ENGINEERING LIBRARY 
 
ENGINEERING LIBRARY 
 
 A paper to be presented at a meeting of 
 the International Engineering Congress, 
 1915, in San Francisco, Cal., Septem- 
 ber 20-25, 1915. 
 
 [Advance Copy. Printed; Not Published. For Release October 1, 1915.] 
 
 WATER WHEELS OF IMPULSE TYPE. 
 
 By 
 
 W. A. DOBLE, Mem. Am. Soc. C. E. 
 
 Chief Engineer, Pelton Water Wheel Co., 
 
 San Francisco, Calif., U. S. A. 
 
 INTRODUCTORY. 
 
 The modern development of this type of hydraulic prime- 
 mover dates back to the "hurdy-gurdy" water wheel constructed 
 by the early gold miners of California. The history of the wheel 
 will be found in Volume 29, 1899, Transactions of The American 
 Institute of Mining Engineers, Page 852, "The Tangential 
 Water Wheel". 
 
 The wheel has been designated by several different names, 
 viz; "Impulse", "Impulse-reaction", "Free-jet", "Spoon- 
 wheel", "Tangential" and "Pelton", but in view of the fact 
 that Pelton developed the characteristic dividing wedge of the 
 buckets, and was the first to develop the wheel from the commer- 
 cial standpoint, the engineering world has adopted the name 
 "Pelton Wheel" as being synonymous of the type, as it is a dis- 
 tinct type of hydraulic prime-mover, differing radically in prin- 
 ciple from the pressure types and the various forms of partial 
 turbines developed in Europe and in the eastern part of the 
 United States. 
 
 EARLY DEVELOPMENT. 
 
 In considering its development from 1850 to 1915, it will be 
 best to divide this time into two periods. First, the "Mining 
 Period", running from 1850 to 1890, during which time the 
 wheel was developed primarily by the miners, and its principal 
 use was in connection with the mining industry. Its design and 
 development were restricted in merit and quality by the rather 
 
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 Ml 01 53 
 
.D6 
 
 C 
 
 
 
crude requirements of the mining industry, and, of course, re- 
 finements in design and construction beyond the requirements of 
 that industry were not justified. The power of each wheel was 
 also limited to comparatively small horsepower output, as the 
 nature of the driven apparatus was such that there was no call 
 for large power output from a single wheel. During this period 
 the effective head or pressure was comparatively low, averaging 
 from 200 to 500 feet. The power developed by the wheels was 
 necessarily used where it was developed, the length of the trans- 
 mission being limited to that feasible for a shaft, belt, or rope 
 drive. 
 
 Second, the "Electrical Period", running from 1890 to date, 
 during which period, radically new and severe requirements 
 were demanded from the makers of the wheel. The size and 
 power output were no longer limited to the requirements of the 
 immediate location of the wheel, but only by the amount of power 
 that could be developed by the water available. The working 
 head was greatly increased, as new conditions justified greater 
 expenditures in the development of the water shed, with its stor- 
 age dams, conduits, regulating reservoirs and penstocks. The 
 problem of successful speed regulation to meet the requirement 
 of operating two or more dynamos in synchronism, or two or 
 more widely separated power plants on the same system of trans- 
 mission and distribution also arose, and involved the necessity 
 of a governing means sufficiently sensitive, accurate and rapid to 
 maintain a uniform speed with instantaneous changes of power 
 demand from zero load to full load and inversely, and with fre- 
 quent large percentages of the total capacity of the water wheel 
 instantly rejected or applied. 
 
 During this period, a further requirement developed, viz., 
 continuous service; whereas, before this period, continuous ser- 
 vice, and all that it means, was an unknown quantity. Long 
 distance transmission, reaching out over wide territories and sup- 
 plying power and light to many commercial industries, towns and 
 cities, gave an entirely new meaning to the term continuous ser- 
 vice, and demanded apparatus of the highest type of engineering 
 design, material and workmanship, to meet its necessities. 
 
 In the mining age, the problem of speed regulation was very 
 
simple, since the early use of such wheels was principally to drive 
 stamp mills, saw mills, etc., where the power output was quite 
 constant and the friction load on the shafting and driven machin- 
 ery formed a large proportion of the power developed. In such 
 cases regulation was accomplished usually by partially closing 
 the gate valve placed back of the nozzle entrance, or as a refine- 
 ment, in wheels using a rectangular slot nozzle, a sliding tongue 
 was inserted in the orifice, that could partially or fully open the 
 orifice. A refinement for wheels using a circular jet was the 
 adoption of the deflecting nozzle, to permit of projecting the 
 entire jet against the buckets of the wheel, or partially or wholly 
 deflecting the jet outside the path of the buckets. Other improve- 
 ments were made, such as in using cast iron instead of wood. etc. ; 
 but, in general, it is reasonable to state that the impulse or Pelton 
 wheel of the Mining Period was comparatively crude in its engi- 
 neering design -and in its construction, though suitable for the 
 work it was called upon to do. Many of these early wheels are 
 still in use, and they were of great service to mankind. 
 
 During the Electrical Age the development of the wheel by 
 modern engineering methods, such as were in vogue in other 
 types of prime-movers, dates back to the first work in long-dis- 
 tance electric transmission, made possible by the invention and 
 development of the static transformer. This would start the con- 
 sideration of this later development with the years 1890-1893 
 with the installation of the Telluride Power Company's Plant, 
 the justly celebrated Pomona Plant, and the plant of the Red- 
 lands Electric Light & Power Co. The progress in the art from 
 that time has gone hand in hand with a similar development in 
 the co-related work of the electrical engineer. Thus the hydro- 
 electric prime-mover has brought about a great and rapid de- 
 velopment in the water wheel, with its accessories, as it has in 
 the development of the dynamo. A similar development has also 
 taken place in steam-electric prime-movers. New problems in the 
 designing of both types of prime-movers particularly those con- 
 nected with safety, reliability and accurate regulation have thus 
 been brought about by the special requirements of the electric 
 dynamo, with the co-related problems introduced by the require- 
 
ments of long-distance transmission, continuous service, and 
 speed regulation of a character heretofore unknown, in combina- 
 tion with the demand for prime-movers of much greater power 
 output, high rotative speed, and to operate under extremely high 
 heads and therefore high water pressures. 
 
 Tracing the development from 1890-1833: the Telluride, 
 Pomona, Redlands, and the other early hydro-electric plants 
 quickly demonstrated that the wheel so successful in the Mining 
 Period was entirely inadequate in its design, material and work- 
 manship to meet the more severe requirements of the hydro- 
 electric generating units. 
 
 During the period from 1890 to date, there has been a con- 
 stant development to satisfy the more and more severe and exact- 
 ing demands of the rapidly growing industry. 
 
 To establish a comparison : in the plant of the Telluride 
 Power Company at Ames, Colorado, installed in 1890, were two 
 hydro- electric single-phase units, each of 150 kw. output, con- 
 sisting of a Pelton wheel directly connected to a Westinghouse 
 generator. These wheels operated under a head of 500 ft. (152 
 m.). 
 
 In the Pomona Plant of the San Antonio Light & Power 
 Co., Pomona, California, installed in 1891, were two hydro- 
 electric single-phase units, each of 120 kw. output, consisting of 
 a Pelton wheel operating under a head of 402 ft. (122 m.) and 
 directly connected to a Westinghouse generator. 
 
 In the Mill Creek Power House No. 1 of the Redlands Elec- 
 tric Light & Power Co., near Redlands, California, installed in 
 June 1892 and first put into operation on September 7, 1893, 
 were two hydro-electric three-phase units, each of 250 kw. out- 
 put, consisting of a Pelton wheel operating under a head of 295 
 ft. (90 m.) and directly connected to a General Electric gen- 
 erator. These were the first three-phase generators made in the 
 United States, and this was the first three-phase transmission 
 system to be put into service in the United States. 
 
 The development since these early installations has been 
 very remarkable, as will be appreciated in completing the com- 
 parison with the more recent developments: there are five or 
 more power plants in the United States where the wheels operate 
 
under heads of approximately 2000 ft. (610 m.) and over, and 
 in Europe one plant operating under a head of 2890 ft. (880 
 m. ) , and one plant recently completed operating under a head of 
 5250 ft. (1720 m.), wherein a single jet of water 1% inches diam- 
 eter develops 3000 horsepower. The increase in the size of the 
 units is more striking, starting with the 150-kw. units at Ames in 
 1890 to the recent generators of 12,500 kw. output and driven by 
 Pelton wheels of 20,000 hp. capacity. To fully appreciate this 
 development, it is necessary to consider that it is the result of 
 only twenty-five years' work, which period covers the entire his- 
 tory of the art of Hydro-Electric Power Generation and Trans- 
 mission. 
 
