Application

Cryogenic safety valves are used in applications in which system overpressure in a cryogenic system is not only an extraordinary emergency but may very well occur several times. In this regard, it should be possible to collect and reuse the cryogenic, vaporising fluid - typically helium - for efficiency and cost reasons.

 

Function

During normal, trouble-free operation of a system, the safety valves must be very tightly sealed in order to prevent fluid leakage to the largest possible extent.

In case of an overpressure building up in the system, the valves must be activated exactly at a specific pressure value and dissipate large, cryogenic mass flows. In doing so, the valuable fluid is not released into the environment, but rather forwarded into a buffer container. In contrast to conventional safety valves, the cryogenic safety valves are therefore always activated at the specified pressure, regardless of the pressure that prevails behind the valve. When the pressure falls below a specific value again, the valves are tightly re-sealed. This is all done automatically, without external energy.

 

Properties

The valves are classified as equipment part with safety function according to PED 2014/68/EU; accordingly, the harmonized standard EN ISO 4126 has been considered in the development.

As the valves are required to release cryogenic gas, they have a vacuum weld-in flange, a cold seat and a cryogenic extension in order to keep the heat input to a minimum. The heat input can be further reduced by means of an optional thermal connection.

The safety function is realised outside the cold box in the warm area by means of a mechanical spring system which will seal the valve tightly up to the defined response pressure. In addition, a pneumatic piston drive allows for the manual opening of the valve.

The specific selection of materials and components guarantees reliable operation in the magnetic field and in the radiation area as well.

General information about cryogenic safety valves

Size nom.:

DN20 or DN40

Pressure nom.:

PN25

Set pressure nom.:

20 bar(g) +/- 0.5 bar

Opening pressure nom.:

21-22 bar(g)

Closing pressure nom.:

> 6 bar(a)

Back pressure (0bar…9bar):

independent

Operating temp. range:

8 – 10 K

Medium:

He

Cryogenic safety valves
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