Issues regarding the inlet flange surface of the safety valve
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Why are the inlet flange surfaces of some safety valves not level (see attached diagram), being higher than the connection flange by a certain amount? (How should the matching flanges and gaskets for such safety valves be selected?) Meanwhile, the inlet flange surfaces of other safety valves are level. I’m seeking advice from those with more experience.
The connection style of the inlet and outlet flanges of the safety valve also complies with the relevant flange standards; generally, an RF face connection method is used. The mating flanges and gaskets shall be selected according to normal piping requirements.
There’s an extra part in the second image; isn’t it no longer a regular flange then?
The medium does not come into contact with the safety valve housing; as shown in the diagram, the nozzle of the safety valve is integrated with the protective cover, and the medium flowing before the safety valve enters directly the nozzle of the internal components. This design is suitable for high pressures (second type)； In the first type, where the flange surface is flush, a portion of the medium remains in contact with the flange, which makes corrosion more likely; it is suitable for low pressures
The first type of RF flange is a convex-flanged type, which can be used for PN1.6 to PN10 MPa.
I’ve seen it on hydrogen high-pressure safety valves – it’s the uneven surface shown in Figure 2
Safety valves generally have different flange connection styles for the inlet and outlet; in some cases, the pressure at the inlet is high, so the standards applied are different from those used for the outlet. In general, markings should be present, allowing the appropriate flanges, gaskets, etc. to be selected according to the relevant standards.
Has the problem been solved, big bro? I’ve encountered this issue too. .
Mother-and-child bolt flanges are available for hydrogen pipelines that have been dried; octagonal gaskets can be used in such cases