GIFT OF Arthur E, Moncaster DRY STEAM THE TRACY STEAM PURIFIER. FOR INSURING DRY AND CLEAN STEAM BEFORE IT LEAVES THE BOILER Patented in the United States Foreign Patents Pending Catalogue No. 10 MANUFACTURED BY THE TRACY ENGINEERING CO. SAN FRANCISCO CALIFORNIA T7 THE TRACY ENGINEERING COMPANY ev Copyrighted 1915 by The Tracy Engineering Co. San Francisco, Cal. Printed by Taylor, Nash & Taylor, San Francisco SAN FRANCISCO, CALIFORNIA INTRODUCTION THERE has never been a time in the history of hu- man eff ort so fraught with rapid evolution and im- provement as has been experienced in the whole range of industrial life in the last few decades. Steam engineering has made great strides in the advent of new and improved forms of prime movers, and has kept well abreast with the advance of the age by notable achievements, with, however, one notable exception. As old as is the art of making steam, and as long as the so-called "dry pipe" for preventing moisture from leaving the boiler with the steam has been used, no substantial im- provement has been made. Owing, however, to the now recognized deficiency of this device, much effort has been directed toward an im- provement, with a result that various substitutes have been brought out from time to time; but from a careful study of the problem, covering a wide range of investigation and experience, we feel warranted in saying that the question of efficient separation had never been solved before the scientific principles embodied in the Tracy Steam Purifier were introduced. The results obtained from the many that are now in daily use have made what may be justly called a new era 726300 THE TRACY ENGINEERING COMPANY in the science of separation, so that the "commercially" dry steam having one, two or three per cent of moisture is no longer a standard, as we are now prepared, by making the Purifier to fit each particular case, as outlined by the purchaser, to actually take out all of the water, together with the added advantage of eliminating all foreign matter that may be entrained or carried over by the steam. The purpose here is to bring the results of our research to the attention of owners of boilers who are desirous of overcoming the difficulties incident to wet steam, and to that end we courteously invite a review of the following pages, which are devoted to a description of how it is done. THE TRACY ENGINEERING CO. San Francisco, February 20, 1915. SAN FRANCISCO, CALIFORNIA CAUSES OF WET STEAM FROM BOILERS INVESTIGATION has shown that there are two entirely differ- ent and distinct conditions under which wet steam leaves a boiler. The most common and best understood one may be des- ignated as "priming," and is present in some degree in any boiler and with any kind of feed water, while the other and less prevalent form is called "foaming." Priming is simply the atomization of water, due to steam emerg- ing from the surface of the water at high velocity. If the particles of water are heavy enough, they drop back to the water level, but the finer spray is carried along with the steam, in proportion to the velocity of the steam in the drum, while on its way to the outlet nozzle of the boiler. It is therefore apparent that restricted liber- ating surface and small steam space contribute to the degree of moisture due to priming. Foaming is an entirely different phenomenon and is caused by impurities in the water, as pure water can not foam. Under some conditions the foaming may be so violent that a mass of bubbles fills the entire steam space of the boiler. During such periods the steam leaves the boiler, not as homo- geneous steam, but in globules of varying size, surrounded by an envelope of water, the total amount of which has given rise to the term "slugs of water," and accounts for the enormous amount of water which leaves the boiler at such times. The degree of foaming depends upon the condition of the water and the rate of firing. At times the entire steam space may be filled with these bubbles, even though elevated steam drums may be used, and this explains why the addition of drums has been found of so little help. At other times the "foam," or bubbles, may exist only as a layer, or "blanket," on the surface of the water, varying in depth according to conditions, but even under such circumstances the THE TRACY ENGINEERING COMPANY steam space is reduced and the steam velocity correspondingly in- creased, so that bubbles are easily entrained by the steam emerging from the water level, at high velocity, on its way to the boiler nozzle. Such mineral matter as may be in suspension is carried over with the water, whether the latter is in the form of spray or envel- opes (of the bubbles) ; foreign matter also exists in the form of " scum," which is light enough to float on the water, or even on the foam. This material, when it reaches the engine, mixes with and absorbs the lubricating oil, and not only reduces the lubrication, but is gritty enough to induce cutting of valves, cylinders, rods and packing, clogs the piston rings of engines, or fouls the blades and reduces the efficiency of turbines. SEPARATION Moisture Due to Priming As previously stated, the moisture in this case exists in more or less finely divided particles of water, light enough to be carried along by the current of steam on its way to the boiler nozzle. Since the density of water is so much greater than that of steam, it has given rise to about all the various forms of separators heretofore on the market, and they depend solely upon the momentum of the water particles for separation. In order to better understand the philosophy of separation, it is well to consider some of the principles involved, and as separators intended for steam pipe lines are the ones most generally known, a diagrammatical form is shown in Figure i, wherein the flow of steam is from left to right. Of this general type there is a very great variety, yet all involv- ing the same principle, whether rotary, direct impact, horizontal or vertical. In nearly all cases there is but ONE path for the entire volume of steam, although some are divided into two paths or ports. SAN FRANCISCO, CALIFORNIA Fig. 1 Regardless of the form of the device, there are four factors in- volved in separation, viz.: Size of water particles. Velocity of steam. Distance the particles of water have to travel ACROSS the current of steam. Immurement of the assembled particles or DROPS of water from the path of steam. All these factors are interdependent. It is obvious the larger the particles of water the more momentum they will have and will force themselves a greater distance through the body of moving steam. Other particles that are too light or are too near the INNER periph- ery pass on with the steam and fail to be eliminated. Again, the higher the velocity of steam, the greater the number and