Plan FIG. 85. FIG. 8J. FIG. 85. Plan and elevation of typical steel mill blooming department showing poor arrangement of enclosed carbon arc lamps and incandescent lamp clusters. The arc lamps are too close to the walls and all the lamps are so low as to cause an objectionable glare for the workmen. FIG. 86. Plan and elevation of typical steel mill blooming department same as shown in Fig. 85, showing improved arrangement of lamps making use of the flame carbon arc type. Note the more symmetrical spacing and the greater distance between lamps and walls thus distributing the light more uniformly over the floor area. Compare with Fig. 85. shows a loading shed where the lamps furnish about 1 1/2 foot- candles. This intensity is in general sufficient, unless the use of very large lamps in small numbers causes marked shadows, where the effect may be much improved by increasing the number of lamps, and possibly using a smaller size of unit. Pattern and Carpenter Shops. The typical shop under this IRON AND STEEL MILL LIGHTING 139 head consists of a long, narrow building with comparatively low ceiling. The surfaces of the wood are usually light in color and the surroundings brighter than in many of the other locations. This feature is an aid to the artificial light. Fig. 88 shows an arrangement of 500-watt tungsten lamps in such a building, where the illumination intensity is sufficient and the distribution of the light uniform. Yards. The lighting here should be sufficient to reduce accidents, and to help in the dispatching of cars loaded with material between the buildings. There is much night work in most steel plants and for this reason the arrangement of the lamps throughout the yard spaces should be given due attention. In general, a diagram of the yards will be a help, since on this the poles may be arranged systematically to secure general lighting with particular reference to the reduction of shadows in dangerous places. Fig. 89 shows a diagram of the lamp arrange- ment in a small yard where the units are planned to illuminate entrances to the buildings and also important points on the tracks and where material is stored. 97. Other Items. The foregoing illustrations as well as the data in Table XII indicate in a general way the work connected with the lighting in and around steel plants, and in this manner the idea has been emphasized that individual treatment must be given to a large number of the cases that arise. The presence of hot metal in some of the buildings is some- times used as an excuse for not installing many lamps, but the light from this source is intermittent and the contrast is made the greater by this cause, and adequate artificial light should be provided for the dark intervals. Much attention has been directed during recent years to acci- dent reduction by preventive measures, as in the surrounding of dangerous moving machine parts with guards. Artificial light will likewise do much to reduce accidents and this feature is one of the very important considerations where the lighting of a given space is in question. The maintenance of the lamps is very important and this subject has been discussed in the chapter under that head. One point of particular interest, however, is a tendency to neglect the upkeep of lamps not calling for regular attention. That is, the tungsten and the mercury vapor lamps do not require trim- ming like the arc lamp, but they should be maintained with the Ill ill! i 1 I i? 15 J t .] ! i !1!1 I g 1 1 ill I 1 1 l*i : Su5M-> > 2 3 III! ssss ill uuguSu in IN Ii| ^ l-i 11 ^ :' II : : Us ; II: j {! I Jf l! I ill ill] 1 E2^ o(S ^i ill fc I ^"2 I! fJ lll 140 IRON AND STEEL MILL LIGHTING 141 same care. An observation of some installations of the former types of lamps shows that sometimes many of the lamps are out of service and apparently no attention is given the matter. One argument advanced by a practical man has been that the use of a large number of medium-sized lamps makes possible Elevation XX XX XX XX XX XX XX X* XX J3 XX XX Plan Plan FIG. 87. FIG. 88. FIG. 87. Plan and elevation of typical steel mill loading shed showing arrangement of flame carbon arc lamps. FIG. 88. Plan and elevation of typical pattern shop showing an arrange- ment of 500-watt tungsten lamps. one or another of the lamps going out without affecting the service to any great extent. If this argument were carried to the extreme, one might conclude that one-eighth or one-fourth of the lamps out of service would not materially affect the light if the bad lamps were uniformly distributed through the 142 FACTORY LIGHTING system. If this were true, they might have been left out of the original installation. The state of affairs amounts to this, that while a few lamps in a distributed system may be out here and there without affecting the uniformity of the illumination to any great extent, the resulting intensity of the illumination is reduced in a definite manner, and if neglect of the renewal and repair of the lamps is persisted in, the old conditions of inadequate lighting are apt Shop 212- -*4 200- W w Plan FIG. 89. Plan of a typical steel mill yard showing suggested arrangement of flame carbon arc lamps. to become permanent. It is thus apparent that to have lamps which do not require regular trimming as does the arc type, while a seeming advantage at the outset, may prove to be a disadvan- tage to the best operation of the lighting equipment if it encour- ages neglect in the regular maintenance. 