Safety Valve Setting

[aida2011]

Hi all

I have read ASME Sec I PG-67 but I am scared I would misinterpret on the safety valve setting because I was getting different answers. I need to confirm with expert here.

1) Referring to : "Any additional valves cannot be set in excess of 3% above design pressure. Set pressure range for saturated steam valves shall not exceed 10% of the highest valve set pressure."

My question, for multiple safety valve installation, if one valve is set to blow at the MAWP, can the second valve set to blow 3% above MAWP? For example if a valve is set at 100 bar, which is its MAWP, can the second valve be set at 103 bar?

Is "highest valve set pressure = MAWP + 3%?


2) Referring to : "After blowing down, all valves shall close at a pressure not lower than 96% of their set pressure, except that all drum valves installed on a single boiler may be set to reseat at a pressure not lower than 96% of the set pressure of the lowest set drum valve."

My question, for multiple valve installation, if the MAWP of my boiler is 100 bar, should the valve reseat at 96 bar?

It looks trivial, I have asked this question to many people, and since they have different answers, I can conclude that many have misinterpreted ASME Code.

Thanks for your help.

Best regards

Aida

 

[LittleInch]

I think you have interpreted this correctly.

On your last point it should be ALL valves should re-seat by 96 bar. This could mean some valves have a set point of 103, but still reseat at 96 according to your example.



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