Compliance with API 526 standard

[Krimskiy]

Dear All,

we are purchasing a two-phase (HC gas / condensate) relief valve for which all suppliers came up with the PSV's not compliant with API 526 standard. The client specified this compliance in their requisition form, however. The non-compliance is related to the maximum set pressure used, with regard to the certain inlet and outlet flange ratings and the orifice size. (our set pressure is higher than the maximum value suggested by API 526 for the inlet/outlet flange combinations of a particular orifice size). Our material is a special stainless steel, whih is generally better than conventional s/s from API 526. Anyway, the relief valves vendors say that the valves are made up to ASME code and certified for gas and liquid (separately), so we should not worry about it

How important is the compliance to API 526? Can you please explain the background reason for this compliance?

 

[e43u8]

Krimskiy,

API 526 valves are a subset of code valves and there are many code valves other than API 526 valves. It's adequate for a code valve had been undergone capacity certification according to ASME tests protocol.

 

[Krimskiy]

What are the other subsets then? Would you use it in HC applications?

 

[e43u8]

Krimskiy,

You can find all subsets of certified relief valves (code valves) and relevant manufacturers details in Red Book (National Board certification). They can be used in HC applications.

 

[The Obturator]

I just started replying here, so please excuse the delay.

To clarify, API-526, or rather API-526 STD, is a user STANDARD not a code. It concerns itself about letter (D to T) orifice steel flanged safety relief valves (spring and pilot operated). More so, it covers standardised inlet x outlet size and their flange rating configurations, max set pressures, temperatures etc. Its intent is to provide a form of standardisation between manufacturers where a given valve from vendor A can be replaced by Vendor Z.

Looks like you have a case where the normal listed set pressure is over the API-526 limit. Your vendor is correct in stating such.

ASME Capacity certification (by National Board) is something else, but generally goes hand it hand with API-526 (API-526 is for process applications and hence ASME VIII UV Unfired vessel). You can have a design to ASME VIII not meeting API-526. Also since your suppliers offered choice of stainless steel is not of the API-526 CF8M grade, the grade proposed should be listed within the ASME listing of permitted materials (or with a code case).

Regardless, per ISO, only the term Safety Valve is used for all overpressure eventualities.