Back pressure safety valves

When dimensioning and selecting safety valves for vessels and installations, it is important that this fitting should not be considered as being separate from its supply and blow-off pipes. The pressure and flow situation in neighbouring pipes and installation components may have an appreciable adverse influence on the functioning of safety valves. The resulting reduction of the mass flow leads to a rise in pressure. In extreme cases, unstable functioning behaviour in the form of flutter and hammering may lead to the valve becoming torn away. An accurate knowledge of the behaviour of safety valves and of the admissible limits in relation to back pressure, is a condition of avoiding the problems described. Various regulations [1,2,3] either specify the admissible back pressure, or refer to the manufacturers of the safety valves.