Single bearing motor for Compressor package - solo run test

[ElecEE8]

Dear All experts,

The question here I have is, how we operate or maintain the solo run test and any others low speed maintenance activities for the single bearing 11kV motor (1.3MW)? I mean to whenever we have a decoupling condition of the motor from its compressor package. The motor has single bearing on NDE side only. This motor was designed for Ethylene Compressor package.

Thanks & Regards

 

[edison123]

You can't run the motor alone with one bearing. Why do you want to run this motor alone?

Muthu

http://www.edison.co.in

 

[ElecEE8]

Dear Edison,
We may need to run this motor alone for maintenance purpose (de-coupling from the compressor) i.e. solo run test/no load test for any trouble shooting.

The Vendor introduce the jacking oil system to support to run this motor alone for de-coupling condition with low speed.

Anybody has an idea on how the jacking oil system is effective on single bearing motor running in de-coupling condition.

 

[edison123]

Post some photos of the motor, jacking oil system etc. I seriously doubt the motor can be run alone with one bearing.

Muthu

http://www.edison.co.in

 

[Skogsgurra]

I think so too. Had a compressor motor with a damaged guide edge. Not much but the rotor got stuck on the stator bore wall as soon as you tried to start it. It must be a hell of a system to keep the rotor of a 3.3 MW machine centered without the second bearing. Any pictures available?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[dArsonval]

One picture or even a couple-three photos will not provide enough information.

To form a better guess or perspective as to IF the motor would function
would require a manufacturer's drawing of the machine. And that's a slim chance
of viewing within this discussion. (Stranger things have happened though.)

I have observed the result of a motor that ran while using only one bearing.
It was a mistake that it was even powered up when it occurred... but it did run.

The size of the machine in this instance is much larger though.

There are motor designs where the motor itself does not have any bearing(s)
arranged in the traditional end bracket-rotor-end bracket configuration.
As is the case with certain styles of compressors.

The OP is suggesting the "vendor" is providing a means to run the motor which
may be suitable, BUT the term vendor does not necessarily imply [Manufacturer].

What does the manufacturer of the apparatus suggest?

John

 

[ElecEE8]

Dear All,

We are actually in discussing with the EPC and Vendor for the mentioned proposal. Note that we are in EPC stage of the project.
We have two issues in discussion;
1- Why it is the single bearing motor has been designed for the compressor? On this we have commented that with this design (single bearing) the motor shall be able to do normal no load test/solo run with de-coupling condition without any damages.
2- The need & effectiveness of jacking oil system to support the low speed turning of the shaft (single shaft comp. & motor), if it is acceptable and implemented. The Motor Vendor explain that the need of jacking oil to support and prevent the damage of bearing of the motor.

Note that motor speed is 375 rpm, 16 poles. The compressor has turning device and its operate by air. This is to support to turning compressor shaft from standstill condition.

 

[edison123]

Are the bearings white metal bearings? The jacking oil system is to lift the compressor and motor rotor for the oil film to develop during start-up. Single bearing motors are quote common for compressors to eliminate cost of one bearing and to reduce overall length. And no, you still cannot not run motor on single bearing.

Muthu

http://www.edison.co.in

 

[electricpete]

Others are probably familiar with your type of machine more than me.

The discussion makes me curious, are we talking horizontal or vertical? If horizontal, then it seems completely obvious that you'd have to go through a lot of work to provide precisely positioned 2nd bearing for any solo run. If it's vertical, it's not quite as black-and-white obvious, but the answer certainly might be the same.

Maybe you can ask the vendor (or whoever is advising you) how they propose to prevent seal damage and/or rotor-to-stator-bore contact during the solo run with only one bearing. Those are some questions you'll need answered satisfactorily before you proceed.


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(2B)+(2B)' ?

 

[waross]

A solo run may be made with the valves held open and the compressor turning but unloaded. That may be a better test in any event.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[dArsonval]

Here are a few pictures of a motor having no bearings.
I may have posted these here long ago, but I'll re-post them again
to help illustrate a motor without any bearings.

Not suggesting the photos depict the OP's motor arrangement or type.
Posting them here to provide additional insight.

The bearings of the machine are housed in a balanced/opposed compressor
having a 14 inch stroke.

The wound rotor and field frame shown in the photos are totally separate
from the compressor and have no end brackets.

At least there is a hand railing to lean on ; )

John

 

[electricpete]

Here are a few pictures of a motor having no bearings.

If I'm reading the pictures right, John's motor has a bearing on the DE and no bearing on the ODE??
So then even when taking credit for a bearing on the driven machine coupled rigidly, the motor rotor is supported in an overhung fashion??

If that's what's in your photo, it's weird and different than what I was envisioning. I was picturing the motor has a bearing on ODE and no bearing on the DE, but is supported through rigid coupling by a driven machine bearing on the driven equipment.
In this case the motor rotor would be supported between bearings when taking credit for the driven machine bearing.

Which end of the op's motor has no bearing (de or nde)?





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(2B)+(2B)' ?

 

[ElecEE8]

Dear All,

It took us couple of week on technical discussion & clarifications with EPC and Vendor (Compressor & Motor). Following are conclusion and agree path forwards;
- Single bearing is not acceptable. Motor will be double bearing since the clarification from Vendors (Compressor and Motors) are not strongly support enough on their proposal in case we want to perform solo run test (de-coupling).
- Jacking oil is no valid / not required for double bearing.

I understood that proposal of single bearing is for cost optimization by EPC & Compressor vendor as mentioned by @edison123.

Thanks a lot for all expert for sharing knowledge.