CHAPTER II.BOILERS.

CHAPTER II.BOILERS.The first boilers were made as a single cylinder of wrought iron set in brick work, with provision for a fire under one end. This was used for many years, but it produced steam very slowly and with great waste of fuel.The first improvement to be made in this was a fire flue running the whole length of the interior of the boiler, with the fire in one end of the flue. This fire flue was entirely surrounded by water.Then a boiler was made with two flues that came together at the smoke-box end. First one flue was fired and then the other, alternately, the clear heat of one burning the smoke of the other when it came into the common passage.The next step was to introduce conical tubes by which the water could circulate through the main fire flue (Galloway boiler).FIG. 1. ORR & SEMBOWER’S STANDARD HORIZONTAL BOILER, WITH FULL-ARCH FRONT SETTING.The object of all these improvements was to get larger heating surface. To make steam rapidly and economically, the heating surface must be as large as possible.FIG. 2. GAAR, SCOTT & CO.’S LOCOMOTIVE BOILER.But there is a limit in that the boiler must not be cumbersome, it must carry enough water, and have sufficient space for steam.The stationary boiler now most commonly used is cylindrical, the fire is built in a brick furnace under the sheet and returns through fire tubes running the length of the boiler. (Fig. 1.)LOCOMOTIVE FIRE TUBE TYPE OF BOILER.The earliest of the modern steam boilers to come into use was the locomotive fire tube type, with a special firebox. By reference to the illustration (Fig. 2) you will see that the boiler cylinder is perforated with a number of tubes from 2 to 4 inches in diameter running from the large firebox on the left, through the boiler cylinder filled with water, to the smoke-box on the right, above which the smokestack rises.FIG. 3. THE HUBER FIRE BOX.It will be noticed that the walls of the firebox are double, and that the water circulates freely all about the firebox as well as all about the fire tubes. The inner walls of the firebox are held firmly in position by stay bolts, as will be seen inFig. 3, which also shows the position of the grate.FIG. 4. HUBER RETURN FLUE BOILER.RETURN FLUE TYPE OF BOILER.The return flue type of boiler consists of a large central fire flue running through the boiler cylinder to the smoke box at the front end, which is entirely closed. The smoke passes back through a number of small tubes, and the smokestack is directly over the fire at the rear of the boiler, though there is no communication between the fire at the rear of the boiler and it except through the main flue to the front and back through the small return flues.Fig. 4illustrates this type of boiler, though it shows but one return flue. The actual number may be seen by the sectional view inFig. 5.FIG. 5. SECTION VIEW OF HUBER RETURN FLUE BOILER.The fire is built in one end of the main flue, and is entirely surrounded by water, as will be seen in the illustration. The long passage for the flame and heated gases enables the water to absorb a maximum amount of the heat of combustion. There is also an element of safety in this boiler in that the small flues will be exposed first should the water become low, and less damage will be done than if the large crown sheet of the firebox boiler is exposed, and this large crown sheet is the first thing to be exposed in that type of boiler.WATER TUBE TYPE OF BOILER.The special difference between the fire tube boiler and the water tube boiler is that in the former the fire passesthrough the tubes, while in the latter the water is in the tubes and the fire passes around them.FIG. 6. FREEMAN VERTICAL BOILER.In this type of boiler there is an upper cylinder (or more than one) filled with water; a series of small tubes running at an angle from the front or fire door end of the upper cylinder to a point below and back of the grates,where they meet in another cylinder or pipe, which is connected with the other end of the upper cylinder. The portions of the tubes directly over the fire will be hottest, and the water here will become heated and rise to the front end of the upper cylinder, while to fill the space left, colder water is drawn in from the back pipe, from the rear end of the upper cylinder, down to the lower ends of the water tubes, to pass along up through them to the front end again.This type of boiler gives great heating surface, and since the tubes are small they will have ample strength with much thinner walls. Great freedom of circulation is important in this type of boiler, there being no contracted cells in the passage. This is not adapted for a portable engine.UPRIGHT OR VERTICAL TYPE OF BOILER.In the upright type of boiler the boiler cylinder is placed on end, the fire is built at the lower end, which is a firebox surrounded by a water jacket, and the smoke and gases of combustion rise straight up through vertical fire flues. The amount of water carried is relatively small, and the steam space is also small, while the heating surface is relatively large if the boiler is sufficiently tall. You can get up steam in this type of boiler quicker than in any other, and in case of the stationary engine, the space occupied is a minimum. The majority of small stationary engines have this type of boiler, and there is a traction engine with upright boiler which has been widely used, but it is open to the objection that the upper or steam ends of the tubes easily get overheated and so become leaky. There is also often trouble from mud and scale deposits in the water leg, the bottom area of which is very small.DEFINITION OF TERMS USED IN CONNECTION WITH BOILERS.Shell—The main cylindrical steel sheets which form the principal part of the boiler.Boiler-heads—The ends of the boiler cylinder.Tube Sheets—The sheets in which the fire tubes are inserted at each end of the boiler.Fire-box—A nearly square space at one end of a boiler, in which the fire is placed. Properly it is surrounded on all sides by a double wall, the space between the two shells of these walls being filled with water. All flat surfaces are securely fastened by stay bolts and crown bars, but cylindrical surfaces are self-bracing.Water-leg—The space at sides of fire-box and below it in which water passes.Crown-sheet—The sheet of steel at the top of the firebox, just under the water in the boiler. This crown sheet is exposed to severe heat, but so long as it is covered with water, the water will conduct the heat away, and the metal can never become any hotter than the water in the boiler. If, however, it is not covered with water, but only by steam, it quickly becomes overheated, since the steam does not conduct the heat away as the water does. It may become so hot it will soften and sag, but