 The details of design of each hydraulic prime-mover are con- 
 trolled and determined by the natural conditions existing at the 
 location where it is to be installed, and under which it is to ope- 
 rate. These natural conditions and limitations differ over a 
 wide range with every installation ; therefore, the hydraulic 
 prime-mover cannot be standardized in design, as is possible 
 with electric generators, steam engines, or steam turbines, but 
 each prime-mover must be specially designed and developed. 
 
 The principal controlling factors of the design are : ( 1 ) The 
 water quantity curve, or the quantity of water available during 
 each period of each day and throughout the year; (2) the total 
 head that it is possible or profitable to develop ; ( 3 ) the presence 
 of satisfactory sites, favorably located, on which to construct 
 storage reservoirs, or equalizing reservoirs, from which the pres- 
 sure pipes will carry the water to the wheels ; (4) the character of 
 the load curve that is to be carried; (5) the most economic speed 
 of rotation of the electric generator or driven machinery; (6) 
 whether or not riparian or irrigators' rights have a controlling 
 interest that will affect the possibilities of water storage during 
 the sag in the daily load curve, so as to permit the water not re- 
 quired during this sag in the load curve to be conserved and 
 available to carry the peaks of the load curve. These conditions 
 primarily determine the general type and capacity of the instal- 
 lation, the number and capacity of the separate units into which 
 the plant will be subdivided, the speed of rotation, the method 
 of speed regulation and whether or not water economizing meth- 
 
ods can be used to an advantage. These controlling factors differ 
 so materially in each installation that they not only affect the 
 general type or arrangement of the design but also the details. 
 
 The general type of unit to be adopted in a given power 
 plant will, therefore, be determined by the particular arrange- 
 ment and characteristics of details to be incorporated in the unit, 
 as required to meet the conditions under which the prime-mover 
 is to operate; it being appreciated that there are in practically 
 every prime-mover certain similar details, differing only in size 
 and mode of operation. 
 
 WHEEL RUNNERS AND BUCKETS. 
 
 The term "wheel runner" contemplates the entire wheel 
 proper, consisting of some form of center, to the rim of which the 
 buckets are attached. There are two general types of wheel con- 
 struction : First, the Double-lug buckets j secondly, the Chain- 
 type or Triple-lug bucket. 
 
 The double-lug bucket is arranged with two lugs cast inte- 
 gral with the bucket. The wheel center consists of a single rim. 
 The two lugs of the bucket are accurately machined to a press 
 fit over the rim of the wheel center and the buckets are held in 
 position on the rim of the wheel center by two bolts, which are 
 pressed into reamed holes passing through the two lugs of the 
 bucket and the rim of the wheel center, thus making a very sub- 
 stantial construction. This type of wheel is shown in Fig 1 and 
 the photograph of the De Sabla buckets (Fig. 2). 
 
 The wheel illustrated in Fig. 1 is operating under 865 ft. 
 (264 m.) head, at 225 revolutions, and develops 3750 horsepower. 
 This wheel is constructed with a forged steel disc, which is car- 
 ried on a cast-steel hub with follower plate. 
 
 One of the four wheels installed in the Mill Creek No. 3 plant 
 of the Southern California Edison Company furnishes an inter- 
 esting illustration of the double-lug type of bucket. This wheel 
 operates under 1900 ft, (580 m.) head at 430 revolutions per 
 minute, developing 1600 horsepower, and has been in continuous 
 service since March 17, 1903. This wheel held the record for 
 some time as operating under the highest head of any wheel in 
 the world. The wheel center consists of an annealed open-hearth 
 

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Fig. 1. Wheel of Double Lug Construction, Puget Sound Power Company. 
 Wheel center made from steel forging bolted to a wheel hub with follower plate. 
 Develops 3750 hp. under 865 ft. (264 m.) effective head, at 225 r.p.m. 
 
 steel casting, the buckets being of special hard bronze. This type 
 of construction is thoroughly satisfactory for all installations 
 where the ratio between the diameter of the jet and the pitch 
 diameter of the wheel is favorable. In this type there are two 
 bolts for each bucket, and where, owing to the large ratio be- 
 
8 
 
 tween the pitch diameter of the wheel and the diameter of the 
 jet, there is ample room for the two bucket bolts and proper lugs 
 on the buckets, this type of construction is thoroughly satisfac- 
 tory. 
 
 The photograph of the De Sabla wheel (Fig. 2) also shows 
 buckets of the double-lug type of construction. This photograph 
 is of particular interest, as it shows the condition of the buckets 
 as they were on February 25, 1915, the wheel having gone into 
 service October 22, 1903, and having been in almost continuous 
 service since that time with practically no expense whatever for 
 maintenance. The construction of this wheel shows a forged 
 nickel-steel disc 4 inches thick at the rim and 10 ft. 4 in. in diam- 
 eter. This forged wheel-center is then bolted directly to a flange 
 forged solid with the hollow nickel-steel wheel shaft. The buck- 
 ets are made of high-carbon open-hearth steel castings. This 
 record will be of particular interest to engineers as showing what 
 can be accomplished in the way of durability and continuity of 
 service from a properly designed "Pelton" wheel. These wheels 
 operate under 1531 ft. (467 m.) head at 240 revolutions per min- 
 ute and develop 3700 horsepower. 
 
 The chain type of construction differs materially from that 
 of the double-lug construction. In the chain-type construction a 
 double rim is required. This is sometimes made of a wheel with 
 a "U"-type rim. Generally, however, it consists of two separate 
 wheel centers, the hubs being so finished as to bring the space 
 between the rims of the two wheels a proper distance apart. The 
 bucket is provided with three lugs, a forward center lug and two 
 rear lugs. Figure 3 shows clearly the arrangements of the lugs 
 of the bucket. Figure 4 shows the assembled wheel runner com- 
 plete. These wheels operate under 1330 ft, (405 m.) head at 360 
 revolutions per minute, and each wheel develops 20,000 horse- 
 power. 
 
 In this design the center or forward lug of the bucket is a 
 close fit between the two rims forming the duplex wheel center. 
 The two rear lugs of the bucket straddle the rims of the wheel 
 center, the spacing of the lugs of the bucket and the drilling of 
 the wheel centers being so designed that the rear lugs of one 
 bucket come directly in line with the for\vard lug of the next 
 
Fig. 2. 
 
 Photograph Showing Condition of the Buckets on No. 1 Water Wheel at the 
 De Sabla Power Plant of the Pacific Gas and Electric Company. 
 
 This wheel operates under 1531 ft. (467 m.) effective head at 240 r.p.m. de- 
 veloping 3750 hp. It was first put into operation on Oct. 22, 1903, and has been in 
 almost continuous service since that time with practically no expense whatever for 
 maintenance. This photograph was taken on !>!>. 25, 1915, by the engineers of the 
 Pacific Gas and Klectric Company to record the condition of the buckets. The white 
 spots in the bowls of the buckets are due to a mineral deposit left by the water in 
 the buckets in drying. The entire surfaces of the buckets are smooth, the edges of 
 the splitter and entrance edges as shown by the plv.>tograph. being sharp. 
 
10 
 
 following bucket, these holes being drilled and reamed in line. A 
 single 1 bolt therefore passes through the rear lugs of one bucket, 
 the double wheel rims of the center and the central or forward 
 lug of the next following bucket, thus connecting up all of the 
 buckets into a continuous chain. By this arrangement it will be 
 observed that there are the same number of bolts as there are 
 buckets, though each bucket is secured to the double wheel rims 
 by two bolts. 
 
 In comparing this type with the double-lug type, it will be 
 observed that the base line of the bucket, or the distance between 
 the supporting bolts, is very much greater in the chain-type or 
 
 Fig. 3. Arrangement of Lugs on Chain Type or Double Lug Type of Construction. 
 
 triple-lug buckets than it is in the double-lug buckets. This type 
 of construction is particularly suitable for all installations where 
 the ratio between the diameter of the jet and the pitch diameter 
 of the wheel is small, that is, where a large diameter of jet is 
 applied to a comparatively small diameter of wheel. This is 
 always the case where a very large power output is required, 
 with a turning speed comparatively high, as proportional to the 
 head of water, thus calling for large buckets on a compara- 
 tively small wheel. It is also especially suitable for extreme 
 cases of large horsepower and high heads, making the wheel 
 runner of the most stable construction. 
 
