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Hello everyone,

Hoping to get some thoughts/suggestions on two recent failures I've investigated. Both are electric motors that failed due to oil ingression - in both cases, the motor was C-face mounted to a gear reducer and the reducer output shaft seal failed allowing oil to leak into the motor. Operating context is packaging conveyors, running indoors, unconditioned environment. Small motors with "lubed-for-life" gear reducers (no oil level ports). Regular visual, temperature, and vibration inspections are already being performed.

Here is where I am getting hung up on determining an effective way of dealing with the failure mode - based on the information I have from my technicians, in both cases there were:

• no external signs of an oil leak
• no noticeable change in temperature or vibration readings on motor/reducer

The lack of temperature/vibration response is confusing to me - has anyone else dealt with this before and found an effective way to monitor the seal condition and/or detect a leak? Hoping I'm overlooking an obvious solution.

------------------------------
Haydn Scott
Maintenance & Reliability Engineer
CertainTeed
Peachtree City, GA
------------------------------

Hayden

Seen this type of issue many times.  There are a number of possibilities.

1. Age of systems - how long did they last?
2. What was the consistency of the seals after failure (ie: were they sticky? brittle?)?
3. Was the OD of the shaft correct and smooth where the seal was in contact?
4. How many failures? 
5. Were the gear motors that failed all within the same age range?
6. Motor and gearbox bearing fits at drive and driven (gearbox)?

A couple of images of the failure might also be helpful (ie: seal).

The lack of a hot spot/temperature and vibration may point us in the direction of lubricant compatibility if the number of failures are high.  We ran into this about a decade ago when we were working on motor rebuilds for the US Navy radar gearboxes.  They had specified an oil and had all of the seals changed to viton.  The only warning of failure was motor failure or oil pouring out of the motors.  During the RCFA we found that the (expensive) viton seals were not compatible with the oil.  The lubricant company (customer service/sales) kept insisting that there was no problem until we were able to obtain the tear sheet on the lubricant which specifically stated that it was not chemically compatible with viton.  We replaced the $35 seal with an $0.85 seal (I seem to remember it was buna, which was counter-intuitive).

Finally, the assembly process, if these failed relatively quickly, if when the motor shaft passes through the seal and the pinion is sharp, bumps the seal lip(s), or has burrs on it, can cause the problem.  In this case the seal will still be pliable but would have what appear to be tears.

Just a few thoughts.

------------------------------
Howard W Penrose, Ph.D., CMRP
Random Past SMRP Chair (2018), 2019+ Govt Relations Smart Grid, Infrastructure and Cybersecurity Working Group Chair,
Chair Technical Standards wind, solar, energy storage, American Clean Power (formerly AWEA), and
President
MotorDoc LLC
Lombard, Illinois
------------------------------

Just to eliminate the obvious... Are the motors rated to be mounted in whichever orientation, horz/vet, they are in ? If they are hollow shaft gearboxes do they have sufficient freedom of movement to not cause the gearbox to "flex" . We see this a lot on small conveyors where they are rigid mounted instead of being allowed to float . This usually causes the output seals to leak more often than the input . When it has been improper mounting we can usually pickup a higher than normal gear mesh frequency but its not going enough to be caught with "normal rule of thumb " alarm levels 

------------------------------
Rick Peterson
Shaw Industries
Rocky Face GA
------------------------------

I have seen this failure mode quite often in conveyor application and it is very challenging to detect the leak or monitor the seal condition as it is all internal component. A deeper vibration analysis could detect it  but it would need a detailed trend and a carefully filtered resonance.

Few things that could potentially cause the problem that you might want to look into if not done already.

1. Motor install orientation ( Breather/weep hole)

• All motors generally have a breather/weep hole that prevent any accumulation of condensate inside the enclosure. By doing so, the breather allow the motor to let air in and out and if it is plugged it could cause seal's premature failure.
• The location of the breather or weep hole depends on the orientation of the motor ( Vertical vs Horizontal ) . On the vertical mount , it is impossible to detect the leak; the oil will drip down the motor and by the time it leaks out at the end , it is too late. On Some Horizontal mount, you might be able to detect the leak early.

       2. Motor install ( Shaft alignment)

             Is the Shaft align properly to prevent any axial movement ?

        3. A motor circuit anlalyzer can help you diagnoze the winding of the motor when it is indeed contaminated with oil and it has very good timing from failure detection to catastrophic failure ( 4 months to one 1 year in some cases). 

