  A boiler is not complete without certain fixtures. There must be a feed-pump or injector, with a supply-pipe, feed-valve, safety feed-valve, and check-valve, in order to supply water properly to the boiler; gauge-cocks, a glass water-gauge, a blow-pipe, with its valve, to reduce the height of the water in the boiler, or to empty it entirely; a safety-valve to allow the steam to escape from the boiler when it exceeds a fixed pressure; a scumming apparatus to remove the foreign matters from the water as much as possible; a steam-pipe to convey the steam to the place where it is wanted; man-holes and hand-holes, with their covers and guards, for examination and cleaning; a non-corrosive steam-gauge, to accurately indicate at all times the amount of pressure in the boiler; and a fusible plug to give warning in case of “low water.” Thus we see that in speaking of a boiler, not only the boiler proper is meant, but also the whole of its fixtures and belongings, of which the following is only a partial list:
All these are attachments to the boiler proper, having direct reference to its internal functions; but in addition there are the lugs, pedestals, or brackets which support the boiler; the masonry in which it is set, with its binders, rods, and wall-plates; the boiler front, with its doors, anchor-bolts, etc.; the arch-plates, bearer-bars, grate-bars, and dampers, and last, but not least, the chimney. These are all equally necessary to enable the boiler to perform its duty properly. And besides, there are required fire-tools, flue brushes and scrapers, and scaling tools, with hose also, to wash out the boiler, to say nothing of hammers, chisels, wrenches, etc. The fittings and attachments of the marine boiler are similar to those belonging to the land steam generators, and vary only in accommodating themselves to their peculiar surroundings. The proper operation of the boiler as to efficiency and economy is largely dependent upon the number, appropriate proportion and harmony of action of its numerous attachments, and the utmost care and skill are requisite for designing and attaching them. It must not be supposed that a complete list and description of all steam boiler attachments are here presented—that were a task beyond the limits of the entire volume. BOILER FRONTS.Boiler fronts are made in many different styles, almost every maker having some peculiar points in design that he uses on his own boilers and which nobody else uses. In the illustrations here given may be seen the four principal designs: 1. The flush front is shown in Fig. 72. 2. The overhanging front as seen in Fig. 73. 3. The cutaway front, Fig. 74. 4. Fronts with breaching as shown in Fig. 75. The flush front is one of the earliest forms of fronts, and though it often gives good satisfaction, yet it is liable to certain accidents. Front for Water Tube Boiler.—Fig. 71. Flush Front.—Fig. 72. As will be seen from cut 72, the front of the smoke arch, in this form of setting, is flush with the front of the brickwork, and the dry sheet just outside of the front head is built into the brickwork. The heat from the fire, striking through the brickwork, impinges on this sheet, which is unprotected by water on the inside. So long as the furnace walls are in proper condition the heat thus transmitted should not be sufficient to give trouble; but after running some time bricks are very apt to fall away from over the fire door, and thus expose portions of the dry sheet to the direct action of the fire, causing it to be burned or otherwise injured by the heat, and perhaps starting a leakage around the front row of rivets when the head is attached to the shell. In the overhanging front this tendency is entirely prevented by setting the boiler in such a manner that the dry sheet projects out into the boiler room. If the brickwork over the fire door falls away when a boiler is set in this manner, Overhanging Front.—Fig. 73. The objection is sometimes raised against the projecting front, that it is in the way of the fireman. To meet this point and yet preserve all the advantages of this kind of front, the cutaway style has come into use. In this form the lower portion or the front sheet is cut obliquely away, so that at the lowest point the boiler projects but little beyond the brickwork. Cutaway Front—Fig. 74. It will be noticed that in the flush and overhanging fronts, the doors open sidewise, swing about on vertical hinges; in the cutaway front the best way to arrange the tube door is to run a hinge along the top of it, horizontally, and to have the door open upward. But with such a disposition of things the door is not easy to handle. For the purpose of support a hook and chain, hanging from the roof should be provided. Front for Manhole.—Fig. 75. Fig. 75 shows a boiler the setting of which is similar in general design to the other three, except that in the place of a cast-iron front it has bolted to it a sheet iron breeching that comes down over the tubes and receives the gases of combustion from them. In Fig. 75 a manhole is shown under the tubes. This, of course, is not an essential feature of the breeching, but it will be seen that manholes can readily be put below the tubes on fronts of this kind, in such a manner as to be very convenient of access. In addition to these more general styles of boiler fronts, there are fronts designed particularly for patent boilers, water-front boilers, etc., which are made, very often, in ornamental and attractive designs. In Fig. 71 is shown a beautiful and appropriate design in use in connection with water tubular boilers. FURNACE DOORS.The chief points to be considered in the design of furnace doors are to prevent the radiation of heat through them, and to provide for the admission of air above the burning fuel in order to aid in the consumption of smoke and unburnt gases. In all cases where the doors are exposed to very rough usage—such, for instance, as in locomotive and marine boilers—the means for admitting air must be of the simplest, and consist generally of small perforations as shown in Fig. 76 which represents Fig. 76. Doors similar to the above provide for the constant addition of limited quantities of fresh air above the fuel, but in actual practice, however, air is only needed above the fire for a few minutes after fresh fuel has been thrown on the grates and then is required in considerable quantities. In the case of land boilers, the furnace doors of which undergo comparatively mild treatment, it is possible to introduce the necessary complications to effect this object. Fig. 77. Fig. 77 shows an arrangement largely in use in New England, in which, by means of a diaphragm, the air is passed back and forth across the heated inner or baffle plate with the very best results. The air is first drawn by the natural draught into the hollow space between the iron door and its lining, through a row of holes A, in the lower part of the door, controlled however, by a slide not shown in the cut, then caused to flow back and forth across the width of the door by simply arranged diaphragms, and finally injected into the furnace through a series of minute apertures drilled in the upper part of the door liner, as indicated in cut at B. It will be seen that while the air may enter the door at a low temperature, it constantly becomes heated during its circulation until the instant it enters the furnace, it is ready to flash into flame with intense heat upon its incorporation with the expanding gases of the furnace. An arrangement in common use in Cornish and Lancashire boilers consists of a number of radial slits in the outer door which can be closed or opened at will in the same manner as an ordinary window ventilator. Other and more complicated arrangements have been frequently devised, which work admirably so long as they remain in order, but the frequent banging to which furnace doors are subjected, even in factory boilers, soon deranges delicate mechanism. Furnace doors should be made as small as possible considering the proper distribution of fuel over the grate area, as otherwise the great rush of cold air, when the door is opened rapidly, cools down the flues and does considerable injury to tube plates, etc.; for this reason it is desirable, when grates are over