Pressure and vacuum relief valve for railway fuel tanker - has two poppet valves compensating for temp. dependent changes mounted within single housing

摘要

Fuel tanker railway wagons are fitted with a pressure relief valve to guard against an explosion and an under pressure valve to guard against an explosion. The two valves are combined in a common housing which is bolted to the top of the fuel tank. The poppet valve is held on its seat by a spring and protects the tank from excessive internal pressure due to a rise in temp. The relief pressure can be adjusted by a dead weight attached to a leaf spring. when the tank is subjected to a low temp. the volume of the fuel contracts so the inward relief valve is opened by the pressure of the external air. This valve also opens to admit air when fuel is being taken from the tank.