Chapter XI: Section 24: “Lever safety valves to be attached to marine boilers shall (4)

The range of application of the steam loop practically covers every requirement for the return of water of condensation. If used in connection with a steam engine, pump, etc., a separator of any simple form is connected in the steam pipe as close as possible to the throttle. From the bottom of the separator the loop is led back to the boiler, and the circulation maintained by it will dry the steam before it is admitted to the cylinder.

There is necessary to its operation a slight fall in temperature at the head of the loop, which is accompanied by a corresponding fall in pressure. The water accumulating in the lower end of the loop next to the separator, as soon as it fills the diameter of pipe, is suddenly drawn or forced to the horizontal by that difference in pressure. It is immaterial how far the water has to be taken back, or how high it is to be lifted. There is one system now in daily operation lifting the condensed water over thirty-nine feet, and another lifting it over sixty-three feet. The strength of the system is increased by length and height, the only limit to its operation being the practicability of erecting the necessary drop leg, the height of which depends on difference in pressures.

Fig. 155 is an illustration of its application to a radiating coil. To understand the philosophy of its action, and referring to the illustration, let us assume that all the valves are open, and full boiler pressure is freely admitted throughout the steam pipe, coil and loop. Now, if the pressure were exactly uniform throughout the whole system, the water in the loop would stand at _a_ on the same level as the water in the boiler. But, as a matter of fact, the pressure is not uniform throughout the system, but steadily reduces from the moment of leaving the dome. This reduction in pressure is due in part to condensation and in part to friction, and although generally small is always present in some degree. The pressure may be intentionally reduced at the valve on the coil, and reduction necessarily results from condensation within the coil itself. A still further reduction takes place through the loop, so that the lowest pressure in the whole system will be found at _a_, the point in the loop furthest from the boiler, reckoned by the flow of steam.

Now it is known that water of condensation invariably works towards, and accumulates in, a “dead end.” This is due to the fact that, as already shown, the pressure is lower at the “dead end” than at any other point in the system, and, as a consequence, there is a constant flow, or sweep, of steam towards the point of least pressure, which flow continues as long as condensation goes on. This sweep of steam carries along with it all the water formed by condensation or contained in the steam, at first in the form of a thin film, swept along the inner surface of the loop, and afterwards, when the accumulation of water is sufficient, in the form of small slugs or pistons of water, which completely fill the pipe at intervals, traveling rapidly towards the dead end. The action of the steam sweep is vastly more powerful than is usually supposed, and, of course, operates continuously and infallibly to deposit the water in the dead end as fast as accumulated.

In practice, water will speedily be carried over by the loop and accumulate in the drop leg until it rises to the level _b_, which would balance the difference in pressure. As the loop will still continue to bring over water, it follows that as fast as a slug or piston of water is deposited by the steam on the top of the column at _b, it overbalances the equilibrium and an equal amount of water is discharged from the bottom of the column through the check valve into the boiler_.

The result of the practical operation of many systems of this ingenious device show advantages as follows:

1. Return of pure water to the boiler and saving the heat contained in said water.

2. Preserving more uniform temperatures, thus avoiding the dangers due to expansion and contraction.

3. Prevention of loss from open drains, drips, tanks, etc.

4. Maintaining higher pressure in long lines of piping, in jackets, driers, etc.

5. Enabling engines to start promptly.

6. Saving steam systems from water, thereby reducing liability to accident.

BOILER MAKERS’ TOOLS AND MACHINERY.

Fig. 156 represents a pair of jack screws. These are invaluable devices for use in boiler-shops, and also in establishments where ponderous machinery has to be shifted or otherwise handled.

But few machine tools are used in making steam boilers, and they are generally as follows:

1st.—_The Rolls_, operated either by hand levers or power; used for bending the iron or steel plates into circular form.

2d.—A wide _power planer_ for trimming the edges of the sheet perfectly straight and true.

3d.—_Heavy Shears_ for trimming and cutting the plates.

4th.—A _Power Punch_ for making the rivet holes.

5th.—A _Disc_ for making the large holes in the tube sheets to receive the ends of the tubes.

6th.—_Rivet heating furnaces_ and frequently _steam riveting machines_.

The hand tools needed by boiler makers are equally few, consisting of _riveting hammers_ and hammers for striking the chisels, _tongs_ to handle hot rivets, _chipping chisels_ used in trimming the edges of plates, _cape chisels_ for cutting off iron or making holes in the sheets, _expanders_ to set the tubes, and also _drift pins_ to bring the punched sheet exactly in line.

Fig. 157 exhibits an improved pattern of the well-known tool—dudgeon expander.

STEAM.

_Steam_ is water in a gaseous state; the gas or vapor of water; it liquifies under a pressure of 14.7 and temperature of 212° F.

_Steam_ is a joint production of the intermingling of water and heat. Water is composed of two gases which have neither color nor taste, and steam is made up of the same two gases with the addition only of that mysterious property called heat by which the water becomes greatly expanded and is rendered invisible. The French have a term for steam which seems appropriate when they call it water-dust.