the great danger is that the thin layer of water near this overheated crown sheet will be suddenly turned into a great volume of steam and cause an explosion. If some of the pressure is taken off, this overheated water may suddenly burst into steam and cause an explosion, as the safety valve blows off, for example (since the safety valve relieves some of the pressure).Smoke-box—The space at the end of the boiler opposite to that of the fire, in which the smoke may accumulate before passing up the stack in the locomotive type, or through the small flues in the return type of boiler.Steam-dome—A drum or projection at the top of the boiler cylinder, forming the highest point which the steam can reach. The steam is taken from the boiler through piping leading from the top of this dome, since at this point it is least likely to be mixed with water, either through foaming or shaking up of the boiler. Even under normal conditions the steam at the top of the dome is drier than anywhere else.Mud-drum—A cylindrical-shaped receptacle at the bottom of the boiler similar to the steam-dome at the top,but not so deep. Impurities in the water accumulate here, and it is of great value on a return flue boiler. In a locomotive boiler the mud accumulates in the water leg, below the firebox.Man-holes—Are large openings into the interior of a boiler, through which a man may pass to clean out the inside.Hand-holes—Are smaller holes at various points in the boiler into which the nozzle of a hose may be introduced for cleaning out the interior. All these openings must be securely covered with steam-tight plates, called man-hole and hand-hole plates.A boiler jacket—A non-conducting covering of wood, plaster, hair, rags, felt, paper, asbestos or the like, which prevents the boiler shell from cooling too rapidly through radiation of heat from the steel. These materials are usually held in place against the boiler by sheet iron. An intervening air-space between the jacket and the boiler shell will add to the efficiency of the jacket.A steam-jacket—A space around an engine cylinder or the like which may be filled with live steam so as to keep the interior from cooling rapidly.Ash-pit—The space directly under the grates, where the ashes accumulate.Dead-plates—Solid sheets of steel on which the fire lies the same as on the grates, but with no openings through to the ash-pit. Dead-plates are sometimes used to prevent cold air passing through the fire into the flues, and are common on straw-burning boilers. They should seldom if ever be used on coal or wood firing boilers.Grate Surface—The whole space occupied by the grate-bars, usually measured in square feet.Forced Draft—A draft produced by any means other than the natural tendency of the heated gases of combustion to rise. For example, a draft caused by letting steam escape into the stack.Heating Surface—The entire surface of the boiler exposed to the heat of the fire, or the area of steel or iron sheeting or tubing, on one side of which is water and on the other heated air or gases.Steam-space—The cubical contents of the space which may be occupied by steam above the water.Water-space—The cubical contents of the space occupied by water below the steam.Diaphragm-plate—A perforated plate used in the domes of locomotive boilers to prevent water dashing into the steam supply pipe. A dry-pipe is a pipe with small perforations, used for taking steam from the steam-space, instead of from a dome with diaphragm-plate.THE ATTACHMENTS OF A BOILER.1Before proceeding to a consideration of the care and management of a boiler, let us briefly indicate the chief working attachments of a boiler. Unless the nature and uses of these attachments are fully understood, it will be impossible to handle the boiler in a thoroughly safe and scientific fashion, though some engineers do handle boilers without knowing all about these attachments. Their ignorance in many cases costs them their lives and the lives of others.The first duty of the engineer is to see that the boiler is filled with water. This he usually does by looking at the glass water-gauge.THE WATER GAUGE AND COCKS.TWO-ROD WATER GAUGE.There is a cock at each end of the glass tube. When these cocks are open the water will pass through the lower into the glass tube, while steam comes through the other. The level of the water in the gauge will then be the same as the level of the water in the boiler, and the water should never fall out of sight below the lower end of the glass, nor rise above the upper end.Below the lower gauge cock there is another cock used for draining the gauge and blowing it off when there is a pressure of steam on. By occasionally opening this cock, allowing the heated water or steam to blow through it, the engineer may always be sure that the passages into the water gauge are not stopped up by any means. By closing the upper cock and opening the lower, the passage into the lower may be cleared by blowing off the drain cock; by closing the lower gauge cock and opening the upper the passage from the steam space may be cleared and tested in the same way when the drain cock is opened. If the glass breaks, both upper and lower gauge cocks should be closed instantly.GAUGE OR TRY COCK.In addition to the glass water gauge, there are the try-cocks for ascertaining the level of the water in the boiler. There should be two to four of these. They open directly outof the boiler sheet, and by opening them in turn it is possible to tell approximately where the water stands. There should be one cock near the level of the crown sheet, or slightly above it, another about the level of the lower gauge cock, another about the middle of the gauge, another about the level of the upper gauge, and still another, perhaps, a little higher. But one above and one below the water line will be sufficient. If water stands above the level of the cock, it will blow off white mist when opened; if the cock opens from steam-space, it will blow off blue steam when opened.The try-cocks should be opened from time to time in order to be sure the water stands at the proper level in the boiler, for various things may interfere with the working of the glass gauge. Try-cocks are often called gauge cocks.TRY COCK.THE STEAM GAUGE.The steam gauge is a delicate instrument arranged so as to indicate by a pointer the pounds of pressure which the steam is exerting within the boiler. It is extremely important, and a defect in it may cause much damage.PRESSURE GAUGE.The steam gauge was invented in 1849 by Eugene Bourdon, of France. He discovered that a flat tube bent in a simple curve, held fast at one end, would expand and contract if made of proper spring material, through the pressure of the water within the tube. The free end operates a clock-work that moves