98. Economy of Superior Lighting Facilities. In a former paragraph it was shown that the economy of good lighting may be reduced to the wages saved through the facilities it affords. In the operations of iron and steel mills, it is often found that the number of workmen for a given floor area is small in comparison IRON AND STEEL MILL LIGHTING 143 to the conditions in ordinary factory buildings. It is perhaps a better scheme, therefore, to base such conclusions here on the advantages of light to an increase in the tonnage output. This feature is evident in those cases where the merits of various divisions of the mill are based on the tonnage scheme. Thus, if the tonnage output in a given department is increased by a certain percentage by improved lighting, the facilities afforded by the lighting are an asset to the equipment of the department. Economy also results if defective work is reduced by better lighting. On the laying-out floor, for example, if a metal plate is defective, but due to the poor lighting it is passed as good material, the plate may go through a considerable number of subsequent operations before a final inspection indicates the defect. The loss of time on this work includes not only that of the original inspector, but also that of the workmen on subse- quent operations, and is a loss to the plant chargeable to insuffi- cient OT poorly distributed light for the original inspector. Hence, it is an advantage and an asset to provide not merely some artificial light, but sufficient illumination to be effective in securing the largest tonnage from a given working force by facilitating the regular operations and preventing accidents and delays, and defective workmanship. The electrical depart- ments should endeavor to inform those responsible for the ex- penditures for electrical equipment as to the merits of im- proved lighting, and to give regard to the relations of sufficient light to the large operations which it continually influences. 1 1 See paper by the author on "Modern Illumination in the Iron and Steel Industry," Transactions Association of Iron and Steel Electrical Engineers, October, 1912. CHAPTER X MACHINE TOOL LIGHTING 99. Importance of Adequate Light on the Machine Tool. As stated in an earlier paragraph, the term light refers to the source or the lamp, while the term illumination refers to the effect produced by the lamp on the work or object to be lighted. The items involved in the illumination of the work in a machine tool include some of the features of the light as well as certain ele- ments in the illumination. The best scheme for lighting in the factory is probably by the over-head system where the lamps are separate from the individual tools, and where the illumination is sufficient in both quantity and in direction to make the work easily visible. In this way the workmen are unhampered by a hand lamp which is apt to be in the way, and the surroundings as well as the small space on the work, are thus properly illuminated. If, on the other hand, the lamp is directly over and close to the work, the operations are somewhat complicated by the relatively dark spaces outside the small portion of the work furnished with plenty of light. To properly light the machine tool the over-head system should first be considered, and if it is necessary to employ an individual lamp in addition to the light supplied from over-head, a study should be made of the best manner in which to mount the lamp on the machine and the means for concentrating the light from the individual lamp at the point of operation. Finally the cost relations should be given due weight as showing the neces- sity for heeding each separate item involved. 