300 HP GE motor
300 HP GE motor
(OP)
Hi,
Looking for any specific application info or general thoughts. This is a long standing problem. We had a Reliance 300 HP DC motor driving a "jumbo" roll on a paper machine. The motors would fail every 2-6 months. Failure was non driven end bearing housing would work itelf loose, then motor would fail. The "theory" was the motor was of poor design. So we changed to GE 300 HP DC motor. These motors are having similar failures: occurring every 2-4 months, had at least 1 of 4 failures was the same non driven end bearing failed, one failure was a motor warranty issue. It is my belief that since the problem seems to be not dependent on manufacturer, and similar failures are happening, that the root cause is more the application and/or the design of the motor mounting. The motor is on steel support some 6 ft in the air driving 40 ton tolls. All our other motors are on concrete slabs and they dont fail at this frequency.
I realize there isnt enough info to have a definite answer but possibly someone has previous similar motor application experience, knows of issues with GE or Reliance motors, or agrees the lack of solid mass for motor mounting is probably a no brainer!?
The problems is long standing here and it has long been viewed as a motor problem....
Thank you for any and all comments!
Looking for any specific application info or general thoughts. This is a long standing problem. We had a Reliance 300 HP DC motor driving a "jumbo" roll on a paper machine. The motors would fail every 2-6 months. Failure was non driven end bearing housing would work itelf loose, then motor would fail. The "theory" was the motor was of poor design. So we changed to GE 300 HP DC motor. These motors are having similar failures: occurring every 2-4 months, had at least 1 of 4 failures was the same non driven end bearing failed, one failure was a motor warranty issue. It is my belief that since the problem seems to be not dependent on manufacturer, and similar failures are happening, that the root cause is more the application and/or the design of the motor mounting. The motor is on steel support some 6 ft in the air driving 40 ton tolls. All our other motors are on concrete slabs and they dont fail at this frequency.
I realize there isnt enough info to have a definite answer but possibly someone has previous similar motor application experience, knows of issues with GE or Reliance motors, or agrees the lack of solid mass for motor mounting is probably a no brainer!?
The problems is long standing here and it has long been viewed as a motor problem....
Thank you for any and all comments!





RE: 300 HP GE motor
Motor load missalignment, this should show as a high temperature of the bearing under load. I have seen this on sleeve bearing motors driving a conveyor via a gearbox. When the conveyor is empty the bearing runs cool but once loaded the bearing overheats.
Or
Current circulating in the motor via the bearing which causes pitting. Many large motors have one bearing insulated from the frame and a grounding brush at the other bearing to short circuit any stray current.
No doubt others can add to this.
Roy
RE: 300 HP GE motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 300 HP GE motor
Any chance you could change to a roller driven by chain with the motor offset a few inches. Then the motor would have no aberrant loading issues, nor be shock abused by loading and unloading of paper rolls.
Is the current to the motors modulated in any fashion?
Keith Cress
kcress - http://www.flaminsystems.com
RE: 300 HP GE motor
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: 300 HP GE motor
Thanks for all the replies. Your comments are in the same general area as mine have been. Now I need to try to prove out the root cause.
Here's some more info to answer some of the questions in your replies.
-The motor is connected to a gear box by a dodge coupling, its a boot style size 140.
-The rolls are "speed match" controlled by a SAF (Brock solutions in Kitchner Ontario) scr drive-each roll motor uses tachometer feedback to confirm the motor speed. The rolls get pressed together, then the drive control system "speed matches" the top and bottom rolls so they run at same speed. The rolls are same size, approx 30 feet long by 4 ft diameter and again are 44 tons each. At start up you can see the amps for each motor oscilating up and down...i.e. the top will rise in amps , taking the bulk of the load, while the bottom roll motor will lower in amps. Then this reverses. This occurs from start up until the paper machine is running at full line speed of typical 2100 feet per minute. Might the motors see strange electrical stresses while the rolls are again pressed together and the drive controls are trying to balance the load and eventually resulting in each motor amps at abotu the same...ramp takes about 10 minutes to line out.
-I also thought of circulating currents; looking into grounding.
- we have inhouse vibration people but they never see anything wrong! bearings also not hot.
Any further comments much appreciated. I am looking for best way to rule in or out the various possible root causes.
Thanks again!
stan
RE: 300 HP GE motor
As others, I would suspect the motor mounting arrangement.
Could you possibly post some pictures of the motor mounting arrangement ?
RE: 300 HP GE motor
RE: 300 HP GE motor
My only word of wisdom is to disassembly the cage and push outer race in a vice to get the balls out. Please don't cut the outter race, it is harder to find there root cause that way. See the below web page
ht
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson
RE: 300 HP GE motor
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: 300 HP GE motor
Thanks again for the many replies. Someone asked for pics of the installation. I think I was successful in uploading 3 pics. One shows the lower motor on a 3.5 ft or so tall stand. The other two show the higher motor frame. One pic shows the frame, the other shows the motor on top- motor has an orange cover on it- keeps it dry :)
Bearings on the drive end 6218, 6216 opposite end.