the pointer.It is important that the steam gauge be attached to the boiler by a siphon, or with a knot in the tube, so that the steam may operate on water contained in the tube, and the water cannot become displaced by steam, since steam might interfere with the correct working of the gauge by expanding the gauge tube through its excessive heat.Steam gauges frequently get out of order, and should be tested occasionally. This may conveniently be done by attaching them to a boiler which has a correct gauge already on it. If both register alike, it is probable that both are accurate.STEAM GAUGE SIPHON.FRONT CYLINDER COCK.There are also self-testing steam gauges. With all pressure off, the pointer will return to 0. Then a series of weights are arranged which may be hung on the gauge and cause the pointer to indicate corresponding numbers. The chief source of variation is in the loosening of the indicator needle. This shows itself usually when the pressure is off and the pointer does not return exactly to zero.SAFETY VALVE.The safety valve is a valve held in place by a weighted lever2or by a spiral spring (on traction engines) or some similar device, and is adjustable by a screw or the like so that it can be set to blow off at a given pressure of steam, usually the rated pressure of the boiler, which on traction engines is from 110 to 130 pounds. The valve is supplied with a handle by which it can be opened, and it should be opened occasionally to make sure it is working all right. When it blows off the steam gauge should be noted to see that it agrees with the pressure for which the safety valve was set. If they do not agree, something is wrong; either the safety valve does not work freely, or the steam gauge does not register accurately.SECTIONAL VIEW OF KUNKLE POP VALVE.SAFETY VALVE.The cut shows the Kunkle safety valve. To set it, unscrew the jam nut and apply the key to the pressure screw. For more pressure, screw down; for less, unscrew. After having the desired pressure, screw the jamnut down tight on the pressure screw. To regulate the opening and closing of the valve, take the pointed end of a file and apply it to the teeth of the regulator. If valve closes with too much boiler pressure, move the regulator to the left. If with too little, move the regulator to the right.This can be done when the valve is at the point of blowing off.PHANTOM VIEW OF MARSH INDEPENDENT STEAM PUMP.Other types of valves are managed in a similar way, and exact directions will always be furnished by the manufacturers.FILLING THE BOILER WITH WATER.There are three ways in which a boiler is commonly filled with water.First, before starting a boiler it must be filled with water by hand, or with a hand force-pump. There is usually a filler plug, which must be taken out, and a funnel can be attached in its place. Open one of the gauge cocks to let out the air as the water goes in.When the boiler has a sufficient amount of water, as may be seen by the glass water gauge, replace the fillerplug. After steam is up the boiler should be supplied with water by a pump or injector.THE BOILER PUMP.There are two kinds of pumps commonly used on traction engines, the Independent pump, and the Cross-head pump.The Independent pump is virtually an independent engine with pump attached. There are two cylinders, one receiving steam and conveying force to the piston; the other a water cylinder, in which a plunger works, drawing the water into itself by suction and forcing it out through the connection pipe into the boiler by force of steam pressure in the steam cylinder.STRAIGHT GLOBE VALVE.ANGLE GLOBE VALVE.It is to be noted that all suction pumps receive their water by reason of the pressure of the atmosphere on the surface of the water in the supply tank or well. This atmospheric pressure is about 15 pounds to the square inch, and is sufficient to support a column of water 28 to 33 feet high, 33 feet being the height of a column of water which the atmosphere will support theoretically at about sea level. At greater altitudes the pressure of the atmosphere decreases. Pumps do not work very well when drawing water from a depth over 20 or 22 feet.Water can be forced to almost any height by pressure of steam on the plunger, and it is taken from deep wells by deep well pumps, which suck the water 20 to 25 feet, and force it the rest of the way by pressure on a plunger.The amount of water pumped is regulated by a cock or globe valve in the suction pipe.A Cross-head boiler pump is a pump attached to the cross-head of an engine. The force of the engine piston is transmitted to the plunger of the pump.The pump portion works exactly the same, whether of the independent or cross-head kind.The cut represents an independent pump that uses the exhaust steam to heat the water as it is pumped (Marsh pump).VALVE WITH INTERNAL SCREW.Every boiler feed-pump must have at least two check valves.A check valve is a small swinging gate valve (usually) contained in a pipe, and so arranged that when water is flowing in one direction the valve will automatically open to let the water pass, while if water should be forced in the other direction, the valve will automatically close tight and prevent the water from passing.SECTIONAL VIEW OF SWING CHECK VALVE.There is one check valve in the supply pipe which conducts the water from the tank or well to the pump cylinder. When the plunger is drawn back or raised, a vacuum is created in the pump cylinder and the outside atmospheric pressure forces water through the supply pipe into the cylinder, and the check valve opens to let it pass. When the plunger returns, the check valve closes, and the water is forced into the feed-pipe to the boiler.SECTIONAL VIEW OF CASE HEATER.There are usually two check valves between the pump cylinder and the boiler, both swinging away from the pump or toward the boiler. In order that the water may flow steadily into the boiler there is an air chamber, which may be partly filled with water at each stroke of theplunger. As the water comes in, the air must be compressed, and as it expands it forces the water through the feed pipe into the boiler in a steady stream. There is one check valve between the pump cylinder and the air chamber, to prevent the water from coming back into the cylinder, and another between the air chamber and the boiler, to prevent the steam pressure forcing itself or the water from the boiler or water heater back into the air chamber.SECTIONAL VIEW OF PENBERTHY INJECTOR.U. S. AUTOMATIC INJECTOR.