100. Cases Provided for by Over-head Lamps. As just stated, the lighting of the machine tool should always be through the medium of a lamp or lamps separate and apart from the machine wherever possible. The side light is a most important item, and it has been found that in many cases the only special feature required for making the lighting from over-head lamps sufficient is to intensify the side light rather than the vertically downward component. The absence of this side component 144 MACHINE TOOL LIGHTING 145 10 146 FACTORY LIGHTING is often the reason why the operator of a machine tool considers an individual lamp necessary. Cases are recorded where machine tools formerly lighted by individual lamps have been provided with better illumination from over-head lamps slightly lowered from the ceiling and pro- vided with suitable reflectors. In many factory sections for every square foot occupied by a machine tool there is a corresponding area used for the storage of materials and supplies needed for the work. Hence, if the Machine Tool FIG. 92. Special bracket designed for individual machine tool lamp. machine tool can be lighted satisfactorily by over-head lamps, the surrounding space receives a corresponding advantage. The over-head lamps in a case of this kind perve the double purpose of lighting the machine tool and the adjoining space as well. Fig. 90 shows a machine tool poorly lighted by a hand lamp close to the work, while Fig. 91 shows the same machine illuminated by tungsten lamps which have been slightly lowered from the ceiling to a height depending on the size of the machine. 101. Points on the Mounting of Individual Lamps. In many machining operations the work must be viewed from below as well as from the side and from above, as in the case of some MACHINE TOOL LIGHTING 147 milling machines. Experiments have been conducted for the purpose of producing sufficiently intense side light in such cases from over-head lamps, but sometimes no amount of light from over-head will reach the important places. To overcome this feature brackets may be mounted on the machine tools somewhat after the illustration in Fig. 92, and in this way the lamp may be moved through a considerable range and in various directions so that the workman may adjust the lamp to suit his requirements. FIG. 93. Special support designed for lamp on a boring mill. In large boring mills individual lamps are also sometimes very necessary, specially when they are placed in high aisles with the overhead lamps so far away that it is impossible to produce the needed amount of side light. Fig. 93 shows one scheme for mounting individual lamps on these machines. The lamp is suspended on a swinging arm, which is attached either to the side wall or to the vertical portion of the machine itself. Large machines require mild general illumination and also high inten- sity at the cutting point. Concentrating the Light Where Required. The average work- man has some idea of the importance of shielding his eyes from the light of a bare lamp, because he often surrounds the bare lamp with a cardboard or metal cone, which while shielding the 148 FACTORY LIGHTING eyes does not add anything to the net efficiency of the lamp. Hence, the light should not only be cut off from the eyes but directed to the object which must be visible for the workman. Fig. 94 shows the approximate distribution of light about a bare incandescent lamp, not provided with a shade or reflector. Here much of the light is wasted in directions not useful to the work, and when the work is viewed from behind the lamp, almost as much light enters the eye as is effective on the work itself. FIG. 94. Approximate distribution curve of a bare or unprotected carbon filament lamp. Much light is wasted in useless directions. Note the direc- tion of the light rays as related to the milling cutter on the right. Fig. 95 shows the approximate distribution of light about a lamp which is equipped with a dark metal shield. This shows that the eye is protected from the glare, but the amount of light on the work is about the same as before, that is, the improvement is only a partial one. Fig. 96 shows the approximate distribution about a lamp equipped with a suitable reflector, and by comparing this illus- tration with the two preceding, it is apparent that here the eye is protected and that most of the light is directed to the point required jDy means of the reflecting surface on the inside of the reflector. MACHINE TOOL LIGHTING 149 Therefore, if the illumination was sufficient without a reflector in the first case, a smaller lamp might be used when equipped with a reflector for directing the bulk of the light to the cutting point. On the other hand, if the light was insufficient with the bare lamp, it will likely be adequate with the addition of a reflector. Figs. 97 and 98 are two views of the same machine. A lamp without a reflector is used in the first case and the glare FIG. 95. Approximate distribution curve of a carbon filament lamp with improvised metal shade. Much light is wasted by absorption on the inside of the shade and only a small proportion of the available light reaches the cutter to the right. is shown by the illustration. In the second case the lamp is equipped with a reflector and the effect is shown by the reduced glare on the photographic reproduction. 