THE STEAM LOOP.

Figs. 153 and 154.

Figs. 153 and 154show a properly designed arrangement of steam connections for a battery of boilers. To the nozzles, risers are attached by means of flanges, and from the upper ends of these risers pipes are led horizontally backwards into the main steam pipe. In this horizontal pipe, the stop valves, one to each boiler, are placed. These valves should have flanged ends as shown, so that they may be easily removed, if repairs become necessary, without disturbing any other portion of the piping. Unlike the engraving, the valve C should be arranged in another position: the stem should, of course, be horizontal or nearly so, in order that the valve may not trap water.

By this arrangement it will be seen that the movements of the boilers and the piping itself are compensated for by the spring of the pipes. The height of the risers should never be less than three feet, and when there are eight or ten boilers in one battery, they should be, if room permits, six to eight feet high, and the horizontal pipes leading to main steam pipe should be ten or twelve feet or more.

This is an attachment to a steam boiler, designed to return water of condensation. It invariably consists of three parts, viz.: the “riser,” the “horizontal” and the “drop leg,” and usually of pipes varying in size from three-fourth inch to two inches. Each part has its special and well-defined duties to perform, and their proportions and immediate relations decide and make up the capacity and strength of the system. It is, in fact, nothing but a simple return pipe leading from the source of condensation to the boiler, and, beyond this mere statement, it is hardly possible to explain it; it has, like the injector and the pulsometer pump, been called a paradox.

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 oversixty-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.

Fig. 155is 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 ataon 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 ata, 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 levelb, 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 atb, 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.

Fig. 156.

Fig. 156represents 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 widepower planerfor trimming the edges of the sheet perfectly straight and true.

3d.—Heavy Shearsfor trimming and cutting the plates.

4th.—APower Punchfor making the rivet holes.

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

6th.—Rivet heating furnacesand frequentlysteam riveting machines.

The hand tools needed by boiler makers are equally few, consisting ofriveting hammersand hammers for striking the chisels,tongsto handle hot rivets,chipping chiselsused in trimming the edges of plates,cape chiselsfor cutting off iron or making holes in the sheets,expandersto set the tubes, and alsodrift pinsto bring the punched sheet exactly in line.

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

Fig. 157.

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

Steamis 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 calledthe singingof 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 isdryat 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 steamis the same as exhaust steam.

Live steamis steam which has done no work.

Dry steamis saturated steam without any admixture of mechanically suspended water.

High-pressure steamis commonly understood to be steam used in high-pressure engines.

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

Saturated steamis 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 steamis 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.

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 undoubtedlywater 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.

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 liberateon the instant the entire contents of the boilerthat 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 anymixture 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 steamalonehas 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 boilersunder steam pressureis 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 withthe 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.

oil valve

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 Oilmay 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 least3⁄16inch in thickness, to be cold riveted, rivets to be not less than3⁄8inch indiameter 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 tank3⁄4inch 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 11⁄2inches 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.”

“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 least3⁄16inch in thickness, to be cold riveted, rivets to be not less than3⁄8inch indiameter 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 tank3⁄4inch 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 11⁄2inches 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) firmlylocated 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.

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) firmlylocated 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 womanto 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 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.

Fig. 158.

This upward action is vividly shown by the illustration on page 242, and byFig. 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 withmoderate 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.

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 preventtheir “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 thatthe unit for chimney constructionshould 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 tubesin 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, 31⁄2in. in diameter, what would be its proportion?

The collective area of the 720 31⁄2-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. 51⁄2in. 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 121⁄4; 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.

pipe trap

p trap

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.

s trap

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.

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

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