 In the construction of the wheel runners for comparatively 
 low heads, cast- iron wheel centers of either the disc or "U"-rim 
 type give good results. For medium high heads, wheel centers of 
 either the disc or k 'U"-rim type made of annealed cast steel are 
 thoroughly satisfactory. For extreme heads and large horse- 
 power output, the wheel centers should be made from chrome- 
 
11 
 
 Fig. 4. Wheel of Chain Type of Construction. Wheel center constructed of 
 two separate centers with hubs. Similar to wheels used in the Drum Power Plant 
 of the Paciic Gas and Elect is Company, developing 20,000 hp. under 1330 ft. 
 (405 m.) effective head at 360 r.p.m. 
 
 nickel steel forgings. In such cases, the attaching bolts are also 
 made of heat-treated chrome-nickel steel and forced into place 
 with 25 tons pressure. The most satisfactory material to use for 
 the buckets is a very high grade high-carbon steel casting. For 
 

12 
 
 the highest heads, it is possible to use drop forgings for the 
 buckets. 
 
 In the construction of the wheels, the accurate dynamic bal- 
 ance of the structure is of the utmost importance, and to insure 
 this, the buckets are balanced in a special apparatus which in- 
 sures a dynamic balance at the maximum runaw r ay speed of the 
 prime mover. 
 
 In the earlier wheels constructed, the breaking off of the 
 buckets was one of the principal sources of failure ; also the great- 
 est single improvement in efficiency of the wheels was secured by 
 the development of the ellipsoidal type of bucket bowls illus- 
 trated in the several photographs, this change alone having im- 
 proved the efficiency of the wheels by over 10%. 
 
 NOZZLES AND SYSTEMS OF CONTROL. 
 
 In general, the needle type of nozzle is invariably used, 
 c characteristic jet from a needle nozzle being illustrated in 
 Fig. 5. This is a flash-light photograph taken through an 
 opening in the side of the wheel housing. The blur at the 
 right hand side of the wheel represents the rapidly revolving 
 buckets of the wheel ; the cone in the center of the jet is the 
 end of the needle bulb. A characteristic needle and nozzle tip 
 is illustrated in Fig.- 6, this being the needle and nozzle tip for 
 the nozzle shown in Fig. 7. 
 
 The determining factor in selecting the type of needle 
 nozzle, which also carries with it the means of regulation of 
 the power output and speed of the prime-mover that will be 
 used in a given plant, depends primarily upon whether or not 
 water economizing control can be used. In those plants that 
 are located on streams where water storage cannot reasonably 
 be secured, or where other power plants are located on the same 
 stream, making it necessary to allow the full flow of the stream 
 to pass the plant, or on those streams where irrigators' or ripar- 
 ian rights have a prime control, thus preventing the storage of 
 water, the simpler stationary needle-controlled nozzle with 
 governor deflector control over the jet, or the needle-regulat- 
 ing deflecting nozzle is used. The stationary needle-regulated 
 jet-deflecting nozzle is shown in Fig. 7 (a jet deflector for a 
 
Fig. 5. Characteristic Jet from Needle-Regulating Nozzle. Photograph taken 
 by flash-light through opening in the side of the wheel housing. The blur at the 
 right hand side of the photograph showing the revolving wheel, the cone of the 
 needle being shown clearly in the center of ths st:eam. The sha.p, true cylind.ical 
 characteristic of the jet, its transparency and absence of spraying is clearly shown 
 by the photograph. 
 
 Fig. 6. 
 
 Characteristic Needle and Nozzle Tip. Needle and nozzle tips from the 
 nozzles shown in Fig. 7. Jet 10 y z inches in diameter. 
 
14 
 
 Fig. 7. Stationary Hand-controlled Needle-regulating Nozzle. Arranged for 
 governor control through the means of a jet deflector, this nozzle projecting a jet 
 10 1 /2 inches in diameter. 
 
 nozzle is shown in Fig. 8). The nozzle is of particular interest, 
 as it projects a jet lO 1 /^ inches in diameter, which is the larg- 
 est single jet of water used at the present time. 
 
 Figure 8 illustrates two nozzles of this type arranged to be 
 supplied with water through $ branch "Y" from a single 
 pipe line, the photograph .clearly showing the arrangement of 
 the deflector, the hand-operated needle control, and the needle- 
 controlled, reversing water-motor-operated gate valves, one of 
 which is bolted to each of the two discharge flanges of the 
 branch "Y". 
 
 The method of mounting the jet deflector is clearly shown. 
 The jet discharging from the end of the nozzle passes through 
 the cylindrical bushing, which is slightly larger than the jet. 
 The speed control is secured by the governor operating on the 
 rockshaft and swinging the deflector more or less, so that it par- 
 tially or entirely deflects the jet outside of the path of the 
 buckets of the wheel. 
 
 The needle-deflecting regulating nozzle is illustrated in 
 Fig. 9. This type of nozzle consists of a nozzle body which 
 
15 
 
If) 
 
 Fig. 9. Needle-regulating Deflecting Nozzle. The needle regulation is by 
 hand control, the deflecting of the nozzle being by automatic governor control with 
 hydraulic counterbalance to balance the weight of the nozzle and the contained water. 
 
 is pivoted to a ball joint, permitting the nozzle to be raised or 
 deflected so as to either direct the full jet into the buckets 
 of the wheel or to partially or entirely direct the jet outside 
 of the path of the buckets of the wheel. 
 
 In both the stationary needle nozzle with the jet deflector 
 and the needle-regulating deflecting nozzle, the needle is 
 usually operated by hand control, the needle being set to utilize 
 
17 
 
 to full advantage the available supply of water. In plants 
 where either of these types of nozzles is installed and where 
 there are forebay reservoirs, economy in the use of water is 
 secured by setting the needle at different times during the day 
 to carry the maximum load on the plant, the needle being set 
 to follow the general load curve of the plant, while the momen- 
 tary load changes and speed control are taken care of by the 
 governor either operating the jet deflector or deflecting the 
 nozzle. 
 
 The system of hand setting of the needle with governor 
 control of the deflecting means is of particular value in semi- 
 arid countries where, due to the influence of evaporation, the 
 daily flow is variable to a very considerable degree ; and also 
 in those power plants where the source of water supply is in 
 the snow fields, the quantity of water varying to a very great 
 degree, depending upon the melting of the snow by the sun. 
 In such plants the operator can set the needle by hand at 
 different times during the day, to utilize to the best advantage 
 the quantity of water available. 
 
 In such plants, where large units are installed, the control 
 of the needle setting is by means of an electric motor with re- 
 mote control from the switchboard, so that the power plant 
 operator can, from the switchboard, set the position of the 
 needle so as to carry any predetermined load that is desired, 
 the needle setting being changed from time to time as the gen- 
 eral condition of the load changes. In such plants the overall 
 consumption of water approximates, in a series of steps, the 
 load curve on the prime-mover. With the needle-regulating 
 deflecting nozzle, the weight of the nozzle with its water con- 
 tents is counterbalanced by an hydraulic cylinder, to relieve 
 the governor of this additional weight, though the inertia due 
 to the weight of the nozzle and its contained water must be 
 overcome by the governor. Both the stationary type of nozzle 
 with jet deflector and the deflecting nozzle give excellent regu- 
 lation, for the reason that there is no change in the velocity of 
 flow of the water in the pressure pipe line, due to governor 
 action. Therefore, very sensitive speed regulation can be main- 
 tained, as the problem of inertia and the time of acceleration 
 
18 
 
 of the column of water in the penstock is not here a factor in 
 the problem of speed control. 
 
 To secure a better economy of water with the use of these 
 types of needle nozzles, automatic devices have been developed 
 so that the governor in rejecting the load on a plant first oper- 
 ates the deflecting means and then brings about a following and 
 gradual re-setting of the needle and nozzle opening. However, 
 these complicated arrangements, at best, are merely adaptations 
 and approximations. 
 
 The ideal type of nozzle, and one that has been used in 
 the most important high-head power plants where sensitive 
 speed regulation and the highest economy in water consump- 
 tion is required, is secured by the needle-regulating nozzle with 
 auxiliary relief-nozzle control, as illustrated in Figs. 10 and 
 11. In general, this type of nozzle consists of a stationary main 
 nozzle body, the power jet directed against the water wheel 
 being controlled by the needle of the main nozzle. This needle 
 is direct operated by the speed governor, bringing about a re- 
 setting of the needle for each change in power demand on the 
 prime-mover, so that there will be delivered to the buckets of 
 the wheel at all times just sufficient water to carry the load on 
 the prime-mover, thus securing a water consumption by the 
 prime-mover strictly proportional to the power output required 
 from it. By this arrangement, maximum economy in the use of 
 water is secured, taking advantage of every sag in the load 
 curve to conserve the water not required to drive the wheel, in 
 order to have this water available to carry the peak loads. 
 
 In the operation of this type of nozzle, to insure against 
 water ram or surges in the pressure pipe line arising out of a 
 sudden reduction of load on the prime-mover, automatically 
 bringing about a correspondingly rapid contraction of the noz- 
 zle orifice and retardation in the flow of water in the pipe line, 
 an auxiliary relief nozzle is provided, which is directly con- 
 nected to and takes its water out of the body of the main 
 nozzle. This auxiliary relief nozzle is likewise provided with a 
 needle control, the jet from this auxiliary nozzle being directed 
 into the tail-race, and at no time brought into contact with the 
 wheel. 
 
