Important stress has been laid upon keeping all floating objects, gravel, etc., away from the acting parts of the pump. In Fig. 104 is presented a cut of an approved strainer which can be removed, freed from obstruction, and replaced by simply slacking one bolt, the entire operation occupying one minute. The advantages of this strainer will be readily apparent.

IMPORTANT PRINCIPLES RELATING TO WATER.

There are some underlying natural laws and other data relating to water which every engineer should thoroughly understand. Heat, water, steam, are the three properties with which he has first to deal.

Weight of one cubic foot of Pure Water.

The weight of a cubic foot of water is about 1000 ounces (exactly 998.8 ounces), at the temperature of maximum density.

The weight of a cylindrical foot of water at 62° F. is 49 lbs. (nearly). The weight of a cylindrical inch is 0.4533 oz.

There are four notable temperatures for water, namely,

Water rises to the same level in the opposite arms of a recurved tube, hence water will rise in pipes as high as its source.

The pressure on any particle of water is proportioned to its depth below the surface, and as the side pressure is equal to the downward pressure.

Water at rest presses equally in all directions. This is a most remarkable property, the upward direction of the pressure of water is equal to that pressing downwards, and the side pressure is also equal.

Any quantity of water, however small, may be made to balance any quantity, however great. This is called the Hydrostatic Paradox, and is sometimes exemplified by pouring liquids into casks through long tubes inserted in the bung holes. As soon as the cask is full and the water rises in the pipe to a certain height the cask bursts with violence.

Water is practically non-elastic. A pressure has been applied of 30,000 pounds to the square inch and the contraction has been found to be less than one-twelfth.

The surface of water at rest is horizontal. A familiar example of this may be noted in the fact that the water in a battery of boilers seeks a uniform level, no matter how much the cylinders may vary in size.

A given pressure or blow impressed on any portion of a mass of water confined in a vessel is distributed equally through all parts of the mass; for example a plug forced inwards on a square inch of the surface of water, is suddenly communicated to every square inch of the vessel’s surface, however large, and to every inch of the surface of any body immersed in it.

Weight and Capacity of Different Standard Gallons of Water.

STORING AND HANDLING OF COAL.

The best method of storing coal is a matter of economy and needs the attention of the engineer.

Coal, as it comes from the mine, is in the best possible condition for burning in a furnace; its fracture is bright and clean, and it ought to be preserved up to the time of using it in such manner as to avoid as much as possible any alteration of its condition so as to prevent deterioration.

So far as actual experience goes it has been found that a brick building, with double walls to promote coolness, with high narrow slits instead of windows, with ventilating holes along the bottom of the walls, having a high-pitched roof with overhanging eaves, and holes for ventilation well sheltered under the eaves, and with ventilators along the edge of the roof, is best suited to keep the coal in the condition most nearly approaching that of the freshly mined. The floor of the building should be preferably paved with brick on edge or flagstones; the doors should be large and kept open in damp weather, and closed when the weather is hot.

Some persons recommend sprinkling the coal occasionally during the hot weather, but it is much better to wet down the paving all around the building outside, and the exposed floor of the building, as well as the walls inside and outside, and let the moisture of the evaporation have its effect upon the coal. It will be found to be amply sufficient for the purpose.

It has been found long since that it is better to have coal sheds dark, as light assists greatly in impairing the fuel.

The best arrangement for a boiler room floor is to have a coal-bin, paved with stone flags, opening into the fire-room by a door, while the fire-room itself should be paved diagonally with brick, set on edge upon a concrete foundation, well rammed to within about three feet of the boiler front, and the remaining space should be floored with iron plates.

The coal should be wheeled from the bins and dumped upon these plates, never on the brick floor. These plates should be laid on an incline of about an inch toward the boilers, and it is well to have a trough or gutter, of about six inches in width, and having a depth of about one and a half inches cast in them, at the edge lying nearest the boilers, so that the water from the gauge-cock, drip-pipes, and that from wetting down the ashes may run into it and drain into a proper sewer-pipe laid under the flooring.

CHEMISTRY OF THE FURNACE.

