vibration of a motor

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One Oxygen compressor motor vibration is increasing along with the time & getting tripped at 100 micron. When we are starting the motor vibration is very less around 10 micron but with the time Drive End side Vertical vibration as well as NDE side horizontal vibration is getting increased. I have taken spectrum
Drive end side at Horizontal direction 1X, 2X, 3X, 4X available & same for Vertical direction also only amplitude is high for Vertical.
Non Drive end side Vertical direction upto 4X available & Horizontal direction only 1X.
Ihave checked probable looseness factor but could not found any abnormality.
Blue matching checked for the Journal bearing with shaft as well as with the bearing housing.
Interference / clearance checked for the bearing with the bearing housing. It is OK.
Can anybody help me?

4/6/072:39 AM

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lancefMember

Is your motor coupled to the compressor? Also, can you run the motor uncoupled to make sure you are not seeing something from the compressor as it heats up.

Also, what kind of compressor (piston, centrifical, etc.)

4/20/0712:29 PM

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janardhanaraoMember

Resonance may be the cause of Vibration. Please check for the same by varying the speed if possible, The vibrations should reduce at certain speed if resonance is the cause.

quote:
Originally posted by tarun:
One Oxygen compressor motor vibration is increasing along with the time & getting tripped at 100 micron. When we are starting the motor vibration is very less around 10 micron but with the time Drive End side Vertical vibration as well as NDE side horizontal vibration is getting increased. I have taken spectrum
Drive end side at Horizontal direction 1X, 2X, 3X, 4X available & same for Vertical direction also only amplitude is high for Vertical.
Non Drive end side Vertical direction upto 4X available & Horizontal direction only 1X.
Ihave checked probable looseness factor but could not found any abnormality.
Blue matching checked for the Journal bearing with shaft as well as with the bearing housing.
Interference / clearance checked for the bearing with the bearing housing. It is OK.
Can anybody help me?

5/9/0711:00 PM

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tarunMember

quote:
Originally posted by Lance F:
Is your motor coupled to the compressor? Also, can you run the motor uncoupled to make sure you are not seeing something from the compressor as it heats up.

Also, what kind of compressor (piston, centrifical, etc.)

No motor is not coupled with compressor. We are trying to solve the problem of the motor only. Compressor does not have any problem. It is a centrifugal compressor main thing is it in decoupled condition. please help.

6/1/079:11 AM

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frankoMember

Janardhana may have point since motors have critical speeds. The structure might have responded to such speed that might have triggered its natural frequency.

By the way, is the motor AC Induction or Synchronous or DC?

cheers!!!

6/4/074:43 AM

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ariesMember

I have similar experience with a 938 KW new motor (3000 rpm) driving a centrifugal compressor. Motor Vibration (at brg housing) as well as bearing temp (bath lubricated Journal brgs) increases over time. It starts with 1.5 mm/s at Motor drive end vertical & reaches 4 mm/s in 10 hrs, similarly next higher level is non drive end horizontal (from 0.9 to 2.5 mm/s). Is it a case of thermal bow??? Spectrum shows mainly 1X. Pl share your opinion.

2/7/087:30 AM

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jonoMember

I have this case like you. A vertical motor (400kW/6.3 kV), the vibration increase up with the time when motor decoupled. There is 1x, 2x, 3x and 4x rpm with fp (pole pass frequency).
The cause of that DE & NDE bearing housings is out of tolerance (oval)

9/29/088:45 PM

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krishnanangareMember

Tarun,

Its problems of shaft bow. If you have course down plot it will shows clearly.
It will increase with oil temperature high.
Please take current analysis, it will shows 2x line frequency and unsteady current.It cannot be resolved easily it requuired stator temeperature to be monitored for air gap variation.

6/17/099:50 PM

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valveMember

quote:
One Oxygen compressor motor vibration is increasing along with the time & getting tripped at 100 micron. When we are starting the motor vibration is very less around 10 micron but with the time Drive End side Vertical vibration as well as NDE side horizontal vibration is getting increased. I have taken spectrum
Drive end side at Horizontal direction 1X, 2X, 3X, 4X available & same for Vertical direction also only amplitude is high for Vertical.
Non Drive end side Vertical direction upto 4X available & Horizontal direction only 1X.

Tarun;

1. with the time : if whta you mean is during transient, then it is likely unbalance. if the increase is after running at operational speed for some time (10 microns to 100 microns), what about the performance of motor winding temperature? you may have issue on the motor that it causes localised heating and cause rotor to bow over the time..next attempt, get someone to themograph the motor body if you do not have rtd for the winding and get proper reading for motor defect analysis..

5/20/1012:30 AM

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