Chapter 228 - Discussion of the protection of pressure vessels by using safety valves-rupture disc-combinations

Abstract

This chapter presents safety considerations in cryogenic test facilities for superconducting magnets and shows the reasons, the risks and furthermore the prevention of the oscillations. Due to safety requirements cryogenic facilities are equipped with safety valve-rupture disc-combinations against overpressure. Spring-loaded safety valves in combination with rupture discs are designed as the “last resort” in the safety hierarchy to protect life and property. Under certain conditions while discharging, so called fluttering or chattering may occur. This behavior is defined as an extremely opening and closing of the valve. The associated mechanical loads can damage the piping and the equipment or cause pressure oscillations with high amplitudes in the inlet piping to the safety devices. The protection of cryogenic facilities against overpressure with safety valve-rupture disc-combinations includes certain risks. Safety valves manufactured from castings may look not very sophisticated, but in their design, accuracy, and function they are delicate instruments and perform an essential role. The installation of safety devices is an integral part of the safety system and must be done very carefully. Special care must be taken to satisfy the stability criterion and for the prevention of chattering of the safety valves discs.