Strange HH vibration @ Pump DE only

Hello everybody

 

I would like to share and get your comments on a strange high vibration issue on a pump DE bearing side. The pump is a centrifugal 4 stage, centerline mounted and driven by a motor (60HZ). See below the vibrations:

Motor NDE-X     =32 um ; Y=19 um

Motor DE-X        =3 um ; Y=5 um

Pump DE-X         =94 um ; Y=62 um

Pump NDE-X      =28 um ; Y=23 um

 

Things confirmed form the plots:

  1. No phase shift during transient and steady state
  2. TIR reviewed during start-up, only 8um at 300RPM
  3. 1X more 80% of direct values
  4. X & Y has close to 90 shift
  5. All bearing temperatures within normal

 

Maintenance activities conducted:

  1. Tried playing with alignment (0-0 & with offset but no improvement)
  2. Instrumentation also verified, probes, proximeter, I/O voltages and swapping still same result
  3. Replace bearing
  4. Coupling installed rotated and also reversed, no change

Please feel free to comment.

 

regards

Best regards

Original Post

Bump tests on motor and pump?

Vibration data, assume dominated by 1x rpm as you state, did vibe data come from displacement probes? Is x a horizontal reading or 45 degrees to TDC?

Have any mages of the installation, what do you know about the machine base

TIR, did you also try and lift the shaft up and down

Dave

Yes as 1X of running speed. Yes proximity probes. By the way i forget to mention theres one velomiter at pump casing reading 5 mm/s. 

Our issue only on pump DE brng and no history of resonance for this pump at 60hz. Machine base is common concrete where the skid is mounted. If foundation related, vibrsation should be not be specific at pump DE only. 

Still need to see some vibe data and/or phase data along with pic of machine installation if at all possible

YES you can have only vibration increase at one bearing location and it can be base related.....

Ron mentions a good point, bearing clearance, just because you have the correct crush what about the bearing to the housing, is it loose? I think I missed in this post you have sleeve bearings in the pump?

Have seen cracked shafts, loose bearing fits, loose/worn coupling components all indicate what you are describing. 

Dave

Dave

it is normal during bearing replacement to check clearance and crush. When i say crush, i usually understand it between top cover and bearing top. So the answer is bearing is not loose for sure. I already told maintenance to check the pump coupling hub as this is tapered with nut drive.

Base related, if i get the chance i will measure the casing vel at bearing down to foot and base.

regards

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