102. Cost Relations of Artificial Light and Machine Tool Operation. The many improvements to machine tools include mechanical features as well as the more efficient methods of driving. There are two other items which are essential if the greatest benefit is to be derived from these improvements, 150 FACTORY LIGHTING namely, the efficiency of the man who operates the machine, and the surroundings of the man, which influence him in his work. Therefore, the efficiency of the operator may be the controlling element in the production resulting from a given machine tool. The artificial light affects the efficiency of the operator contrib- uting either to his success or failure, depending on whether it is adequate or inadequate on dark days and at night. The development of machine tools has generally overlooked the devel- FIG. 96. Approximate distribution curve of a carbon filament lamp equipped with a well-designed reflecting shade. Most of the available light is directed to the cutter at the right. opment of proper lighting features as a distinct portion of the machine itself, this item in the main being left to the judgment of the one who installs it and has its operation under control. Fig. 99 and Table XIII show the items chargeable against a particular machine tool 1 . It will be seen that the cost for energy and maintenance of the lamp is the smallest item. These charges may be larger or smaller than the average, but are selected 1 From article by A. G. Popcke in Electric Journal, Dec., 1909, p. 760. MACHINE TOOL LIGHTING 151 152 FACTORY LIGHTING from a typical case, and the main point to note is that the lighting is almost a negligible expense in comparison to the other charges, although it may be the cause for the failure of the workman on a given piece of material. In one factory section, the cost of energy and maintenance per individual lamp amounted to 25 cents per month. The operator who depends on this lamp may receive $3.00 per day, hence the cost of the lamp is equal to the wages for two minutes per day. A workman can easily lose that amount of time and far more if he is handicapped in every motion by an insufficiency of light at certain portions of the day, or at night, and when losses due to defective work are added to the losses of time, they may greatly exceed the cost for the best available light. TABLE XIII. CHARGES PER HOUR AGAINST A TYPICAL MACHINE TOOL Variable charges $1 . 100 Salaries. . 600 Wages of operator 300 Interest 150 Depreciation 150 Fixed charges 060 Power, for motor drive 020 Power, for individual lamp 001 Total.... $2.381 Fig. 64 shows these relations in a more definite manner for various conditions, and therefore it may be stated that while the light is one of the smallest items connected with the operation of a machine tool, it is in reality more important in its results than some other items. 103. Physical Size of the Individual Lamp. The individual lamp should be as small as is consistent with good practice in the handling of the lamps. Evidently the size of the lamp may be reduced if a reflector is used and by the reduction of the size of the entire unit, it will be less likely to be in the way when handled by the operator, and it can thus be placed closer to the point of work than otherwise. 104. Extension Lines. In some cases the lamps cannot con- veniently be attached to the machinery but must be used in the form of extension lines. If the number of these flexible lines is very great, the maintenance is apt to be large unless special care is taken in the makeup of the line. MACHINE TOOL LIGHTING 153 The usual form is a length of flexible lamp cord to which a wood handle and a socket are attached at one end and an attach- ment plug to the other. Here the cord is frequently mashed or cut, thus wearing off the insulation, the plug may be dropped and broken, and the unprotected socket is often left lying on the floor and is stepped on and broken. The lamp guard usually employed is weak in construction and may be mashed if stepped on. A study of these weak points resulted in the design of an extension line made up of flexible deck cable to one end of which Variable Charges Salaries Wages Interest Depreciation. Fixed Charges Power Individual Lamp 20 40 Cents bO 100 FIG. 99. Charges per hour against a typical machine tool, showing the comparative insignificance of the lighting cost in terms of the total. is attached a special wood guard into which the socket is fastened, and to which the lamp guard is also fastened. This combination socket and lamp guard is able to withstand a great deal of wear and tear, and the metal part of the guard is strong enough to bear the weight of a man on account of its reinforcing ribs. A wood handle forms a part of the whole and is so proportioned that a workman can easily manipulate the line to suit his requirements . At the other end of the line a wood attachment is screwed to the plug connection so that there is no cause for the wire to be broken off where it enters either the plug or the socket. Fig. 