High Motor bearing temperature

[653jon]

We experience high Motor bearing temperatures during warmer climate (ambient unto 27 degC). These are sleeve bearing motors oil ring lubricated along with lube mist. The Alarm/Trip are 90/100 DegC and the bearing temperatures reach up to Alarm limits.The bearings were inspected on a couple of motors and found no damage.

Any similar experience to anybody?

 

[MikeHalloran]

Have the oil coolers been cleaned lately?

I.e., what changed?


Mike Halloran
Pembroke Pines, FL, USA

 

[electricpete]

These are sleeve bearing motors oil ring lubricated along with lube mist.

Sleeve bearing requires that distribution groove not be allowed to go empty, which can be accomplished by oil ring. Typically (from what I've seen), there is no external cooling, just a reservoid below the bearing for the ring to dip into with enough volume and external surface area to keep the oil reasonably cool. Is that what you have? I haven't seen mist used with sleeve bearings - as far as I can gather it is somtimes used as sort of constant-fed purge gas in the bearing housing to prevent intrusion of moist or contaminated air.

Your ambient temperature is not particularly hot.

It would be worthwhile to review the viscosity of the lubricant you're using. (Higher than necessary can make bearing run too hot), but can't be so low as to lose oil film. Can you provide shaft journal diameter, bearing length, shaft speed (rpm) and type of oil (viscosity and preferably viscosity index), approximate weight of rotor, and what is connected to the motor (what type of load and are there gears or just coupling).

Are you able to see the oil ring with the machine running to verify it is spinning and delivering a good quantity of oil?
When bearings were inspected did they show signs of misalignment? (angle wear pattern within the bearing).
How about dry-roll/blue check of bearing to verify no unusual geometry?
Was bearing clearance checked? (too tight can make machine run hot).
Any unusual sludge in the reservoir?
Outside of bearing housing external - any unusual fouling?
Had the behavior of the beairngs changed since installation or they have always run this hot?

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(2B)+(2B)' ?

 

[electricpete]

Also have you validated the temperature measurements (for example remove temperature probe during shutdown period and check its response to known temperatures).

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(2B)+(2B)' ?

 

[653jon]

Thanks for the reply.
The oil viscosity is VG32. The purge mist is in place to keep the moisture ingression away.
The bearings were opened on a couple of motors, as recommended by Electrical folks to look for
damaged bearings and low clearance. The bearings were clean and clearances were within the limits.
The oil ring is not visible from outside.The motor is directly coupled to pumps.
This happens on many sleeve bearing motors.

when the machine is stopped, the temperatures returned to ambient. This happens during
the summer weather.

 

[waross]

Is the temperature DIFFERENCE between the bearings higher in the summer than in the winter? Maybe you are seeing a normal condition.

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

 

[electricpete]

You consider it normal to have 90C bearing temperature in 20C ambient?

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(2B)+(2B)' ?

 

[electricpete]

Sorry 27C ambient. These are higher bearing temperature (rises) than I'm used to seeing.

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(2B)+(2B)' ?