This is what takes place in the formation of steam in a vessel containing water in free communication with the atmosphere. At first, a vapor is seen to rise that seems to come from the surface of the liquid, getting more and more dense as the water becomes hotter. Then a tremor of the surface is produced, accompanied by a peculiar noise which has been called _the singing_ of the liquid; and, finally, bubbles, similar to air bubbles, form in that part of the vessel which is nearest to the fire, then rise to the surface where they burst, giving forth fresh vapor.

The curious fact must be here noted that if water be introduced into a space entirely void of air, like a vacuum, it vaporizes instantaneously, no matter how hot or cold, so that of an apparent and fluid body there only remains an invisible gas like air.

That steam is _dry_ at high pressure is proved by an experiment which is very interesting. If a common match head is held in the invisible portion of the steam jet close to the nozzle, it at once lights, and the fact seems convincing as to complete dryness, as the faintest moisture would prevent ignition even at the highest temperature. This experiment proves dryness of the steam at the point of contact, but if throttling exists behind the jet, the steam supplied by the boiler may be in itself wet and dried by wire drawing.

_Dead steam_ is the same as exhaust steam.

_Live steam_ is steam which has done no work.

_Dry steam_ is saturated steam without any admixture of mechanically suspended water.

_High-pressure steam_ is commonly understood to be steam used in high-pressure engines.

_Low-pressure steam_ is that used at low pressure in condensing engines, heating apparatus, etc., at 15 lbs. to the inch or under.

_Saturated steam_ is that in contact with water at the same temperature; saturated steam is always at its condensing point, which is always the boiling point of the water, with which it is in contact; in this it differs from superheated steam.

_Superheated steam_, also called steam-gas, is steam dried with heat applied after it has left the boiler.

_Total heat of steam_ is the same as steam heat.

_Wet steam_, steam holding water mechanically suspended, the water being in the form of spray.

Specific gravity of steam is .625 as compared to air under the same pressure.

The properties which make it so valuable to us are:

1. The ease with which we can condense it.

2. Its great expansive power.

3. The small space in which it shrinks when it is condensed either in a vacuum chamber or the air.

A cubic inch of water turned into steam at the pressure of the atmosphere will expand into 1,669 cubic inches.

WATER HAMMER.

The fact that steam piping methods have not kept pace with the demands of higher pressures and modern practice is evidenced by the increasing number of accidents from the failure of pipes and fittings.

There has not been, for the rapid increase of pressure used, a proportionate increase in strength of flanges, number and size of bolts used, and more generous provision for expansion and contraction. Valves and fittings also require greater attention in their design, construction and manipulation.

It is well known that the presence of condensed water in pipes is a source of danger, but little is known of what exactly goes on in the pipe. We have the incompressible liquid, the expansive gas, and the tube with a “dead head” or dead end as it is called, or where the end of the pipe is closed. Seeing that the tube or pipe is capable of withstanding all the pressure that the steam can give, it is difficult to account for the tremendous repelling force, which is, undoubtedly, brought into operation in explosions or ruptures of steam pipes carrying what are now comparatively low pressures.

The cause of the bursting is undoubtedly _water hammer or water ram_, which accompanies large, long steam pipes, filled with condensed water.

If steam be blown into a large inclined pipe full of water, it will rise by difference of gravity to the top of the pipe, forming a bubble; when condensation takes place, the water below the bubble will rush up to fill the vacuum, _giving a blow directly against the side of the pipe_. As the water still further recedes the bubble will get larger, and move farther and farther up the pipe, the blow each time increasing in intensity, for the reason that the steam has passed a larger mass of water, which is forced forward by the incoming steam to fill the vacuum. The maximum effect generally takes place at a “dead end.”

In fact, under certain conditions, a more forcible blow is struck when the end of the pipe is open, as, for instance, when a pipe crowned upward is filled with water, one end being open and the steam introduced at the other. A bubble will in due time be formed at the top of the crown, when the water will be forced in by atmospheric pressure from one end and by steam pressure from the other, and the meeting of the two columns frequently ruptures the pipe.

The remedy for this is simple, the pipes must be properly located so as to drain themselves or be drained by rightly located drip cocks. The drip should be the other side of the throttle valve, and if steam is left on over night this valve should be left open enough to drain out all the water.

HAZARDS OF THE BOILER ROOM.

Where there is great power, there is great danger.

When the pressure is increased, the danger is increased.

When the pressure is increased, diligence, care and scrutiny should be increased.

During the twelve years between 1879 and 1891 there were recorded 2,159 boiler explosions; these resulted in the death of 3,123 persons, and in more or less serious injury to 4,352 others. Besides these there were innumerable other accidents during the same period, caused by other means, which emphasizes the gravity of this cautionary “chapter of accidents.”

Every boiler constructed of riveted plate and carrying a high head of steam, holds in constant abeyance, through the strength of a disruptive shell, a force, more destructive in its escaping violence than burning gunpowder. To the casual observer there is no evidence of this; and it is only when a rupture takes place of such a character as to liberate _on the instant the entire contents of the boiler_ that we get a real demonstration of the fact. Unfortunately a steam boiler never grows stronger, but deteriorates with every day’s age and labor, subjected, as it is, to all sorts of weakening influences; and fractures often occur, which, if not at once repaired, would speedily reduce the strength of the boiler to the point of explosion.