 The movement of the needle of the auxiliary relief nozzle 
 
19 
 
 is inverse to that of the needle of the power nozzle. This is 
 clearly illustrated in Fig. 10. This inverse action is accom- 
 plished by means of the controlling lever, one end of which is 
 connected to the operating means of the governor, the move- 
 ment of the power needle being secured through link connec- 
 tions between the cross-head on the shank of the power needle 
 and the controlling levers. The lower end of this lever is 
 
 Fig. 10. Typical Arrangement of the Needle-regulating Nozzle with Auxiliary 
 Relief Control. Shows the arrangement of the lever control for the main needle, 
 and control of the relief needle, through the differential-cataract. 
 
 attached to a .cross-head on the piston rod of the differential- 
 eataraet, which is attached to a cross-head on the stem of the 
 needle of the auxiliary relief nozzle. These levers are ful- 
 erummed between the 1 wo needle connections. It is evident, 
 therefore, assuming that the differential-cataract be locked in 
 one position, that a closing movement of the needle of the 
 power no/xle would bring about a corresponding opening of 
 the auxiliary relief nozzle, and vice versa. However, such an 
 inverse action is neither required nor desirable, as it would not 
 secure the desired economy in the consumption of water. There- 
 fore, the differential-cataract is introduced between the cross- 
 
20 
 
 head on the stem of the needle of the auxiliary relief nozzle 
 and the lower end of the operating levers. 
 
 This differential-cataract is so adjusted that provided a 
 load change is either so gradual or of such an amount as not 
 
 Fig. 11. The Nozzle of the 16,000 hp. Units being Installed in the Power 
 Plant of the Los Angeles Aqueduct. Shows arrangement of auxiliary-needle relief 
 control. Movement of the power needle and the auxiliary-relief needle is controlled 
 trom a central governor through a large rockshaft connecting up the governor with 
 both nozzles. Hand control mechanism is provided and arranged so that either or 
 both nozzles can be controlled by governor or by hand. This nozzle projects a jet 
 8% inches in diameter under 870 ft. (265 m.) effective head, developing 16,000 hp. 
 at 200 r.p.m. 
 
 to set up disturbances and excessive pressure rises in the pres- 
 sure pipe line, a yielding or slipping action takes place in the 
 differential-cataract, which permits the auxiliary relief nozzle 
 to remain closed. Under such conditions, therefore, there is no 
 
21 
 
 discharge of water from the auxiliary relief nozzle. In case, 
 however, a load change takes place which brings about a clos- 
 ing movement of the power nozzle of sufficient magnitude to 
 cause excessive pressure rises in the pressure pipe line, or where 
 the load change is very sudden, which would bring about the 
 same results, the time element control of the differential cat- 
 aract causes the auxiliary relief nozzle to be opened to an 
 amount sufficient to prevent such pressure rises. Immediately 
 the closing action of the needle of the power nozzle has ceased, 
 then the needle of the auxiliary relief nozzle commences to 
 close at a rate which has been adjusted and which will not 
 bring about objectionable pressure rises in the pipe line. 
 
 The performance of the needle nozzle with auxiliary relief 
 control is absolute, the movement of the needles of the two 
 nozzles being from the same prime-mover, namely, the servo- 
 motor of the governor. This gives an absolute assurance 
 against accidents, and insures the maximum water economy in 
 the operation of the prime-mover with a variable load. The 
 movement of the needles in the two nozzles thus interconnected 
 and operated from the same source of power, insures absolute 
 safety, higher water economy and is more reliable than a gov- 
 ernor-operated means of deflecting the jet, and an indirect 
 control over the operation of the needle. 
 
 The speed regulation secured by the needle-regulating 
 nozzle with auxiliary relief control is satisfactory for the most 
 exacting conditions. With a proper proportioning of the oper- 
 ating elements, an absolute control is secured over the pressure 
 rises that can take place in the pipe line due to an instan- 
 taneous rejection of full load on the prime-mover, which would 
 bring about an instantaneous closing of the needle of the 
 power nozzle. The pressure rises can be kept at any percent- 
 age desired, and in special cases a negative pressure rise can be 
 accurately secured with instantaneous closing from full open- 
 ing of the needle of the power nozzle. 
 
 Fig. 11 shows the nozzles for a double-overhung type of 
 unit, developing 16,000 horsepower. These nozzles are ar- 
 ranged with a central governor control, operating the nozzles 
 of the power and auxiliary relief nozzles through the rock- 
 shaft extending between the two nozzles. Arrangements are 
 
22 
 
 made for independent hand-control of the needles of each noz- 
 zle, should it be desired to operate either one or both sides by 
 hand control. The nozzles illustrated in Figure 11 project a jet 
 8 l / inches in diameter, the head of water at the plant being 
 940 feet. 
 
 The auxiliary relief nozzles are designed to secure a nega- 
 tive pressure rise of over 10% with an instantaneous rejection 
 of full load on the prime-mover. The negative pressure rise 
 with sudden rejections of large proportions of the load im- 
 proves the speed regulation of the prime-mover. 
 
 The latest developments in large prime-movers equipped 
 with the needle-regulating nozzles with auxiliary relief control 
 is to mount the servo-motor of the governor directly on the power 
 nozzle, the piston of the servo-motor being mounted on the stem 
 of the needle of the power nozzle. The controlling elements and 
 pendulum head of the governor are mounted directly on the 
 nozzle. This construction is illustrated in Figure 12. A com- 
 parison of the design in Fig. 12 and the nozzle arrangement as. 
 shown in Fig. 11 will demonstrate the advantage of this latest 
 development. 
 
 I >y the arrangement of the piston of the servo-motor of the 
 governor directly on the stem of the needle of the power nozzle, 
 the most sensitive regulation can be secured, as all lost motion 
 and delay due to torsion in the rockshafts and lost motion in the 
 connecting elements is eliminated. In units of large power, this 
 is a most important factor. 
 
 GOVERNORS. 
 /^ 
 
 The modern governor is essentially a pressure oil-operated 
 
 ' device, arranged with a speed sensitive element, a servo-motor 
 for operating the regulating elements, pilot and relay valves to 
 insure a quick response of the servo-motor to the tendency of, 
 
 s^speed changes as indicated by the speed sensitive element. Mod- 
 ern governors will indicate and correct speed changes of from 
 a /4 to y<> of 1%, and are sensitive to a degree permitting a full 
 stroke of the governor to be made in approximately from 1% 
 seconds to 2 seconds time. 
 
 Governors are of two general types: One where the gov- 
 
23 
 
24 
 
 ernor itself is a completed machine, as a product of separate 
 manufacture, and arranged with a terminal shaft by which the 
 gate or nozzle-operating gearing of the prime-mover is con- 
 trolled and operated. Governors of this type are practically a 
 stock manufacture, and are sufficiently flexible in design so that 
 they can be satisfactorily connected up to medium and small 
 size units; such a governor is illustrated by Fig. 13. The oil 
 supply for this governor is contained in the base. The oil pres- 
 sure to operate the servo-motor is secured through means of the 
 gear pump shown. The speed sensitive element operates the 
 pilot valve, which in turn operates the relay valve which controls 
 the oil supply to the cylinder of the servo-motor. The servo- 
 motor is connected to a terminal shaft, to which the operating 
 elements of the prime-mover are connected. The character of. 
 regulation secured from governors of this type is thoroughly 
 satisfactory for the exacting demands of hydro-electric power, 
 generating stations. 
 
 A modification of this type of governor arranged with a 
 vertical terminal shaft is illustrated in Fig. 14. This type of 
 governor is used with vertical shaft Pelton wheels, the terminal 
 shaft of the governor being vertical and extended to the wheel 
 pit, where it .operates the controlling elements of the unit. It 
 will be noted that this governor is fully enclosed, the speed ele- 
 ment being mounted at the top. The hand wheel at the side is 
 for hand-control, should it be desired at any time to operate the 
 prime-mover in this manner. 
 
 Governors for very large units are illustrated in Fig. 15, 
 which shows what is termed a "direct-motion governor", com- 
 plete with its independent oil pump, oil-air-pressure storage tank, 
 and controlling mechanism. This governor has a capacity of 
 40,000 ft.-pounds, the speed element and controlling valves being 
 sensitive to a degree necessary to indicate speed changes of % 
 of 1%. Through the means of the duplex pilot valve and relay 
 valve construction, the governor can be adjusted to make a full 
 stroke in less than I 1 /-) seconds. On actual test, the governor 
 illustrated made a complete stroke in 1.2 seconds time. How- 
 ever, such rapid moving governors are not required except in 
 extraordinary cases. The principal feature of the design of this 
 
25 
 
 Fig. 13. Standard Type of Oil-pressure Operated Self-contained Governor. 
 
