Air Cooled Condenser vacuum testing
Air Cooled Condenser vacuum testing
(OP)
Dear all
We have recently switched 3 complete cells of our Air Cooled Condenser system.
The old ones were cut and new ones were welded.
The test that is being done (before plant startup) is a positive leak test.
We pressurize the system up to 500-700mbar (design pressure) and check pressure loss.
However, since it is a vacuum system we would like to test under vacuum conditions before plant startup.
Is there any procedure, API or recommended practice for that?
Best regards,
AndreChE
We have recently switched 3 complete cells of our Air Cooled Condenser system.
The old ones were cut and new ones were welded.
The test that is being done (before plant startup) is a positive leak test.
We pressurize the system up to 500-700mbar (design pressure) and check pressure loss.
However, since it is a vacuum system we would like to test under vacuum conditions before plant startup.
Is there any procedure, API or recommended practice for that?
Best regards,
AndreChE





RE: Air Cooled Condenser vacuum testing
Cheers,
gr2vessels
RE: Air Cooled Condenser vacuum testing
RE: Air Cooled Condenser vacuum testing
Household soap or detergents are not permitted as substitutes for bubble testing solutions.
Regards
rhg
RE: Air Cooled Condenser vacuum testing
RE: Air Cooled Condenser vacuum testing
rmw
RE: Air Cooled Condenser vacuum testing
You have to take the advice with a grain of salt and pepper;- The leak test is not an integrity test of the equipment, it is only a leak test. You have to judge for yourself the consequences of air leaking into the system, also how critical is the leaking itself (you need to quantify the leak, to determine if you can live with it or not). The most onerous test is probably the helium leak test, if you have located the joint which leaks. However, it is a very expensive exercise and not really relevant, since any joint sealing water will almost certainly leak for helium (small molecular size), no matter how much you tighten the joint. Also, an internal light pressure test (bubble test) is not representative, since the vacuum test may fail where the pressure leak test is OK. As for Duwe's shaving cream, it is practical if you can afford the ingress of soap in the process flow...First of all, you do your homework selecting the best gasket suitable for vacuum conditions, without breaking the flange bolts or bending the flanges.
Cheers,
gr2vessels
RE: Air Cooled Condenser vacuum testing
We did X-ray 100%, penetrating liquids test and pressure test at 500 mbar with air.
It was accepted by authorities.
Vacuum test to be done in startup of the ACC
AndreChE
RE: Air Cooled Condenser vacuum testing
Only disadvantage is that a Mass Spectrometer calibrated and set up for He will require a complete new setup and cal for H2.
The above notwithstanding; AndreChE you have done plenty already. Either the PT - dye penetrant testing - or the hydro would both have found any leaks. Don't overthink the problem - a full 'hard' vacuum is only (-)14.7 psig.
RE: Air Cooled Condenser vacuum testing
RE: Air Cooled Condenser vacuum testing
Similar equipment to He testing.
Call a testing company such as Conco Sysetms.
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Plymouth Tube
RE: Air Cooled Condenser vacuum testing
H2 = Mol Weight of 2, and will find ANYTHING resembling a leak. Moderatly easy to detect.
RE: Air Cooled Condenser vacuum testing
Most commercial applications are in the 10e-4 range and involve viscous flow.
For viscous flow in a leak there is very little differences between gases and detection becomes the critical issue.
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Plymouth Tube
RE: Air Cooled Condenser vacuum testing
Regards
rhg
RE: Air Cooled Condenser vacuum testing
Helium leak testing has been around since dirt was invented. I just recommended reading about it. I didn't say it would be cheap or easy. In cases where I have seen it used very effectively around water cooled steam condensers, the turbines were generally inside of buildings or in the vicinity of large structures at ground level.
With your A/C condenser being up in the sky, you would have to develop a plan to miminize the amount of helium (or any other of the leak test gasses mentioned) in the vicinity of known joints. Doing it when the wind doesn't just kill you would be mandatory.
If you are leak testing just to check the integrity of initial construction and installation joints, that probably would suffice because you can use a targeted approach.
If on the other hand, you were leak testing trying to find a leak of undetermined origin and all the welded and flanged joint areas had been checked, the massive size of an A/C condenser might make a general search prohibitive.
I once saw an air leak so difficult to find that the staff finally resorted to just spraying Helium under the belly of a large steam turbine (almost 1000 MW) and lo and behold after several wild sprays they got a hit and then with some more targeted spraying, narrowed it down to a 3/4" pipe plug left out of a turbine ventilator valve housing.
It might or might not be the answer for you.
rmw
RE: Air Cooled Condenser vacuum testing
Best regards,
gr2vessels
RE: Air Cooled Condenser vacuum testing
Possibly so if the vessel is in toxic service and the nozzle/manway flanges have been opened during installation to check for leak tightness.