Safety valves for steam can be set to meet one of three requirements. For boilers ( Section V) above 15 psig, valves must be sized on capacity tables which reflect a 3% accumulation.


V Stamp which applies to all ASME Section I valves installed on boilers operating at a pressure greater than 15 psig.

HV stamp which applies to all ASME Section IV valves installed on boilers operating at 15 psig or less.

UV stamp which applies to all ASME Section VIII valves installed on unfired steam using equipment.

For boilers ( Section V) above 15 psig, valves must be sized on capacity tables which reflect a 3% accumulation. Boilers operating at 15 psig or less (Section HV), safety valves must be set no higher than 5 psig above the boiler pressure.

For unfired vessels (Section UV), safety valves must be set to prevent the pressure from rising 10% or 3 psig, which ever is greater, above the maximum operating pressure of the vessel. Accumulation is the amount of pressure change in percent of set pressure required for the valve to go to full capacity.

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