forty inches in width to have two doors to each furnace, which can be fired alternately. The great loss arising from a rush of cold air on opening the furnace doors for replenishing the fires with fuel has led to costly experiments to produce “a mechanical stoker,” or self boiler feeding arrangement for supplying the coal as needed. FUSIBLE PLUGS.In some States the insertion of fusible plugs at the highest fire line in boilers is compelled by law under a heavy penalty. Its design is to give the most emphatic warning of low water, and at the same time relieve the boiler of dangerous pressure. Fig. 78. Fig. 79. Figs. 78 and 79 exhibit two of the forms most commonly used, and on the succeeding page, in cut 80, is shown the device in operation where the water has sunk to a dangerously low level. In the illustration the device is shown in connection with a locomotive boiler, in the common tubular boiler the plug is usually inserted in the rear head of the boiler, so that in case of its operation it will not endanger the fireman. These devices are designed to be screwed into the boiler shell at the safety line. The Figs. 78 & 79 exhibit their construction. The part to be screwed into the boiler is called the shell and is commonly made of brass; the internal part is plug and is made of a soft metal like banca tin or a compound consisting of lead, tin and bismuth. This composition melts easily at the proper point to allow escape, where the water has sunk to a dangerously low level. There is considerable diversity in the make up of the material used for filling the plug, which must not have its melting point at anything less than the temperature of the steam lest it should “go off” at the wrong time. FUSIBLE SAFETY PLUG If the accident of low water occurs at a time where it is important to continue operations with the least possible delay, a pine plug may be driven in the opening left by the melting of the fusible metal. In any event it is but a short job to renew the fusible cap, it being only necessary to unscrew the nut and insert a new cap, the rest of the device remaining intact. The plug should be renewed occasionally and the surface exposed inside the boiler be kept free from scale and deposit. It is to be understood that the fusible portion extends entirely through the shell of the boiler and when melted out makes a vent for the water or steam. All marine boilers in service in the United States are required to have fusible plugs, one-half inch in diameter, made of pure tin, and nearly all first-class boiler makers put them in each boiler they build. GRATE BARS.Fig. 81. The Grate Bars are a very important part of the furnace appliances. These consist of a number of cast iron bars supported on iron bearers placed at and across the front and back of the furnace. Innumerable forms of grate bars have been contrived to meet the cases of special kinds of fuel. The type in common use is represented in Fig. 82. Fig. 82. These cuts show a side view and a section of a single bar, and a plan of three bars in position. Each bar is in fact a small girder, the top surface of which is wider than the bottom. On each bar are cast lugs, the width of which determines the size of the opening for the passage of air. This opening varies in width according to the character of the fuel; for anthracite 3/4 inch is a maximum, while the soft coals 5/8 to 3/4 inch is often used; for pea and nut coal still smaller openings than either of those are used, i.e. 1/4 and 3/8 inches. For wood the opening should be a full inch in width. For long furnaces the bars are usually made into two lengths, with a bearer in the middle of the grate, as shown in Fig. 83. As a rule long grates are set with a considerable slope towards Fig. 83. Fig. 84. Rocking and shaking grates are now very extensively used; these combine a dumping arrangement, and very largely lessen the great labor of the fireman, and by allowing the use of slack and other cheap forms of fuel are very economical. Several patents are issued upon this form of grate bars all working on essentially the same principle. Fig. 84 exhibits an efficient form of a shaking grate. As shown in the cut, the grates are arranged to dump the ashes and clinkers. By the reverse motion the flat surface of the grates are restored. Trouble with grate bars comes from warping or twisting caused by excessive heat, and burning out, produced by the same cause—this explains the peculiar shape in which grates are made—very narrow and very deep. A free introduction Grate bars are usually placed so as to incline towards the rear, the inclination being from one to two inches; this facilitates somewhat the throwing of the coal into the furnace. The proportion between grate and heating surface should be determined by the kind of fuel to be used. The greatest economy will be attained when the grate is of a size to cause the fire to be forced, and have the gases enter the chimney only a few degrees hotter than the water in the boiler. If the grate is too large to admit of forcing the fire, the combustion is naturally slower, and consequently the temperature in the furnace is lower, and the loss from the escaping gases is greater. It must be borne in mind that the only heat which can be utilized is that due to the difference in temperature between the fire and the water in the boiler. For example, if the temperature in the furnace be 975°, and the water in the boiler have a temperature due to 80 pounds of steam, viz.: 325°, it is evident that the heat which can be utilized is the difference between them, or 2/3 of the total heat. Now if the fire be forced, and the furnace temperature raised to 2600°, 7/8 of the total heat can be utilized; so it can be readily seen that the grate should be of such a size as to have the fire burn rapidly. The actual ratio of grate to heating surface should not in any case be less than 1 to 40, and may with advantage, in many cases, be 1 to 50. This proportion will admit of very sharp fires, and still insure the greater portion of the heat being transmitted to the water in the boiler. The water grate bars, invented in 1824, and since frequently applied to locomotives and marine boilers, do not seem to grow in popular favor, and are scarcely known in stationary boilers. The objections urged against them are the expense of maintenance, their fittings and attachments, and the possibility of serious consequences should they rupture or burn out. WATER GAUGE COCKS.It is of the first importance that those in charge of a boiler shall know with certainty the position of the water level within the boiler. Fig. 85. These attachments, also called Try cocks, are usually placed in a conspicuous and accessible position on the front of boilers. They are so arranged that one will blow only steam, one at the working level of the water, and the third at the lowest water level or say three inches above the highest point of the fire line of the boiler. The cut, Fig. 85, exhibits them as commonly arranged. It is not essentially requisite, that the cocks themselves should be placed at the point indicated, so long as they have pipes projecting internally into the boiler, with their ends corresponding to the height of water above mentioned. In order that these cocks may readily be cleaned out, a plug is usually fitted into bit of cock opposite the port or opening of the plug, upon removing which a pricker can be readily inserted. The gauge or cocks should be tested many times each day, and when opened the top one should always give steam and the bottom one water. They should be allowed to remain open long enough to make sure whether steam or water is issuing from the cock. This is a matter of instruction, but the beginner with a little experience can detect the difference by the sound. In so universal an appliance as this there are very many forms and arrangements, but they all work upon the same principle as stated above. GLASS GAUGES.These are the second and auxiliary arrangements for ascertaining the water line. Nearly all boilers are supplied with both try cocks and glass gauges, and so important is it considered to be correctly informed as to the water line that a third method consisting of a float which is carried on the water surface, is sometimes added to the