Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Journal Bearing Temperature Spikes of Centrifugal Compressor

Journal Bearing Temperature Spikes of Centrifugal Compressor

Journal Bearing Temperature Spikes of Centrifugal Compressor

I work in Ammonia plant and we're experiencing a problem in our Ammonia Compressor. The temperatures of both journal bearings of centrifugal ammonia compressor (which is driven by steam turbine directly) increase in spike form, without any change in bearing temperatures of steam turbine, and without any effect in radial or axial vibration values.
Could anyone suggest a reason for such a behavior?

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

Because there is a flexble coupling (most likely it is not rigid, unless we talk huge frame/power size and typically power gen.), one could assume that the turbine and compressor behave like rotordynamically uncoupled.

If journal bearing metal temperature increases significantly, this increases oil film temperature which in turn effect load carrying and damping capability of bearings. So I am wondering how come this does not reflect on vibrational readings according to your statement.

Could it be an instrumentation problem?
Has there been changes in process which increased loading on compressor and/or its speed?
Lube oil supply, any noticed change in supply temperature, oil quality (via sample analysis)?
Any changes in lube oil system parameters (oil return temperature, heat exchanger temperatures, lube oil supply pressure, etc). Turbine may be subjected to same as compressor but may accomodate better changes in oil supply conditions (e.g. different bearing design etc.).
Has there been start/restart of machine performed recently?

Small note: you mention "axial' vibrations, these are displacements monitored due to axial thrust acting on rotor.

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

It is worth to mention that the lube oil system is one for both turbine and compressor, hence lube oil pressure and temperature are the same for all four bearings.
We've checked also the instrumentation, each bearing temperature on separate module, so there are no chance of instrumentation malfunction.
If it is a matter of load, axial displacement and axial bearing temperature would have been affected, which does not occur.

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

It was implicit in my post that lube oil system is common. I would not infer process loading from axial displacement info, as you move operating point in compressor map, there is no such a formula that correlates directly displacement to the process conditions as far as I know. Loading info (speed, process variables, etc) should be obtained from control system historian (i.e., control room, DCS, etc.). This is on a side note. Root cause still to be investigated and I think machine monitoring log info, should be investigated in conjunction with the process info at hand.

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

We had a similar event recently. Both radial bearings in a large motor driver went into alarm for high temperature. Our event was sustained and not just a spike. There was no other evidence of a real problem. We initially thought it could not be an instrument problem because we were seeing increased temperatures on two bearings. We were wrong.

An instrument engineer found a bad card in the Bently 3500 rack. They changed out the card and we have not had any problems since then. We considered shutting down a gas plant when we thought this was a real bearing failure.

Johnny Pellin

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

This doesn't sound mechanical to me. How short / long (duration) and how tall (temperature) are the spikes?

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

have you ever checked the temperature of the oil coming out of the bearings? if the bearing temperature rises the oil temperature should also rise, not necessarily in the same order of magnitude though. if you notice spikes in the bearing temperature and no corresponding change in the oil temperature flowing out of the bearing, a instrumentation error would be the most likely cause.

RE: Journal Bearing Temperature Spikes of Centrifugal Compressor

looks like an instrument fault

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close