------------------------------
Cheick Rouamba
Maintenance Manager
Richmond TX
------------------------------

Few things to check I would recommend

1. Make sure you are filling the right amount of oil, Usually technicians have tendency to overfill. Check OEM manual how much quantity of oil should be there in gearbox
2. Check and confirm oil compatibility with seal material. (As already mentioned by other members)
3. Any option to perform oil analysis? Check for oil contamination? viscosity and other factors. Oil analysis is only for determining RCA. It might indicate seal material wear or contamination issues due to wear of gears
4. How is oil refilled? If technicians draw off oil from 58 gallon drums into smaller cans and use it for refilling oil, then ensure there is no cross contamination as technicians tend to use same cans for different oils
5. Even though these gearboxes are filled for life, gears tend to wear overtime. (Have you checked backlash of gears and their physical condition?) wear material of gears can contaminate the oil and this can cause seal to fail.. Therefore, its good practice to change oil entirely atleast once a year.

------------------------------
Mohammed Haroon Shaikh PMP
Engro Vopak Terminal Ltd
Karachi
------------------------------

Original Message:
Sent: 01-08-2024 09:37 AM
From: Cheick Rouamba
Subject: Motor Failure from Oil Ingression

I have seen this failure mode quite often in conveyor application and it is very challenging to detect the leak or monitor the seal condition as it is all internal component. A deeper vibration analysis could detect it  but it would need a detailed trend and a carefully filtered resonance.

Few things that could potentially cause the problem that you might want to look into if not done already.

1. Motor install orientation ( Breather/weep hole)

• All motors generally have a breather/weep hole that prevent any accumulation of condensate inside the enclosure. By doing so, the breather allow the motor to let air in and out and if it is plugged it could cause seal's premature failure.
• The location of the breather or weep hole depends on the orientation of the motor ( Vertical vs Horizontal ) . On the vertical mount , it is impossible to detect the leak; the oil will drip down the motor and by the time it leaks out at the end , it is too late. On Some Horizontal mount, you might be able to detect the leak early.

       2. Motor install ( Shaft alignment)

             Is the Shaft align properly to prevent any axial movement ?

        3. A motor circuit anlalyzer can help you diagnoze the winding of the motor when it is indeed contaminated with oil and it has very good timing from failure detection to catastrophic failure ( 4 months to one 1 year in some cases). 

------------------------------
Cheick Rouamba
Maintenance Manager
Richmond TX
------------------------------

Thanks for the responses so far - I'm going to try to address all the questions in one post so apologies if this gets long.

There have been two failures in the last month - one the motor was about 1 year in-service, reducer about four years; on the other failure the components were in service about seven years. Anecdotally I have seen four or five of these failures a year, all in the same packaging/conveying section. Motor and reducer manufacturers vary, but the orientation/mounting arrangement and drive type (timing belt) is the same.

Howard, since these are "lubed for life" reducers I hadn't considered the seal/lubricant compatibility but it is probably worth a look. As far as assembly goes, I was wondering if uneven or improper torque on the C-face bolts would contribute to premature seal failure?

Rick, the motors are rated for the orientation and mounting. The gearbox mounting will vary - based on the photos I attached maybe you can tell me whether what you are describing needs to be investigated further.

Cheick, I'm glad you mentioned MCA - the motors are smaller and a lower criticality than what I would typically apply that to, but I had thought about that as a way to detect contamination if other prevention/detection isn't effective. What would you recommend for an initial test frequency?

I have attached some photos showing the failed components on the most recent failure and a couple photos of the application on the last two.

------------------------------
Haydn Scott
Maintenance & Reliability Engineer
CertainTeed
Newnan GA
------------------------------

Thanks for uploading the pictures. That brought a lot of context to the issue.

Based on the picture , I believe it might be worth looking into an axial overload issue on the shaft and the seal is the weakest point of the system.

• Is the pulley/sprokets aligned ?  can you see if you have any axial play on the drive shaft ?
• is the belt properly tensioned ( timing belt when too tight create unwanted axial loading)
• Do you think redesigning it to a direct mount is feasible or cost effective ?  Timing belt alignment are sometimes challenging.

The black motor looks like a Servo motor , they are designed for high torque application  but since f they failed , l am leaning towards an alignment problem that is causing axial load to the seal.

It depends but I typically get a good fault diagnostic at 100 hz when I use MCA.  Like you mentionned if it is low criticality asset , it might not be worth it.

------------------------------
Cheick Rouamba
BSME-MS-CMRP
Maintenance Manager
Richmond, Tx
------------------------------

Original Message:
Sent: 01-08-2024 03:38 PM
From: Haydn Scott
Subject: Motor Failure from Oil Ingression

Thanks for the responses so far - I'm going to try to address all the questions in one post so apologies if this gets long.

There have been two failures in the last month - one the motor was about 1 year in-service, reducer about four years; on the other failure the components were in service about seven years. Anecdotally I have seen four or five of these failures a year, all in the same packaging/conveying section. Motor and reducer manufacturers vary, but the orientation/mounting arrangement and drive type (timing belt) is the same.