26 
 
 Fig. 14. Special Type of Governor Arranged with Vertical Terminal Shaft to be 
 Used in Conjunction with Vertical-shaft "Pelton" Units. 
 
27 
 
 Fig. 15. A New Type Direct-motion Oil-pressure Operated Governor of 40,000 ft.-lb. 
 Capacity, Complete with Independent Oil Pump and Oil-Storage Tank. 
 
28 
 
 governor is that the terminal shaft is connected directly to the 
 oscillating shaft operating the gate controlling elements, thus 
 avoiding lost motion due to linkage connections. To secure the 
 rapid action of this governor, large oil ports are required, neces- 
 sitating a very large relay valve. This is taken care of by the 
 duplex pilot valve and relay valve construction. 
 
 The most recent work, however, in governing apparatus is 
 the direct application of the piston of the servo-motor of the 
 *i '..viTiior to the end of the stem of the power needle. A small 
 governor of this type is illustrated in Fig. 1.6, this governor being 
 
 Fig. 16. Small size direct motion governor mounted directly on the nozzle body 
 and arranged for water operation. 
 
 designed to operate with water pressure, and for this reason a 
 strainer is provided. The same type of governor is also arranged 
 to operate from an independent, oil pressure source. Governors 
 of this kind give excellent regulation. 
 
 A modification of this type of governor is illustrated in Fig. 
 17, which shows a 24-inch Pelton wheel arranged for belt drive; 
 speed and power control of this unit are through the means of 
 the governor operating a jet deflector, the needle nozzle being 
 out rolled bv hand. A modification of this type of unit is illus- 
 
20 
 
 Fig. 17. A Standard "Pelton" 24-inch Water Motor arranged with Oil- 
 operated Direct-motion Governor. Speed and power output of wheel controlled 
 through means of jet deflector. Motor equipped with needle-regulating nozzle 
 hand control. 
 
 trated in Fig. 19, which shows a similar wheel direct connected 
 to a 15-kw. generator mounted on a continuous bed-plate. For 
 units of this small size, owing to the insignificant fly-wheel value 
 of the revolving elements, good regulation requires the mounting 
 of a fly-wheel on the shaft. 
 
 Kxcellent regulation is secured from these small units, as 
 will be noted from Fig. 18, showing a tachograph record of a 
 test mjide on the unit illustrated by Fig. 19. The four upper 
 charts represent the speed control of the governor when instantly 
 applying and rejecting full load on the unit, then three-quarter 
 load on the unit, and then one-half load on the unit. In con- 
 
30 
 
31 
 
 Fig. 19. "Pelton" Hydro-Electric Unit, 15 KW. Capacity. Arranged with 
 direct-motion pressure oil-operated governor operating on jet deflector with needle- 
 regulating nozzle hand controlled. This type of unit is particularly well suited for 
 small isolated plants. This unit operates under 257 ft. (78 m.) effective head, 
 developing 20 hp. at 1020 r.p.m. 
 
 ducting this test the load was secured by a water rheostat, the 
 load application and rejection being secured by opening and 
 closing the main switch, thus bringing about an instantaneous 
 change of load condition. 
 
 A further test on this unit for governing was carried out by 
 removing the fly-wheel, and the two lower charts show the effect 
 of this change. 
 
 MAIN SHAFTS. 
 
 In prime-movers of small and medium size, shafts forged 
 from 0.30 to 0.40 carbon open-hearth steel, properly annealed, are 
 thoroughly satisfactory for the purpose. For large prime- 
 movers, however, the shafts should be made from fluid-com- 
 pressed, chrome-nickel steel ingots, hollow forged and oil tem- 
 pered. Shafts of this type have now been in continuous service 
 for twelve years. They have proved to be absolutely satisfactory 
 and the bearing journals have taken on a high polish. AYith the 
 
32 
 
 single-overhung type units, it is preferable to provide the shaft 
 with a flange forged solid with the shaft, the wheel center being 
 bolted to this flange. This makes a thoroughly reliable construc- 
 tion and facilitates erection at the site of the power house. With 
 the double-overhung type, at least the wheel runner on one end 
 must be pressed on to the shaft, so as to allow the shaft to be 
 pressed into the hub of the rotor of the generator; otherwise a 
 very expensive shaft design must be provided, with an enlarge- 
 ment in the center at least as large as the flanges. This con- 
 struction is not usually justified. 
 
 MAIN BEAEINGS. 
 
 The very heavy weight of the revolving parts of modern 
 large hydro-electric prime-movers together with the high surface 
 speed of the shaft in its bearings have brought about a develop- 
 ment of a very massive high-speed bearing. Bearings of this 
 type are illustrated in Figs. 20 and 21. The main bearing shown 
 in Fig. 21 is constructed for a shaft diameter of 20 inches, with 
 
 Fig. 20. Heavy-pressure High-speed Bearings. Shows arrangement of lubri- 
 cating-oil rings, and the construction of the removable revolving shell. Also shows 
 arrangement of water-cooling tubes through oil storage in base of bearing. 
 
33 
 
 a length of bearing shell of 69 inches, the total weight of this 
 bearing as shown being 11,000 pounds. This is one of the bear- 
 ings of a 16,000 horsepower unit rotating at 200 revolutions per 
 minute. 
 
 The bearing surfaces are provided with oil by revolving oil 
 rings, the temperature of oil in the bearing base being controlled 
 by water-cooling tubes. In addition, provisions are made for 
 
 
 
 Fig. 21. Typical High-speed Heavy-pressure Bearings. This bearing was 
 constructed for a shaft diameter of 20 inches, with a length of bearing shell of 69 
 inches. Weight of bearing 11.000 pounds. 
 
 supplying fresh oil to the bearing through sight-feed lubricators 
 and drawing out the used oil through an overflow, so that from 
 time to time, while the plant is in operation, the oil in the bear- 
 ing can be withdrawn and replaced with fresh oil that has been 
 filtered. These bearings are arranged so that the bearing shells 
 CMII be rotated around the shaft and removed without lifting the 
 shaft from the bearings. They arc also provided with air seals 
 at the end of the bearing to prevent leakage of oil from the bear- 
 
a a. 
 
 i! 
 
 
 al 
 
 
 
35 
 
 ings. Hinged covers are provided with ample sized openings, so 
 that the operator can place his hand directly inside the bearings 
 and on the shaft, to check the temperature and condition of the 
 bearing surfaces. Thermometers are also installed in the bear- 
 ings to indicate the temperature of the film of oil between the 
 surface of the shaft and the surface of the bearing. 
 
 A further control of the temperature of the bearing is also 
 secured in large units by discharging a small spray of water 
 through the hollow shaft. This method keeps the shaft cool, is 
 thoroughly satisfactory and efficient, and should always be in- 
 stalled on the largest high-power units. The arrangement for 
 applying the water to the end of the shaft is illustrated in Fig. 
 12, where, at the end of the shaft opposite to the water wheel, the 
 spray nozzle is shown. Due to the partial vacuum existing in 
 the wheel housing, this fine spray of water is drawn through the 
 shaft, producing thereby a most efficient cooling medium. 
 
 These bearings have proved to be absolutely satisfactory 
 under the most severe conditions of heavy pressure and high 
 speed. The older form of so-called spherical self-aligning bear- 
 ings are not now used on the heaviest type of units. 
 
 WHEEL HOUSINGS. 
 
 The general type and construction of housing, or casing, in 
 which the wheel is to revolve is illustrated in Fig. 22. For best 
 practice each wheel should rotate in a separate housing to prevent 
 interference from discharged water. The lower part of these 
 housings is preferably made of iron castings, the upper housing, 
 or cover, being preferably made of steel plate riveted into a cast 
 iron frame. The joints in this plate work are riveted hot, chipped 
 and caulked, so as to be water-tight. This type of housing for 
 large units is preferable to a housing made entirely of cast iron, 
 as it is lighter to handle and eliminates any danger of breakage. 
 AVhore the shaft of the water wheel passes through the side of 
 the housing, leakage of water through the opening is prevented 
 by means of a centrifugal disc and water guard. This device 
 makes a frictionless packing. In small units it is preferable to 
 make the housing of cast iron. 
 
36 
 
 CONTEOL GATES. 
 
 A very important feature in all hydro prime-movers is the 
 main control gate or valve, the general type in use being of a 
 single-disc gate construction. In the earlier plants hand-operated 
 gates were deemed sufficient. A later development brought about 
 the use of gates operated by an hydraulic cylinder, as shown in 
 Fig. 35 of the Crane Valley No. 1 Power Plant. The latest de- 
 velopment in disc gate valves is where the gate disc is operated 
 by a reversible water wheel. A gate of this type is illustrated in 
 Fig. 23. This type of gate has proved more reliable and satis- 
 factory in service than the hydraulic- cylinder operated gate 
 valve, as grit and foreign substances in the water which have a 
 tendency to clog the valves and cylinders of hydraulic-cylinder 
 operated gate valves do not affect the operation of the reversible 
 water motor. 
 
