Does a PSV has a MAWP?

[UnOwen]

Hello

I have a very simple question.
Does a PSV itself has a MAWP? I am just asking as I have never seen it on a data sheet or a name plate but since the PSV has a CRN I assume it has a MAWP associated to it.

Thanks

 

[mk3223]

IMO, it could be set by the flange pressure rating of the valve.

 

[UnOwen]

Would make sense on a flanged PSV. How about a threaded PSV? I assume a PSV is considered as "fitting" and as it has a CRN it has a MAWP. However, I have never seen an MAWP on any PSV data sheet, test report or Name Plate.
If the PSV does have a MAWP it must be higher as or equal to the MAWP of the vessel its protecting. However, I clould not find anything if a PSV does have a MAWP like a pump has for instance.

 

[DGrayPPD]

Does this post help?

http://www.eng-tips.com/viewthread.cfm?qid=159483

 

[UnOwen]

Hi

Thanks but I am not asking how the set pressure of the PSV relates to the MAWP of the vessel. What I am asking is, if the PSV as a device itself has a MAWP?

Lets assume I have a vessel, which MAWP is 215 PSIG. So I would set my PSV at 215 PSIG or lower. However, the PSV itself is a registered fitting/valve and has a CRN number.
The MAWP of the PSV (if there is one) can be and should be much higher than the MAWP of the vessel. However, I have not seen any MAWP noted on any PSV data sheet or name plate.

So the question is really does the PSV has a MWAP.

 

[mk3223]

The MAWP of the PSV valves should be based on the valve ratings similar to the gate/globe valves and control valves for either flanged or threaded connections. The MAWP data isn't shown on the PSV name tag because it isn't required same as the other valves.

 

[The Obturator]

I think it is wrong to use the SRV inlet flange rating as the so called PSV MAWP. Why? For the simple fact that larger SRV's are not fully rated (per API-526). There is no MAWP for a SRV, but if it is required for whatever reason, then I suggest the set pressure (+ overpressure) be used. Why? the valve design would be limited to the spring selection for the set pressure. Any higher (or lower), than set P will mean a spring change.
Therefore for a set pressure of 200 PSIG, a PSV with 10 % overpressure, the "MAWP" would be 220 PSIG. In that instance, it is not designed to operate higher, therefore this should be the PSV MAWP.

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

 

[don1980]

I think I understand what you're asking, but be aware that the term "MAWP" is specific to ASME pressure vessels. All pressure equipment has limiting values for pressure, and those pressure values vary depending on the temperature. You can't define a mechanical stress limit by just stating pressure alone. The mechanical stress limits (P&T values) for API 526 PRVs (D-T orifice valves) are found in the API 526 document tables. For the most part, these limits match the limits for a corresponding ANSI flange, but there are some differences. For other types of PRVs (non-API 526) the manufacturer's catalog will define the limits.

 

[BFZHA]

Since the PSV or PRV are designed and installed to open at set pressure to protect vessels and piping systems against overpressure, I think it make no sens to define a MAWP : PSV will not protect "itself". As stated by B31.3 "The Maximum relieving pressure is the maximum system pressure during a pressure relieving event." and also "The design pressure for pressure relief is the maximum design pressure permitted, considering all components in the piping system.".
The PSV is the last protective barrier before the catasprophe and in this case if it fails it is the whole installation that will be damaged, nothing serves to assign to it a MAWP because it must open at set pressure.