Superheater and Reheater Safety Valve Requirement(PG-68)
Superheater and Reheater Safety Valve Requirement(PG-68)
(OP)
Dear Sir,
At the present we has the problem on main steam safety valve - passing. Now we kill this valve via install gag for SH outlet to stop leaks and protect valve. Then, can someone/specials list explain me for PG-68.2 as [i]" The discharge capacity of the safety valve, or valves on an attached superheater may be included in determiing the number and size of the safety valves for the boiler, provide there no intervening valves between the superheat safety valve and the boiler, and provided the discharge capacity of the safety valve, or valves on the boiler, as distinct from the superheater is at least 75% of the aggregate valve capacity required." For the at least 75%of the aggreate valve capacity required, for example BMCR is 2285 t/hr*75% = 1713 t/hr it means we able to install gag on safety valve and re-calculated the relieve capacity if more than 1713 t/hr is accept by code? please advise
At the present we has the problem on main steam safety valve - passing. Now we kill this valve via install gag for SH outlet to stop leaks and protect valve. Then, can someone/specials list explain me for PG-68.2 as [i]" The discharge capacity of the safety valve, or valves on an attached superheater may be included in determiing the number and size of the safety valves for the boiler, provide there no intervening valves between the superheat safety valve and the boiler, and provided the discharge capacity of the safety valve, or valves on the boiler, as distinct from the superheater is at least 75% of the aggregate valve capacity required." For the at least 75%of the aggreate valve capacity required, for example BMCR is 2285 t/hr*75% = 1713 t/hr it means we able to install gag on safety valve and re-calculated the relieve capacity if more than 1713 t/hr is accept by code? please advise





RE: Superheater and Reheater Safety Valve Requirement(PG-68)
If you have gagged the PSV on the superheater, then you have no relief capability on the superheater and that is not in compliance with ASME Sec I.
RE: Superheater and Reheater Safety Valve Requirement(PG-68)
I think your understanding from mentioned ASME statement cannot be correct. Actually it means the relief capacity of the main safety valve(s) on the steam drum plus the relief capacity of the safety valve(s) on the superheater should be equal to the total capacity of the boiler provided that the relief capacity of the main safety valve(s) to be at least 75% of the boiler capacity; then it doesn't mean that there would be a room for gagging the safety valve(s) on the superheater.
RE: Superheater and Reheater Safety Valve Requirement(PG-68)
Thank you for your advise and explain krub.
The total relieving capacity is (Drum 1pc + +6pc + SH 2pc + PCV) = 2458.29 t/h. If i kill 1 SH valve, it will be 2458.29 – 177.5 = 2280.79t/h. It can satisfy the BMCR-2280 t/h but normally we operated with TMCR-2191 t/h. It not compliance with ASME Sec I?