A careful estimate by a Broadway Chemist of the contents or constituents of a ton of coal presents some interesting facts, not familiar certainly to unscientific minds. It is found that, besides gas, a ton of ordinary gas coal will yield 3,500 pounds of coke, twenty gallons of ammonia water and 140 pounds of coal tar. Now, destructive distillation of this amount of coal tar gives about seventy pounds of pitch, seventeen pounds of creosote, fourteen pounds of heavy oils, about nine and a half pounds of naphtha yellow, six and one-third pounds of naphthaline, four and three-fourth pounds of alizarine, two and a fourth pounds of solvent naphtha, one and a fifth pound of aniline, seventy-nine hundredths of a pound of toludine, forty-six hundredths of a pound of anthracine, and nine-tenths of a pound of toluches—from the last-named substance being obtained the new product, saccharine, said to be 230 times as sweet as the best cane sugar.

From an engineer’s standpoint the main constituents of all coal are carbon and hydrogen; in the natural state of coal these two are united and solid; their respective characters and modes of entering into combustion, are however essentially different. The hydrogen is convertable into heat only in the gaseous state; the carbon, on the contrary, is combustible only in the solid condition. It must be borne in mind that neither is combustible while they are united.

There are, however, other elements existing in coal in its natural state, and new ones are formed during burning or combustion as will be noted in the succeeding paragraphs.

For raising steam the process of combustion consists in disentangling, letting loose or evolving the different elements locked up in coal; the power employed in accomplishing this is heat. The chemical results of this consumption of the fuels may be divided into four stages or parts.

First stage, application of existing heat to disengage the constituent gases of the fuel. In coals this is principally mixed carbon and hydrogen.

Second stage, application or employment of existing heat to separate the carbon from the hydrogen.

Third stage, further employment of existing heat to increase the temperature of the two combustibles, carbon and hydrogen, until they reach the heat necessary for combination with the air. If this heat is not obtained, chemical union does not take place and the combustion is imperfect.

Fourth and last stage, the union of the oxygen of the air with the carbon and hydrogen of the furnace in their proper proportions, when intense heat is generated and light is also given off from the ignited carbon. The temperature of the products of combustion at this final stage depend upon the quantity of air in dilution. Sir H. Davy estimates this heat as greater than the white heat of metals.

In the first stages heat is absorbed, but is given out in the last. When the chemical atoms of heat are not united in their proper proportions, then carbonic oxide, mixed carbon and hydrogen, and other combustible gases escape invisibly, with a corresponding loss of heat from the fuel.

When the proper union takes place, then only steam, carbonic acid and nitrogen, all of which are incombustible, escape.

The principal products, therefore, of perfect combustion are: steam, invisible and incombustible; carbonic acid, invisible and incombustible.

The products of imperfect combustion are: carbonic oxide, invisible but combustible; smoke, partly invisible and partly incombustible.

Steam is formed from the hydrogen gas given out by the coals combining with its equivalent of oxygen from the air. Smoke is formed from the hydrogen and carbon which have not received their respective equivalents of oxygen from the air, and thus pass off unconsumed. The color of the smoke depends upon the carbon passing off in its dark, powdery state.

The heat lost is not dependent upon the amount of carbon alone, but also upon the invisible but combustible gases, hydrogen and carbonic oxide; so that while the color may indicate the amount of carbon in the smoke, it does not indicate the amount of the heat lost; hence, the smokeless locomotive burning coke may lose more heat in this way than that arising from the imperfect burning of coal under the stationary engine boiler.

A practical and familiar instance of imperfect combustion is exhibited when a lamp smokes and the unconsumed carbon is deposited all about in the form of soot. When the evolving or disengagement of the carbon is reduced by lowering the wick to meet the supply of oxygen, the carbon is all consumed and the smoke ceases. What takes place in a lamp also occurs in a furnace, so that the proper supply of air is a primary thing, relating to economy, both as regards its quantity and its mode of admission to a fire.

The economical generation of heat is one thing, the use made of that heat afterwards is another. Combustion may be perfect, but the absorption of heat by a boiler may be inferior.

The chief agents operating in the furnace are carbon, hydrogen and oxygen, and their union in certain proportions produces other bodies, as water or steam, carbonic acid, besides others of less practical importance.