In the case of a boiler we have, first, a vessel of certain strength, to resist strains; and second, expansive steam and water contained therein. It must be plain that if the strength of the vessel is superior to the internal pressure there can be no explosion, and also, on the contrary, if we allow the pressure to go above the strength of the vessel, that there must be a rupturing and an explosion, but it will be in the weakest place of that vessel.

Experiments by the most eminent men have failed to discover any mysterious gas formed by boiling water, or by any mixture of air and water. Boilers have been built for the express purpose of trying to explode them under various conditions of high and low water, and nothing in regard to the sudden generation of any gas has been discovered. Again, disastrous explosions that have occurred have been of vessels that contained no water, and were not in contact with fire, flame or heated air, but were supplied by steam some distance away.

The destructive efforts of the vaporization attendant upon explosions seem to be due to the subsequent expansion of the steam so formed, rather than to the intensity of its pressure; low or high steam _alone_ has very little to do with boiler explosions; nor high or low water necessarily.

The one great cause of boiler explosion is the inability of the boiler to withstand the pressure to which it is subjected at the time, and this may be brought about by any one of the following causes, viz.:

1. Bad design, in which the boiler may not be properly strengthened by stays and braces; deficient water space, preventing the proper circulation of the water.

2. Bad workmanship, caused by the punching and riveting being done by unskilled workmen.

3. Bad material, blisters, lamination, and the adhesion of sand or cinders in the rolling of the plate.

4. By excessive pressure, caused by the recklessness of the engineer, or by defective steam-gauges or inoperative safety-valves.

5. Overheating of the plates, caused by shortness of water. When water is poured on red-hot surfaces it does not touch the surface, but remains in the spheroidal state at a little distance from it, being apparently surrounded by an atmosphere of steam. It assumes this state above 340°; when the temperature falls to about 288° it touches the surface and commences boiling.

6. By accumulation of scale, mud, or other deposit, which prevents the water gaining access to the iron. This causes the seams to leak, the crown-sheet to bulge or come down.

One is unable to find any proof that boilers do generally explode at about starting time, nor is that statement, to the best of information, founded on any basis of fact, but was first affirmed by parties who had designed a boiler especially arranged to avoid that imaginary danger.

No one supposes that inspection will absolutely prevent all explosions; but rigid inspection will discover defects that might end in explosion.

Low water is dangerous from the fact that it leaves parts of the boiler to be overheated and the strength of iron rapidly decreases in such a case. In fact, an explosion caused by low water might be expected to be less disastrous than if the water was higher, other conditions being equal, from the fact of there being less water at a high temperature ready to flash into steam at the moment of liberation.

Testing new boilers _under steam pressure_ is both dangerous and unwise—the hot water expansion test is just as efficient, less costly and safe in every respect—hence, there is no occasion for a steam test. A manufacturer was testing a boiler in the way mentioned when a rivet in a brace blew out and the contents of the boiler rushed out, striking a man in the face, and parboiling him from head to foot. Another who was inspecting the boiler, was struck on the head and enveloped in steam and water; another was also scalded from the shoulders down; another was injured about the arms; a fifth man was scalded and severely injured about the back. The apartment was so filled with steam that the victims could not be rescued until all the damage mentioned had been done to them.

Danger from exploding steam pipes is greater than supposed. An inspector in a pipe works was testing a tube by means of a double-action hydraulic pump; the pipe suddenly burst with the pressure of 5,000 pounds to the square inch, and the water striking the unfortunate man on his face, he was killed on the spot.

There is a tendency on the part of engineers to trust too implicitly in their steam gauges. These are usually the only resort for determining the steam pressure under which the boiler may be working. But the best gauges are liable to err, and after long use to require a readjustment. It is fortunate, however, that the error is usually upon the safe side of indicating more than the actual pressure.

Any boiler that has been standing idle for a few weeks or months is a dangerous thing to enter, and no one should attempt it until it has been thoroughly ventilated by taking off all the man hole and hand-hole plates and throwing water into it. This is due to the presence of a gas which is generated from the refuse and mud, or scale, which, to a greater or less degree, remains in all boilers. Contact with fire is certain to result in an explosion. Not long since a locomotive was in a roundhouse, where it had been waiting some weeks for repairs. Some of the tubes were split and a man was pulling them out. He had only removed one or two when, putting in his lamp to see what remained, there was a fearful explosion which shook the shop. There are many other places which are unsafe to enter when they have been long closed, such as wells, pits of any kind, and tanks. Precisely what the nature of the gas is no one seems to know, but it is assuredly settled that a man who goes into it with a light seldom comes out unharmed.

The gas most likely to fill idle boilers in cities is sewer gas, that gets in through the blow-off pipe, which is left open and generally connects with the sewer; hence, the connection with the sewer by the blow-off pipes should receive attention.

Boilers are sometimes unexpectedly emptied of their contents by the operation of the principle of the syphon; a boiler is so piped that a column of water may be so formed as to draw out of the boiler its entire contents. Danger ensues if this is done while the boiler is being fired.

FUEL OIL.

