ASME SEC 1 PSVs set point
ASME SEC 1 PSVs set point
(OP)
Dears
We have 3 PSVs in our Boiler and the boiler operating pressure is 40Kg/cm2g. Can you please inform us, at what pressure we need to set each safety valve. As per code how much gap we need to keep on each psv?
Presently it is
1st PSV - 45Kg/cm2g,
2nd PSV - 49Kg/cm2g
3rd PSV - 49Kg/cm2g
Is it correct? Your valuable advice pls.
Thanks
We have 3 PSVs in our Boiler and the boiler operating pressure is 40Kg/cm2g. Can you please inform us, at what pressure we need to set each safety valve. As per code how much gap we need to keep on each psv?
Presently it is
1st PSV - 45Kg/cm2g,
2nd PSV - 49Kg/cm2g
3rd PSV - 49Kg/cm2g
Is it correct? Your valuable advice pls.
Thanks





RE: ASME SEC 1 PSVs set point
You state ASME I, so presumably you have installed a suitably qualified SV with a "V" stamp. What I do not know from your question is whether these valves are installed separately or in parallel/series/tandem. Hence, is your question "gap" relative to each valves setting tolerance or the staggering of set pressures around a nominal setting of 40 Kg/cm2 ?
Per ASME I rules the following applies where P = set pressure
Valve to be fully open at 3 % Overpressure (P x 1.03)
(up to 6 % is allowed in the case of multiple valve installation - caution staggered settings required).
Blowdown (closing) 2 to 4 % (% of set pressure below the set pressure)
(P x 0.98) to (P x 0.96)
At 40 Kg/cm2 the set pressure tolerance is +/- 10 PSI (+/- 0.70 Kg/cm2)
No temperature correction is applicable since the SV would normally have been set on steam.
Above all, the set pressure should never be greater than the protected vessels maximum allowable allowable pressure MAWP.
Hope that helps.
Per ISO, only the term Safety Valve is used for all overpressure eventualities regardless of design.
RE: ASME SEC 1 PSVs set point
Thanks for your feedback. "V" stamped ASME Section 1 Safety Vales are installed in our boiler separately.(One Drum having 2 SVs with different set point 45 & 49 KGc/cm2g - 1st floor). 3rd PSVs is located in the ground floor with 49Kg/cm2g set pressure. During in-place test(on line popping test) we need to test all the three psvs.
My question is, if the operating pressure is 40Kg/cm2g, on what basis we can decide 1st PSV set pressure, 2nd PSV set pressure & 3rd PSV set pressure. I want to make sure these psvs set points are correct.( I am not asking the set pressure tolerance during the test).
We have 3 boilers in our plant. In two boilers, psv set point is 45 & 49 Kg/cm2g. However on the third boiler, psv set points are 49, 55 & 56 Kg/c2mg(1st SV, 2nd SV & 3rd SV set points).
All the three boilers are operating @ 40Kg/cm2g. However in boiler set pressure is totally different from the other two boilers.
So I need to know, on what basis we can decide each pzvs set pressure? We are thinking to revise the set pressure of 2 Boilers SVs.
Thanks
RE: ASME SEC 1 PSVs set point
A good publication to answer questions such as yours can be found within the Pentair (Crosby) Engineering Hanbook which you can find here http://tycoflowcontrol-na.com/valves/Images/PVCMC-... refer to page 3.3
Per ISO, only the term Safety Valve is used for all overpressure eventualities regardless of design.
RE: ASME SEC 1 PSVs set point