Oxygen is an invisible gas, has no smell, and remains permanently in receptacles, unchanged by time. It can be obtained in an experimental quantity by heating the chlorate of potash, and collecting the gas given off in a bladder or jar. It is a trifle heavier than common air, i.e., 1.106 times and a cubic foot at 32° temperature weighs 1.428 ounces. It is one of the most abundant bodies in nature, and is combined with many others in a great variety of ways.

Carbon is one of the most interesting elementary substances in nature. It is combustible and forms the base of charcoal, and enters largely into mineral coal. It is a mineral capable of being reduced to a feathery powder, and is found in many different forms. It is obtained by various processes: from oil lamps as lamp-black; from coal as coke, and from wood as charcoal; the mineral particles of carbon in a state of combustion render flame luminous from either gas, oil or candles.

Carbon unites with iron to form steel, and with hydrogen to form the common street gas. Carbon is considered as the next most abundant body in nature to oxygen. In the furnace the carbon of the fuel unites with the oxygen of the air to produce heat; if the supply of air is correctly regulated, there will be perfect combustion, but if the supply of air be deficient, combustion will be imperfect.

Hydrogen is an invisible gas, and the lightest known body in the world, being many times lighter than oxygen. It is combustible and gives out much heat. In our gas establishments it is made in large quantities and combined with carbon for illuminating streets, shops and dwellings. It is the source of all common flame. When united with sulphur in coal mines it becomes explosive. By passing a current of steam through a hot iron tube partly filled with filings, hydrogen gas is given off and burns with a pale yellow flame.

The more hydrogen, therefore, there is in the fuel, the greater in general is its heating power. But it must be borne in mind that the element of hydrogen is, nevertheless, to a greater or less degree neutralized by the other element, oxygen, when it is present as a constituent of the fuel; since the affinity of hydrogen for oxygen is superior to that of carbon, and the oxygen saturated with hydrogen is converted into steam and rises in this form from the fuel bed without producing heat. Thus it is that the more oxygen there is in the fuel the less is its power for developing heat by combustion.

Nitrogen is also an elementary body. It neither supports life nor combustion; it is lighter than air and has no taste or smell. One cubic foot at 32° temperature weighs a trifle less than one ounce.

Sulphur is also an elementary body, of a yellow color, brittle, does not dissolve in water, is easily melted, and inflammable. It is also called brimstone or burnstone, from its great combustibility. It burns with a blue flame, and with a peculiar, suffocating odor.

Carbonic Acid Gas is formed by the burning of sixteen parts of oxygen and six parts of carbon. Its specific gravity is 1.529; it is fatal to life, and it also extinguishes fire.

Carbonic Oxide is a colorless, transparent, combustible gas, which burns with a pale blue flame, as may be seen at times on opening a locomotive fire-box door. Its presence in a furnace is evidence of imperfect combustion from a deficient supply of air, as it indicates that only eight parts of oxygen instead of sixteen parts have united with six parts of carbon.

Table.

The following table exhibits the comparative amounts of water which can be, under perfect conditions, evaporated from the substances named:

The last four substances are compounds, and the last three consist almost wholly, or chiefly of carbon and hydrogen. The total heating power of average coal is, it may be noted to advantage, about 12.83 pounds of water upon the same conditions as above described. Hydrogen, it is seen, stands pre-eminently at the head of the list for heating power, represented by the evaporation of 64¹⁄₄ pounds of water, whilst carbon, the next in order, and the staple combustible element in fuel, has only a heating power of 14³⁄₄ pounds of water.

HEAT-PROOF AND ORNAMENTAL PAINTS.

Steam pipes, boiler fronts, smoke connections and iron chimneys are often so highly heated that the paint upon them burns, changes color, blisters and often flakes off. After long protracted use under varying circumstances, it has been found that a silica-graphite paint is well adapted to overcome these evils. Nothing but boiled linseed oil is required to thin the paint to the desired consistency for application, no dryer being necessary. The paint is applied in the usual manner with an ordinary brush. The color, of course, is black.