The long experimental use of petroleum or natural oil as a combustible has developed but one serious objection to its wide spread and popular adoption; that objection arises from its liability to ignite and cause destruction by fire; but

THE HAZARDS OF FUEL OIL may be remedied by the observance of the following rules adopted by a certain fire underwriters’ association:

“Vault to be located so that the oil it contains can burn without
endangering property and have a capacity sufficient to hold twice the
entire quantity of oil the tanks within can contain.

Location of vault to be left to the approval of the Superintendent of
Surveys. Distance from any property to be regulated by size of tank.

Vaults to be underground, built of brick, sides and ends to be at
least 16 inches thick and to be made water tight with hydraulic
cement; bottom to be water tight, concrete, dished toward centre, and
inclined to one end so as to drain all overflow or seepage to that
end, said incline to be to the end opposite to that from which the
tank is to be tapped; top to be supported with heavy iron I-beams,
with arches of solid brick sprung from one beam to its neighbors, and
to have at least twelve inches of dirt over the masonry.

Vault to be accessible by one or more large man-holes, which, when
not in use, are to be kept locked by a large padlock of three or more
tumblers, key to be held by some responsible party.

A trough must run from one end of the vault to the other, directly
under each tank, and in the same direction as the tank or tanks.

Tank to be of boiler iron or steel, at least 3/16 inch in thickness,
to be cold riveted, rivets to be not less than 3/8 inch in
diameter and not over 1 inch apart between centres; the entire outer
surface of tank to have two good coats of coal tar or mineral paint
before the tank is placed in position.

No tank shall be over 8 feet in diameter by 25 in length, nor shall
any vault have over two tanks.

When tank is set, the bottom of the tank must be 3 inches above the
concrete floor of the vault, and must be in saddles of masonry not
less than twelve inches in thickness, built from the concrete floor
of the vault, said saddles not to be more than 3 feet apart between
centres, and laid in hydraulic cement, with an opening through centre
for drainage.

Tank must incline 1 inch per 10 feet in length toward the end from
which it is to be tapped, said incline of the tank to be opposite to
the incline at the bottom of the vault.

The filling pipe, man-hole, telltale or indicator, pump supply
connection, steam connection, overflow pipe and ventilating pipes,
where they connect with tank, must be made petroleum tight by the use
of litharge and glycerine cement.

Flanges to make tank 3/4 inch in thickness to be riveted on the
inside so as to furnish a satisfactory joint where connections are
made, must be used.

Filling pipe connection must have gas-tight valve between the tank
and hose coupling, which must be kept closed and locked unless the
tank is being filled. Each tank must have ventilating pipes at least
1-1/2 inches in diameter, one of which must connect with one end
of the top of the tank and must be in the form of an inverted J, a
union to be placed in pipe just below the bend, within which shall
be placed a diaphragm of fine wire gauze; the other ventilating pipe
must be at the other end of the top of the tank and must be conducted
to the inside of the smoke stack or into the open air at least 10
feet above the surface, so that all the gases that form in the tank
will be constantly changed.

Tank must have indicator to show height of oil in tank at all times,
said indicator to be so arranged as to allow no escapement of gases
from tank. All pipes leading from the tank to the pump or place of
burning, must incline toward the tank, and have a fall of at least 2
feet from bottom of stand pipe to top of storage tank, and must be so
constructed that the feed pipe from stand pipe to burners shall be
entirely above burners, so that no pockets of oil can be formed in
any one of the pipes between the main tank, stand pipe, oil pump or
place of burning.

The vault shall be air tight as near as possible, and must have
two ventilating pipes of iron of 4 inches diameter, both inlet and
outlet pipes to reach within 6 inches of the bottom of the vault, the
outlet ventilating pipe to rise above surface 8 feet, and the inlet
ventilating pipe to rise above surface 6 feet.

Syphon to be arranged so as carry out any seepage or leakage into the
vault, and discharge same upon the ground, where its burning would
not endanger surrounding property.”

_The following are a part of the rules adopted by the German Government to prevent accidents in mills and factories: they are equally applicable in all places where steam power is used_:

“All work on transmissions, especially the cleaning and lubricating
of shafts, bearings and pulleys, as well as the binding, lacing,
shipping and unshipping of belts, must be performed only by men
especially instructed in or charged with such labors. Females and
boys are not permitted to do this work.

The lacing, binding or packing of belts, if they lie upon either
shafting or pulleys during the operation, must be strictly
prohibited. During the lacing and connecting of belts, strict
attention is to be paid to their removal from revolving parts, either
by hanging them upon a hook fastened to the ceiling, or in any
other practical manner; the same applies to smaller belts which are
occasionally unshipped and run idle.

While the shafts are in motion they are to be lubricated, or the
lubricating devices examined only when observing the following
rules: (1) The person performing this labor must either do it while
standing upon the floor, or by the use of (2) firmly located
stands on steps, especially constructed for the purpose so as to
afford a good and substantial footing for the workman; (3) firmly
constructed sliding ladders, running on bars; (4) sufficiently high
and strong ladders, especially constructed for this purpose, which
by appropriate safeguards (hooks above or iron points below) afford
security against slipping.

All shaft bearings are to be provided with automatic lubricating
apparatus.

Only after the engineer has given the well-understood signal, plainly
audible in the workrooms, is the engine to be started.