Havent doen a thorough bearing analyses because we all thought the problem was the Reliance motor design...but now that the GE is failing in similar manner, I am having bearings looked at.
Our vibration on site people check things often and find no out of ordinary vibrations,heat,etc.
Anyone familiar with controls schemes to "speed match" two rolls that are run from separate motors and scr drives? I am thinking our start up is not best. We run the rolls "pressed" together (hydraulic presses them together)from 0 to 2000 Feet per minute. What should the control system be doing as far as driving the 2 motors during this time? Should one be pulling the other?
Thanks again,
stan
RE: 300 HP GE motor
thx
RE: 300 HP GE motor
RE: 300 HP GE motor
I am assuming this is a press section. Typically the primary drive will be run in speed, the other driven rolls will be run in torque mode as helpers. If Brock did the integration, I would doubt that your problem is the control scheme, those guys are very good with web applications.
If I understand correctly, motor is close coupled to a gear box and the ODE bearing is failing? Only thing I can think of is alignment and I'm sure you have already checked.
We do put all our motors on steel frames encased in concrete. Good Luck.
RE: 300 HP GE motor
Keith Cress
kcress - http://www.flaminsystems.com
RE: 300 HP GE motor
You could install a tapered cone roller bearing on the front end and see what happens. I know about these things and how difficult it is to get mechanical to buy into the fact that they may have a problem that is effecting your motor. You could change the shaft end bearing without a lot of fuss. Even if the allignment is corrected chances are it will not stay corrected due to the weakness of the supporting framework. If a different bearing on the front end of the motor would solve the problem it would be more economical than reworking the framework, if that is in fact the source of the trouble.
Tom
None of us is as smart as all of us.
RE: 300 HP GE motor
Keith Cress
kcress - http://www.flaminsystems.com
RE: 300 HP GE motor
One method of preloading is to use back to back bearings and shims in the bearing cap.
Stan. One thing that may help and may be an easier sell to the mechanical side is plating the supports.
I would consider stiffening the supports with 1/2 in sheet steel. Fill in the openings in the stand with welded in place sheet.
I would try first filling all openings at right angles to the motor shaft. The top and bottom welds will be the ones that do the job. The welds on the side will tend to deflect the sides of the support members under load and may still allow overall deflection and vibration.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 300 HP GE motor
Tom
None of us is as smart as all of us.
RE: 300 HP GE motor
Tom
None of us is as smart as all of us.
RE: 300 HP GE motor
Would seem to me that the opposite,(from drive end), bearing would be better as the roller bearing since it's going to have the larger side loading.
But then this is all fairly moot since this is a direct drive situation. Though a bearing change might still help.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 300 HP GE motor
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: 300 HP GE motor
It has been a while since I ran into that problem, to tell you the truth I cannot remember the bearing specs except that it was a roller bearing my first impulse was tapered roller and first impulses are usually correct, but the more it was discussed the more doubt I had about the accuracy of my recollection. It may have been a double tapered roller installed on the front end (Drive end). If the gentleman is interested in the theory and feels it worth investegating it, he would be well advised to contact an electric motor manufactures rep. and find out from him exactly what type of bearing should be used for a belted load and while he is talking with them discuss the present motor problem with them and get their recomendations. If it were me in that predicament I would have already gotten them involved and I would not let them sell me a bill of goods on the issue, I would keep pressing until I got a satisfactory answer and solution to this delima.
Tom
None of us is as smart as all of us.
RE: 300 HP GE motor
Does the motor current go above the rated current during that start-up you describe? If so, the extra forces during the start-up could be hurting too.
RE: 300 HP GE motor
Thanks all for the many excellent replies.
I am digesting the info and agree the problem is somewhere in the motor stands (steel) causing loading affects that are damaging the bearings prematurely.
I am also looking at the way we start up the two motors that are supposed to work together via the controls. We may have made change in start up operation that is causing stresses that the motor bearing is seeing.Thsi may not be the root cause but may be contributory.
We do have a motor shop that has worked onthis issue for many years. Unfortunately a theory was presented by an employee here and belived byall, that the previous motor (Reliance) had an inherant design flaw, which we all believed. Since we tried the new GE motors and are seeing same failures, we realize the theory was not accurate. During all the previous bearing failure w/ Reliance motor, it appears no one did any bearing analyses. I am now doing that with the latest failure!
I believe the root cause is in the motor mounting/alignment/startup controls ....it can't be much else!
Thaksn again.
stan
RE: 300 HP GE motor
RE: 300 HP GE motor
RE: 300 HP GE motor
Since both of them are ball bearings, one of them (usually the ODE) must be free to move axially to accommodate thermal expansion. The bearing cups of this nolocating bearing should not touch the bearing.
Another thing - Bearings seem undersized for a 300 HP motor. What is the motor speed ?
RE: 300 HP GE motor
Tom
None of us is as smart as all of us.
RE: 300 HP GE motor
Keith Cress
kcress - http://www.flaminsystems.com