Fusible Plugs:
Hot wheels, flat tyres and fusible plugs have been in the news of late but I wonder how many of those involved in the hands on side of aviation know that fusible plugs have been around for more than 100 years.
Early 19th century English steam locomotive engineers installed fusible plugs in locomotive boilers after a series of catastrophic boiler explosions. These explosions were related to an unnoticed drop in water level within the boiler which then raised both boiler temperature and pressure and as there was no such thing as a blow off safety valve the boiler would explode. The problem was solved by installing lead plugs in the top of the boiler nearest to the fire box (the hottest part of the boiler). When the temperature within the boiler became excessive the lead plugs would melt and allow the steam to escape and a possible explosion was averted. The engine lost power but could still continue to operate.
Clever people those old time engineers.
Prince of Dzun