electricpete
Electrical
This is a 22-pole 327-rpm 3500-horsepower 13.2-kv vertical induction motor. At the top a Kingsbury tilting pad thrust bearing and titling pad radial bearing in a water-cooled oil reservoir. At the bottom, greased angle-contact ball bearing with preload washer (momentary upthrust is taken by the bottom bearing). This is circ water pump motor mounted on a tall pump discharge head.
1 - The key info is in the section labeled "present condition" Please provide an opinion based on this present condition info.
2 - There is some additional prior history which muddies the waters quite a bit but may shed some light. If you have time to sort through that mess, you are free to read the history and offer an additional opinion.
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Here are the symptoms of the machine in it's present condition:
==================================
Motor is installed in the plant on top of pump discharge head in the uncoupled condition.
High 1X vibration 7 mils both directions at top of the motor, 2-3 mils at bottom of the motor and axially. (sister machines run less than 2 mils all around and usually less than 1 mil).
Phase sypmtoms match "static unbalance" perfectly. i.e.
* 90 degree phase shift as move 90 degrees around the motor circumference.
* 0 degrees phase shift from top to bottom of the motor.
Bump test shows one horizontal direction has resonance at 400cpm and the other horizontal direction has a resonance at 500cpm. (we have previously installed a brace to raise the resonance frequency in this direction from running speed up to 500cpm).
Coastdown test shows vibration changes from 7 mils to 1.2 mils within 1 second of powerdown. Phase does not change during this period. Later as machine coasts down, phase changes by 10 or 20 degrees only. These coastdown results were repeated by two different people with different equipment during two separate coastdown tests.
ALL of the above info refers to machine in uncoupled state so misalignment is not an issue.
What conclusions do you draw from the above?
===========================================
===Some additional prior history=====
===========================================
Now some additional prior history which probably only muddies the water.
Machine ran smooth <2 mils before it was removed for routine refuribhsment.
Machine ran <2 mils upon final test at repair shop (although there is some question about the base that was used for this test).
Machine ran rough when installed at the plant after refurbishment. 10 mils both directions at 1x.
Machine was again pulled out for return to the shop which had previously performed the refurbishment.
High vibration was reproduced when machine returned to the shop (run on rubber pads - shop feels rubber pads are closer to our tall slender plant mount than their stout rigid steel test stand is).
Endplay checked/adjusted to manufacturer's sped 0.015". Radial pad clearance checked/adjusted to manufacturer's spec 5 mils. Airgap checked at top of the motor. All readings within 80 mils +/- 6%. Couldn't get to bottom of the motor.
High vibration was balanced out at the shop to < 1 mils. Balancing done on rubber pads.
Machine moved to steel base and still <= 2mils vibration.
Machine returned to the plant again.
Reinstalled in the plant and saw the results above under "present condition"
There is an antirotation device above the upper bearing since there is no discharge check valve (would by gynormous in these 11-foot pipes). This is the same configuration as the sister pumps. Tested with and without the rotating ratchet pawl plate and no significant change vibration
========================
All vibrations throughout are predominantly 1x and are non-directional (approx same in both horizointal directions) and data are taken uncoupled either in shop or at plant.
All measurements were obtained using accelerometer placed onto bearing housing.
========================
Please feel free to offer any thoughts or questions about this (the sooner the better!). We are a little bit stumped by the power-down behavior and what it's telling us.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
1 - The key info is in the section labeled "present condition" Please provide an opinion based on this present condition info.
2 - There is some additional prior history which muddies the waters quite a bit but may shed some light. If you have time to sort through that mess, you are free to read the history and offer an additional opinion.
===========================
Here are the symptoms of the machine in it's present condition:
==================================
Motor is installed in the plant on top of pump discharge head in the uncoupled condition.
High 1X vibration 7 mils both directions at top of the motor, 2-3 mils at bottom of the motor and axially. (sister machines run less than 2 mils all around and usually less than 1 mil).
Phase sypmtoms match "static unbalance" perfectly. i.e.
* 90 degree phase shift as move 90 degrees around the motor circumference.
* 0 degrees phase shift from top to bottom of the motor.
Bump test shows one horizontal direction has resonance at 400cpm and the other horizontal direction has a resonance at 500cpm. (we have previously installed a brace to raise the resonance frequency in this direction from running speed up to 500cpm).
Coastdown test shows vibration changes from 7 mils to 1.2 mils within 1 second of powerdown. Phase does not change during this period. Later as machine coasts down, phase changes by 10 or 20 degrees only. These coastdown results were repeated by two different people with different equipment during two separate coastdown tests.
ALL of the above info refers to machine in uncoupled state so misalignment is not an issue.
What conclusions do you draw from the above?
===========================================
===Some additional prior history=====
===========================================
Now some additional prior history which probably only muddies the water.
Machine ran smooth <2 mils before it was removed for routine refuribhsment.
Machine ran <2 mils upon final test at repair shop (although there is some question about the base that was used for this test).
Machine ran rough when installed at the plant after refurbishment. 10 mils both directions at 1x.
Machine was again pulled out for return to the shop which had previously performed the refurbishment.
High vibration was reproduced when machine returned to the shop (run on rubber pads - shop feels rubber pads are closer to our tall slender plant mount than their stout rigid steel test stand is).
Endplay checked/adjusted to manufacturer's sped 0.015". Radial pad clearance checked/adjusted to manufacturer's spec 5 mils. Airgap checked at top of the motor. All readings within 80 mils +/- 6%. Couldn't get to bottom of the motor.
High vibration was balanced out at the shop to < 1 mils. Balancing done on rubber pads.
Machine moved to steel base and still <= 2mils vibration.
Machine returned to the plant again.
Reinstalled in the plant and saw the results above under "present condition"
There is an antirotation device above the upper bearing since there is no discharge check valve (would by gynormous in these 11-foot pipes). This is the same configuration as the sister pumps. Tested with and without the rotating ratchet pawl plate and no significant change vibration
========================
All vibrations throughout are predominantly 1x and are non-directional (approx same in both horizointal directions) and data are taken uncoupled either in shop or at plant.
All measurements were obtained using accelerometer placed onto bearing housing.
========================
Please feel free to offer any thoughts or questions about this (the sooner the better!). We are a little bit stumped by the power-down behavior and what it's telling us.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
