Total end play on electric motors driving pumps
Total end play on electric motors driving pumps
(OP)
I would like some input from others involved with rotating equipment in either a refinery or power generation plant.
What would some of you consider excessive end play in an electric motor that is driving a centrifugal pump?
We have had several pumps which had gotten into a pattern of changing the mechanical seals every couple of days. We changed the pump, rebuilt the pump, changed the seal, ect. It was found that the electric motor had 0.025 of end play. After contacting the motor manufacturer and a motor shop, they both indicated that they would not consider 0.025 on the electric motor excessive. However, after we changed out the electric motor with 0.025 end play, the mechanical seal problems stopped. The shim pack type couplings which we are using are good per data sheet for about 0.031. The total axial thrust in pumps using angluar contact bearings is usually set at 0.002 -0.004. I would like some general input and guidance on when some of you think an electric motor needs to be replaced or rebuilt; is 0.015 too much? 0.020 too much?
Thank You.
What would some of you consider excessive end play in an electric motor that is driving a centrifugal pump?
We have had several pumps which had gotten into a pattern of changing the mechanical seals every couple of days. We changed the pump, rebuilt the pump, changed the seal, ect. It was found that the electric motor had 0.025 of end play. After contacting the motor manufacturer and a motor shop, they both indicated that they would not consider 0.025 on the electric motor excessive. However, after we changed out the electric motor with 0.025 end play, the mechanical seal problems stopped. The shim pack type couplings which we are using are good per data sheet for about 0.031. The total axial thrust in pumps using angluar contact bearings is usually set at 0.002 -0.004. I would like some general input and guidance on when some of you think an electric motor needs to be replaced or rebuilt; is 0.015 too much? 0.020 too much?
Thank You.





RE: Total end play on electric motors driving pumps
My reaction (right or wrong) about your situation is as follows: The only way I can imagine that reducing the motor endplay makes your seal last long is if your motor endplay was limiting axial movement... that shouldn't be the case if you have much smaller endplay at the pump. Are you sure the pump endplay is set correctly?
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RE: Total end play on electric motors driving pumps
However, with all that said, the end play you mention of 0.025" would be excessive for most bearing configurations.
Our motor repair specifications require the following:
“Shaft Endplay (D) - shall be between 0.001” and 0.003” for back-to-back thrust bearing applications and approximately 10 times the internal radial clearance of the bearing (posted in bearing manufacturers application books) for single radial bearing applications. This figure will vary from about 0.006” to 0.026” depending on the bearing size.”
We have had to work closely with our motor repair shops to get them to adhere to this specification.
Johnny Pellin
RE: Total end play on electric motors driving pumps
RE: Total end play on electric motors driving pumps
Johnny Pellin
RE: Total end play on electric motors driving pumps
RE: Total end play on electric motors driving pumps
10 times the internal radial clearance works for me. After using this on a couple of bearings I know we have running in our electric motors, I am comfortable with the range of axial movement this yields. I would like to know if this is a figure you developed there where you work, or if this is an industry standard used by electric motor manufacturers. This is the first time I have heard this rule of thumb for determining acceptable axial movement in electric motors.
Thank you for the valuable info.
RE: Total end play on electric motors driving pumps
Johnny Pellin