Another paint, which admits of some variety in color, is made by mixing soapstone, in a state of fine powder, with a quick-drying varnish of great tenacity and hardness. This will give the painted object a seemingly-enameled surface, which is durable and not affected by heat, acids, or the action of the atmosphere. When applied to wood it prevents rotting, and it arrests disintegration when applied to stone. It is well known that the inside of an iron ship is much more severely affected by corrosion than the outside, and this paint has proven itself to be a most efficient protection from inside corrosion. It is light, of fine grain, can be tinted with suitable pigments, spreads easily, and takes hold of the fibre of the iron or steel quickly and tenaciously.

Turpentine well mixed with black varnish also makes a good coating for iron smoke pipes.

Much brighter and more pleasant appearing engine rooms can be made by making the surfaces white. Lime is a good non-conductor of heat, and it has the further quality of protecting iron from rust, so it would appear that whitewash was as good a material with which to cover boiler fronts, smoke stacks, steam pipes, etc., as any other substance.

To prepare whitewash for this purpose it is only necessary to add a little salt or glue to the water used for dissolving the lime, as either of these substances will make it stick readily and it cannot afterward be easily rubbed off; but perhaps the best way to prepare the whitewash would be to boil a pound of rice until it has become the consistency of starch, all of the solid particles having been broken up by boiling, and add this solution to the solution of lime in water.

This last preparation is also very good for outside work, for after it has been applied and has an opportunity to dry, no amount of rain will wash it off and its appearance is almost equal to white paint, and no amount of heat ordinarily met with will discolor it, although the heat of the fire box doors, if it was applied in such place, would give it a brownish cast of color. Even the brick setting of a boiler looks very much better when nicely whitewashed than when of its natural color, and if the ceiling and walls of the boiler room are also whitewashed the effect is quite pleasing, more healthful and conduces greatly to cleanliness.

Any engineer who tries this, renewing the whitewash as frequently as he would paint, will give this plan of painting pipes and boiler front the preference over the use of any kind of black paint.

PRESSURE RECORDING GAUGE.

This device is an ingenious mechanism actuated by clock work and the varying pressures of steam formed within the boiler; it records the time and the pressure upon a revolving roll of paper and preserves an accurate account of the varying conditions which have existed within the boiler.

The advantages derived from its use may be thus summarized: 1, It is a monitor constantly teaching the fireman to be careful to maintain an equal pressure of steam. 2, This uniform steam made possible by the use of the gauge is productive of the greatest possible economy. 3, The even strain maintained insures a long life to the boiler and a minimum of repairs. 4, It is the vindication of an attentive and careful fireman and allows him due credit for his skill and faithfulness, which is too often ill appreciated for lack of a reliable record.

Although described as a boiler room fixture, where it is frequently found in position, the proper place for this admirable device is in the steam user’s office, thus establishing a nerve connection, between engineer and owner, relating to the safety and economy of the power-plant to their mutual great advantage.

HORSE POWER AS APPLIED TO BOILERS.

By general agreement a horse power as applied to steam boilers is thirty (30) pounds of feed water at a temperature of 100 degrees Fahr. converted into steam in 1 hour at 70 pounds gauge pressure.

The standard is all that can be asked because the same test will determine two things; first the steam making capacity of the boiler and second its evaporative efficiency, which is all that is necessary to know in determining the commercial rating of boilers.

But it is a fact that, without an engine attached, there is no such thing as calculating the horse power of a boiler upon general principles. A well constructed engine with a given pressure of steam upon a piston of a given area and moving at a certain velocity in feet per minute, will always and under all conditions develop the same power so long as the boiler is able to furnish a sufficient quantity of steam to keep up that pressure; and it matters not whether the steam is taken from a boiler rated at 60 horse power or 30.

An evidence of the fact that there is no standard rule for calculating the horse power of boilers that can be depended upon, is that no two engine builders send out the same sized boilers with the engine of the same rated power. Experience has taught them that to furnish steam sufficient to work their engines up to their ratings that a certain sized boiler is required, and what would be considered 30 horse power by one manufacturer might be considered 35 or more by another—the difference being in the economy of the engine of using the steam, and not in the boiler for making it.