(American Injector Co.)All three of these check valves must work easily and fit tight if the pump is to be serviceable. They usually close with rubber facings which in time will get worn,and dirt is liable to work into the hinge and otherwise prevent tight and easy closing. They can always be opened for inspection, and new ones can be put in when the old are too much worn.Only cold water can be pumped successfully, as steam from hot water will expand, and so prevent a vacuum being formed. Thus no suction will take place to draw the water from the supply source.There should always be a globe valve or cock in the feed pipe near the boiler to make it possible to cut out the check valves when the boiler is under pressure.It is never to be closed exceptwhen required for this purpose.Before passing into the boiler the water from the pump goes through theheater. This is a small cylinder, with a coil of pipe inside. The feed pipe from the pump is connected with one end of this inner coil of pipe, while the other end of the coil leads into the boiler itself. The exhaust steam from the engine cylinder is admitted into the cylinder and passes around the coil of pipe, afterwards coming out of the smoke stack to help increase the draft. As the feed water passes through this heater it becomes heated nearly to boiling before it enters the boiler, and has no tendency to cool the boiler off. Heating the feed water results in an economy of about 10 per cent.AUTOMATIC INJECTOR.The Injectoris another means of forcing water from a supply tank or well into the boiler, and at the same time heating it, by use of steam from the boiler. It is a necessitywhen a cross-head pump is used, since such a pump will not work when the engine is shut down. It is useful in any case to heat the water before it goes into the boiler when the engine is not working and there is no exhaust steam for the heater.There are various types of injectors, but they all work on practically the same principle. The steam from the boiler is led through a tapering nozzle to a small chamber into which there is an opening from a water supply pipe. This steam nozzle throws out its spray with great force and creates a partial vacuum in the chamber, causing the water to flow in. As the pressure of the steam has been reduced when it passes into the injector, it cannot, of course, force its way back into the boiler at first, and finds an outlet at the overflow. When the water comes in, however, the steam jet strikes the water and is condensed by it. At the same time it carries the water and the condensed steam along toward the boiler with such force that the back pressure of the boiler is overcome and a stream of heated water is passed into it. In order that the injector may work, its parts must be nicely adjusted, and with varying steam pressures it takes some ingenuity to get it started. Usually the full steam pressure is turned on and the cock admitting the water supply is opened a varying amount according to the pressure.First the valve between the check valve and the boiler should be opened, so that the feed water may enter freely; then open wide the valve next the steam dome, and any other valve between the steam supply pipe and the injector; lastly open the water supply valve. If water appears at the overflow, close the supply valve and open it again, giving it just the proper amount of turn. The injector is regulated by the amount of water admitted.PLAIN WHISTLE.In setting up an injector of any type, the following rules should be observed:All connecting pipes as straight and short as possible.The internal diameter of all connecting pipes should be the same or greater than the diameter of the hole in the corresponding part of the injector.When there is dirt or particles of wood or other material in the source of water supply, the end of the water supply pipe should be provided with a strainer. Indeed, invariably a strainer should be used. The holes in this strainer must be as small as the smallest opening in the delivery tube, and the total area of the openings in the strainer must be much greater than the area of the water supply (cross-section).The steam should be taken from the highest part of the dome, to avoid carrying any water from the boiler over with it. Wet steam cuts and grooves the steam nozzle. The steam should not be taken from the pipe leading to the engine unless the pipe is quite large.Before using new injectors, after they are fitted to the boiler it is advisable to disconnect them and clean them out well by letting steam blow through them or forcing water through. This will prevent lead or loose scale getting into the injector when in use.Set the injector as low as possible, as it works best with smallest possible lift.Ejectors and jet pumpsare used for lifting and forcing water by steam pressure, and are employed in filling tanks, etc.BLAST AND BLOW-OFF DEVICES.In traction engines there is small pipe with a valve, leading into the smoke stack from the boiler. When the valve is opened, the steam allowed to blow off into the smoke stack will create a vacuum and so increase the draft. Blast or blow pipes are used only in starting the fire, and are of little value before the steam pressure reaches 15 pounds or so.The exhaust nozzle from the engine cylinder also leads into the smoke stack, and when the engine is running the exhaust steam is sufficient to keep up the draft without using the blower.Blow-off cocksare used for blowing sediment out of the bottom of a boiler, or blowing scum off the top of the water to prevent foaming. A boiler should never be blown out at high pressure, as there is great danger of injuring it. Better let the boiler cool off somewhat before blowing off.SPARK ARRESTER.Traction engines are supplied as a usual thing with spark arresters if they burn wood or straw. Coal sparks are heavy and have little life, and with some engines no spark arrester is needed. But there is great danger of setting a fire if an engine is run with wood or straw without the spark arrester.DIAMOND SPARK ARRESTER.Spark arresters are of different types. The most usual form is a large screen dome placed over the top of the stack. This screen must be kept well cleaned by brushing, or the draft of the engine will be impaired by it.In another form of spark arrester, the smoke is made to pass through water, which effectually kills every possible spark.TheDiamond Spark Arresterdoes not interfere with the draft and is so constructed that all sparks are carried by a counter current through a tube into a pail where water is kept. The inverted cone, as shown in cut, is made of steel wire cloth, which permits smoke and gas to escape, but no sparks. There is no possible chance to set fire to anything by sparks. It is adapted to any steam engine that exhausts into the smoke stack.1Unless otherwise indicated, cuts of fittings show those manufactured by the Lunkenheimer Co., Cincinnati, Ohio.[return]2This kind of safety valve is now being entirely discarded as much more dangerous than the spring or pop valve.[return]

