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Thread: Strange Leak
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19-08-2010, 09:04 PM #1
Strange Leak
Last friday i started pressure testing a carrier 19xl centrif after rebuilding the compressor,we pressured up to 1104.1 kpa then myself and my collegue went over the system with a fine tooth comb checking for leaks using leak spray,no leaks were found however when we returned to site yesterday the pressure had dropped by 21kpa(around 3psig) so off we went looking for a leak then bingo we found a leak on the condensor releif valve reducing bush which definateley wasn't there on friday, it took both of us with a little help from my 2 foot stillsons and a scaffold tube to remove the 4" bush so basically what i'm asking is there any logic/cause behind this leak or has this happend to anyone before. like i previously said the leak wasn't there on friday
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19-08-2010, 09:24 PM #2
Re: Strange Leak
Sealant not properly applied leaving a shortage somewhere. Then the pressure slowly working on the sealant in the thread and pushing its' way out.
Brian - Newton Abbot, Devon, UK
Retired March 2015
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19-08-2010, 09:26 PM #3
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19-08-2010, 10:12 PM #4
Re: Strange Leak
Ah, OK.
So you've just been lucky that it held this long then.Brian - Newton Abbot, Devon, UK
Retired March 2015
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19-08-2010, 10:16 PM #5
Re: Strange Leak
possibly
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19-08-2010, 10:20 PM #6
Re: Strange Leak
.
Life's challenges
Just because it was not leaking, it is leaking now.
Life is like that, accept it and be glad you found it.
Personaly if you ask me it has been on the way out
for ages and the pressure test finished it off.
collrunnings.
.
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20-08-2010, 06:36 AM #7
Re: Strange Leak
James.
When pressurised leak testing the carrier Centrif you mention.
Do you not have to consider a bursting disk?
Or do these not have one?
Excuse my ignorance but why did you use such a high leak test pressure.
Given the normal operating pressures of a centrif.
Could this high pressure of caused the leak in the first place?
I have not worked on many myself, but those that I have.
Work at very low pressures.
Hence my question.
Cheers Grizzly
Grizzly
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20-08-2010, 01:42 PM #8
Re: Strange Leak
What substance did you use for the leak test?
If you add a small amount of Helium to the OFN, you can find the smallest leak as the Helium molecules are very small.
As Grizzly said, there is no need to test the system at a pressure above maximum conditions.
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20-08-2010, 05:31 PM #9
Re: Strange Leak
Last edited by james10; 20-08-2010 at 05:35 PM.
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20-08-2010, 05:33 PM #10
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20-08-2010, 06:06 PM #11
Re: Strange Leak
As soon as you said the comp was on R22 James.
What you have done makes absolute sense.
OFN is fine for leak checking on R22.
I agree about the costs re Helium as well!
Also am I correct in the fact that Helium is flammable?
I have heard of guys using it on R407c where the gas molecules are smaller than Nitrogen.
But I have yet to meet someone who has actually done so!
An earlier post did say something about Nitrogen with a trace of Helium? added?
Does anyone know about this?
Grizzly
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20-08-2010, 06:24 PM #12
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20-08-2010, 07:38 PM #13
Re: Strange Leak
Some thoughts because the original poster is from Europe and some seems not to be aware about international regulations.
Cast irons pieces have to pressurized at 1.3 x max pressure.
LP and HP may have different test pressures, related to their max allowable pressure.
You may not add a synthetic refrigerant to trace a/the leak. He, Argon,... is allowed.
If you add to the OFN some He which penetrates better then every other gas, how will you then detect this leaking helium? Handheld He-sniffers are not available, only heavy and very expensive mass spectrometers can do the job.
Cool Runnings gave the same answer as I should gave you. Pressure test showed you the leak or bursted a weakening place in the bushing.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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20-08-2010, 07:57 PM #14
Re: Strange Leak
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20-08-2010, 08:37 PM #15
Re: Strange Leak
Just a note, in the uk BOC sell a nitrogen/helium mix especially for pressure testing, it's alot cheaper than using pure helium. I've only ever used it in small x-size, not sure if they sell larger size bottles..
Ginge
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20-08-2010, 08:43 PM #16
Re: Strange Leak
James10, I wasn't referring to you, and you're right, regulations doesn't cover all the cases.
Therefore, there's now a questionnaire going around to all the EU-members asking if revisions have to be made.It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.
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20-08-2010, 08:52 PM #17
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20-08-2010, 11:35 PM #18
Re: Strange Leak
I've had two leaks this week which turned out to be on the txv outlet, in both cases it was the first thing i checked as its a favourite leak point and got nothing, no oil either, after about two hours looking elsewhere i came back to the txv to find it covered in bubbles and now leaking well!
I can only think that temperature is a factor as in both cases the plant had just been running before testing and would have gradually warmed up while off.
Jon
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23-08-2010, 06:34 PM #19
Re: Strange Leak
There are hand held helium detectors out there; expensive being a relative term, they start at around $1500. US and do not require Vacuums. I have no personal experience with them but have leak detected with helium many times using a focused ultrasonic device and be assured, helium will leak from joints that won't leak with nitrogen alone. According to our Gas Guru: testing with 5% over N2 at pressures over 150 Psi the High Tech sniffers will give an indication near the leak of a higher concentration than that of the contained gas...And the better hand helds will get into the 10 PPB concentrations.
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25-09-2010, 07:41 AM #20
Re: Strange Leak
Hi Guys, please forgive my ignorance but sometimes I'm lost with the abbreviations: what OFN means?
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25-09-2010, 08:04 AM #21
Re: Strange Leak
Oxygen Free Nitrogen!
You Would never want to pressurise with oxygen. It explodes in contact with oils and greases!
GrizzlyLast edited by Grizzly; 25-09-2010 at 08:10 AM.
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25-09-2010, 04:20 PM #22
Re: Strange Leak
Thank You Grizzly for the reply...
BTW, oxygen has NEVER been an option... :-)
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