 Furthermore, the reversible water motor has a very heavy 
 starting torque, which is of value in commencing the opening 
 stroke of a gate valve which may have remained shut for some 
 period of time, as in such cases there is a tendency for a gate 
 disc to stick to its seat. 
 
 In the reversible water-wheel operated gate valve, the main 
 gate stem is provided with a safety limit stop, so that in the open- 
 ing or closing movement of the gate it protects the gate against 
 stress which would be set up in the structure, due to over-opening 
 or over-closing the gate by careless operation. 
 
 For prime-movers operating under the highest heads and 
 where the units are of very large power output, the disc gate 
 valve is not the best form, owing to the enormous pressure 
 brought upon the seats of the gate ring and to the cutting action 
 on these seats due to eddy currents set up in the water passing 
 through the throat of the gate. 
 
 The ideal type of control gate for use with the largest size 
 units and under extremely high heads is the "uniform-flow 
 needle gate valve" illustrated in Fig. 24. In the control of 
 water under high heads, it has been demonstrated that the needle 
 type of valve is the proper design to adopt. The construction, as 
 shown in Fig. 24, consists primarily of a needle-regulating valve 
 
37 
 
 Fig. 23. Single-disc Type Gate Valves, Operated by Reversible Water Motors. 
 

 
38 
 
 controlled by an hydraulic cylinder, with a terminal slow-closing 
 safety element. This slow-closing safety element consists of an 
 extension of the piston rod which passes into a labyrinth in the 
 cylinder head. The closing of the valve is permitted to take place 
 by discharging the pressure fluid from this cylinder. As the 
 valve approaches the closing position, the extension stem enters 
 the labyrinth shown, and gradually restricts the escape of fluid 
 from the cylinder. This resistance effect is cumulative, so that 
 absolutely no shock or jar can be brought on the pipe line. 
 
 Fig. 24. Uniform-flow Needle Gate Valves Designed for the Largest Size Unitg 
 Under Extreme Conditions of Head. 
 
 From the design it will be observed that owing to the uni- 
 form flow through the valve, no eddy currents can form. The 
 seat is of such form that the water flows smoothly over, prevent- 
 ing the cutting out due to eddies forming in the disc type of gate 
 valve. This type of gate valve can also be inspected. This is 
 provided for by the telescopic section of the valve body which 
 can be drawn back into the pipe line, permitting inspection with- 
 
39 
 
 Fig. 25. "Ensign" Vortex Baffle Plate. 
 
 out disturbing any of the parts supported by the foundations. 
 By this method a complete inspection and replacement of all of 
 the working or wearing parts of the valve can be made. 
 
 It will be observed that a by-pass valve is arranged so that 
 under normal operating conditions the main valve would be 
 opened with an equilibrium of pressure on both sides of the 
 valve. However, it is designed and constructed so that in case 
 of emergency the valve can be safely opened with the full pres- 
 sure of water on one side. This type of valve incorporates in its 
 design and construction the elements that are essential for a safe 
 and satisfactory operating valve under the most extreme condi- 
 tions of high pressure and large power units. 
 
 BAFFLE PLATES. 
 
 With prime-movers operating under high heads, it is neces- 
 sary to provide some device to bring to rest the water discharged 
 from the deflecting nozzle when the jet is deflected from the 
 wheel, also to take care of the discharge of the auxiliary relief 
 nozzles where this discharge cannot take place through a free 
 
40 
 
 channel. This problem is an extremely difficult one, but has been 
 most satisfactorily solved by the ' ' Ensign Vortex ' ' type of baffle 
 plate, illustrated in Fig. 25. The action of this baffle plate is 
 similar to that of the Pelton bucket, excepting that the discharge 
 instead of leaving the sides of the bucket, is brought through an 
 angle of approximately 270 degrees, so that the water expends 
 its energy in discharging against itself. These baffle plates have 
 been tested out under heads of water of over 2000 ft. (600 m.) 
 and are absolutely successful in destroying the velocity in the 
 water without commotion, and show practically no signs of wear. 
 The original baffles of this type were installed in the Mill Creek 
 No. 3 Plant of the Southern California Edison Company, which 
 was started March 17, 1903, operating with 1900-ft. (580 m.) 
 head, the wheels developing 1600 horsepower. These baffles are 
 in service today and show practically no indication of wear. 
 
 TYPES OF DESIGN. 
 
 In general, the most favorable design of hydraulic prime- 
 mover, where the conditions of installation permit, is the single- 
 overhung horizontal-shaft type, the general arrangement being 
 
 Fig. 26. Characteristic Type of Exciter Unit Used on Large Plants. Operates 
 under 360 ft. (110 m.) effective head at 720 r.p.m., developing 44 hp. 
 
41 
 
 Fig. 27. Small-size Wheel with Direct-motion Governor Mounted on Nozzle Body 
 and Controlling the Needle Direct. 
 
 effected by a modification of the detail elements, such as regulat- 
 ing elements, etc., and their mode of operation. 
 
 Figure 26 illustrates an exciter unit, consisting of a Pelton 
 wheel driving a direct-current exciter and an induction motor, 
 the power output of the wheel being regulated by a hand-con- 
 trolled needle nozzle. In the operation of such a unit, sufficient 
 water is discharged against the wheel to carry somewhat more 
 that the excitation load on the generator. This causes the induc- 
 tion motor to act as a generator, discharging into the main bus 
 bars to which the induction motor is connected. This induction 
 motor acts as a speed control, in that it rotates practically in 
 synchronism with the main generators, but has the advantage of 
 sonic slip, so that speed variation on the main unit is modified 
 due to the slippage of the inductor generator and to the fly-wheel 
 value of the revolving elements of the exciter unit. 
 
 A further advantage of this type is that in case of interfer- 
 ence, such as clogging of the water-wheel nozzle, which would 
 otherwise bring the exciter to rest, immediately that the power 
 
42 
 
 developed by the water wheel begins to fall off, the induction 
 motor carries the exciter unit. This type of exciter is now being 
 installed in the largest hydro-electric stations and has proven 
 thoroughly satisfactory for the purpose. 
 
 A type of Pelton wheel arranged for exciter drive and pro- 
 vided with a direct-motion governor mounted directly on the 
 nozzle is illustrated in Fig. 27. This type of unit is also used 
 for small isolated plants. 
 
 An hydro-electric unit suitable for small plants is illustrated 
 in Fig. 28. This shows an ideal two-bearing single-overhung 
 unit, the revolving element of the generator being mounted be- 
 tween the bearings, the water wheel being mounted on one end 
 of the shaft overhanging one bearing, and the fly-wheel being 
 mounted on the opposite end of the shaft, overhanging the oppo- 
 site bearing. This unit contains a direct-motion governor, ope- 
 
 Fig. 28. Typical Single-overhung Horizontal-shaft Type Unit for Small Isolated 
 Plants, Plantation Work, etc., Speed control is by means of a direct-motion governor 
 o::e.-ating directly on the controlling needle. Operates under 90 ft. (27.5 m.) effective 
 head at 350 r.p.m., developing 18 hp. 
 
Fig. 29. Typical Hydro-electric Unit for Installation in Small Power Plants. 
 Arranged with needle-regulating nozzle hand control, with governor operating de- 
 flecting jet. Operates under 584 ft. (178 m.) effective head at 600 r.p.m., develop- 
 ing 300 hp. 
 
 rating the needle direct. In addition, there is an auxiliary hand- 
 control, should it be desired. Units of this type are particularly 
 well adapted to small isolated power plants, such as on planta- 
 tions and for small towns. 
 
 In installations where it is not desirable to vary the quantity 
 of water by the governor operating directly on the needle, the 
 jet-deflecting control is used. A medium-sized unit with this 
 type of control is illustrated in Fig. 29. With this unit the set- 
 ting of the needle is done by hand, the momentary speed control 
 being secured by the governor operating the jet deflector; units 
 of this type ranging in size from 100 horsepower to 1000 horse- 
 power are very satisfactory in service. 
 
 An hydro- electric unit of medium size and involving the 
 most advanced construction is illustrated in Fig. 30. In this 
 unit it will be noted that the speed governor is incorporated 
 within the nozzle construction, and the unit is further equipped 
 with the needle-control auxiliary relief type of nozzle. The unit 
 is arranged with two main bearings, the revolving element of the 
 
44 
 
 generator being placed between the bearings, the water wheel 
 being mounted on one end of the shaft and the fly-wheel on the 
 other. The entire unit is mounted on a combined heavy cast-iron 
 base, securing thereby a most rigid construction. This unit in- 
 volves all of the improvements of the highest grade large power 
 units. 
 
