We recently installed a system 1 from Bently Nevada. It runs 24-7, and shows everything. I was wondering if the phase principles are the same for proxcimity probes. Bently uses two probes at a 45 degree angle calling them x and y. We have one major machine on this system, and it is showing a high 1x peak and about 200 degrees difference in phase across the coupling. I think it is parallel misalignment. I have looked for orbit information, but no one puts out much info on how to read orbits. I have only just started looking at the software running this program. I really like sitting in my office and looking at the machine. I will still have to go out and do a walk around of the machine tho. Main advantage is I can look at the condition of the machine much more often. I think my company plans on eventually putting all our major machines on this system.

I think that you have to look at what type of machines you have and what type of coupling is between them. The dynamics of the machines seperately or together may be more important than static forces.

You also can look at coastdown plots. If the machines have fluid film bearings you can determine where the shaft rides in the bearing and the movement (not vibration) within the bearing.

Bearing temperatures can help (bearing metal temperature). Oil temperature rise across the bearing relates to bearing loading and misalignment.

Check out Bently's web site which has extensive information about orbits, turbo-machinery analysis, etc.

For some reason, we have installed a Bently system on a supply fan with rolling element bearings. (guess the project manager did not know any better) This means that orbits are basically useless, for when there is any shaft movement, the bearings are BAD. Hope you are monitoring journal bearings!

Have a good day and 10-4 on the monitoring from the office.

Gary B

I assume this is some kind of turbomachinery on fluid film bearings and your question is if you can apply the same phase diagnostic principles as with balance of plant equipment (rigid rotors, antifriction bearings and casing vib data).

The diagnostic techniques, which work for me, when it comes turbomachinery (flexible rotor machines on fluid film bearings; shaft-relative vibration data), are somewhat different than those for BOPE. Guess this is because the X-Y orthogonal pairs of prox-probes offer more/different information than casing transducers and flexible rotor machines have different rotor dynamics than rigid. (Hmmm, or may because I worked for Bently in may previous life ). So, as Bill pointed out, it's not only orbit plots that need to be examined and although coupling misalignment may result in out-of-phase 1x vectors, it would be worth reducing the available System 1 data before making a call; otherwise you may get caught by things like excess runout, etc. There should be sufficient information in Sys1 (providing it captured s/up or s/down) to find out what's causing this apparently out of phase high 1x.

As for getting up to speed with using the System1 data, there are few good books around: “Machinery Malfunction Diagnosis and Correction” by Robert C Eisenmann, and “Fundamentals of Rotating Machinery Diagnostics” by Don Bently & Charlie Hatch. I believe Bently Nevada still offers turbomachinery diagnostics training and so does Romadyn, which is run by few ex-Bently guys and is based on D. Bently’s book.

Regards
Val

One of the X-Bently guys is not Ex; his name is still Bently. Although I believe he has to refer to himself as 'Don' or something else because of an agreement with Bently Nevada (GE).

Perhaps he could use the name X-Bently man.

Some general information:

See article "What are Shaft Orbits, Anyway?"
http://imd.us/downloads.html

Browse the B/N Orbits newsletter archives:
http://www.bently.com/search/orbitarchives.asp

Val makes some good points, you need to be a bit careful about makeing phase comparisons until you understand the system and how it is installed. Are both machines configured to the same keyphasor? Are the probes really at 45-45 on both machines? Are you looking at compensated or uncompensated data? How much runout is on the shaft? What are the vibration amplitudes? What is the coupling type?

All of this could cause the 200 degree phase difference. There is a very good chance that there is nothing wrong....

There was at one time a ex Bently guy working at Sunray. You might look him up if he is still there.

quote:

I think my company plans on eventually putting all our major machines on this system.

As Trump's theme song says money..money..money..money....MONEY!