Then, again, a boiler that might furnish a sufficient quantity of steam to work a certain type of engine up to 40 horse power without forcing the fire might, with another style of engine, in order to generate the same power and perform the same duty, require to be forced beyond the limits of safety or economy. Therefore, considering the varying conditions under which all steam boilers are placed, there is no such a thing as any reliable standard rule for calculating the horse power of boilers, but only an approximate one at the best.

Hence it is best to select an engine of a certain power, and then let the same manufacturers furnish a boiler to correspond with it; and so long as the two are adapted to each other and the boiler of sufficient capacity to work the engine up to its full ratings, it matters but little whether the boiler figures the same horse power or not.

It has been found in practice that it is not good economy to carry pressure higher than eighty pounds in single cylinder automatic cut off engines.

As pressures increase, it becomes possible to use more economical engines, reducing water consumption per horse power per hour, thus requiring a smaller amount of heating surface and grate surface, that is to say, a smaller boiler and furnace for a given power.

For pressure between eighty and one hundred and twenty pounds, the compound engine gives the best results, while for higher pressures triple and quadruple expansion engines are the most economical.

Rule for Estimating Horse Power of Horizontal Tubular Steam Boilers.

Find the square feet of heating surface in the shell, heads and tubes, and divide by 15 for the nominal horse power.

The office of a boiler is to make steam and its real efficiency or the measure of its utility to the purchaser is measured by the amount of water it can turn into steam in a certain length of time and the amount of coal it requires to do this work.

An ordinary 54″×16′ boiler with forty 4″ tubes, 25 sq. ft. of grate surface and 800 sq. ft. of heating surface, in a general way is a 75 h. p. boiler, but good practice will get from it 100 h. p., and the very best modern engines 200 h. p.

BOILER SETTING.

The method, either ill or good in which steam boilers are “set” or arranged in their brick work and connections, will vary the quantity of fuel used by as much as one-fifth; hence the importance of knowing the correct principles upon which the work should be done.

The portion of the steam plant called “the boiler” is composed of two parts—the boiler and the furnace, and the latter may be considered a part of the “setting” as it is mainly composed of brick work.

Two kinds of brick are used in boiler setting—the common brick for walls, foundations and backing to the furnace, and so-called fire-brick, which should be laid at every point where the fire operates directly upon the furnace and passages.

Fire brick should be used in all parts of the setting which are exposed to the hot gases. It is better to have fire brick lining tied in with red brickwork, unless the lining is made 13¹⁄₂ inches thick, when it can be built up separate from outside walls. This arrangement will require very heavy walls. As usual, but 9 inches fire brick lining is used in the fireplace and 4¹⁄₂ inches behind the bridge wall. Joints in the fire brick-work should be as thin as possible.

Fig. 106 represents some of the different shapes in which fire brick are made to fit the side of the furnace. They are called by special names indicated by their peculiar form, circle-brick, angle-brick, jamb-brick, arch-brick, etc. The common fire brick are 9″×4¹⁄₂″×2¹⁄₂″ in size, as shown in the figure.

The peculiar quality in fire bricks is their power to resist for a long time the highest temperatures without fusion; they should be capable of being subjected to sudden changes of temperature without injury, and they should be able to resist the action of melted copper or iron slag. Fire brick are cemented together with fire clay which is quite unlike the ordinary mortar which is most suitable for common brick.

The setting as well as construction of boilers differs greatly, but in all the end to be sought for is a high furnace heat, with as little waste as possible, at the chimney end. To attain this there must be (1) a sufficient thickness of wall around the furnace, including the bridge, to retain as nearly as may be every unit of heat. (2) A due mixture of air admitted at the proper time and temperature to the furnace. (3) A proportionate area between the boiler and the surface of the grates for the proper mixing of the gases arising from combustion. (4) A correct proportion between the grate surface, the total area of the tubes and the height and area of the chimney.

The principal parts and appendages of a furnace are as follows:

The furnace proper or fire box, being the chamber in which the solid constituents of the fuel and the whole or part of its gaseous constituents are consumed.

The grate, which is composed of alternate bars and spaces, to support the fuel and to admit the air.

The dead-plate, that part of the bottom of the furnace which consists of an iron plate simply.

The mouth piece, through which the fuel is introduced and often some air. The lower side of the mouth piece is the dead plate.