two named. Fig. 86. The glass water gauge column consists of an upright casting bolted to the front of the boiler, in which are fixed two cocks having stuffing boxes for receiving the gauge glass. The lower of these cocks is also fitted with a drain cock for blowing out the glass. The try cocks are frequently placed on the above-mentioned standard or column. The action of the gauge glass is to show the level of the water in the boiler by natural gravitation and the best position for it is in view of the engine room, as close to the boiler as possible and preferably in the middle line of its diameter, at such height that its lowest portion is about two inches above the highest part of the fire line of the boiler, and its centre, nine inches above that, making the total visible portion of glass eighteen inches long. Glass water gauges sometimes have pipe connections top and bottom. The object of this arrangement is to have an undisturbed water level in the glass by carrying one pipe to the steam dome and the other near to the bottom of the boiler; the one position not being so liable to be affected by foaming and the other by the boiling of the water. Cocks should always be fitted to the boiler ends of these pipes, in order that The glasses are liable to burst and become choked up with dirt. The former defect is easily repaired by shutting off the cocks in connection with the boiler and putting in a new glass. The mud or sediment is cleaned out by opening the above-mentioned drain or blow-out cock and allowing the steam or water, or both, to rush through the glass, which will effectually blow out all sediment and leave the glass in good condition again to show the height of the water in the boiler. In opening the cocks connected with the glasses, it should be done cautiously, as the glass is liable to burst. A strip of white running the whole length of the glass on the side toward the boiler is a great help in observing the variations of the water line in the tube. It is not needed to remove the gauge glasses to clean them. There are good fixtures in the market that by taking out the plug in the top, the glass may be cleaned with a bit of wicking on the end of a stick. A slight scratch will break the glass, hence do not use wire. Use soft rubber gaskets when setting the glass, screw up until all leaking stops. Don’t let the glass come in contact with the metal anywhere. Don’t try to reset the glass with an old hard gasket. Two glasses from the same bundle will not act alike. The glasses used to show the water line are made of a soft glass known as “lead glass,” and are easily cut, or broken square across. Most of them can be broken by filing a notch at the point at which it is necessary to break them. After filing the notch, place the thumbs as if you would break the glass; it will crack easily, and the fracture be straight and clean. If the tube be brittle, as some are, to avoid cutting the hands wrap two pieces of paper around the glass, each side of the notch. If the ends are rough or uneven, they can be made smooth by filing or by the grindstone. The Manchester, Eng., Boiler Association attribute more accidents to inattention to water gauges than to all other causes THE MUD DRUM.The mud drum is attached to a boiler with the expectation that it will catch and hold the larger portion of the sediment precipitated from the water. The mud drum to be effective should be protected from the heat of the fire, for so soon as it receives sufficient heat to boil the water within it can no longer serve the purpose for which it was intended as all the sediment which may have gathered would be expelled by the ebullition of the water. When the drum is located under the boiler it is not in a good position to catch the sediment, as the boiling water produces sufficient current to carry the sediment to the top, or keep it violently agitated, so that there is little opportunity for it to be deposited anywhere so long as the boiler is making steam. Afterward when the water is quiet the sediment for the most part is deposited on the tubes and the curve of the shell; the small portion falling into the neck of the drum serves principally to show the inefficiency of the device. Located under the boiler as it generally is, makes it extremely difficult to get at for examination, and as a consequence of its being enclosed, as it must be, to be of much importance, it is subject to greater deterioration than would otherwise be the case, and as the enclosure to be most efficient would enclose the neck also, the BAFFLE PLATES.These are a device sometimes used inside steam boilers to check the too sudden flow of steam towards the exit pipe, they are simply plate to baffle the rush of the steam so as to avoid foaming. In Fig. 90 baffle plate is illustrated by the division casting against which the steam strikes on its passage from the boiler to the engine. The liners or inner plates of the boiler doors are baffle plates. DEAD PLATE.This is a flat plate of iron immediately inside the furnace door and is used in many boilers in order to insure the more perfect combustion of the coal. When the fresh fuel is laid on, it is placed on the dead plate instead of on the grate; in this position the coal is coked, the gases from the coal being ignited as they pass over the already intensely hot fuel in the furnace, the fuel from the dead plate is pushed forward to make place for another charge to be put on the dead plate. But more frequently, as elsewhere described, the fuel is thrown over and across the dead plate directly upon the hot fire. STEAM WHISTLES.These are of two kinds, known as the bell-whistle and organ-tube whistle; the latter is now fast superseding the former on account of the simplicity of construction and superior tone. An improved form has a division in the tube so as to emit two distinct notes, which may be in harmony, or discord, and when sounded together may be heard a long distance. It is important that the whistle shall sound as soon as the steam is turned on; to ensure this great care must be taken to keep the whistle-pipe free from water. THE STEAM GAUGE.The principle of construction of the dial steam gauge is, that the pressure may be indicated by means of a pointer in a divided dial similar to a clock face, but marked in division, indicating pounds pressure per square inch instead of hours and minutes. Figs. 87 and 88 show the ordinary style of gauge which consists of an elliptical tube, connected at one end to a steam pipe in communication with the boiler pressure and at the other end with gearing to a pointer spindle as shown in cut. An inverted syphon pipe is usually formed under the gauge, its object being to contain water and thus prevent the heat of the steam injuring the machinery of the gauge, or distorting its action by expansion. Fig. 87. Fig. 88. Fig. 89. A small drain cock should be fitted to the leg of the syphon of a steam gauge, leading to the boiler, at a level with the highest point the water can rise in the other leg, otherwise an increased pressure will be indicated, due to the head of water which would otherwise collect in the boiler leg of the syphon. Steam gauges indicate the pressure of steam These gauges are apt to get out of order in consequence of water lodging in the end of the heat tube and corroding the latter. It may be easily known when they are out of order by raising the pressure of the steam in the boiler and watching when it commences to blow off at the safety valve, and then noting the position of the index finger. The pressure registered by the finger should, of course, then correspond with the known blow off pressure of the valves; if it does not, one or the other or both of these instruments must be out of order; therefore, when this is the case and a disagreement occurs, the steam gauge may be presumed to need correction. It should also be noted that the steam gauge finger points to zero when steam pressure is cut off. A two-way cock should be used for closing the connection between the steam gauge and the boiler, and at the same time to let air into the steam gauge. The steam should never be allowed to act directly on a steam gauge when located in cold situations where they are liable to freeze. The valve on the boiler should be closed