Explosion of Boiler. It is not always possible to determine the real cause of a boiler explosion, since it sometimes happens that all evidence is obliterated. It has been said that all boiler explosions are due to the fact "that the pressure inside the boiler is greater than the strength of the material of which the boiler is constructed". Failure is due to one of two causes, namely, insufficient strength to withstand the ordinary working pressures, or a gradual increase of pressure in excess of that which it was designed to carry.
Lack of strength may be due to incorrect design, defective material and workmanship, or reduction in size of plates, stays, etc., due to corrosion, wear and tear, and neglect. Overpressure is usually due to defective safety valves or to safety valves set by pressure gages which indicate pressures much less than the real amount.
Collapse of Flue. If a flue collapses while in service, the escaping steam and water will usually extinguish the fire. When the pressure is reduced sufficiently, an iron or wood plug can usually be driven into the ends of the tube in question, which will effect an emergency repair and permit the locomotive to return under its own steam. It may be necessary to run under a reduced steam pressure. The injectors should be used in reducing the pressure to make sure of plenty of water being kept in the boiler. Iron plugs are preferable but, if they are not at hand, wood plugs may be used. The iron plugs are placed with a long bar. The wood plugs are made on the end of a pole and partially cut off, so that when placed they can easily be broken off. The plug will burn slightly but not to any great extent inside the end of the flue. If the failure occurs in a flue located back of the steam pipes, it may be necessary to let the boiler cool down before the temporary repair can be made. If the steam obscures the back end of the flue, it sometimes can be drawn up the stack by starting the blower.
If a fitting is accidentally broken off permitting steam or water to blow out, or if a hole is made in any way which permits the escape of steam or water, either can be temporarily repaired in the manner indicated above. Metal plugs are preferable but wood can be used if necessary. In plugging flues or any holes where steam or water is escaping, care must be exercised to prevent being struck by the plug in case it blows out.
Table of Contents; Page 179; Page 181; Index