The fire door: Sometimes the duty of the fire door is performed by a heap of fuel closing up the mouth of the furnace.

The furnace front is above and on either side of the fire door.

The ash pit. As a general rule the ash pit is level, or nearly so, with the floor on which the fireman stands, and as for convenient firing, the grate should not be higher than 28 to 30 inches, the depth of ash pit is thereby determined.

The ash pit door is used to regulate the admission of air.

The bridge wall.

The combustion or flame chamber.

The arrangement of the space behind the bridge wall is found usually to be in some one of the following forms: Level from bridge wall to back (Fig. 107). A square box, depth ranging from 15 inches to 6 feet (Fig. 108). A gradual rise from bridge to back end of boiler, where only six inches is found and generally circular in form (Fig. 109). A gradual slope toward back, leaving a distance of about 36 inches from boiler (Fig. 110).

The advocates of Fig. 107 claim that the office of the flame is to get into as close contact with the bottom as possible, and this form compels the flame to do so. In burning soft coal this form is found to soot up the bottom of the boiler very badly.

Fig. 108 is followed more extensively than any other, the variations being the depth of chamber; with depth generally from 36 to 40 inches.

Fig. 109 has nothing to commend it, except in cases where bridge is too low.

Fig. 110 is followed a great deal and gives very good satisfaction. This form allows for the theory of combustion, namely, the expansion of the gases after leaving bridge wall.

Space behind the bridge wall should be enlarged, as it will reduce the velocity of fire gases, and thus have them give up more of their heat to the boiler.

The bridge wall should not be less than 18 inches at bottom, but may be tapered off toward top to 9 or 13 inches.

Setting of Water Tube Boilers.

On page 67, Fig. 26, is exhibited a steam boiler with inclined tubes. The setting in this style of boilers is as follows:

A brick wall is laid for the front with suitable openings for the doors of the furnace and ash pit, and protected on the outside by a front of cast iron, and on the inside by a lining of fire brick.

At the back of the grates a bridge wall is run up to the bottom of the inclined water tubes, so that the hot gases that arise over it must circulate among the tubes.

A counter wall is laid on an incline from the top of the tubes to the back of the drum. This is laid on perforated plates or bars and is covered with fire brick. A wall is also built at the lower and back end of the tubes to carry them.

Back of the whole is the outer wall with openings for giving access to the tubes and smoke chambers. Side walls are raised to enclose the same and are arched at the top to come nearly in contact with the drum, which is carried partly by brackets and partly by the connections to the tubes.

Points Relating to Boiler Setting.

Long and heavy boilers are best suspended from two beams or girders by two or three bolts at each end. Boilers over 40 feet long should have three or even four sets of hangers, as the case may require.

Side brackets resting on masonry may be used for short boilers. If used on long boilers, side plates or expansion rollers should be used at one end of boiler. There ought to be not more than two brackets on one side, so divided that the distance between them is about three-fifths of the total length of the boiler, or the distance from ends of boiler to center of bracket is equal to one-fifth the length of boiler.

The side walls in boiler-setting should not be less than twenty inches with a two inch air space; the rear wall may vary from 12 to 16 inches according to the size of the boiler; the front wall 9 inches and the bridge wall may be from 18 to 24 and perfectly straight across the rear of the furnace. If the boilers are supported by side walls, the outside walls should be not less than 13 inches thick and have pilasters where the boiler is resting.

Flues touching the boiler above the water space should be emphatically condemned.

Unless the boiler walls are very heavy, they should be stayed by cast or wrought iron bunch stays, held together by rods at tops and bottoms.

It is dangerous to have large spaces in which gases may collect for sudden ignition, producing the so-called “back draft.”

Connections between the rear end of the boiler and brickwork is best made with cast-iron plates or fire-brick, suspended, when boilers are suspended, as the expansion and contraction will destroy an arch in a short time. If resting on mud-drum stand, this connection can be arched, as in this case the rear end of boiler will remain stationary.

If the draughts from the different boilers come in the same direction, or nearly so, no special provision is necessary, but if the draught enters from directly opposite directions a centre wall should be provided.

An advantage claimed for water in the ash pit is: by the dropping of hot ashes and cinders from the grate into the water, steam is generated, which, in passing through the hot coal lying on the grate, is there divided into oxygen and hydrogen, thus helping the combustion.