and the water allowed to drip out, and, before the steam is turned on from the boiler, the drip on the gauge should be closed, in order that sufficient steam may be condensed in the pipe to furnish the quantity of water necessary to keep the steam from striking the gauge. A ready method for being always able to prove the correctness of your steam gauge. When steam is at some point not over half the usual pressure, place the ball on the safety valve at the point where it commences to blow off and mark the place. Move the ball twice as far from the fulcrum as this mark, and it should blow off at twice the pressure as indicated by the gauge, or it is not right. Any other relative distance may be used to advantage. STEAM SEPARATOR.This appliance, which is also called an interceptor or catch water, is generally a T shaped pipe. Fig. 90. This, although not a boiler fixture or fitting, is intimately connected with them: it is an appliance fast coming into use both for land and marine engines, to guard against the danger to steam engine cylinders arising from “the priming” of the boilers when the steam is used at a high pressure with high speed of the piston. The separator is usually placed in the engine room, so as to be well in sight. The steam is led down the pipe round a diaphragm plate and then up again to the engine steam pipe. By this means any priming or particles of water that may be brought from the boiler with the steam will fall to the bottom of the interceptor or catch water, from whence it can be blown out, according to the arrangement of the pipes, by opening the drain cock fixed on the bottom. It has a water gauge fixed on the lower end, so as to show whether water is accumulating; and the engineers attention is required to see that this water is from time to time blown off. In the illustration, Fig. 90, is shown the simplest form in which the device can be made. The arrows exhibit the direction in which the steam travels, the aperture whence the water is to be blown out and the place for attachment of a water column. In practical construction the separator should have a diameter twice that of the steam pipe and be 21/2 to 3 diameters long. It is often made with a round top and flat bottom and sometimes with both ends hemispherical. The division plate should extend half the diameter of the steam pipe below the level of the bottom of the steam pipe. In Fig. 91 is shown an improved form of a steam separator which consists of a shell or casing in which there is firmly secured a double-ended cone. On this cone there are cast a number of wings, extending spirally along its exterior. On entering the separator the steam is spread and thrown outward by the cone and given a centrifugal motion by the spiral wings. These wings are constructed with a curved surface. It will be noticed that the steam on entering the separator is immediately expanded from a solid body into an annular space of equal volume to the steam pipe, whereby its particles are removed from the centre and thus receive a greater amount of centrifugal motion. The entrained water or grease, etc., is thus precipitated against, and flows along the shell of the separator, and is collected in a well of ample proportions at base of separator, where it is entirely isolated from the flow of dry steam. Fig. 91. SENTINEL VALVE.It was formerly required for each marine boiler to have a small valve loaded with a weight to a few pounds per square inch above the working pressure, so that in case of the safety valves sticking fast and the gauge being false, an alarm might be given when there was an excess of pressure. Such valves were about 3/4 inch in diameter and sometimes as small as 3/8. An arrangement of a small safety valve attached to a whistle has been introduced, but with advances in other directions relating to safety these specialties are now getting to be only known by name. DAMPER REGULATORS.These are well-known devices for so controlling the draught of the chimney that the steam pressure in the boiler will be increased or decreased automatically, that is, without the aid of a person. The regulator shown in Fig. 92, which is one of many excellent forms on the market, has the power to move the damper in both directions by water pressure, exerting a force on the end of the lever of nearly 200 lbs., thus compelling a certain and positive motion of the damper when a variation in the boiler pressure takes place. It will open or close the damper upon the variation of less than one pound of pressure. The close regulation affords a test for the correctness of the steam gauge. Fig. 92. This regulator, by using the water pressure from the boiler as a motive power, becomes a complete engine without the connecting rod and crank, having a balanced piston valve, the valve stem of which is enlarged where it passes through the upper end of the chest into a piston of small area, working in a small open ended cylinder cast on the chest. The pressure forcing this piston outward is counterbalanced by weights as shown in illustration. The differential motion is accomplished by the device shown at the top of small cylinder. FUEL ECONOMIZER AND FEED WATER PURIFIER.This device, shown in Fig. 93, is designed to utilize the waste products of combustion as they pass from the furnace to the chimney. Its use permits a high and consequently efficient temperature under the boilers and yet saves the excess of heat. It acts also as a mechanical boiler cleaner, furnishing a settling It will be readily understood that the openings between the vertical tubes are ample for the chimney flue area and that the device is located between the chimney and the boiler, with the waste furnace heat passing between the tubes. Fig. 93. The economizer shown in Fig. 93 consists of sections of vertical 41/2 boiler tubes fitted to their top and bottom headers by taper joints. The top headers are provided with caps over each tube to permit cleaning out the sediment and remove and replace any tube that may become damaged. The several top headers are connected together at one end by lateral openings and the bottom headers are also connected as shown in cut, having hand holes opposite each bottom header to provide for cleaning out. Mechanical scrapers are made to travel up and down each tube to keep them clear of soot. These are controlled by an automatic mechanism and driving head, as shown in Fig. 93. The important features about the economizer are, 1, its adaptability to any type of boiler, 2, the saving attained by utilizing that heat which has necessarily been an almost total waste, 3, the purifying of the water by means of the intense heat and slow circulation of the feed water. SAFETY VALVES.Fig. 94.(Sectional View.) The safety valve is a circular valve seated on the top of the boiler, and weighted to such an extent, that when the pressure of the steam exceeds a certain point, the valve is lifted from its seating and allows the steam to escape. Safety valves can be loaded directly with weights, or the load can be transmitted to the valve by a lever. Again, the end of the lever is sometimes held down by a spring, or the spring may be applied directly to the valve seat. Fig. 94 (2 views) exhibits a spring loaded safety valve. These are generally provided with a reaction lip, surrounding the seat, which causes them to open much further, and thus enables them to discharge a larger volume of steam than a lever valve of equal diameter. The operation can be easily understood by examining the figures. As soon as the steam pressure is high enough to lift the valve disc clear from its seat, the steam will escape around the valve seat as in an ordinary lever safety valve, but instead of escaping directly into the atmosphere, the current of steam is turned downward against the reaction lip, by the curved projection on the valve disc, which can be seen in the figure. The steam pressure is thus assisted in holding the valve open, as well as raising it much higher, giving a larger opening than would be the case if the valve were lifted by the pressure alone. Spring loaded valves are mostly used on marine boilers, locomotives and portable boilers, and wherever outside disturbances interfere with the action of a weight. A “pop” safety valve is a common form of