PSV rating outside of API 526 table 1

[aizat.mzaki]

Dear All,

If I need to have a PSV that is not available in API 526 selection table i.e. N size orifice with inlet rating of 2500# and outlet rating of 300# but a PSV manufacturer quote they can supply such PSV.

My question as below:

1.Does that PSV still can qualified for the necessary ASME UV stamp / API compliance, even though it no longer following API 526 table?

2.If no, can I have any other alternative for the PSV e.g. using 2 X 100% of smaller orifice PSV that have 2500# inlet x 300# outlet as per API 526 table to ensure design compliance to API.

Appreciate advice.

Best Regards,

 

[The Obturator]

Hi, To answer you;-

1. Yes. The SRV having pressure above API-526 limits, can be "UV/NB" Code Stamped, provided the manufacturer obtains such acceptance and certification from the USA National Board. It could be an extension of the makers already qualified valve type or of a new design. It probably will require the manufacturer to pay costs etc., to the certifying body.

API Compliance can also be maintained where the pressure limits etc., are not not exceeded (ie., you could have same centre to face dimensions of a large valve that exceeds the set pressure). This is all to be in agreement between vendor and client.

2. Smaller SRV's operating in parallel is the traditional solution to the above. Bear in mind the additional cost of piping, leak paths, spares, maintenence etc of such a set up. Do not forget to use staggered set pressures and 16% overpressure as allowed by API-520.

Always also consider pilot operated SRV as they are capabe of higher set and back pressures.

Hope that helps.


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

 

[aizat.mzaki]

Thank a lot avalveman for the great insight.

Really appreciate your input.

Best Regards,