The first boilers were made as a single cylinder of wrought iron set in brick work, with provision for a fire under one end. This was used for many years, but it produced steam very slowly and with great waste of fuel.

The first improvement to be made in this was a fire flue running the whole length of the interior of the boiler, with the fire in one end of the flue. This fire flue was entirely surrounded by water.

Then a boiler was made with two flues that came together at the smoke-box end. First one flue was fired and then the other, alternately, the clear heat of one burning the smoke of the other when it came into the common passage.

The next step was to introduce conical tubes by which the water could circulate through the main fire flue (Galloway boiler).

FIG. 1. ORR & SEMBOWER’S STANDARD HORIZONTAL BOILER, WITH FULL-ARCH FRONT SETTING.

The object of all these improvements was to get larger heating surface. To make steam rapidly and economically, the heating surface must be as large as possible.

FIG. 2. GAAR, SCOTT & CO.’S LOCOMOTIVE BOILER.

But there is a limit in that the boiler must not be cumbersome, it must carry enough water, and have sufficient space for steam.

The stationary boiler now most commonly used is cylindrical, the fire is built in a brick furnace under the sheet and returns through fire tubes running the length of the boiler. (Fig. 1.)

The earliest of the modern steam boilers to come into use was the locomotive fire tube type, with a special firebox. By reference to the illustration (Fig. 2) you will see that the boiler cylinder is perforated with a number of tubes from 2 to 4 inches in diameter running from the large firebox on the left, through the boiler cylinder filled with water, to the smoke-box on the right, above which the smokestack rises.

FIG. 3. THE HUBER FIRE BOX.

It will be noticed that the walls of the firebox are double, and that the water circulates freely all about the firebox as well as all about the fire tubes. The inner walls of the firebox are held firmly in position by stay bolts, as will be seen inFig. 3, which also shows the position of the grate.

FIG. 4. HUBER RETURN FLUE BOILER.

The return flue type of boiler consists of a large central fire flue running through the boiler cylinder to the smoke box at the front end, which is entirely closed. The smoke passes back through a number of small tubes, and the smokestack is directly over the fire at the rear of the boiler, though there is no communication between the fire at the rear of the boiler and it except through the main flue to the front and back through the small return flues.Fig. 4illustrates this type of boiler, though it shows but one return flue. The actual number may be seen by the sectional view inFig. 5.

FIG. 5. SECTION VIEW OF HUBER RETURN FLUE BOILER.

The fire is built in one end of the main flue, and is entirely surrounded by water, as will be seen in the illustration. The long passage for the flame and heated gases enables the water to absorb a maximum amount of the heat of combustion. There is also an element of safety in this boiler in that the small flues will be exposed first should the water become low, and less damage will be done than if the large crown sheet of the firebox boiler is exposed, and this large crown sheet is the first thing to be exposed in that type of boiler.

The special difference between the fire tube boiler and the water tube boiler is that in the former the fire passesthrough the tubes, while in the latter the water is in the tubes and the fire passes around them.

FIG. 6. FREEMAN VERTICAL BOILER.

In this type of boiler there is an upper cylinder (or more than one) filled with water; a series of small tubes running at an angle from the front or fire door end of the upper cylinder to a point below and back of the grates,where they meet in another cylinder or pipe, which is connected with the other end of the upper cylinder. The portions of the tubes directly over the fire will be hottest, and the water here will become heated and rise to the front end of the upper cylinder, while to fill the space left, colder water is drawn in from the back pipe, from the rear end of the upper cylinder, down to the lower ends of the water tubes, to pass along up through them to the front end again.

This type of boiler gives great heating surface, and since the tubes are small they will have ample strength with much thinner walls. Great freedom of circulation is important in this type of boiler, there being no contracted cells in the passage. This is not adapted for a portable engine.

In the upright type of boiler the boiler cylinder is placed on end, the fire is built at the lower end, which is a firebox surrounded by a water jacket, and the smoke and gases of combustion rise straight up through vertical fire flues. The amount of water carried is relatively small, and the steam space is also small, while the heating surface is relatively large if the boiler is sufficiently tall. You can get up steam in this type of boiler quicker than in any other, and in case of the stationary engine, the space occupied is a minimum. The majority of small stationary engines have this type of boiler, and there is a traction engine with upright boiler which has been widely used, but it is open to the objection that the upper or steam ends of the tubes easily get overheated and so become leaky. There is also often trouble from mud and scale deposits in the water leg, the bottom area of which is very small.

Shell—The main cylindrical steel sheets which form the principal part of the boiler.

Boiler-heads—The ends of the boiler cylinder.

Tube Sheets—The sheets in which the fire tubes are inserted at each end of the boiler.

Fire-box—A nearly square space at one end of a boiler, in which the fire is placed. Properly it is surrounded on all sides by a double wall, the space between the two shells of these walls being filled with water. All flat surfaces are securely fastened by stay bolts and crown bars, but cylindrical surfaces are self-bracing.

Water-leg—The space at sides of fire-box and below it in which water passes.

Crown-sheet—The sheet of steel at the top of the firebox, just under the water in the boiler. This crown sheet is exposed to severe heat, but so long as it is covered with water, the water will conduct the heat away, and the metal can never become any hotter than the water in the boiler. If, however, it is not covered with water, but only by steam, it quickly becomes overheated, since the steam does not conduct the heat away as the water does. It may become so hot it will soften and sag, but the great danger is that the thin layer of water near this overheated crown sheet will be suddenly turned into a great volume of steam and cause an explosion. If some of the pressure is taken off, this overheated water may suddenly burst into steam and cause an explosion, as the safety valve blows off, for example (since the safety valve relieves some of the pressure).