safety valve and takes its name from the fact that it takes a little more pressure to raise it off its seat than what it is set at, consequently it releases itself with a “pop.” Fig. 95. Fig. 95 shows a form of dead weight safety valves when a is the valve which rests on the seating b. The valve is attached to the circular casting A, A, A, so that both rise and fall together. The weights W, W, etc., are disposed on the casting in rings, which can be adjusted to the desired blow off pressure. Owing to the center of gravity of the casting and weight being below the valve, the latter requires no U. S. Rules Relating to Safety Valves.Extract from rules and regulations passed and approved Feb. 25, 1885, by the United States Board of Supervising Inspectors of Steam Vessels: Section 24. “Lever safety valves to be attached to marine boilers shall have an area of not less than one square inch to two square feet of the grate surface in the boiler, and the seats of all such safety valves shall have an angle of inclination of forty-five degrees to the centre line of their axis. “The valves shall be so arranged that each boiler shall have one separate safety valve, unless the arrangement is such as to preclude the possibility of shutting off the communication of any boiler with the safety valve or valves employed. This arrangement shall also apply to lock-up safety valves when they are employed. “Any spring-loaded safety valves constructed so as to give an increased lift by the operation of steam, after being raised from their seats, or any spring-loaded safety valve constructed in any other manner, or so as to give an effective area equal to that of the aforementioned spring-loaded safety valve, may be used in lieu of the common lever-weighted valve on all boilers on steam vessels, and all such spring-loaded safety valves shall The following size “Pop” Safety Valves are required for boilers having grate surfaces as below:
Professor Rankin’s Rule.—Multiply the number of pounds of water evaporated per hour by .006, and the product will be the area in square inches of the valve. The U. S. Steamboat Inspection Law requires for the common lever valve one square inch of area of valve for every two square feet of area of grate surface. United States Navy Department deduced from a series of experiments the following rule: Multiply the number of pounds of water evaporated per hour by .005, and the product will be the area of the valve in square inches. Rule adopted by the Philadelphia Department of Steam Engine and Boiler Inspection: 1. Multiply the area of grate in square feet by the number 22.5. 2. Add the number 8.62 to the pressure allowed per square inch. Divide (1) by (2) and the quotient will be the area of the valve in square inches. This is the same as the French rule. The maximum desirable diameter for safety valves is four inches, for beyond this the area and cost increase much more rapidly than the effective discharging around the circumference. There should not be any stop valve between the boiler and safety valve. The common form of safety valve is shown in Fig. 96. Here the load is attached to the end B of the lever A, B, the fulcrum of which is at c. The effective pressure on the valve, and consequently the blowing off pressure in the boiler can be regulated within certain limits, by sliding the weight W along the arm of the lever. In locomotive engines, as well as on marine boilers, the weight would on account of the oscillations, be inadmissible and a spring is used to hold down the lever. In the calculations regarding the lever safety valve, there are five points to be determined, and it is necessary to know four of these in order to find the fifth. These are: (1) The Steam Pressure, (2) The Weight of Ball, (3) The Area of Valve, (4) The Length of Lever, (5) The Distance from the Valve Centre to the Fulcrum. Fig. 96. In making these calculations it is necessary to take into account the load on the valve due to the weight of the valve-stem and lever. The leverage with which this weight acts is measured by the distance of its centre of gravity from the fulcrum. The centre of gravity is found by balancing the lever on a knife edge, and the weight of the valve-stem and To find the area of the valve: Rule.—Multiply the length of the lever by the weight of the ball, and divide the product by the distance from the valve centre to the fulcrum, and to the quotient add the effective weight of the valve and lever, and divide the sum by the steam pressure. Example.
To find the pressure at which the valve will blow off: Rule.—Multiply the length of the lever by the weight of the ball; divide this product by the distance from the valve centre to the fulcrum, and to the quotient add the effective weight of the lever and valve, and divide the sum by the area of the valve. Example.
To find the weight of ball: Rule.—Multiply the steam pressure by the area of the valve, and from the product subtract the effective weight of the valve and lever, then multiply the remainder by the distance from the valve centre to the fulcrum, and divide the product by the length of the lever. Example.
To find the length of lever: Rule.—Multiply the steam pressure by the area of the valve, and from the product subtract the effective weight of the valve and lever, then multiply the remainder by the distance from the valve centre to the fulcrum, and divide the product by the weight of the ball. Example.
Every boiler should be provided with two safety valves, one of which should be put beyond the control of the attendant. Safety valves that stick will do so even though tried every day, if they are simply lifted and dropped to the old place on the seat again. If a boiler should be found with an excessively high pressure, it would be one of the worst things to do to start the safety valve from its seat unless extra weight was added, for should the valve once start, it would so suddenly relieve the boiler of such a volume of steam as would cause a rush of water to the opening, and by a blow, just the same as in water hammer, rupture the boiler. Such a condition is very possible to occur of itself when a safety valve sticks. The valve holds the pressure, that gets higher and higher, until so high that the safety valve does give way and allows so much steam to escape that the sudden changing of conditions sets the water in motion, and an explosion may result. The noise made by a safety valve when it is blowing off may be regarded in two ways. First, by it is known that the valve is capable of performing its proper function, and that there is, therefore, a reasonable assurance that no explosion will result from excessive pressure of steam or other gas, and on the other hand too much noise of this kind indicates wasted fuel. The hole of the safety valve may be 2, 3 or 4 inches; that does not say that the area is 3.1416, 7.06 or 12.56 square inches, but the area is that which is inside of the joint. The valve opening may be, say 2 inches, but the circle of contact of valve to seat may be of an average diameter of 21/8 inches, if so, all the close calculations otherwise will not avail. In the first place, the area of 2 inches equals 3.1416; that of 21/8 diameter equals 3.5466, showing a difference of .4 square inches. Note.Very extended rules issued by the U. S. Government for calculating the safe working pressure, dimensions and proportions of the safety valves for marine boilers are reprinted in “Hawkins’ Calculations” for engineers. When a safety valve is described as a “2 inch safety valve,” etc., it means that two inches is the diameter of the pipe; hence the following rule and examples for finding the area. Rule for finding Area of Valve Opening. Square the diameter of the opening and multiply the product by the decimal .7854. Example. What is the area of a three inch valve? Now then: 3 × 3 = 9 × .7854 = 7.06 square inches, Ans. Note.—A shorter method of calculating by .7854 in larger sums is to multiply by 11 and divide by 14, for decimal .7855 = the fraction 11/14th. Note: .7854 is the area of a circular inch. When valves rise from their seats under increasing steam pressure they do so by a constantly diminished ratio which has been carefully determined by experiment and reduced to the following table.