If any work other than lubricating and cleaning of the shafting is to
be performed while the engine is standing idle, the engineer is to
be notified of it, and in what room or place such work is going on,
and he must then allow the engine to remain idle until he has been
informed by proper parties that the work is finished.

Plainly visible and easy accessible alarm apparatus shall be located
at proper places in the workrooms, to be used in case of accident to
signal to the engineer to stop the engine at once.

_All projecting wedges, keys, set-screws, nuts, grooves or other
parts of machinery, having sharp edges, shall be substantially
covered._

All belts or ropes which pass from the shafting of one story to that
of another shall be guarded by fencing or casing of wood, sheet-iron
or wire netting four feet, 6 inches high.

The belts passing from shafting in the story underneath and actuating
machinery in the room overhead, thereby passing through the ceiling
must be enclosed with proper casing or netting corresponding in
height from the floor to the construction of the machine. When the
construction of the machine does not admit of the introduction of
casing, then, at least, the opening in the floor through which the
belt or rope passes should be inclosed with a low casing at least
four inches high.

Fixed shafts, as well as ordinary shafts, pulleys and fly-wheels,
running at a little height above the floor, and being within the
locality where work is performed, shall be securely covered.”

The most simple and efficient of all substances for fire extinguishment is sulphur. This, by heat, absorbs oxygen and forms sulphurous acid, the fumes of which are much heavier than the air. The quantity required would be small. Besides sulphur, which gives every satisfaction, both in its effects and from its low cost, we find a similar property in another active and cheap substance, ammonia. An automatic sulphur extinguishing apparatus can be made of various forms.

If night repairs, Sunday, or any other work which requires the use of artificial light (especially portable lights of any kind) becomes necessary, more than one man should be employed, one of whom should be capable of starting the engine or pump instantly in case of fire.

In guarding against explosion it is conceded that the main reliance is to have the boiler made strong enough to stand both the regular load or any unexpected strain caused by the stoppage of the engine; it is also the tendency of the times to proceed towards higher and higher figures in steam pressure, until now it is not unfrequent to see 150 lbs. to the square inch indicated by the gauge; the larger the boiler, also, the more economically it can be run and this, as in the two cases before cited, requires extra precautions in building the boiler with great regard to strength in every part.

The following rules posted in a certain factory are most excellent for their directness:

“Wear close-fitting clothes; have a blouse or jacket to button close
around the waist and body; have sleeves to fit arms closely as far
up as the elbow; never wear a coat around machinery; never approach
a pair of gears or pulleys from the driving side; never attempt to
save time by potting, or trying to pot on any fast-moving belts
without slacking up or stopping entirely to do it. Never allow an
inexperienced person to go through the mills without an attendant;
never allow a woman to go through a mill, no matter how many
attendants, while in motion; never attempt to go through the mill in
the dark, you may forget the exact location of some dangerous object
and seek to avoid it, but it is still there, noiselessly waiting a
chance to wreck you; never allow any dangerous place to go unguarded;
keep your eye open while oiling; never relax your vigilance for an
instant, it may cost you your life. If you feel a gentle tug on your
clothes, grab, and grab quick, anything you can cling to, and don’t
let go till after the clothes do.”

WATER CIRCULATION.

Water consists of an innumerable quantity of extremely minute particles called molecules. These particles have the property of being able to glide over, under, and to and from each other almost without resistance or friction. When water is heated in a boiler the action that takes place is this: As the heat is applied, the particles nearest the heated surfaces become expanded or swollen, and are so rendered lighter (bulk for bulk) than the colder particles, they are therefore compelled to rise to the highest point in the boiler.

This upward action is vividly shown by the illustration on page 242, and by Fig. 158, where the warmer particles are ascending and the cooler ones are descending by a process which is endless so long as heat is applied to the lower part of the containing vessel.

The cause of circulation is the result of an immutable law of nature (the law of gravitation), and is so simple that with moderate care in its manipulation failures in arranging steam heating apparatus are next to impossible. A very slight experience suffices to show that a pipe taken from the top of a boiler and given a direct or gradual rise to the point furthest from the boiler, and then returned and connected into it at the bottom will, upon the application of heat, cause the water to circulate. It is not necessary that the water should boil or even approach boiling point, to cause circulation, as in a properly constructed apparatus the circulation commences soon after the heat is applied and immediately the temperature is raised in the boiler. It is a very common error to suppose that the circulation commences in the flow or up pipe, whereas it is just the reverse. The circulation is caused by the water in the return pipe and can be described as a stream of heated particles flowing up one pipe from the boiler and a stream of cooler particles flowing down another pipe into the boiler; or it might be described as a means of automatically transporting heated water from the lower to the upper parts of a building, and providing a down flow of cold water to the boiler to be heated in turn.

Those having in charge the erection of hot-water systems for heating buildings, will do well to remember that the circulation they expect depends entirely upon the expansion of particles when heated, and that they must avoid as much as possible friction, exposure of flow pipes to very low temperature, and frequent or numerous short bends.

When properly arranged the action of “the steam loop” is a very good illustration of the circulation of hot water and steam, the flow is continuous, rapid and positive.