size of particles that will be swept along without separation. With these fundamental physical laws in mind, attention is direc- ted to the manner in which the problem of separation is met by the Tracy Steam Purifier. THE TRACY ENGINEERING COMPANY Figure 2 shows a horizontal cross-section of vertical GUTTER baffles. The steam enters the spaces between the gutters in the front row, thus dividing the steam into thin vertical streams. These streams, or "ribbons," flow directly toward the open side of the gutters in the second row, where each ribbon is divided into two Fig. 2 thinner streams which make a right-angled turn in passing through the narrow vertical ports constituting the space between the two rows of gutters. After passing these ports the steam passes on through the remaining series of gutters, in order to reach the cen- tral conduit leading to the boiler outlet. Instead of there being only ONE or TWO passages through the separator large enough to accommodate the ENTIRE flow of steam, it is here divided into HUNDREDS of THIN streams, so small that a particle of water has but a minute distance to travel to get out of the path of the steam into the PROTECTION of the gutters, where there is NO current. 10 SAN FRANCISCO, CALIFORNIA Here, also, not only is the steam divided into many thin streams, to reduce the distance the water has to travel to get out of the cur- rent, but instead of only ONE turn, wherein centrifugal force may act, there is turn after turn in the reverse direction, through a whole SERIES of gutters. The aggregate area of the ports is several times that of the boiler nozzle, and the resulting low velocity, together with the thin streams, progressive separation and extremely great superficial surface in the gutters, makes it IMPOSSIBLE for even the finest particles of water to escape. Moisture Due to Foaming The preceding analysis dealt with particles of water surrounded by steam, whereas the following analysis deals with globules of STEAM surrounded by WATER. What a vast difference this makes in the matter of separation only those who have systematically attempted to handle the latter may know. Most of the standard makes of separators will do very good work in the first instance, but extensive investigation leads to the conviction that not one can by any possibility handle the second case. As a matter of fact, separation is most needed at times of foam- ing, for it is at such periods that the greatest danger and trouble occur. As before stated, foaming is simply the result of impurities in water under violent agitation, and is represented by a mass of minute globules of steam, each surrounded by a coating of water. This mass rests on the surface of the water in the boiler and forms a blanket, so to speak, over the whole area, and the steam, as it emerges from the water on its way to the outlet nozzle, has to pass through this comparatively "feathery" mass, with the result that some of the globules, or bubbles, with their coatings are carried along with the steam. 11 THE TRACY ENGINEERING COMPANY The percentage of moisture in the steam leaving the boiler may be comparatively small if the foam is of no appreciable depth, but will increase as the depth increases, till the most aggravated state arrives when the entire steam space is filled with foam. Nothing is more manifest than the impossibility of efficient separation in the standard devices when the entire device is filled with a HOMOGENEOUS mass of these globules there being no chance for centrifugal force to act or differential momentum to take place. It is evident, therefore, that before any separation can be effected the bubbles must first beROKEN and the moisture form- ing their "skins "be reduced to a state of SOLID WATER. In this state, and this only, can the moisture be eliminated, and the design herein described accomplishes this end. GENERAL ARRANGEMENT To show how the gutters are arranged with reference to the conduit, the latter being the passageway for the steam after it leaves the gutters, reference is made to Figure 3. This cut shows a vertical transverse section through the Puri- fier and illustrates the vertical gutters as they appear in the cast- iron housing. Steam enters at each side (right and left side of cut) and passes through the banks of baffles to the central conduit. The separated water gravitates down the inside of the gutters to the floor of the Purifier housing, from which it falls back to the water level in the boiler, while the dry steam passes out through the conduit which is in direct communication with the boiler nozzle as shown in Figure 4. GUTTERS SELF-CLEANING ' The gutters do not clog, even with water in the boiler carrying several hundred grains of solid matter per gallon. The best evidence of this is a plant, where the water is extremely bad, that has been using Purifiers for two years and the gutters remain perfectly clean. 12 SAN FRANCISCO, CALIFORNIA Fig. 3 The reason for this is that there can be no scale deposit, such as occurs on boiler-heating surfaces, owing to the absence of temper- atures that would evaporate the moisture ; while any solid matter in suspension, or even any scum that reaches the baffles, is washed off by the water itself, there being enough at all times for this purpose. INSTALLATION The Purifiers are made to pass through a 10x15 manhole and in lengths which can be easily handled in the restricted spaces pre- vailing inside the boiler. A cast-iron nozzle tee, or elbow, is pro- vided for attachment to the main steam outlet of the boiler, and the 13 THE TRACY ENGINEERING COMPANY Purifier elements are bolted to the tee, the outer element of the Purifier, when necessary, being supported by a bracket. Fig. 4 PURIFIERS NEED NO ATTENTION After the Purifiers are installed no care or attention whatever is required, as the water drains directly to the boiler automatically without the use of return traps or pumps, and incidentally without loss of heat. PURIFIERS IN CONJUNCTION WITH SUPERHEATERS Reference to the figures in the following table shows that a superheater capable of giving 150 F. of superheat when supplied with dry steam at 200 pounds gauge pressure will have its super- heat reduced about 14 F. for each per cent of moisture in the enter- ing steam, and if the latter carried 3 per cent of moisture, which is within the limit of what is called "commercially dry," the super- heat would be only 108 F., and would be entirely eliminated if the moisture reached 7 per cent. This reduction in superheat would cause an increase in the steam consumption of turbines and engines of approximately i per cent for each 10 reduction in superheat. 14 SAN FRANCISCO, CALIFORNIA evaporae mo yutYalent to Me S/7o/ B.t.u. req ou> the Superh Uf)[)er f/yure Lover fiqures 10 cS [V 10 90> ^v^ *t K) ^ ty * fc <0 <0* 0} S 8 K K +>* K^ K e cvjt