Conventional relief valve material 1

[Indy]

Hi,
I have a question about the material of a conventional psv material on seawater service. Is x750 a suitable spring material for seawater service?

Thank you

 

[The Obturator]

Generally yes, but if you have a large orifice, the cost adder would be very high. Best to consider a bellows PRV where the bellows is Inconel 625. Consider also the spring to be coated in nylon, or other polymer. What size PRV are you discussing and what are the other materials?

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[Indy]

Thanks for the reply. This leads on to another question regarding material. If we have a piping and valve specification that does not mention materials for pressure safety valves but mentions materials to be used for other types of valves are there general rules that can be applied so that the valve body, bonnet and trim is compatible with the piping specification which in this case is super duplex?

Thanks

 

[The Obturator]

(Revised reply)

To answer your question. If there is a piping and valve material specification, issued with the enquiry covering 'valves', but not specifically for Pressure Relief Valves, it is highly probable that this will apply to the PRV's. It will probably relate to a piping specification that states the material grade and other requirements, such as NDE, against the size/rating. There will also probably be a Material Data Sheet (MDS) covering the specific grade material. You should always check with the client if it applies to the PRV's as you may be offering something that is not really required, or for that matter, not understood. PRV's are end of line valves. They are not in tn constant flow.

If the spec applies, limit the MDS/piping spec to the body and bonnet castings only. Other parts should be of a compatible commercial grade material. Applying controlled material requirements to the PRV internals may prove expensive. In all cases, tell the client what you have offered. Try to limit any additional specific material requirements to the nozzle and disc insert only - these are the only wetted parts when the valve is closed which is 99.99% of the time.

There is no written rule. You just need to exercise common sense and ask the client the right question(s). At the end of the day, it is user responsibility to OK the selected material.


Per ISO-4126, only the term Safety Valve is used regardless of application or design.