Safety
Steam engines possess boilers and other components that are pressure vessels that contain a great deal of potential energy. Steam escapes and boiler explosions (typically BLEVEs) can and have caused great loss of life in the past. While variations in standards may exist in different countries, stringent legal, testing, training, care with manufacture, operation and certification is applied to ensure safety. See: Pressure vessel
Failure modes may include:
- over-pressurisation of the boiler
- insufficient water in the boiler causing overheating and vessel failure
- build up of sediment and scale which caused local hot spots, especially in riverboats using dirty feed water
- pressure vessel failure of the boiler due to inadequate construction or maintenance.
- escape of steam from pipework/boiler causing scalding
Steam engines frequently possess two independent mechanisms for ensuring that the pressure in the boiler does not go too high; one may be adjusted by the user, the second is typically designed as an ultimate fail-safe. Such safety valves traditionally used a simple lever to restrain a plug valve in the top of a boiler. One end of the lever carried a weight or spring that restrained the valve against steam pressure. Early valves could be adjusted by engine drivers, leading to many accidents when a driver fastened the valve down to allow greater steam pressure and more power from the engine. The more recent type of safety valve uses a non-adjustable spring-loaded valve. This type is normally not adjustable and is considerably safer.
Lead fusible plugs may be present in the crown of the firebox. If the water level drops, such that the temperature of the firebox crown increases significantly, the lead melts and the steam escapes, warning the operators, who may then manually drop the fire. Except in the smallest of boilers the steam escape has little effect on dampening the fire. The plugs are also too small in area to lower steam pressure significantly, depressurizing the boiler. If they were any larger, the volume of escaping steam would itself endanger the crew.
Read more about this topic: Steam Engine
Famous quotes containing the word safety:
“There is always safety in valor.”
—Ralph Waldo Emerson (1803–1882)
“Once women begin to question the inevitability of their subordination and to reject the conventions formerly associated with it, they can no longer retreat to the safety of those conventions. The woman who rejects the stereotype of feminine weakness and dependence can no longer find much comfort in the cliché that all men are beasts. She has no choice except to believe, on the contrary, that men are human beings, and she finds it hard to forgive them when they act like animals.”
—Christopher Lasch (b. 1932)
“For hours, in fall days, I watched the ducks cunningly tack and veer and hold the middle of the pond, far from the sportsman;... but what beside safety they got by sailing in the middle of Walden I do not know, unless they love its water for the same reason that I do.”
—Henry David Thoreau (1817–1862)