Smoke-box—The space at the end of the boiler opposite to that of the fire, in which the smoke may accumulate before passing up the stack in the locomotive type, or through the small flues in the return type of boiler.

Steam-dome—A drum or projection at the top of the boiler cylinder, forming the highest point which the steam can reach. The steam is taken from the boiler through piping leading from the top of this dome, since at this point it is least likely to be mixed with water, either through foaming or shaking up of the boiler. Even under normal conditions the steam at the top of the dome is drier than anywhere else.

Mud-drum—A cylindrical-shaped receptacle at the bottom of the boiler similar to the steam-dome at the top,but not so deep. Impurities in the water accumulate here, and it is of great value on a return flue boiler. In a locomotive boiler the mud accumulates in the water leg, below the firebox.

Man-holes—Are large openings into the interior of a boiler, through which a man may pass to clean out the inside.

Hand-holes—Are smaller holes at various points in the boiler into which the nozzle of a hose may be introduced for cleaning out the interior. All these openings must be securely covered with steam-tight plates, called man-hole and hand-hole plates.

A boiler jacket—A non-conducting covering of wood, plaster, hair, rags, felt, paper, asbestos or the like, which prevents the boiler shell from cooling too rapidly through radiation of heat from the steel. These materials are usually held in place against the boiler by sheet iron. An intervening air-space between the jacket and the boiler shell will add to the efficiency of the jacket.

A steam-jacket—A space around an engine cylinder or the like which may be filled with live steam so as to keep the interior from cooling rapidly.

Ash-pit—The space directly under the grates, where the ashes accumulate.

Dead-plates—Solid sheets of steel on which the fire lies the same as on the grates, but with no openings through to the ash-pit. Dead-plates are sometimes used to prevent cold air passing through the fire into the flues, and are common on straw-burning boilers. They should seldom if ever be used on coal or wood firing boilers.

Grate Surface—The whole space occupied by the grate-bars, usually measured in square feet.

Forced Draft—A draft produced by any means other than the natural tendency of the heated gases of combustion to rise. For example, a draft caused by letting steam escape into the stack.

Heating Surface—The entire surface of the boiler exposed to the heat of the fire, or the area of steel or iron sheeting or tubing, on one side of which is water and on the other heated air or gases.

Steam-space—The cubical contents of the space which may be occupied by steam above the water.

Water-space—The cubical contents of the space occupied by water below the steam.

Diaphragm-plate—A perforated plate used in the domes of locomotive boilers to prevent water dashing into the steam supply pipe. A dry-pipe is a pipe with small perforations, used for taking steam from the steam-space, instead of from a dome with diaphragm-plate.

Before proceeding to a consideration of the care and management of a boiler, let us briefly indicate the chief working attachments of a boiler. Unless the nature and uses of these attachments are fully understood, it will be impossible to handle the boiler in a thoroughly safe and scientific fashion, though some engineers do handle boilers without knowing all about these attachments. Their ignorance in many cases costs them their lives and the lives of others.

The first duty of the engineer is to see that the boiler is filled with water. This he usually does by looking at the glass water-gauge.

TWO-ROD WATER GAUGE.

There is a cock at each end of the glass tube. When these cocks are open the water will pass through the lower into the glass tube, while steam comes through the other. The level of the water in the gauge will then be the same as the level of the water in the boiler, and the water should never fall out of sight below the lower end of the glass, nor rise above the upper end.

Below the lower gauge cock there is another cock used for draining the gauge and blowing it off when there is a pressure of steam on. By occasionally opening this cock, allowing the heated water or steam to blow through it, the engineer may always be sure that the passages into the water gauge are not stopped up by any means. By closing the upper cock and opening the lower, the passage into the lower may be cleared by blowing off the drain cock; by closing the lower gauge cock and opening the upper the passage from the steam space may be cleared and tested in the same way when the drain cock is opened. If the glass breaks, both upper and lower gauge cocks should be closed instantly.

GAUGE OR TRY COCK.

In addition to the glass water gauge, there are the try-cocks for ascertaining the level of the water in the boiler. There should be two to four of these. They open directly outof the boiler sheet, and by opening them in turn it is possible to tell approximately where the water stands. There should be one cock near the level of the crown sheet, or slightly above it, another about the level of the lower gauge cock, another about the middle of the gauge, another about the level of the upper gauge, and still another, perhaps, a little higher. But one above and one below the water line will be sufficient. If water stands above the level of the cock, it will blow off white mist when opened; if the cock opens from steam-space, it will blow off blue steam when opened.

The try-cocks should be opened from time to time in order to be sure the water stands at the proper level in the boiler, for various things may interfere with the working of the glass gauge. Try-cocks are often called gauge cocks.

TRY COCK.

The steam gauge is a delicate instrument arranged so as to indicate by a pointer the pounds of pressure which the steam is exerting within the boiler. It is extremely important, and a defect in it may cause much damage.

PRESSURE GAUGE.

The steam gauge was invented in 1849 by Eugene Bourdon, of France. He discovered that a flat tube bent in a simple curve, held fast at one end, would expand and contract if made of proper spring material, through the pressure of the water within the tube. The free end operates a clock-work that moves the pointer.

It is important that the steam gauge be attached to the boiler by a siphon, or with a knot in the tube, so that the steam may operate on water contained in the tube, and the water cannot become displaced by steam, since steam might interfere with the correct working of the gauge by expanding the gauge tube through its excessive heat.

Steam gauges frequently get out of order, and should be tested occasionally. This may conveniently be done by attaching them to a boiler which has a correct gauge already on it. If both register alike, it is probable that both are accurate.

