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Posted by RTCROSRW on October 05, 2006 at 11:36:47:
In Reply to: flash tank posted by george on September 06, 2007 at 14:06:02:
: We have #4 high pressure steam boilers(fire tubes) operating @125#, with a MAWP of 150#. Our old flash/blowdonw(atmospheric) tank needed replacement.The company doing the replacement has an R stanp in good standing.(checked via National Board web site). Our old flash tank had a MAWP of 150#. The new tank has a MAWP of 75# With a thermostatic blending valve( like those installed in low pressure plants).How could the new tank have a lower MAWP? Was a mistake made........... THANKS!
If your tank is vented and not pressurized then i do not see a big issue but you should always have a minimum of 2 vents on the tank, if it is pressurized then you could have trouble. your vendors R stamp is for repairs not magic. if you have the 75 rating then you must have enough relief valves to handle maximum load from the boilers, if it is 150 then they may allow you to derate the relief valve sizing. If you go to the Boiler operators guide, forth edition by kohan page 596 they have a great picture of what a boiler feed tank explosion looks like.