 In the medium and larger sized units, cast-iron base plates 
 are neither necessary nor desirable, owing to the very heavy first 
 cost and weight ; and furthermore, as in all large units, it is neces- 
 sary to depend upon the stability of the foundation construction. 
 In units of this type, the combined shaft which carries the water 
 wheel and the revolving elements of the generator and the bear- 
 ings are furnished by the builder of the water wheels. An ex- 
 ample of this type of construction is illustrated in Fig. 31. The 
 wheel runner is of the disc construction and is bolted against a 
 
 
 Fig. 30. Ideal Type of Small Horizontal-shaft Single-overhung Hydro-electric 
 Unit Arranged with Needle-regulating Auxiliary-relief Nozzle with Direct Governor 
 Control. Operates under 300 ft. (91.5 m.) effective head at 300 r.p.ra., developing 
 100 hp. 
 
flange forged solid with the water-wheel generator shaft. The 
 bearings are arranged to be mounted on substantial cast-iron 
 base plates, which are bedded directly into the concrete founda- 
 tions. This type of construction is preferable on all medium and 
 large sized units. 
 
 A single-overhung hydro-electric unit of the most modern 
 construction and of large power output is illustrated in Fig. 12. 
 This represents an hydraulic prime-mover now under construc- 
 
 
 Fig. 31. Single Overhung Horizontal-shaft Construction. Wheel operates under 
 1200 ft. (366 m.) effective head at 600 r.p.m., develojing 1400 hp. 
 
 lion, mid has embodied in it all of the most recent developments 
 mid improvements in the art. In this prime-mover a single jet 
 of water is applied to the buckets of a single wheel, the wheel 
 being mounted on the extreme end of the combined water-wheel 
 generator shaft and being of disc construction bolted directly 
 against the Hange forged solid with the hollow chrome-nickel 
 steel oil-tempered shaft. The wheel construction shown in this 
 drawing is of the double-lug type, for the reason that the head 
 of water under which it is to operate, namely, 1650 ft. (500 m.) 
 effective head with a turning speed of 300 revolutions per min- 
 
46 
 
 ute secures a favorable ratio between the diameter of the power 
 jet and the pitch diameter of the wheel, so that a thoroughly 
 stable construction could be secured with this type of bucket con- 
 struction. Were the power output of the wheel larger, it would 
 have required the chain-type or triple-lug construction. 
 
 It will be observed that the servo-motor controlling the 
 power output and speed of the unit is carried directly on the 
 power nozzle, the piston of the servo-motor being mounted di- 
 rectly on the extended stem of the power needle; the pendulum 
 head and speed sensitive element with the controlling elements 
 are mounted on the main nozzle body. This unit is arranged to 
 take pressure oil for operating the governor from an independent 
 oil-pressure pumping system. 
 
 In addition to the control by the speed sensitive element of 
 the governor, should it be necessary or desirable at any time to 
 control the power output and speed by hand-regulation, it will 
 be observed that a small valve with return mechanism is mounted 
 directly above the servo-motor of the governor. This valve is so 
 constructed with a hand lever that the control of the unit from 
 governor-control to hand-control can be instantly changed by a 
 single movement of the lever operating a four-way valve. On 
 the top of this four-way valve, the hand-control valve is mounted, 
 and is so constructed that by rotating the hand-control wheel, 
 through the means of the floating lever, a corresponding setting 
 of the needle is secured. In other words, if it is desired to carry 
 a half load on this generator, the hand control valve can be set 
 for half position. The power needle will automatically come to 
 this point, and will be maintained at this position until re-set, 
 through the means of the floating lever connections. 
 
 A further device installed in the governor of this unit is a 
 load-limiting device, so as to meet the conditions of operations of 
 the power plant, the maximum amount of load which the unit 
 can carry being thus limited. This is of particular importance 
 during seasons of water shortage when it is not desired to have 
 the j ) rime-mover take an excess quantity of water. The arrange- 
 ment of the auxiliary relief control is secured through the levers 
 as shown in the drawing. The water supplied to this unit is con- 
 trolled by a single- disc gate valve operated by a reversible water 
 
47 
 
 motor with needle nozzle control. The construction of the cen- 
 trifugal water disc and collar to prevent the escape of splash 
 water from the housing, is also illustrated. At the extreme end 
 of the shaft is located the spray nozzle for introducing cooling 
 water through the hollow shaft, this cooling water being drawn 
 through the shaft by the vacuum in the wheel housing and dis- 
 charged into the tail-race. 
 
 A further improvement incorporated in this unit, and which 
 has proven to be of great advantage in units located in hot coun- 
 tries, is the arrangement of the tail-race ventilator. This device 
 is so arranged as to take advantage of the partial vacuum that 
 exists in the wheel pit due to the action of the wheel as a blower 
 and the ejector action of the nozzle. Due to this device, the hot 
 air is drawn out of the generator pit and discharged through the 
 tail-race. This type of unit is ideal in every way, and is the 
 preferable one to use wherever the conditions permit of its instal- 
 lation. A number of units of this type of approximately 10,000 
 horsepower each have been installed, and have proven to be 
 thoroughly satisfactory under the severe conditions of regular 
 operation. The principal advantages of this type are the highest 
 possible efficiency, the simplest form of construction, with the 
 least number of working parts to take care of, while the manner 
 of carrying the shaft gives assurance against the bearings wear- 
 ing out of line and causing trouble. This type is particularly 
 favorable in the total overall cost of the installed equipment, as 
 it simplifies the pipe fittings and connections, reduces the cost of 
 foundation construction and requires only a single tail-race. 
 
 Where the single-overhung type can not be constructed with 
 the power output and speed desired with the available water 
 pressure, the double-overhung type is used ; this differs from the 
 single-overhung type in mounting a wheel on both overhanging 
 ends of the combined generator and water-wheel shaft. 
 
 The double-overhung type of unit is likewise arranged with 
 two bearings, the revolving element of the generator being 
 mounted between the bearings. A single shaft is used, the rotor 
 of the generator being located between the bearings, with a wheel 
 mounted on each end of the shaft overhanging the bearings. 
 Kaeh wheel is driven by a single jet of water. In the largest 
 
units it would consist of a design similar to that shown in Fig. 
 12, with a second wheel mounted on the opposite end of the shaft. 
 
 With the double-overhung type it is possible to make a 
 prime-mover of double the power output, maintaining the same 
 speed of rotation, w r ith the same conditions of water pressure. 
 Where the double-overhung type is used with automatic water- 
 economizing nozzles, it is preferable to mount a separate gov- 
 ernor on each nozzle, and in this way eliminate all long governor 
 rock-shafts and connections. The double-overhung type of prime- 
 mover has been installed in a large number of the most import-; 
 ant plants, with units ranging in capacity of from 12,000 to 
 20,000 horsepower. 
 
 In those installations where the head of water available is 
 low, as compared with the quantity of water, and where it is, 
 desired to maintain a comparatively high speed of rotation, mul- 
 tiple-jet horizontal-shaft type units have been constructed, and 
 such conditions are thoroughly satisfactory. In this type, 
 
 Fig. 32. Horizontal-type Single-overhung Double- jet Wheel with Auxiliary- 
 relief Nozzle, and "Ensign" Vortex Baffle Plate. This wheel operates under 490 ft. 
 (150 m.) effective head at a speed of 300 r.p.m., developing 1900 hp. 
 
49 
 
 usually two jets of water are applied to each wheel from the same 
 nozzle body, the jets being approximately 90 degrees apart. This 
 type has been successfully developed with a single-overhung hor- 
 izontal-shaft unit, with two jets on a single wheel, a unit of this 
 type being illustrated in Fig. 32. In this unit the power output 
 and speed regulation is controlled by the governor operating the 
 needles. An auxiliary relief nozzle is shown attached to one side, 
 discharging against an "Ensign" vortex baffle plate to take up 
 the energy in the jet from the relief nozzle. 
 
 Where a single-overhung double- jet unit will not give the 
 power at the desired speed under the conditions of water pres- 
 sure at the plant, a double-overhung horizontal-shaft type with 
 two jets on each wheel, making four jets in all on the unit, has 
 been developed. In this type the needles controlling the jets to 
 the two wheels are controlled from a central governor through a 
 rockshaft extending across the back of the unit. On each end of 
 this rockshaft a lever is mounted which operates the auxiliary 
 relief nozzle. For larger power units than that illustrated in 
 Fig. 32, a number of very successful units have been built, of 
 from 11,000 to 15,000 horsepower each, using two wheels on each 
 side of the generator, making four wheels per unit ; and each 
 wheel is driven by two jets, thus making eight jets in all. This 
 type is especially well adapted where the water is of such char- 
 acter as to be unsuitable for the pressure type of turbines. Fur- 
 thermore, owing to the high efficiency of the unit, and especially 
 due to the flat efficiency curve, it is much more favorable for 
 overall twenty-four-hour water economy than turbines. In units 
 of this type four bearings are used, the rotor of the generator 
 being mounted between the two main bearings, and at each end 
 of the unit an outboard bearing is provided, the two water wheels 
 being located on the shaft between one main bearing and one 
 outboard bearing. A unit of this type i& illustrated in Fig. 33 ; 
 and Fig. 34 is a 15,000 horsepower unit similar to the one illus- 
 trated in Fig. 33, which represents a unit of 10,500 horsepower. 
 
