Stop exploding boilers with one of these!!
Steam locomotives use boilers to generate steam. To prevent the boiler to be overpressurised a device called a safety valve is used. This releases a small amount of pressure before resealing.
This model is of a Ross pop safety valve. This style was most commonly used in the UK post-1948.
Based upon the British standard design as drawn in the 'Handbook for Railway Steam Locomotive Enginemen'
Once it is printed check all of the surfaces mate correctly you should be able to blow the bottom casing and hold the valve down with little gas leakage. the same with the top casing and valve. Once put together if you blow the bottom casing the top should nudge up if you reduce the pressure the top should still hold. This is until a low enough pressure that the spring is able to close both valves with a satisfying "pop" (Hence the name).
This safety valve works by the pressure from the boiler acting on the area of the bottom valve when the blowing off pressure is reached the top lifts. the steam is now acting upon both the top and bottom valve surfaces so a significantly lower pressure must be reached before the valves shut.
I wouldn't recommend running this on steam but if anyone does let me know.