Air test pressure on boilers
Air test pressure on boilers
(OP)
Is there a maximum test pressure allowed for pressurizing a boiler with air to look for leaks in power boilers? I don't see one in the boiler code. We try to limit pressure due to stored energy.





RE: Air test pressure on boilers
For conducting in-service leak checks if no weld repairs were performed, there is no Code guidance. However, you are wise to use a cap on air pressure - we limit air squeezes to 25 psig.
RE: Air test pressure on boilers
RE: Air test pressure on boilers
RE: Air test pressure on boilers
It may be that we're talking about very different boilers here. I'm in the UK, and I normally only deal with gas / oil fired smoke-tube boilers producing about 17000 to 30000 1b/hr steam at around 50 to 120 pounds/in2. I have regularly pressure tested them with water, under instructions from our insurer / engineer surveyor. I seem to recall doing the same thing with ship-board boilers when I was an apprentice (thirty years ago!).
Perhaps you're talking about relative large (presumably water tube) power station boilers? In any case, I'd be interested to know (for my own education) why a hydraulic / water pressure test is not acceptable in the circumstances your'e thinking of.
Thanks,
Brian
RE: Air test pressure on boilers
Last, but equally important, some of the steam circuit heavy wall components take literally days to cool. The introduction of water for a pressure test increases thermal gradients and stresses in these heavy wall components that can accelerate fatigue damage – like ligament cracking in the bores of superheater and reheater outlet headers, and welded nozzle attachments.
RE: Air test pressure on boilers
Please excuse my ignorance as the boilers I work with are babies compared to those with which you are familiar!
RE: Air test pressure on boilers
Once a boiler is placed in-service a new set of Code rules applies in most if not all US Jurisdictions. These repair code rules deal with in-service inspection and weld repairs. Two basic concerns to assure safe operation.
For the in-service inspection any number of tests up to and including a pressure test can be performed to check for leaks. The adequacy of design was already established so there is no need to revisit this issue.
As part of an in-service inspection of a boiler to continue operation, visual and crawl-thru inspections are conducted, a review of previous repairs and operating history. The pressure test should only performed to check for missed boiler tube leaks not to re-assure integrity of the boiler or to take the boiler component to failure. There are plenty of approaches to evaluate the condition of boiler components without the need for subjecting them to elevated pressure at ambient temperature.
We have specific requirements to assure safe operation of boilers and pressure vessels and these requirements are mandated by local authorities. Pressure testing is sometimes used by several Jurisdictions when a boiler reaches a specific age. Again, I look at this as a false sense of security and can do more harm than good. As a boiler ages, understanding the failure mechanism(s) that cause tube leaks and annual or semi-annual inspections by competent personnel will avoid the necessity for a proof test.
RE: Air test pressure on boilers
In particular, the newer alloys ( P91) are very brittle atlower temperatures. Many catastrophic failures during pnuematic tests can be traced to nil ductility, and this can be expected at low temps in eld zones.
RE: Air test pressure on boilers
After a wetting incident, me, during testing in the winter I prefer air or N or N + He.
RE: Air test pressure on boilers
I didn't think there was a code limit for these low pressure checks since obviously the boiler will be expected to carry its rated pressure with steam or water.
Metengr, you stated that you limit pressure checks to 25 lbs. Considering that the boiler may soon be carrying 2700 psi drum pressure or maybe 550 psi reheat is the 25 psi limit even required for safety or just to limit time to pressurize and depressurize the boiler.
RE: Air test pressure on boilers
RE: Air test pressure on boilers