Howard, since these are "lubed for life" reducers I hadn't considered the seal/lubricant compatibility but it is probably worth a look. As far as assembly goes, I was wondering if uneven or improper torque on the C-face bolts would contribute to premature seal failure?

Rick, the motors are rated for the orientation and mounting. The gearbox mounting will vary - based on the photos I attached maybe you can tell me whether what you are describing needs to be investigated further.

Cheick, I'm glad you mentioned MCA - the motors are smaller and a lower criticality than what I would typically apply that to, but I had thought about that as a way to detect contamination if other prevention/detection isn't effective. What would you recommend for an initial test frequency?

I have attached some photos showing the failed components on the most recent failure and a couple photos of the application on the last two.

------------------------------
Haydn Scott
Maintenance & Reliability Engineer
CertainTeed
Newnan GA
------------------------------

Yes, improper mounting of the motor to the gearbox (two different types?) could cause eventual failure. 

------------------------------
Howard W Penrose, Ph.D., CMRP
Random Past SMRP Chair (2018), 2019+ Govt Relations Smart Grid, Infrastructure and Cybersecurity Working Group Chair,
Chair Technical Standards wind, solar, energy storage, American Clean Power (formerly AWEA), and
President
MotorDoc LLC
Lombard, Illinois
------------------------------

Original Message:
Sent: 01-08-2024 03:38 PM
From: Haydn Scott
Subject: Motor Failure from Oil Ingression

Thanks for the responses so far - I'm going to try to address all the questions in one post so apologies if this gets long.

There have been two failures in the last month - one the motor was about 1 year in-service, reducer about four years; on the other failure the components were in service about seven years. Anecdotally I have seen four or five of these failures a year, all in the same packaging/conveying section. Motor and reducer manufacturers vary, but the orientation/mounting arrangement and drive type (timing belt) is the same.

Howard, since these are "lubed for life" reducers I hadn't considered the seal/lubricant compatibility but it is probably worth a look. As far as assembly goes, I was wondering if uneven or improper torque on the C-face bolts would contribute to premature seal failure?

Rick, the motors are rated for the orientation and mounting. The gearbox mounting will vary - based on the photos I attached maybe you can tell me whether what you are describing needs to be investigated further.

Cheick, I'm glad you mentioned MCA - the motors are smaller and a lower criticality than what I would typically apply that to, but I had thought about that as a way to detect contamination if other prevention/detection isn't effective. What would you recommend for an initial test frequency?

I have attached some photos showing the failed components on the most recent failure and a couple photos of the application on the last two.

------------------------------
Haydn Scott
Maintenance & Reliability Engineer
CertainTeed
Newnan GA
------------------------------

In the first example with the Baldor motor , Sometimes its hard to get the shaft to slide into the gearbox and techs will use the mounting bolts to pull the motor into the gearbox . This will damage the input shaft seal in most cases and slowly lead to failure. The second example with the frame mounted servo type motor; forces on the output shaft , excessive tension on belts or chains, warped rollers when mated to a hollow shaft roller , etc, cause the gearbox shaft to act as a lever. The force has to go somewhere and will damage seals and usually motor bearings since they are often smaller 

------------------------------
Rick Peterson
Shaw Industries
Rocky Face GA
------------------------------

Original Message:
Sent: 01-08-2024 03:38 PM
From: Haydn Scott
Subject: Motor Failure from Oil Ingression

Thanks for the responses so far - I'm going to try to address all the questions in one post so apologies if this gets long.

There have been two failures in the last month - one the motor was about 1 year in-service, reducer about four years; on the other failure the components were in service about seven years. Anecdotally I have seen four or five of these failures a year, all in the same packaging/conveying section. Motor and reducer manufacturers vary, but the orientation/mounting arrangement and drive type (timing belt) is the same.

Howard, since these are "lubed for life" reducers I hadn't considered the seal/lubricant compatibility but it is probably worth a look. As far as assembly goes, I was wondering if uneven or improper torque on the C-face bolts would contribute to premature seal failure?

Rick, the motors are rated for the orientation and mounting. The gearbox mounting will vary - based on the photos I attached maybe you can tell me whether what you are describing needs to be investigated further.

Cheick, I'm glad you mentioned MCA - the motors are smaller and a lower criticality than what I would typically apply that to, but I had thought about that as a way to detect contamination if other prevention/detection isn't effective. What would you recommend for an initial test frequency?

I have attached some photos showing the failed components on the most recent failure and a couple photos of the application on the last two.

------------------------------
Haydn Scott
Maintenance & Reliability Engineer
CertainTeed
Newnan GA
------------------------------