motor bearing high temperature?
motor bearing high temperature?
(OP)
I'm having trouble diagnosing what may be causing the top motor bearing on a 5-stage vertical, centrifugal pump to shutdown on high temperature alarm. The motor was sent off for inspection. The following was returned on the inspection report:
Prior to disassembly, a no load run test was done. The upper bearing temperature stabilized after two hours at 148 degrees F. The bottom bearing leveled at 115 degrees F. Vibration levels did not exceed .004 inch/sec in any direction. All parameters appeared to be normal. Total end play was found to be .012 inch.
Inspection of the upper bearing revealed that the rollers had been loading hard on the top edge of the outer race which had a dark blue color from overheating. The reason for the overloading could not be determined but can possibly be a defective bearing or caused by defective components in the pump.
The failed bearing will be sent to the bearing manufacturer for a failure analysis.
Meanwhile the motor will be reassembled and no load tested with a new bearing. If the test is satisfactory the motor will be returned to the site. Once it is reinstalled the amp draw should be closely monitored, if above normal it could be an indication of a problem with the pump.
Does anybody have any input or suggestions on what to look for?
Prior to disassembly, a no load run test was done. The upper bearing temperature stabilized after two hours at 148 degrees F. The bottom bearing leveled at 115 degrees F. Vibration levels did not exceed .004 inch/sec in any direction. All parameters appeared to be normal. Total end play was found to be .012 inch.
Inspection of the upper bearing revealed that the rollers had been loading hard on the top edge of the outer race which had a dark blue color from overheating. The reason for the overloading could not be determined but can possibly be a defective bearing or caused by defective components in the pump.
The failed bearing will be sent to the bearing manufacturer for a failure analysis.
Meanwhile the motor will be reassembled and no load tested with a new bearing. If the test is satisfactory the motor will be returned to the site. Once it is reinstalled the amp draw should be closely monitored, if above normal it could be an indication of a problem with the pump.
Does anybody have any input or suggestions on what to look for?





RE: motor bearing high temperature?
RE: motor bearing high temperature?
On the surface, it sounds like the high temperature condition was a result of thrust from the pump (since you didn't have a high temperature during uncoupled run later). One possibility could be high pump thrust compared to bearing rating.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: motor bearing high temperature?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: motor bearing high temperature?
Electricpete, yes a temperature trend is available prior to shutdown and it should a steady increase in temp., not an instantaneous spike. The normal operating temperature is about 175 deg. While the trip temperature, I believe, is 200 deg. The pump was operating as it always has as far as service. The lower motor bearing operated under normal conditions with no apparent rise in temperature. Vibrations at the motor bearings were not significant. The upper bearing is oil lubricated with no internal water cooling.
RE: motor bearing high temperature?
RE: motor bearing high temperature?
RE: motor bearing high temperature?
As it is a hollow shaft motor and I assume the top bearing is carrying the hydraulic thrust and rotating component weight I cannot see how this can be a "pump problem" - it sounds like a bearing problem either a faulty fit in the housing, wrong bearing rating for the load or a fault with lubrication. What does the report from the bearing manufacturer say.
RE: motor bearing high temperature?
B) Check with the electric motor manufacturer for maximum allowable bearing thrust load.
C) Compare A with B.
RE: motor bearing high temperature?
RE: motor bearing high temperature?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: motor bearing high temperature?
Artisi - who/what were you quoting? I can't find the context."
I was quoting the last sentence from the OP
RE: motor bearing high temperature?
I have found this method to be quite effective especially in basket case bearing failures. If nothing else it gives one more time to analyse the problem and possible elimination of one data point.
I have used these peoples products with excellent results on many a bearing problem.
http://www.le-inc.com/index.jsp
RE: motor bearing high temperature?
What oil is recommended? What was the oil level, and how was that measured? How did the oil look? Clear or murky? I'd probably invest $50 oil analysis to confirm the right oil was installed, and it was not water contaminated.
These guys would run at least an ISO 32 oil in a high thrust motor with ball thrust bearing, and at least ISO 68 in a motor with spherical roller bearings, and an ISO 150 (!!) if the room temp was consistently 80 F.
Viscosity is one of the most important characteristics of oil ( and grease ). If the oil viscosity is just plain low it takes a heap of fancy additives to save my neck.