The following useful table was prepared by the Novelty Iron Works, New York.
FEED WATER HEATERS.Fig. 97. There are two forms of feed water heaters: (1) The closed heater, where the feed water passes through tubes, which are enclosed in a shell, through which the exhaust steam passes. (2) The open heater, in which the steam and water come into contact. In the latter the water is sprayed into a space, through which the exhaust steam passes, or is run over a number of inclined perforated copper plates, mingled with the exhaust steam. The original feed water heater called a “pot heater,” consisted of a vessel so constructed that the feed water was sprayed through the exhaust steam into a globe formed tank, from the bottom of which the heated water was pumped into the boiler; its name was originally the “pot heater,” but as it was open to the air through the exhaust pipe, it was, with its successively improved forms called the open heater. All the heat imparted to the feed water, before it enters the boiler, is so much saved, not only in the cost of fuel, but by the increased capacity of the boiler, as the fuel in the furnace will not have this duty to perform. There are two sources of waste heat which can be utilized for this purpose: the chimney gases and the exhaust steam. The gases escaping to the chimney after being reduced to the lowest possible temperature contain a considerable quantity of heat. This waste of heat energy may be largely saved by the device illustrated on page 186. Fig. 98. How much saving is obtained under any given condition is a question requiring for its solution a careful calculation of all of the conditions which have a bearing on the subject. Exhaust steam under atmospheric pressure only has a sensible temperature of 212 degrees, but exhaust steam contains also a large number of heat units which are given up when the steam is condensed into water; for this reason it might be thought possible to raise the temperature of the feed water a few degrees higher even than the sensible temperature of the exhaust steam. But this should not be expected, on account of the radiation of heat that would occur above that of the steam. The steam which escapes from the exhaust pipe dissipates into the atmosphere or discharges into the condenser over nine It is important to note these two statements: 1, That neither live steam feed water heaters, nor 2, injectors save the heat from the escaping steam. It is also well to remember that it requires a pound of water to absorb 1.146 heat units, and that this quantity of heat is distributed through the whole quantity of water, and as a pound of steam is the same as a pound of water, it may be understood that at 212° each pound of exhaust steam contains 1,146 heat units; ten pounds of steam contain 11,460 heat units distributed through the mass, etc.: thus, to explain still further: To evaporate water into steam, it must first be heated to the boiling point, and then sufficient heat still further added to change it from the liquid to the gaseous state, or steam. Take one pound of water at 32 degrees and heat it to the boiling point, it will have received 212° - 32° = 180 heat units. A heat unit being the amount of heat necessary to raise one pound of water through one degree at its greatest density. To convert it into steam after it has been raised to the boiling point, requires the addition of 966 heat units, which are called latent, as they cannot be detected by the thermometer. This makes 180 + 966 = 1146 heat units, which is the total heat contained in one pound of water made into steam at the atmospheric pressure. And at atmospheric density the volume of this steam is equal to 26.36 cubic feet, and this amount of steam contains 1,146 units of heat, distributed throughout the whole quantity, while the temperature at any given point at If by utilizing the heat that would otherwise go to waste, the temperature of the feed water is raised 125 degrees, the saving would be 125/1146 of the total amount of heat required for its evaporation, or about 11 per cent. Thus it can be seen the percentage of saving depends upon the initial temperature of the feed water, and the pressure at which it is evaporated. For example, a boiler carrying steam at 100 pounds pressure has the temperature of the feed water raised from 60 to 200 degrees, what is the percentage of gain? By referring to a table pressure of “saturated steam,” it will be seen that the total heat in steam at 100 pounds pressure is 1185 heat units. These calculations are from 32 degrees above zero, consequently the feed must be computed likewise. In the first case, the heat to be supplied by the furnace is the total heat, less that which the feed water contains, or 1185 - 28 = 1157 heat units. In the second case it is 1185 - 168 = 1017 heat units, the difference being 1157 - 1017 = 140, which represents a saving of 140/1157 or about 12 per cent. Where feed water is heated no more than 20 degrees above its normal temperature the gain effected cannot amount to more than 2%, not sufficient to pay for the introduction and maintenance of a feed water heating device, no matter how simple, but if the temperature of the water can be increased 60 degrees the gain will be in the neighborhood of 5%. To make feed water heating practical and economical it would be necessary to increase the temperature of the water about 180 degrees at least, and to do this, using the exhaust from a non-condensing engine without back pressure, would require such a capacity of heater as would give fully 10 square feet of heating surface to each horse power of work developed, and to raise the temperature above this would require a certain amount of back pressure or an increased capacity of heater, so that the subject In the same way has been calculated the following table, showing percentages of saving of fuel by heating feed-water to various temperatures by exhaust steam, otherwise waste: Percentage of saving. ( Steam at 60 pounds gauge pressure.)