NOTE.—When the steam loop is properly connected, the stop valve at the boiler should always be left open and full pressure maintained in the steam pipe over night or over Sunday. The loop will keep up a powerful circulation, returning all water to the boiler as fast as condensed. On starting up in the morning, it is only necessary to open the waste cocks and blow out what little water may have condensed in the cylinders themselves. The throttle may then be opened and the engine started with the steam as dry as if it had been running continuously.

CHIMNEYS AND DRAUGHT.

Draught, in chimneys, is caused by the difference between the weight of the air outside and that inside the chimney. This difference in weight is produced by difference in heat.

Now, heated air has a strong tendency to rise above cool air and a very slight difference will cause an upward flow of the heated particles, and the hotter the air, the brisker the flow.

As these particles ascend it leaves a space which the cooler air eagerly hastens to fill; in the boiler furnace, the hot air pushing its way up the chimney, is replaced through the grate bars with cool, fresh air.

It is the mingling of this fresh air with the combustibles that produces heat, and the power of the draught is absolutely necessary to the reliable operation of the furnace.

An excess of draught can be corrected by the use of a damper or even by the closing of the ash pit doors, but no more unhappy position for an engineer can be imagined than a deficiency of draught.

This lack is produced by, 1st, too little area in the chimney flue; 2d, by too low a chimney; 3d, by obstructions to the flow of the gases; 4th, by the overtopping of the chimney by adjacent buildings, hills or tree tops. There are other causes of failure which practice develops; hence, the draught of a new chimney is very often an uncertain thing until every-day trial demonstrates its action.

The draught of steam boilers and other furnaces should be regulated below the grate and not in the chimney. The ash pit door should be capable of being closed air tight, and the damper in the chimney should be kept wide open at all times unless it is absolutely necessary to have the area of the chimney reduced in order to prevent the gases from escaping too fast to make steam.

When two flues enter a larger one at right angles to it, opposite each other, as is frequently the case where there is a large number of boilers in a battery, and the chimney is placed near the center of the battery, the main flue should always have a division plate in its center between the two entering flues to give direction to the incoming currents of gases, and prevent their “butting,” as it may be termed. The same thing should always be done where two horizontal flues enter a chimney at the same height at opposite sides.

In stationary boilers the chimney area should be one-fifth greater than the combined area of all the tubes or flues.

For marine boilers the rule is to allow fourteen square inches of chimney area for each nominal horse power.

The draught of a chimney is usually measured in inches of water. The arrangement most commonly made use of for this purpose consists of a U-shaped glass tube connected by rubber tubing, iron pipe, or other arrangement, with some part of the chimney in such a way that the draught will produce a difference of level of water in the two legs of the bent glass tube.

The “Locomotive” suggests that _the unit for chimney construction_ should be a flue 81 feet high above the level of the grates, having an area equal to the collective area of the tubes of all the boilers leading to it, the boilers being of the ordinary horizontal return tubular type, having about 1 square foot of heating surface to 45 square feet of heating surface.

Note the above conditions, and, in case of changing the above proportions, it should be observed that the draught power of chimneys is proportional to the square root of the height, so we may reduce its area below the collective area of the boiler tubes _in the same proportion that the square root of its height exceeds the square root of 81_.

For example, suppose we have to design a chimney for ten boilers, 66 in. in diameter, each having 72 tubes, 3-1/2 in. in diameter, what would be its proportion?

The collective area of the 720 3-1/2-in. tubes would be 6,017 square inches, and if the chimney is to be but 81 feet high, it should have this area, which would require a flue 6 ft. 5-1/2 in. square.

But, suppose, for some reason, it is decided to have a chimney 150 feet in height, instead of 81 feet. The square root of 150 is 12-1/4; the square root of 81 is 9; and we reduce the area of the chimney by the following proportion: 12.25:9 = 6,017:4,420 square inches, which would be the proper area, and would call for a chimney 5 ft. 6 in. square, and similarly if any other height were decided upon.

PLUMBING.

The art of working in lead is older than the pyramids. For thousands of years hydraulics and plumbing as an occupation engaged the principal attention of engineers. King David used lead pipe, so did Archimedes; the terraces and gardens of Babylon were supplied with water through leaden pipes. Steam fitting, with galvanized pipe and an elaborate system of connections and devices is a new department of mechanism—almost of the present generation—and at first sight would seem able soon to supercede lead piping of all kinds, but it is safe to say that nothing can ever take the place of lead, for this admirable metal can be made to answer where no other material can be worked; for instance, lead pipe can be made to conform to any angle or obstruction where no other system of piping will. Hence, plumbing as a useful and ornamental art will never go out of date, and engineers of every branch will do well to study its principles and methods so as to meet the ever-recurring and perplexing questions connected with sewerage, water supply, etc.

Every engineer should at least know how 1, _to join lead pipe_—to make a “wipe joint,”—as in a hundred emergencies this knowledge will be of worth. 2, how to make a temporary stopping of leaks; 3, how to bend pipe with sand or springs; 4, how to “back air pipes” from sinks; 5, how to use force pumps; 6, how to arrange the circulating pipes in hot-water boilers; 7, how to make solder; 8, how to repair valves, etc., etc.

PIPING AND DRAINAGE.

The three illustrations on page 298 are designed to represent traps set in lead pipe and show vividly the difference between this material and iron piping.