A dry brick will absorb a pound of water, and it is the water in the mortar that causes it to set, and harden. To prevent this loss of the water of crystalization, and give it time to harden and adhere to the brick, the brick must be well saturated with water, before they are laid.

Whenever steam is allowed to come in contact with mortar or cement an injurious effect is produced. The action of the steam is much more rapid than that of air and water, or water alone, when in abundance, as the effect of the steam in every case is to soften the mortar and penetrate to a greater depth than water could possibly do.

The distance between the rear head of the boiler and brickwork should not be less than 12 inches.

In setting steam boilers, allowance must be made for the expansion and contraction of the structure and this is usually done by placing rollers under the rear lug or side bearing of the boiler. Care should be exercised that the boiler rests are always in good condition so that they may move freely and not place the boiler in any danger of sticking and buckling.

Kindling a Furnace Fire.

In kindling a coal fire in a furnace the phosphorus of a match inflames at so low a temperature (150 degrees Fahr.) that mere friction ignites it, and in burning (combining with oxygen of the air) it gives out heat enough to raise the sulphur of the match to the temperature of ignition (500 degrees Fahr.), which, combining in its turn with the oxygen of the atmosphere, gives out sufficient heat to raise the temperature of the wood to the point of ignition (800 degrees Fahr.), and at this temperature the wood combines with oxygen supplied by the air, giving out a temperature sufficient to raise the coal to the point of ignition (1000 degrees Fahr.), and the coal then combines with the free oxygen of the air, the ensuing temperature in the furnace varying, according to circumstances, from 3000 degrees to 4000 degrees Fahr. Thus we see that the ignition of the coal is the last of a series of progressive steps, each increasing in temperature.

And in each step it will be noted that a combination of oxygen is the essential connecting link and that the oxygen is supplied in each instance at the same average temperature—this fact contains a “point” relating to supplying furnaces with so called “hot air.”

Sawdust Furnace.

Referring also to page 33 for information relating to the burning of sawdust and shavings S. S. Ingham, in the Stationary Engineer, says upon this important matter:

“Regarding a furnace for burning sawdust, I submit the accompanying cuts. I have built numbers of these oven furnaces for burning this fuel in the south, and all have given excellent results. The dimensions are for 60″ × 16′ return tubular (4″ tubes) boiler with stack 50 per cent. greater area than the flues; a good draft is necessary.” It will be understood that the upper cut is designed to show end view of the furnace whose side is shown in sectional view at the bottom of the page.

GAS PIPE.

PIPES AND PIPING.

Next in importance after the skill necessary for the steam generator and the engine, is the proper arrangement and care and management of the pipes and valves belonging to a steam plant.

It is the first thing an engineer does in taking charge of a new place, to ascertain the exact course and operation of the water, steam, drain and other pipes.

Examiners for licensing marine and land engineers base their questions much more to ascertain the applicant’s knowledge of piping than is generally known; hence the importance of the “points” in the succeeding pages relating to this subject.

Pipes are used for very many purposes in connection with the boiler room, and of course vary in size, in material and in strength, according to the purposes for which they are designed. There are pipes for conveying and delivering illuminating gas; pipes for conveying and delivering drinking water, and for fire purposes; pipes for draining and carrying off sewage and surface water; pipes for delivering hot water under high pressure, for heating purposes and power; pipes for delivering live steam under pressure, for heating purposes and power; pipes for delivering compressed air, for purposes of power and ventilation; pipes for conveying mineral oils, etc.

In Figs. 111, 112 113 and 114 are given approximate sizes of gas pipe and boiler tubes, taken from the catalogue of one of the oldest steamfitting establishments in the country. It will be observed that the size of gas pipe is computed from the internal diameter, while boiler tubes are estimated from the outside: thus, 3 in. gas pipe has an external diameter of 3¹⁄₂ inches, while 3 in. boiler tubes have an outside diameter of 3 inches only. It may be noted that boiler-tubes are made much more accurately as to size than gas pipe; this is especially true of the outside surfaces which are much smoother in one case than in the other.

BOILER TUBES.