A good feed-water heater of adequate proportions should readily raise the temperature of feed-water up to 200° Fahr., and, as is seen by inspection of the table, thus effect a saving of fuel, ranging from 14.3 per cent. to 9.03 per cent., according as the atmospheric or normal temperature of the water varies from 32° Fahr. in the height of winter, to 100° Fahr. in the height of summer. The percentage of saving which may be obtained from the use of exhaust steam for heating the feed water, with which the boiler is supplied, will depend upon the temperature to which the water is raised, and this, in turn, will depend upon the length of time that the water remains under the influence of the exhaust steam. This should be as long as possible, and unless a sufficient amount of heating surface is employed in the heater best results cannot be expected. It does not necessarily require all the exhaust steam—or the whole volume of waste steam passing from the engine to bring the feed water up to the temperature desired, and the larger the heating appliance the smaller proportion is needed—hence heaters are best made with two exits nicely proportioned to avoid back pressure and at the same time utilize enough of the exhaust to heat the feed water. An impression prevails among many who are running a condenser on their engine that a feed water heater can not be used in connection with it; large numbers of heaters running on condensing engines with results as follows: the feed water is delivered to the boiler at a temperature of 150° to 160° Fahr., depending on the vacuum: the higher the vacuum the less the heat in the feed water. A heater applied to a condensing engine generally increases the vacuum one to two inches. When cold water is used for the feed water, the saving in fuel by the use of the heater is from 7 to 14 per cent. When feed water is taken from the hot well, it will save 7 to 8 per cent. Where all the steam generated by a boiler is used in the engine and the exhaust passed through a heater it is found by actual experiment, where iron tubes are used in the heater, that approximately ten square feet of heating surface will be required for each 30 lbs. of water supplied to the boiler at a temperature of 200 degrees Fahr. Ten square feet of heating surface in the feed water heater also represents one horse power. CAPACITY OF CISTERNS.The following table gives the capacity of cisterns for each twelve inches in depth: Supposing it was required to find the weight of the water in any cistern or tank; it can be ascertained by multiplying the number of gallons by the weight of one gallon, which is 81/3 pounds, 8.333. For instance, taking the largest cistern in the above table containing 3671 gallons: 3671 × 8.33 = 30579.43 pounds. The table above gives the capacities of round cisterns or tanks. If the cistern is rectangular the number of gallons and weight of water are found by multiplying the dimensions of the cistern to get the cubical contents. For instance, for a cistern or tank 96 inches long, 72 inches wide, and 48 inches deep, the formula would be: 96 × 72 × 48 = 331,776 cubic inches. As a gallon contains 231 cubic inches; 331,776 divided by 231 gives l,436 gallons, which multiplied by 8.33 will give the weight of water in the cistern. For round cisterns or tanks, the rule is: Area of bottom on inside multiplied by the height, equals cubical capacity. For instance, taking the last tank or cistern in the table: Area of 24 inches (diameter) is 452.39, which multiplied by 12 inches (height) gives 5427.6 cubic inches, and this divided by 231 cubic inches in a gallon gives 23 gallons. Supposing the tank to be 24 inches deep instead of 12 inches, the result would be, of course, twice the number of gallons. Rule for Obtaining Contents of a Barrel in Gallons. Take diameter at bung, then square it, double it, then add square of head diameter; multiply this sum by length of cask, and that product by .2618 which will give volume in cubic inches; this, divided by 231, will give result in gallons. WATER METERS.Water meters, or measurers (apparatus for the measurement of water), are constructed upon two general principles: 1, an arrangement called an “ inferential meter” made to divert a certain proportion of the water passing in the main pipe and by measuring accurately the small stream diverted, to infer, or estimate the larger quantity; 2, the positive meter; rotary piston meters are of the latter class and the form usually found in connection with steam plants. They are constructed on the positive displacement principle, and have only one working part—a hard rubber rolling piston—rendering it almost, if not entirely, exempt from liability to derangement. It measures equally well on all sized openings, whether the pressure be small or great; and its piston, being perfectly balanced, is almost frictionless in its operation. Constructed of composition (gun-metal) and hard rubber, it is not liable to corrosion. An ingenious stuffing-box insures at all times a perfectly dry and legible dial, or the registering Fig. 99. Fig. 99 is a perspective view of the meter, showing the index on the top. It is shown here as when placed in position. The proper threads at the inlet and outlet make it easy of attachment to the supply and discharge pipes. The hard rubber piston (the only working part of the Meter) is made with spindle for moving the lever communicating with the intermediate gear by which the dial is moved. The water, through the continuous movement of the piston, passes through the meter in an unbroken stream, in the same quantity as with the pipe to which it is attached when the opening in the meter equals that of the service pipe; the apparatus is noiseless and practically without essential wear. “Points” Relating to Water Meters.In setting a meter in position let it be plumb, and properly secured to remain so. It should be well protected from frost. If used in connection with a steam boiler, or under any other conditions where it is exposed to a back pressure of steam or hot water, it must be protected by a check valve, placed between the outlet of the meter and the vessel it supplies. It is absolutely necessary to blow out the supply pipe before setting a new meter, so that if there be any accumulation of sand, gravel, etc., in it, the same may be expelled, and thus prevented from entering the meter. Avoid using red lead in making joints. It is liable to work into the meter and cause much annoyance by clogging the piston. This engraving, Fig. 100, shows the counter of the Meter. It registers cubic feet—one cubic foot being 748/100 U. S. gallons and is read in the same way as the counters of gas meters. Fig. 100. The following example and directions may be of service to those unacquainted with the method: If a pointer be between two figures, the smallest one must always be taken. When the pointer is so near a figure that it seems to indicate that figure exactly, look at the dial next below it in number, and if the pointer there has passed 0, then the count should be read for that figure. Let it be supposed that the pointers stand as in the above engraving, they then read 28,187 cubic feet. The figures are omitted from the dial marked “ONE,” because they represent but tenths of one cubic foot, and hence are unimportant. From dial marked “10,” we get 7; from the next marked “100,” we get 8; from the next marked “1,000,” we get the figure 1; from the next marked “10,000,” the figure 8; from the next marked “100,000,” the figure 2. The Fish Trap used in connection with water meters is an apparatus (as its name denotes) for holding back fishes, etc. THE STEAM BOILER INJECTOR.For safety sake, every boiler ought to have two feeds in order to avoid accidents when one of them gets out of order, and one of these should be an injector. This consists in its most simple form, of a steam nozzle, the end of which extends somewhat into the second nozzle, called the combining or suction nozzle; this connects with or rather terminates in a third nozzle or tube, termed the “forcer.” At the end of the combining tube, and before entering the forcer, is an opening connecting the interior of the nozzle at this point with the surrounding area. This area is connected with the outside air by a check valve, opening outward in the automatic injectors, and by a valve termed the overflow valve. The operation of the injector is based on the fact, first demonstrated by Gifford, that the motion imparted by a jet of steam to a surrounding column of water is sufficient to force it into the boiler from which the steam was taken, and, indeed, into a boiler working at a higher pressure. The steam escaping from under pressure has, in fact, a much higher velocity than water would have under the same pressure and condition. The rate of speed at which steam—taking it at an average boiler pressure of sixty pounds—travels when discharged into the atmosphere, is about 1,700 feet per second. When discharged with the full velocity developed by the boiler pressure through a pipe, say an inch in diameter, the steam encounters the water in the combining chamber. It is immediately condensed and its bulk will be reduced say 1,000 times, but its velocity remains practically undiminished. Uniting with the body of water in the combining tube, it imparts to it a large share of its speed, and the body of water thus set in motion, operating against a comparatively small area of boiler pressure, is able to overcome it and pass into the boiler. The weight of the water to which steam imparts its velocity