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 11⁄2 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.”