 General practice with Pelton hydraulic prime-movers has 
 been to use the horizontal type, as it usually represents the most 
 favorable first cost when taking into consideration the total cost 
 of the plant, including the foundations. It further has the ad- 
 
50 
 
 Pig. 34. One of Four 15,000-lip. Units, Horizontal-shaft Type with Four 
 Wheels and Two Jets to Each Wheel. Arranged with auxiliary-relief-control nozzles, 
 operating under 380 ft. (116 m.) effective head at 200 r.pjn. 
 
 vantage of simplicity of construction and arrangement of parts 
 available for inspection, lubrication and cleaning. Under cer- 
 tain conditions, however, vertical-shaft types of Pelton hydraulic 
 prime-movers have been installed with excellent results and favor- 
 able first cost. This type is especially suitable for comparatively 
 low head plants, where the water contains large quantities of 
 sand, grit or salt and where pressure-type turbines could not be 
 successfully operated. These vertical-shaft units are usually ar- 
 ranged with a wheel runner mounted on the lower end of the 
 vertical shaft, the entire weight of the generator and the wheel 
 runner being carried on a single thrust bearing, the shaft being 
 further provided with vertical guide bearings. With prime- 
 movers of this type, six jets can be installed on a single-wheel 
 
51 
 
 runner. Thus developing under a low head a comparatively 
 large power output from a single wheel, and at a favorable speed 
 of rotation. 
 
 A modern plant is illustrated in Fig. 35, this being an in- 
 terior of the Crane Valley No. 1 Plant of the San Joaquin Elec- 
 tric Light & Power Company. These units are 6000 horsepower 
 each, and operate under 1360 ft. (415 m.) head at 400 revolutions 
 per minute. Four units are installed in the plant. These units 
 
 Fig. 35. Interior of the Crane Valley No. 1 Plant of the San Joaquin Light 
 & Power Company, Containing Four 6000-hp. Units. Operates under 1360 ft. (415 
 m.) effective head at 400 r.p.m., developing 6100 hp. Power output and speed con- 
 trol being taken care of by needle-regulating auxiliary-relief-control nozzles. 
 
 are equipped with the auxiliary relief-control nozzles. It will be 
 observed that the gate valves are operated by hydraulic cylin- 
 ders. These units are of the two-bearing single-overhung type. 
 After this plant was completed a very careful efficiency test was 
 conducted by J. G. White & Company. Figure 36 shows thej 
 efficiencies secured on this test. This represents a characteristic 
 curve from a Pelton wheel. 
 
52 
 
 1 
 
 C/ 
 
53 
 
54 
 
 In conducting this test, as it was only possible to segregate 
 the actual electrical losses, and as there were no means for seg- 
 regating the windage and friction of the generator, these latter 
 losses are included in the efficiency curve. 
 
 The most recent plant is the Drum Power Plant of the Pa- 
 cific Gas and Electric Company, this being illustrated in Fig. 37. 
 In this plant are at present installed two hydro-electric units, 
 double- overhung type, of 20,000 horsepower output each, operat- 
 ing under 1330 ft. (445 m.) head at 360 revolutions per minute. 
 The wheels are of the chain-type construction illustrated in Fig. 
 4. This plant is equipped with needle-regulating deflecting noz- 
 zles, the regulating needles being equipped with remote electric- 
 motor control from the switchboard. 
 
 The reason for adopting the needle-regulating deflecting 
 nozzles in this plant was due to the fact that six power plants in 
 scries will be installed, taking water from the same source of 
 supply. As there were not available sites in the canyon through 
 which the water canal is carried to install regulating reservoirs, 
 it was necessary to arrange a system of control which would per- 
 mit of now of water to the lower plants without momentary 
 interruption. When this plant is completed, it will include four 
 20,000 horsepower units. 
 
 An illustration of the adaptation of the Pelton wheel to a 
 modern mining plant is illustrated in Fig. 38, which shows the 
 interior view of the power plant of the Granby Consolidated 
 Mining, Smelting & Power Company, Anyox, B. C. In this plant 
 Pel ton wheels are connected to a large piston blowing-engine, a 
 larv piston air-compressor, to three rotary air-blowers of the 
 Connersville type, and also to the electric generators and excit- 
 ers for the electrolytic process. 
 
 It has been the intent of this paper to submit briefly to the 
 interested engineer the principal types of prime-movers that 
 have been developed, with their methods of regulation, and only 
 those types have been described and illustrated which have 
 proven thoroughly reliable and satisfactory under the severe con- 
 ditions of regular service operation. The art is one that is con- 
 stantly developing. The limitations as to power output and 
 speed have not as yet been reached and are only limited by the 
 
55 
 
 Fig. 38. Interior of a Modern Mining Plant, the Granby Consolidated Mining. 
 Smelting & Power Company, Anyox, B. C. 
 
 The plant consists of three water wheels connected to rotary air blowers of the 
 Connersville type, each wheel developing 775 hp. under 374 ft. (114 m.) effective 
 head, at 115 r.p.m. 
 
 Two water-wheel generator units, each wheel developing 1400 hp. under 370 
 ft. (113 m.) effective head at 400 r.p.m. 
 
 One water wheel for motor-generator set, developing 75 hp. under 370 ft. 
 (113 m.) effective head, at 900 r.p.m. 
 
 One water wheel for Connersville blowing engine, developing 1400 hp. under 
 374 ft. (114 m.) effective head at 75 r.p.m. 
 
 One water wheel for Nordberg air compressor, wheel developing 800 hp. under 
 374 ft. (114 m.) effective head at 84 r.p.m. 
 
 necessities of the particular installation. As to the limits of ca- 
 pacity, they are restricted only by the profitable demand for the 
 power and by the quantity and head of water available ; the only 
 practical limitations as to the head or pressure under which a 
 power plant can be constructed, is the cost of the pressure pipe 
 line. 
 
 Plans have been developed which demonstrate that an 
 hydraulic prime-mover, thoroughly satisfactory from the stand- 
 point of first cost, upkeep and reliable operation, can be con- 
 structed for heads in excess of 6000 ft. in a single drop, and in 
 
56 
 
 units as large as 30,000 horsepower each, the limitations being 
 the question of the cost and the difficulties of securing a satis- 
 factory pressure pipe line, an available source of water supply 
 which can be developed at a reasonable cost, and a satisfactory 
 market for the power generated. Other than this, the results to 
 bo secured from units of this capacity and operating under these 
 conditions would be absolutely satisfactory in regular operating 
 service. It is not predicted that this represents the limit of ca- 
 pacity or head. It would indicate, however, the approach to a 
 limit, as representing possibly the maximum conditions of a reli- 
 able water supply that can be secured within a reasonable cost of 
 development and within a reasonable distance of a profitable 
 market. 
 
 The several illustrations which have been introduced in this 
 paper have been selected from regular shop photographic record 
 prints as being the best means of illustrating the general develop- 
 ment of the art and improvements in the details of construction 
 and in the systems of regulation, and from this standpoint will 
 be of interest to engineers. 
 
 The efficiency to be secured from an Impulse Prime-Mover 
 is affected by the type of the unit, the head or pressure that it is 
 to operate under, and the speed of rotation ; these factors deter- 
 mining the ratio of the jet and the pitch diameter of the wheel. 
 
 A characteristic efficiency curve, showing the results from a 
 medium sized prime-mover under actual operating conditions, is 
 shown in the efficiency curve of the Crane Valley No. 1 Power 
 Plant, Fig. 36. 
 
 Under exceptionally favorable conditions the efficiency of a 
 Pelton hydraulic prime-mover will range between 83% and 86%, 
 depending upon the special limitations of the installation. It is 
 anticipated that these extremely favorable efficiencies will be 
 somewhat improved, and with heads in excess of 3000 ft. with 
 large sized power units, it is reasonable to predict an efficiency 
 of approximately 90%. 
 
 In considering these questions of efficiency, it must be appre-. 
 ciated that they are based upon the prime-movers installed in. 
 actual operating plants and on the basis of regular commercial 
 service, and represent the total overall efficiency of the prime- 
 mover. 
 
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