gives it a momentum that is greater in the small area in which its force is exerted than the boiler pressure, although its force has actually been derived from the boiler pressure itself. The following cut 101 represents the outline of one of the best of a large number of injectors upon the market, from which the operation of injectors may be illustrated. S. Steam jet. V. Suction jet. Fig. 101. The steam enters from above, the flow being regulated by the handle K. The steam passes through the tube S and expands in the tube V, where it meets the water coming from the suction pipe. The condensation takes place in the tubes V and C, and a jet of water is delivered through the forcer tube D to the boiler. Connection passages are made to the chamber surrounding the tubes C, D, and to the end of tube V. If the pressure in this surrounding chamber becomes greater than that of the atmosphere, the check valve P is lifted and the contents are discharged through the overflow. So long as the pressure in this chamber is atmospheric, the check valve P remains closed, and all the contents must be discharged through the tube D. There are three distinct types of live steam injectors, the “simple fixed nozzle,” the “adjustable nozzle,” and the “double.” The first has one steam and one water nozzle which are fixed in position but are so proportioned as to yield a good result. There is a steam pressure for every instrument of this type at which it will give a maximum delivery, greater than the maximum delivery for any other steam pressure either higher or lower. The second type has but one set of nozzles, but they can be so adjusted relative to each other as to produce the best results throughout a long range of action; that is to say, it so adjusts itself that its maximum delivery continually increases with the increase of steam pressure. The double injector makes use of two sets of nozzles, the “lifter” and “forcer.” The lifter draws the water from the reservoir and delivers it to the forcer, which sends it into the boiler. All double injectors are fixed nozzle. All injectors are similar in their operation. They are designed to bring a jet of live steam from the boiler in contact with a jet of water so as to cause it to flow continuously in the direction followed by the steam, the velocity of which it in part assumes, back into the boiler and against its own pressure. As a thermodynamical machine, the injector is nearly perfect, since all the heat received by it is returned to the boiler, except such a very small part as may be lost by radiation; consequently its thermal efficiency should be in every case nearly 100 per cent. On the other hand, because of the fact that its heat energy is principally used in warming up the cold water as it enters the injector, its mechanical efficiency, or work done in lifting water, compared with the heat expended, is very low. The action of the injector is as follows: Steam being turned on, it rushes with great velocity through the steam nozzle into and through the combining tube. This action induces a flow of air from the suction pipe, which is connected to the combining tube, with the result that a more or less perfect vacuum is formed, thus inducing a flow of water. After the water commences to flow to the injector it receives motion from the jet of steam; it absorbs heat from the steam and finally condenses it, “Points” Relating to the Injector.In nine cases out of ten, where the injector fails to do good service, it will be either because of its improper treatment or location, or because too much is expected of it. The experience of thoroughly competent engineers establishes the fact that in almost every instance in which a reliable boiler feed is required, an injector can be found to do the work, provided proper care is exercised in its selection. The exhaust steam injector is a type different from any of the above-named, in that it uses the exhaust steam from a non-condensing engine. Exhaust steam has fourteen and seven-tenths (14.7) pounds of work, and the steam entering the injector is condensed and the water forced into the boiler upon the same general principle as in all injectors. The exhaust steam injector would be still more extensively used were it not for a practical objection which has arisen—it carries over into the boiler the waste oil of the steam cylinder. Some injectors are called by special names by their makers, such as ejectors and inspirators, but the term injectors is the general name covering the principle upon which all the devices act. The injector can be, and sometimes is, used as a pump to raise water from one level to another. It has been used as an air compressor, and also for receiving the exhaust from a steam engine, taking the place in that case of both condenser and air pump. The injector nozzles are tubes, with ends rounded to receive and deliver the fluids with the least possible loss by friction and eddies. Double injectors are those in which the delivery from one injector is made the supply of a second, and they will handle water at a somewhat higher temperature than single ones with fixed nozzles. The motive force of the injector is found in the heat received from the steam. The steam is condensed and surrenders its latent heat and some of its sensible heat. The energy so given up by each pound of steam amounts to about 900 thermal units, each of which is equivalent to a mechanical force of 778 foot pounds. This would be sufficient to raise a great many pounds of water against a very great pressure could it be so applied, but a large portion of it is used simply to heat the water raised by the injector. The above explanation will apply to every injector in the market, but ingenious modifications of the principles of construction have been devised in order to meet a variety of requirements. That the condensation of the steam is necessary to complete the process will be evident, for if the steam were not condensed in the combining chamber, it would remain a light body and, though moving at high speed, would have a low degree of energy. Certain injectors will not work well when the steam pressure is too high. In order to work at all the injector must condense the steam which flows into the combining tube. Therefore, when the steam pressure is too high, and as a consequence the heat is very great, it is difficult to secure complete condensation; so that for high pressure of steam good results can only be obtained with cold water. It would be well when the feed water is too warm to permit the injector to work well, to reduce the pressure, and consequently the temperature of the steam supplied to the injector, as low pressure steam condenses much easier, and consequently can be employed with better result. Throttling the steam supplied by means of stop valves will often answer well in this case. The steam should not be cold or it will not contain heat units enough to allow it to condense into a cross section small enough to be driven into the boiler. This is the reason why exhaust injectors fail to work when the exhaust steam is very cold. It also explains why such injectors work well when a little live steam is admitted into the exhaust sufficient to heat it above a temperature of 212°. Leaks affect injectors the same as pumps, and in addition, the accumulation of lime and other mineral deposits in the jets stops the free flowing of the water. The heat of the steam is the usual cause of the deposits, and where this is excessive it would be well to discard the injector and feed with the pump. The efficient working of the injector depends materially upon the size of the jet which should be left as the manufacturer makes it; hence in repairs and cleaning a scraper or file should not be used. For cleaning injectors, where the jets have become scaled, use a solution of one part muriatic acid to from nine to twelve parts of water. Allow the tubes to remain in the acid until the scale is dissolved or is so soft as to wash out readily. The lifting attachment, as applied to any injector, is simply a steam jet pump. It is combined with the injector proper and is operated by a portion of the steam admitted to the instrument. Nearly all the successful injectors on the market are made with these attachments, and will raise water about 25 feet, if required, from a well or tank below the boiler level. Where an injector is required to work at different pressures it must be so constructed that the space between the receiving tube and the combining tube can be varied in size. As a rule this is accomplished by making both combining and receiving tubes conical in form and arranging the combining tube so that it can be moved to or from the receiving tube, and the water space thereby enlarged or contracted at will. The adjustment of the space between the two tubes by hand is a matter of some difficulty, however; at least it takes more time and patience than the average engineer has to devote to it, and the majority of the injectors in use are therefore made automatic in their regulation. The injector is not an economical device, but it is simple and convenient, it occupies but a small amount of space, is not expensive and is free from severe strains on its durability; moreover, where a number of boilers are used in one establishment, it is very convenient to have the feeding arrangements separate, so that each boiler is a complete generating system in itself and independent of its neighbors. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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