STEAM GAUGE SIPHON.FRONT CYLINDER COCK.

STEAM GAUGE SIPHON.

FRONT CYLINDER COCK.

There are also self-testing steam gauges. With all pressure off, the pointer will return to 0. Then a series of weights are arranged which may be hung on the gauge and cause the pointer to indicate corresponding numbers. The chief source of variation is in the loosening of the indicator needle. This shows itself usually when the pressure is off and the pointer does not return exactly to zero.

The safety valve is a valve held in place by a weighted lever2or by a spiral spring (on traction engines) or some similar device, and is adjustable by a screw or the like so that it can be set to blow off at a given pressure of steam, usually the rated pressure of the boiler, which on traction engines is from 110 to 130 pounds. The valve is supplied with a handle by which it can be opened, and it should be opened occasionally to make sure it is working all right. When it blows off the steam gauge should be noted to see that it agrees with the pressure for which the safety valve was set. If they do not agree, something is wrong; either the safety valve does not work freely, or the steam gauge does not register accurately.

SECTIONAL VIEW OF KUNKLE POP VALVE.SAFETY VALVE.

SECTIONAL VIEW OF KUNKLE POP VALVE.

SAFETY VALVE.

The cut shows the Kunkle safety valve. To set it, unscrew the jam nut and apply the key to the pressure screw. For more pressure, screw down; for less, unscrew. After having the desired pressure, screw the jamnut down tight on the pressure screw. To regulate the opening and closing of the valve, take the pointed end of a file and apply it to the teeth of the regulator. If valve closes with too much boiler pressure, move the regulator to the left. If with too little, move the regulator to the right.

This can be done when the valve is at the point of blowing off.

PHANTOM VIEW OF MARSH INDEPENDENT STEAM PUMP.

Other types of valves are managed in a similar way, and exact directions will always be furnished by the manufacturers.

There are three ways in which a boiler is commonly filled with water.

First, before starting a boiler it must be filled with water by hand, or with a hand force-pump. There is usually a filler plug, which must be taken out, and a funnel can be attached in its place. Open one of the gauge cocks to let out the air as the water goes in.

When the boiler has a sufficient amount of water, as may be seen by the glass water gauge, replace the fillerplug. After steam is up the boiler should be supplied with water by a pump or injector.

There are two kinds of pumps commonly used on traction engines, the Independent pump, and the Cross-head pump.

The Independent pump is virtually an independent engine with pump attached. There are two cylinders, one receiving steam and conveying force to the piston; the other a water cylinder, in which a plunger works, drawing the water into itself by suction and forcing it out through the connection pipe into the boiler by force of steam pressure in the steam cylinder.

STRAIGHT GLOBE VALVE.ANGLE GLOBE VALVE.

STRAIGHT GLOBE VALVE.

ANGLE GLOBE VALVE.

It is to be noted that all suction pumps receive their water by reason of the pressure of the atmosphere on the surface of the water in the supply tank or well. This atmospheric pressure is about 15 pounds to the square inch, and is sufficient to support a column of water 28 to 33 feet high, 33 feet being the height of a column of water which the atmosphere will support theoretically at about sea level. At greater altitudes the pressure of the atmosphere decreases. Pumps do not work very well when drawing water from a depth over 20 or 22 feet.

Water can be forced to almost any height by pressure of steam on the plunger, and it is taken from deep wells by deep well pumps, which suck the water 20 to 25 feet, and force it the rest of the way by pressure on a plunger.

The amount of water pumped is regulated by a cock or globe valve in the suction pipe.

A Cross-head boiler pump is a pump attached to the cross-head of an engine. The force of the engine piston is transmitted to the plunger of the pump.

The pump portion works exactly the same, whether of the independent or cross-head kind.

The cut represents an independent pump that uses the exhaust steam to heat the water as it is pumped (Marsh pump).

VALVE WITH INTERNAL SCREW.

Every boiler feed-pump must have at least two check valves.

A check valve is a small swinging gate valve (usually) contained in a pipe, and so arranged that when water is flowing in one direction the valve will automatically open to let the water pass, while if water should be forced in the other direction, the valve will automatically close tight and prevent the water from passing.

SECTIONAL VIEW OF SWING CHECK VALVE.

There is one check valve in the supply pipe which conducts the water from the tank or well to the pump cylinder. When the plunger is drawn back or raised, a vacuum is created in the pump cylinder and the outside atmospheric pressure forces water through the supply pipe into the cylinder, and the check valve opens to let it pass. When the plunger returns, the check valve closes, and the water is forced into the feed-pipe to the boiler.

SECTIONAL VIEW OF CASE HEATER.

There are usually two check valves between the pump cylinder and the boiler, both swinging away from the pump or toward the boiler. In order that the water may flow steadily into the boiler there is an air chamber, which may be partly filled with water at each stroke of theplunger. As the water comes in, the air must be compressed, and as it expands it forces the water through the feed pipe into the boiler in a steady stream. There is one check valve between the pump cylinder and the air chamber, to prevent the water from coming back into the cylinder, and another between the air chamber and the boiler, to prevent the steam pressure forcing itself or the water from the boiler or water heater back into the air chamber.

SECTIONAL VIEW OF PENBERTHY INJECTOR.U. S. AUTOMATIC INJECTOR.(American Injector Co.)

SECTIONAL VIEW OF PENBERTHY INJECTOR.

U. S. AUTOMATIC INJECTOR.(American Injector Co.)

U. S. AUTOMATIC INJECTOR.

(American Injector Co.)

