Hello!

Has anybody done VA on chillers/compressors?

What frequencies would I be looking for, for a reciprication compressor and at what amplitude levels to whatch out for??

Cheers,

Baza!

Hi Baz
I used to monitor a few chillers some time ago one thing that I did find out was that the ones I was checking had white metal bearings.
I just happened to be passing when one was stripped down.
All I can say is get as much info as possible and collect data accordingly

We currently have compressors and chillers that we monitor at our facility.
What type of system do yo want to use - a Pro-Active Maintenance System, or a Predictive Maintenace System. Once this has been established, this will give you a good indicator of what checks and the frequency of checks you will be performing.
You will need to do your homework if you want to have an effective program. The follwoing information is a must:
1. Vendor of each major component (Then contact the Vendor and get a list of all bearings used in the complete unit).
2. RPM of each component that you are checking.(Then it is a good idea to make an Excel spreadsheet program that will generate the fundamental frequencies of each component.
3. Use an amp meter to record the current being drawn by each leg of the driver motor (this will give a good intication of the conditin of the windings in the motor. (Check and record the amps when the motor is NOT loaded). Trend this data!
4. Identify the locations that you want to collect data from by determining "WHAT" you want to learn from the checks you perform.
5. Identify the locations and what checks that you want to perform to verify the information you collected in step 4 is correct and diagnosis is correct. (Always - if possible - use a secondary check to CONFIRM the primary check. This will help you in correct diagnosis and keep you from crying "wolf".)
6. Get a schematic of the chillers and compressors. Know the machine(s)! Begin generating a history of the machines as soon as possible. Even small un-important data MAY be helpful diagnosing problems later on.

We monitor ours. A lot depends on the type. Hermetic machines are difficult, because they are so enclosed, but there are locations fairly close to the shell on some where you can take decent measurements. I read an article several years ago that stated you should drop your alarm leves on a hermetic chiller by a factor of 10 ( ie, if your normal alarms are .2 ips, they should be .02 on a hermetic ).

Semi-hermetics are easier, since the motor is more exposed. Many chillers do use sleeve bearings, but they often use a thrust bearing which is a ball, so it's important to look for both kinds, especially on the outboard end of the motor.

Many chillers also use a gear set to increase the speed of the impellor.

Open-drive chillers are much like other coupled machines.

So, sleeve bearings, gears, thrust bearings, and a large rotating impellor driven by a motor- pretty much like other industrial equipment, as far a vibration monitoring goes.

Oil sampling is also important, if you have that kind of program in place.

Thanks for your replies.

All I know is that I will going to a site where there are say, a dozen recipricating compressors and they want to know if the vibration levels are acceptable???
I'm afraid thats all the information I have.

Sorry - left out recips. There a different animal completely! Standard vibration stuff works pretty well on the motors, but on the compressor end you really need to take time synchronous data based on piston stroke. In other words, you need to know top dead center, and the timing if it is multiple stage. But there are also some other things that might help, if they can implement them. Oil analysis has saved us a fortune on recip compressors. also, record the load on the compressors if possible. It might help you determine differences between machines.

If all you can do is take traditional vibration data, you are going to see lots of harmonics -2x rpm for each piston should be predominant. It is essential to take time waveform data. You may be able to pick out looseness in rod end bearings ( often looks like a truncated waveform at the end of the stroke ). Structural loosenss is often a problem with recip machines, simply due to their motion. Inspect hold down bolts and piping connections.

Sorry if it seem I'm rambling, but recip machines are much more difficult for me to analyze - not impossible, but more difficult. I'm sure there are others on thes board who know much more than I do about analyzing recips.

Thanks Stan.

I've just found out that they're Carrier Compressors and are Recips. The model No.is O6E if that means anything???

We currently have nearly 2500 chillers under contract for vibration analysis and have been successful for nearly 15 years. We have a team of analysts who have specialized on vibration analysis on chillers. If you still need help, please contact me.

james.b.carrel@jci.com

Have you published any papers or articles then for this application?

Hi Josh. I have not published any articles.

jbcarrel. From time to time, I'm asked the question, 'can we reduce our service contracts on our chillers by carrying out VA?'. I currently have a VibXpert analyser from Pruftechnik but have limited knolege and/or experiance on chillers.
Any help or advice you could give me, ie. what to test for, what to look out for etc; would be great.

Cheers,

Barry.

Sorry, the question was for jbcarrel because he has dealt with 2500 chillers for 15 years. Hope he doesn't mind to share his expertise with this board.