100 shows the fittings for this form of line, which although some- what more expensive than the ordinary kind, will wear several times as long, thus proving an economy in the end. 105. Shadow Contrasts. Sometimes the individual hand lamp is needed to help in the making of delicate fittings by the shadow contrast between the respective edges of the material. This particular effect can hardly be secured in any other way than by the use of a lamp in the hand of the workman. This applies 154 FACTORY LIGHTING to the work on dies and to some assembly operations. Here of course the hand lamp is an aid and not a hindrance. One reason for emphasizing a case of this kind is to show how impossible it is to establish set rules in factory lighting. To do so may result in disadvantages to certain workmen where the work is of a special nature, and no amount of argument will change the actual state of affairs. We must adapt the illumina- Twin Flexible Deck *S Cable \ Wooden Bushing V Attachment Wood Guard for Socket ^ w Hook for Su pporting Lamp Reflector FIG. 100. Extension line for individual hand lamp for use in shops and designed specifically for long wear under rough conditions. tion to the requirements of vision and not compel vision to accommodate itself to unsuitable illumination. Let the illuminat- ing engineer or the foreman take the place of the workman, looking at what he must see and observing whether the conditions are right. The workman may know that conditions are not right, and not know why nor what the proper remedy may be. He may ask for a certain kind of lamp when the difficulty would be best obviated by something entirely different. MACHINE TOOL LIGHTING 155 106. Candle-power of Individual Lamps. By directing the light to the point where most needed with a reflector, it may be possible to reduce the size of an individual lamp, that is, to use a smaller lamp than otherwise. This should be left to the judg- ment of the foreman in charge, and while the operating man is interested in lowering the energy and maintenance charges in every possible way, the use of a smaller lamp should not be based on the saving in energy, but on whether the work can be per- formed satisfactorily with a smaller lamp. Hence, whether the lamps are to be made smaller or larger, a step of this kind should only be taken if there are distinct advantages to the work- men by so doing. The intensity of the illumination furnished by individual lamps close to the work is ordinarily as great as that considered adequate from over-head lamps, but it is usually on a small space and the eye under these conditions requires more light than otherwise. If, therefore, tests are undertaken to find whether the individual lighting is sufficient, something should be allowed for the additional illumination needed from the indi- vidual lamp over and above that which might be enough from lamps mounted well over-head. 107. Concluding Items. The underlying thought in all illumination work in the factory should be effectiveness. This is of course true in the mounting of individual lamps and in directing the light from these lamps where it is most needed. Attention should, however, be drawn again to the relatively great advantages of the over-head lighting method wherever this scheme can take the place of individual lamps, but where the latter are necessary, they should be supplied without hesitation. Factory foremen can co-operate with the workmen in show- ing them how to use the individual lamps and to appreciate the simple principles of illumination affecting their workman- ship. The imparting of such information to the workmen is all the more important when one considers that even after an indi- vidual lamp has been installed with due regard to the setting of the lamp and to the reflector for sending the light in the right direction, these features may be so little appreciated by the employe that they may not be used to good advantage. To the other factors bearing on shop economy, satisfactory lighting will doubtless be added in the near future even in those cases where but little attention has been given it thus far. 156 FACTORY LIGHTING Efforts to improve the illumination and to reduce the glare now so often prevalent, should ultimately result in improved eye- sight among factory workmen. This humane consideration, when taken in conjunction with the other economical advantages afforded by such improvements, commends artificial lighting as being due more interest and attention than it has received during past years. INDEX Alba reflectors, 92 Am. Inst. of Elec. Eng., 51 American Machinist, 95 Arc lamps, bracket for, 37 flame carbon, 1, 4, 5, 8 in power house, 122 maintenance items for, 52 mesh screen for globe, 39 metallic flame or magnetite, 1, 4,5,8 record blank for maintenance of, 60 wire supports for, 111 Asso. of Iron and Steel Elec. Eng., 143 Basement lighting in power house, 118 Blooming mill lighting, 136 Boiler room lighting in power house, 118 Bolt, toggle, 30 Boring mill, support for lamp, 147 Bracket for arc lamp, 37 for machine tool lighting, 146 Buildings involved in steel mills, 126 Candle-power, chart of, 4 of lamps, 3, 155 relation to mounting height, 12 Carbon filament lamps, 1, 3, 4, 5, 8 Carpenter shop lighting, 138 Ceiling, conditions in factory, 102 construction, 31 height in factory, 101 substitute for, 95 Chains for supporting reflectors, 38 Charts for maintenance records, 59 Circuits, lighting, 106 power and lighting, separate, 40 series and multiple, 39 supply, 7, 40 Classification of lighting, general, 2 Cleaning reflectors and globes, 56 Coal bin and conveyor lighting, in power house, 118 Column numbering, 55 Control circuits, 36 Cooling table lighting, 134 Cooper Hewitt lamp, 8 Cost factors, drafting room lighting, 93 factory lighting, 98, 113 iron and steel mill lighting, 142 machine tool lighting, 149 office lighting, 77 of wiring per outlet, 31 power house lighting, 116 relations, artificial light and machine tools, 149 maintenance, 49 wages to light, 99 Crane clearance, 4, 21 D Data of iron and steel mill lighting^ systems, 140 tungsten lighting systems, 26 Daylight conditions, 7 Design, illumination, 6 problem, 20 Dirt on reflectors, losses produced by, 46, 48, 49, 50, 51 Drafting room lighting, combined direct and indirect light- ing for, 92 complaints of, 87 cost factors, 93 difficult conditions, 85 157 158 INDEX Drafting room lighting, eliminating shadows, 86 fixture combinations, 94 four lamp fixtures used for, 91 general requirements of, 85 illumination features, 93 mercury vapor lamps in, 97 practical investigation of, 86 substitute ceiling for, 95 Economy in drafting room lighting/93 factory lighting, 98, 113 iron and steel mill lighting, 142 machine tool lighting, 149 office lighting, 77 power house lighting, 116 switch control, 14 wiring, 41 Effective illumination, 4 Efficiency of lighting system, 16, 22 values, 17 Electrical considerations in steel mills, 125 Electric circuits, table of, 8 Journal, 150 Engine room lighting in power house, 117 Erecting shop lighting, 133 Estimates, 30 Extension lines, 152, 154 Factory lighting, ceiling conditions 102 height, 101 cost factors, 98, 99, 113 field of various lamps in, 104 general requirements, 102 nature of work, 101 new ideas of, 98 new lamps available for, 98 over-head method, 103 popular ideas of, 100 practical case, high mounting, 110 moderate ceiling height, 107 relation of wages to lighting costs, 98, 99, 113 Factory lighting, space conditions between floor and ceiling, 101 surroundings, 102 various items included under, 101 Flame carbon arc lamps, 1, 4, 5, 8 Flanging shop lighting, 134 Flux, light, 16 Following up wiring work, 34 Foot-candle, 17 Foundry lighting, 130 Gas lamps, 1 Gem lamps, 8 General lighting, 3 Glass and metal reflectors com- pared, 104 reflectors, points to be consid- ered, 105 H Hand rack for reflectors, 57 Holders, reflector, 36 Holophane Company, 9 reflectors, 9, 14 Illumination 2, 4 design, 6 quality of, 5 rule, 18, 19 special note, 27 uniformity of, 9 Indirect and semi-indirect lighting, 83 substitute ceiling for, 95 Inspecting lighting systems, 52 Inspection of the location to be lighted, 6 report, 54, 55 route, 53 Installation work, 28 a few lamps at a time, 43 in relation to maintenance, 41 Intensity values, recommended, 23 standards of, 129 INDEX 159 Iron and steel mill lighting, adapta- tion of lamps to, 130 blooming mills, 136 buildings involved, 126 cooling tables, 134 cost factors, 142 electrical considerations, 125 erecting shops, 133 flanging shops, 134 foundry, 130 general items, 125 general requirements, 127 hot metal as a factor, 139 importance of over-heading lighting, 128 laying out floors, 134 loading sheds, 137 machine shops, 132 maintenance of, 139 open-hearth furnaces, 132 pattern and carpenter shops, 138 yards, 139 Items involved in a lighting system, 58 Lamps, candle-power of individual, 155 carbon filament, 1, 3, 5, 8 field of various types, 104 flame carbon arc, 1, 4, 5, 8 gas, 1 gem, 8 mercury vapor, 1, 4, 5, 8 metallic flame or magnetite arc, 1, 4, 5, 8 metallized filament or gem, 1, 4,8 Moore tube, 1', 4 Nernst, 1, 4, 5, 8 physical size of, 5, 152 renewal of, 47 size of, discussed, 10, 21 spacing of, 12, 21, 74, 77 supporting the, 35 switch control of, 14,. 