electricpete
Electrical
- May 4, 2001
- 16,774
We have several large vertical motors with Kingsbury thrust bearings on top where the oil reservoir is cooled by water cooling coils submersed in the oil.
We recently got bit by a very slow water leak which appeared immediately after the motor was overhauled... even though our spec requires a leak check. The method used by repair shop for leak check was as follows:
fill cooling coil with water > 95% volume.
pressurize remaining space with 90 psig air.
Close air valve, remove air supply, wait for pressure drop over 10 minutes or so.
During troubleshooting of the coil we did our own air pressure drop test. This one completely full of air... for 30 minutes had zero pressure drop. BUT, the problem did show as a very small leak by snooping.... suggests our test (completely air filled) was not sensitive enough.
I suspect that even though the shop test was more sensitive (smaller volume of air), it may not have been sensitive enough for this small leak (they didn't snoop).
We are looking for other methods that are effective in finding small leaks, don't require unreasonable effort, and don't introduce any other problems.
Other methods under consideration:
- is there a way to do a water pressure drop with no air? Fill with water and then pressurize with tiny-capacity hand-driven positive displacement pump?
- air with snoop I don't think is good method. Relies too much on being able to get to all the possible leak sites. And wondering... how bad is it if snoop is not fully removed from the reservoir.
- how about air in the coils while cavity is filled with water or oil... look for bubbles.
I am interested to hear what other people find to be a good leak test to specify for this type of application (doesn't require unreasonable effort, and don't introduce any other problems, doesn't rely on perserverance/judgement of the testers)
We recently got bit by a very slow water leak which appeared immediately after the motor was overhauled... even though our spec requires a leak check. The method used by repair shop for leak check was as follows:
fill cooling coil with water > 95% volume.
pressurize remaining space with 90 psig air.
Close air valve, remove air supply, wait for pressure drop over 10 minutes or so.
During troubleshooting of the coil we did our own air pressure drop test. This one completely full of air... for 30 minutes had zero pressure drop. BUT, the problem did show as a very small leak by snooping.... suggests our test (completely air filled) was not sensitive enough.
I suspect that even though the shop test was more sensitive (smaller volume of air), it may not have been sensitive enough for this small leak (they didn't snoop).
We are looking for other methods that are effective in finding small leaks, don't require unreasonable effort, and don't introduce any other problems.
Other methods under consideration:
- is there a way to do a water pressure drop with no air? Fill with water and then pressurize with tiny-capacity hand-driven positive displacement pump?
- air with snoop I don't think is good method. Relies too much on being able to get to all the possible leak sites. And wondering... how bad is it if snoop is not fully removed from the reservoir.
- how about air in the coils while cavity is filled with water or oil... look for bubbles.
I am interested to hear what other people find to be a good leak test to specify for this type of application (doesn't require unreasonable effort, and don't introduce any other problems, doesn't rely on perserverance/judgement of the testers)