Lead is one of the elementary substances of which the world is formed; it ranks with gold, silver, tin, etc., in being an unmixed metal. It melts at about 617° Fahrenheit, and is, bulk for bulk, 11-4/10 heavier than water (gold being 17-5/10 heavier and wrought iron 7-7/10 heavier). The tenacity of lead is extremely low, a wire 1/18th of an inch breaks with a weight of 28 lbs.; in comparison, its tenacity is only one-twentieth that of iron; it is so soft that it may be scratched with the thumb nail. If a very strong heat is applied lead boils and evaporates; it transmits heat very slowly; of seven common metals it is the worst conductor, therefore it is good for hot water pipes. Mixed with a sufficient quantity of quicksilver it remains liquid.

An advantage to be found in the use of lead is its durability and comparative freedom from repairs. In London, soil and drain water pipes which have been fixed 300 to 500 years are as good now as the day they were first made—while iron pipe cannot be expected to last over 10 or 20 years or 30 at the utmost.

Fig. 159 represents the general system of house piping and drainage applicable also to shops, public buildings, etc. A exhibits the drain or sewer. A-C represents the sewer connection, so called with a running trap, B. “C” at the end of the lower pipe exhibits a soil pipe elbow, with hand hole for cleaning out closed by a screw plug. This drain should have a regular fall or inclination and this elbow provides for that. C-D shows the rain water leader (conductor).

E and F is a soil pipe 3, 4, 5, or 6 inches in diameter. Note, pipes draining water closets are called “soil pipes”; those draining other fixtures “waste pipes.” N and O represent water-closet flanges; F and H are roof connections; L exhibits double and single =Y= branches to receive waste-pipes from baths, bowls, or sinks. The plumber makes this connection, always trapping the lead waste-pipe and then soldering it to a _brass_ nipple.

LEAD PIPE JOINTS.

It has been remarked that after learning how to make “a wipe joint,” everything is easy relating to the plumber’s trade; hence, the importance of the following directions.

To learn the art, previous practice with short pieces of pipe is recommended. This trial piece can be clamped as shown in Fig. 160 and used over and over until practice has been had.

There are many names for the process of lead joint-making, such as the flow-joint, the ribbon joint, the blown joint, the astragal joint, etc., to express the different positions and uses for which they are needed, but in the main they are made as follows:

1. The lead pipe to be joined is sawn square off with the proper toothed saw—attention being paid to making the end absolutely true, across the pipe.

2. One end of the pipe to be joined is first opened by driving in a wooden wedge, shaped like a plumb-bob, called the “turn pin.” Care should be exercised at this time not to split the end, 1/4 inch opening is usually enough, which leaves the pipe as shown at D, Fig. 161. Now, clean the internal part of the joint all around the part required for soldering—this cleaning can be done with the plumber’s shave hook or with a pocket knife. To complete this preparation “touch” the part with grease from a tallow candle.

3. Next is the preparation of the male part of the joint. This must be rasp-filed down to fit the enlarged opening. It is important to have a good fit throughout; hence, inside the enlarged opening must be also rasp-filed and the two surfaces to come nicely together before the solder is applied.

4. At this stage a paste called “plumber’s soil” must be applied outside 3 inches from the end of each piece of pipe; this is shown by the line E F in Fig. 161, also at A B, Fig. 160; the line of the soiling should be very even and true in order to assure a workmanlike job and the soiling put on as before stated, _3 to 5 inches beyond the solder line on each side_.

As the melting point of lead is 612 degrees or thereabouts, it is necessary to have solder melt at a lower temperature, and that made under the rule given will melt at 440 to 475 degrees.

No tool to a plumber is more important than the cloth used in joint making. To make it, take a piece of new mole skin or fustian, of moderate thickness, 12 inches long by 9 inches wide, fold it up one side 4 inches; then 4 inches again, and again 4 inches; then fold it in the middle, which will make your cloth 4 × 4-1/2 inches, and of 6 thickness. After this is done, sew up the ragged ends to keep it from opening. Then pour a little hot tallow on one side and the cloth is ready for use. In Fig. 160-a is shown, H, a hand holding the cloth C in the process of “wiping the joint,” which will now be described.

First place a small piece of paper under the joint to catch the surplus solder D and begin soldering as follows: Take the felt F in the right hand and with it hold the ladle three parts full of solder. To see that it is not too hot hold your hand within 2 inches or so of the solder; if it quickly burns your hand it is too hot; if you can only just hold your hand this distance, use it; but if you cannot feel the heat, the solder is too cold.

When you begin to pour your solder upon the joint do it very lightly and not too much at a time in one place, but keep the ladle moving backward and forward, pouring from E to J, first on one side of the joint to the other and from end to end.

Pour also an inch or two up the soiling, as shown at E to make the pipe of proper temperature, _i.e._, to the same heat as the solder. The further, in reason, the heat is run or taken along the pipe, the better the chance of making the joint.

Keep pouring and with the left hand hold the cloth C to catch the solder and also cause the same to tin the lower side of the pipe and to keep the solder from dropping down. This cloth, so important in joint making is elsewhere described. By the process of steady pouring the solder now becomes nice and soft and begins to feel shaped, firm and bulky.