25 tantalum, 1, 4 tungsten, 1, 4, 5, 8, 42 Lamps, types of, 10, 21, 104 Quartz, 1, 4, 5 Laying out floor lighting, 134 Light, 2 flux, 16 quality of, 5 side components of, 13, 105 Lighting circuits, 106 Lighting systems, inspection of, 52 items included under, 58 Loading shed lighting, 134 Locating the outlets on the ceiling, 44 Losses due to dirt on reflectors, 48, 49, 50, 51 Low ceilings, difficulties of, 3 Lumen, 16, 22 M Macbeth-Evans Glass Co., 92 Machine shop lighting, 132 Machine tool lighting, bracket for, 146 candle-power of lamps for, 155 charges per hour against ma- chine tool, 152 concentrating the light, 147 cost relations, 149 extension lines, 152, 154 importance of sufficiency, 144 mounting the lamps on the tools, 146 over-head lamps for, 144 physical size of lamps for, 152 shadow contrasts, 153 support for lamp on boring mill, 147 Maintenance, 46 cost relations, 49 importance of system, 47 items- involved, 51, 52 record blanks for, 59, 60, 61 records for, 57 relation to in.stal.at ion. 41 report on inspection, 54, 55 results of care in, 62 simplicity essential, 61 standards in equipment, 62 storage of materials, 62 160 INDEX Maintenance, table of information, tungsten lamps, 59 truck for, 56 washing division^ 56 trough, 58 Mercury vapor lamps, 1, 4, 5, 8 in drafting room, 97 in power house, 122 record blanks for maintenance of, 60 Mesh screen, for globes, 39 for reflectors, 36 Metal and glass reflectors compared, 104 Metallic flame or magnetite arc lamps, 1, 4, 5, 8 Metallized filament or gem lamps, 1, 4, 5, 8 Moore tube lamp, 1, 4 Mounting height of lamps, 13, 23 N National Elec. Light Asso., 52 Nernst lamp, 1, 4, 5, 8 New ideas of lighting, 1 Numbering columns, 55 O Office lighting, cost factors, 77 design factors, 74 general requirements, 65 high ceilings, 76 indirect and semi-indirect light- ing, 83 investigation of typical room, 66 narrow room, 78 odd dimensions, 76 practical example, 75 rectangular room, 81 simple rules, 72 small room, 79 spacing distances of lamps in, 74, 77 Open-hearth furnace lighting, 132 Over-all dimensions of lamps, chart, 5 Over-head lighting for machine tools, 144 in factory buildings, 103 in iron and steel mills, 128 Pattern shop lighting, 138 Physical dimensions of lamps, 3, 4 Point additions, 17, 23 Popcke, A. G., 150 Power house lighting, arc lamps in, 122 basement, 118 boiler room, 118 coal bins and conveyors, 118 economy of good lighting, 116 engine room, 118 general hints, 124 general requirements, 115 intensity required, 123 maintenance of, 124 mercury vapor lamps in, 122 modern viewpoint, 116 practical case, medium sized lamps, 119 relation to operation, 115 simple principles important, 122 transformer compartments, 118 tungsten lamps in, 120 water gages, 124 Practical features of lighting, 2 Pull switch, 37 Q Quality of light and illumination, 5 Quartz lamp, 1, 4, 5 Records of maintenance, 46, 57, 59 arc lamps, 60 mercury vapor lamps, 61 tungsten lamps, 60 Redirection of liglit, 9 Reflectors and globes, 9 alba, 92 chains for supporting, 38 cleaning, 56 glass and metal compared, 104 hand rack for carrying, 57 holders for, 36 holophane, 9, 14 losses due to dirt, 46, 48, 49, 50 51 INDEX 161 Reflectors and globes, meshed screens for, 36, 39 points to be considered, 105 truck for handling, 56 washing division, 56 trough for, 58 Renewel of lamps, 47 Report on inspection, maintenance, 54, 55 Requirements of, dra r tingroom light- ing, 85 factory lighting, 102 iron and steel mill lighting, 127 office lighting, 65 power house lighting, 115 Results of good lighting, 1 Rule for calculations, 18, 19 Rules, for office lighting, 72 Underwriters', 34 S Scale of drawing, 16 Semi-indirect lighting, 83 substitute ceiling for, 95 Shadow contrasts, 153 effect and spacing of lamps, 11 elimination, 86 Shop lighting, 132 Side components of the light, 13, 105 Size of lamps, 10, 21 Space between floor and ceiling, 7 Spacing and shadow effect, 11 of lamps, 12, 21, 74, 77 Specifications, 16 Specific lighting, 3 Standards in lighting equipment, 62 Storage in maintenance division, 62 Stringer boards, 45 Substitute ceiling for semi-indirect lighting, 95 Supply circuits, 7, 40 Supporting the lamps, 35 Switch, control, 14, 25 economy of, 14 indication of, 16 pull, 37 wall, 36 Tantalum lamp, 1, 4 Toggle bolt, 30 Transformer compartment lighting in power house, 118 Truck for maintenance, 56 Tungsten lamp, 1, 4, 5, 8, 42 in power house, 120 inspection report for, 55 maintenance items of, 51, 52 record blank for maintenance of, 60 table of information for, 59 Type forms, lighting of, 96 of lamp, 10, 21, 104 U Underwriters' rules, 34 Uniformity of illumination, 9 W Wages, relation of lighting costs to, 99 Wall switch, 36 Washing division for reflectors, 56 trough, 58 Water gages in power house, 124 Wiring plan, 29, 41, 44 Working drawing, 15 Yard lighting, 139 11 RETURN TO the circulation desk of any University of California Library or to the NORTHERN REGIONAL LIBRARY FACILITY Bldg. 400, Richmond Field Station University of California Richmond, CA 94804-4698 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 2-month loans may be renewed by calling (415) 642-6753 1-year loans may be recharged by bringing books to NRLF Renewals and recharges may be made 4 days prior to due date DUE AS STAMPED BELOW cm SEP JUL 2 6 1995 flCT 9 1995 JUL 2 11997 JUN 1 2 2005 UNIVERSITY OF CALIFORNIA LIBRARY