Fluidyne Deadweight Safety valve consists of a valve seat where the pressure in the boiler or pressure vessel when it exceeds the normal working pressure lifts the valve seat with its weight. The excess pressure fluid therefore escapes through the pipe to the atmosphere, until the pressure reaches its normal value. It is the simplest type of safety valve; it is suitable for stationary boilers and pressure vessels only, because it cannot withstand the jerks and vibration of mobile boilers or pressure vessels. Another disadvantage of this valve is the heavy weight required to balance the pressure. Hence, it is not suitable for high pressure boilers.