All three of these check valves must work easily and fit tight if the pump is to be serviceable. They usually close with rubber facings which in time will get worn,and dirt is liable to work into the hinge and otherwise prevent tight and easy closing. They can always be opened for inspection, and new ones can be put in when the old are too much worn.

Only cold water can be pumped successfully, as steam from hot water will expand, and so prevent a vacuum being formed. Thus no suction will take place to draw the water from the supply source.

There should always be a globe valve or cock in the feed pipe near the boiler to make it possible to cut out the check valves when the boiler is under pressure.It is never to be closed exceptwhen required for this purpose.

Before passing into the boiler the water from the pump goes through theheater. This is a small cylinder, with a coil of pipe inside. The feed pipe from the pump is connected with one end of this inner coil of pipe, while the other end of the coil leads into the boiler itself. The exhaust steam from the engine cylinder is admitted into the cylinder and passes around the coil of pipe, afterwards coming out of the smoke stack to help increase the draft. As the feed water passes through this heater it becomes heated nearly to boiling before it enters the boiler, and has no tendency to cool the boiler off. Heating the feed water results in an economy of about 10 per cent.

AUTOMATIC INJECTOR.

The Injectoris another means of forcing water from a supply tank or well into the boiler, and at the same time heating it, by use of steam from the boiler. It is a necessitywhen a cross-head pump is used, since such a pump will not work when the engine is shut down. It is useful in any case to heat the water before it goes into the boiler when the engine is not working and there is no exhaust steam for the heater.

There are various types of injectors, but they all work on practically the same principle. The steam from the boiler is led through a tapering nozzle to a small chamber into which there is an opening from a water supply pipe. This steam nozzle throws out its spray with great force and creates a partial vacuum in the chamber, causing the water to flow in. As the pressure of the steam has been reduced when it passes into the injector, it cannot, of course, force its way back into the boiler at first, and finds an outlet at the overflow. When the water comes in, however, the steam jet strikes the water and is condensed by it. At the same time it carries the water and the condensed steam along toward the boiler with such force that the back pressure of the boiler is overcome and a stream of heated water is passed into it. In order that the injector may work, its parts must be nicely adjusted, and with varying steam pressures it takes some ingenuity to get it started. Usually the full steam pressure is turned on and the cock admitting the water supply is opened a varying amount according to the pressure.

First the valve between the check valve and the boiler should be opened, so that the feed water may enter freely; then open wide the valve next the steam dome, and any other valve between the steam supply pipe and the injector; lastly open the water supply valve. If water appears at the overflow, close the supply valve and open it again, giving it just the proper amount of turn. The injector is regulated by the amount of water admitted.

PLAIN WHISTLE.

In setting up an injector of any type, the following rules should be observed:

All connecting pipes as straight and short as possible.

The internal diameter of all connecting pipes should be the same or greater than the diameter of the hole in the corresponding part of the injector.

When there is dirt or particles of wood or other material in the source of water supply, the end of the water supply pipe should be provided with a strainer. Indeed, invariably a strainer should be used. The holes in this strainer must be as small as the smallest opening in the delivery tube, and the total area of the openings in the strainer must be much greater than the area of the water supply (cross-section).

The steam should be taken from the highest part of the dome, to avoid carrying any water from the boiler over with it. Wet steam cuts and grooves the steam nozzle. The steam should not be taken from the pipe leading to the engine unless the pipe is quite large.

Before using new injectors, after they are fitted to the boiler it is advisable to disconnect them and clean them out well by letting steam blow through them or forcing water through. This will prevent lead or loose scale getting into the injector when in use.

Set the injector as low as possible, as it works best with smallest possible lift.

Ejectors and jet pumpsare used for lifting and forcing water by steam pressure, and are employed in filling tanks, etc.

In traction engines there is small pipe with a valve, leading into the smoke stack from the boiler. When the valve is opened, the steam allowed to blow off into the smoke stack will create a vacuum and so increase the draft. Blast or blow pipes are used only in starting the fire, and are of little value before the steam pressure reaches 15 pounds or so.

The exhaust nozzle from the engine cylinder also leads into the smoke stack, and when the engine is running the exhaust steam is sufficient to keep up the draft without using the blower.

Blow-off cocksare used for blowing sediment out of the bottom of a boiler, or blowing scum off the top of the water to prevent foaming. A boiler should never be blown out at high pressure, as there is great danger of injuring it. Better let the boiler cool off somewhat before blowing off.

Traction engines are supplied as a usual thing with spark arresters if they burn wood or straw. Coal sparks are heavy and have little life, and with some engines no spark arrester is needed. But there is great danger of setting a fire if an engine is run with wood or straw without the spark arrester.

DIAMOND SPARK ARRESTER.

Spark arresters are of different types. The most usual form is a large screen dome placed over the top of the stack. This screen must be kept well cleaned by brushing, or the draft of the engine will be impaired by it.

In another form of spark arrester, the smoke is made to pass through water, which effectually kills every possible spark.

TheDiamond Spark Arresterdoes not interfere with the draft and is so constructed that all sparks are carried by a counter current through a tube into a pail where water is kept. The inverted cone, as shown in cut, is made of steel wire cloth, which permits smoke and gas to escape, but no sparks. There is no possible chance to set fire to anything by sparks. It is adapted to any steam engine that exhausts into the smoke stack.

1Unless otherwise indicated, cuts of fittings show those manufactured by the Lunkenheimer Co., Cincinnati, Ohio.[return]

2This kind of safety valve is now being entirely discarded as much more dangerous than the spring or pop valve.[return]

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