vibration analysis on semi-hermetic compressor

[joeywpittman]

i'm working on a trane compressor m# CRHR600C-7RA0
s# J08031266AR which was installed about 6-months ago. it is making a unusual noise (sound like metal on metal) the compressor has a one-year warranty from the rebuild company. i want to try to get it replaced while it is still under warranty. my problem is that the compressor is still working properly. i fell like it is going to go out eventually. Has any one ever heard on getting a vibration analysis done on a semi-hermetic compressor. i fell that if i had a vibration report, i would have grounds to get the compressor replaced under warranty. (it is not slugging liquid, there is a superheat of 12deg)

 

[CESSNA1]

JOEYWPITTMAN: In general, vibration analysis of reciprocating machinery is a difficult. There is so much going on in the equipment that it is difficult to impossible to pinpoint a particular problem.

Rotating equipment like pumps are different cand can be fairly easily analyzed.

If the npoise is unusual and was not present on the previous compressor, or other compressors, you may want to call the rebuild company.


Regards
Dave

 

[MachineryWatch]

Joey,

I agree with Dave that vibration analysis of recip machines is not as straightforward a process as vibration analysis on "regular" machines like pumps and motors with no reciprocating parts. However, if you can invest in a day with an experienced vibration analyst doing some testing it should pay off. It has worked in other similar situations, but there is no way anyone not familiar with your relationship with the rebuild company can predict how it will turn out.

If you are dealing with a reputable company, you should be able to bring it to their attention and work out some agreement. Perhaps even a solution that involves them paying for the consultant if there truly is a problem with the machine and it is the rebuilder's fault. I have come in as the consultant in this kind of situation several times. As long as both parties agree beforehand that they are willing to live with the results of the analysis. On the other hand if there is some process condition related source for the problem that is unique to the installation that is the result of the end user's application, and not the rebuilder, then your company could be responsible for paying the outside analyst.

The analyst's results will be better and more conclusive if there are other identical units at the site that he can test, as well for comparison, and if operators at the site can shift load to the desired compressor that is being tested, when the analyst is capturing his data.

Even with a reciprocating compressor a good vibration diagnostics consultant should be able to get to the bottom of this for you. It really should be someone with no ties to either company and that both parties agree on, in order that both parties feel comfortable with the results.

Skip Hartman

http://www.machinerywatch.com

 

[electricpete]

One of the few things you can diagnose fairly easily on compressors is rolling bearing faults. Ignore the syncronous stuff and look at the non-syncrounous stuff for indication of bearing fault.

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[electricpete]

I was assuming this was a reciprocating compressor.... which will have lots of harmonics.

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[MikeHalloran]

Okay, so it's not slugging liquid refrigerant.

Could it be slugging lube oil?

What tiny piping detail was not the same after the compressor was replaced?



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA