Safety Valves and Steam Absorption Chillers

Jim_2

Does anyone have any thoughts or comments on what the steam safety valve set pressure should be for a steam system serving a steam absorption chiller?
The chiller is 400+ ton, York, design steam inlet pressure is 12psi.
What if the operating pressure were reduced, say to 8psi?
Thanks

Tony Conner

Operating Pressure...

...doesn't matter. The manufacturer will have designed and built the unit to meet, or just sneak under, the ASME codes. If the design operating pressure is 12 PSIG, then probably the safety device (safety valve, or rupture disk) will have to lift at 15 PSIG max. This keeps it out from under the ASME boiler and pressure vessel codes.

I get into discussions on stuff like this all the time. Plant people will say that their steam heating system is "low pressure" because it runs at 10 PSIG. I tell them that the safety valve that protects the system lifts at 30 PSIG, so that makes it "high pressure". And it does.

keith

good point

the fact that it operates as a low pressure system does not change the fact that it must be rated for the discharge setting of the relief valve. Or else the weak point of the system becomes the not so safe "safety valve".

canuckDale

ASME is an old institution.

But hell, it's premised on safety!

Yes. Under 15psi and non-heating keeps it out of ASME I,IV,VI and VII...but, it was built to adhere to Section VIII.

Whatever the MAWP (maximum allowable working pressure) is stamped on the vessel is the be all.

I've had the same discussions as Tony eluded to. If it's 230*F water (not high temp) why is the boiler limited to 30psi HW yet only 15psi steam? When they go, they both create the same damage?