When in this shape and in a semi-fluid condition quickly put the ladle down, and instantly with the left hand shape one side of the joint always beginning at the outsides, or at that part next the soiling; then take the cloth in the right hand and do the other side, _finishing on the top_; a light run of the cloth all round the joint will, if the solder has not set and you have been quick with your work, give the appearance of a turned joint. After a little practice the joint may be made without changing the cloth from one hand to the other.

_The secret of joint making is getting the lead to the heat of the solder and in roughly shaping the solder, while in the semi-fluid state._

Good mechanical fitting is the result of two things—good judgment and a delicate sense of touch.

REPAIRING PIPES WITH PUTTY JOINTS.

First get the pipe _thoroughly dried_, and with some quick drying gold size paint the part to be repaired; then get some white lead and stiffen it with some powdered red lead, so as to make it a hardish putty, place a thin layer of this, say 3/8th inch to 1/2 inch in thickness, over the bursted part of the pipe, and with some good strong calico, painted with the gold size, neatly wrap the red lead to the pipe, using 3 or 4 thicknesses of the painted calico; then with some twine begin at one end, laying the twine in several layers in rotation until it has, like the calico, several thicknesses.

If properly done this will be strong enough to withstand any ordinary pressure on the pipes and if more is required the putty can be made from dry red lead and gold size. In making all white and red lead joints, first, see that the parts are thoroughly dry; second, see that the parts are not dirty with rust, &c.; next, well paint the parts with good, stiff paint before putting the putty on to form the joint.

BENDING LEAD PIPE.

If any ordinary piece of light lead pipe 1-1/2 inches in diameter is taken and pulled or bent sharply around it will crimple or crinkle at the throat; the larger and thinner the pipe the more it will become distorted.

There are many methods of making these bends in lead pipe, some with dummies, others with bolts, balls, etc., others cut the bends at the back, at the throat, or the two sides of the bend.

For small pipes, such as 1/2 to 1 inch and extra heavy, they may be pulled round without trouble or danger, but for a little larger size SAND BENDING is largely practiced as follows:

Take the length of pipe, say 5 feet, fill and well ram it with sand 2 feet up, then have ready a metal pot of very hot sand to fill the pipe 1 foot up, next fill the pipe up with more cold sand, ramming it as firmly as possible, stop the end and pull round the pipe, at the same time hammering quickly working the lead from the throat towards the back, which can be done if properly worked. N. B.—Care must be used not to reduce or enlarge the size of the bore at the bend.

BENDING WITH WATER.—It is a well-known fact that for such work, water is incompressible, but may be turned or twisted about for any shape provided it is enclosed in a solid case. To make the bend—the end of the pipe is stopped and a stop cock soldered into the other end; take the pipe at the end and pull it around, being careful that the water does not cool and shrink, and hammering quickly to take out the crinkle.

BENDING WITH BALLS.—This method is practiced with small pipe and also to take “dints” out in case of sand and water bending when a ball is sent through. Method: suppose the pipe to be two inches, then a ball is required 1/16 in. less than the pipe, so that it will run through the pipe freely. Now pull the pipe round until it just begins to flatten, put the ball into the pipe and with some short pieces of wood, say 2 in. long by 1-1/2 in. in diam., force the ball through the dented part of the pipe. The ball will run through all the easier if “touched” over with a candle end. Care must be used in forcing the ball back and forth not to drive it through the bend.

TABLE.—WEIGHT OF SHEET LEAD.

---------+-----+-----+-----+-----+-----+-----+-----+-----+-----
Inside | 3/8 | 1/2 | 5/8 | 3/4 | 1 |1-1/4|1-1/2|1-3/4| 2
Diameter | | | | | | | | |
---------+-----+-----+-----+-----+-----+-----+-----+-----+-----
| weight per foot, lbs., oz.
AAA, | 2- 8| 3- 0| 3- 8| 4-12| 6- 0| -- | -- | -- | --
AA, | 1- 8| 2- 0| 2-12| 3-12| 4-12| 6- 0| 8- 0| 8- 8| 9- 0
A, | 1- 4| 1-12| 2- 8| 3- 0| 4- 3| 4-12| 6- 8| 6- 8| 7- 0
B, | 1- 4| 1- 4| 2- 0| 2- 4| 3- 4| 3-12| 5- 0| 5- 0| 6- 0
C, | -10| 1- 0| 1- 8| 1-12| 2- 8| 3- 0| 4- 4| 4- 0| 4-12
D, | - 7| -12| 1- 0| 1- 4| 2- 0| 2- 8| 3- 8| -- | --
E, | -- | - 9| -12| 1- 0| 1-10| 2- 0| 3- 0| -- | --

Sheet lead is not the same weight,
bulk for bulk, owing to difference
in organic formation, but a cubic
foot may be said to weigh 709 lbs.
A square foot 1″ thick, 59 „
„ „ „ 1/8″ „ 7-1/2 „
„ „ „ 1/10″ „ 6 „
„ „ „ 1/12″ „ 5 „
„ „ „ 1/15″ „ 4 „
„ „ „ 1/20″ „ 3 „

Sheet lead is sometimes made as thin as writing paper.

PLUMBER’S SOLDER.