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Greetings

As a maintenance guy I was notified about a abnormal vibration in a sewage pump.The pump was showing low running current and abnormal noise, the flow rate was also low when compared to a identical pump.And we  were planning to do a shutdown to overhaul the pump but with in a week pump failed .I had taken the vibration from the pump and compared with other pumps ,all measuring points on pump were identical Except NDE side of pump. High g and velocity was present in NDE.So I decided to take fft and Envelop of the signal. High Vane pass frequency 5.88m/s was present in Velocity FFT with harmonics and in envelop BPFO 1.61g (6324 skf) and Speed 1.06g and it’s harmonics was present .Pump is running on a VFD with RPM 994 and 3 vane impeller.So my doubt   what is the root cause of the failure ,whether high VPF lead to Bearing losseness or bearing looseness lead to VPF. When the pump was dismantled impeller was loose ,wear plate was damage and bearing casing was also damage .As I am new to vibration I hope you would be able to guide me.

Thankyou

Attachments

Images (4)
  • E01A946D-2A49-4B56-A4C1-58D63F9A086F: BPFO Harmonics envelop
  • 7851B5C1-78CC-4142-8B08-37F93E42B964: Speed Harmonics
  • 7EE1125F-5429-4F91-B94A-A09BEB62921D: VPF in velocity FFT
  • 1438A048-7076-4723-85E4-39396A333636: ACC vs Time NDE
Tags: High Vanepass Vibration, BPFO, pump, VPF, Bearing

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Sometimes, the data collected is not a good representative of the condition of the machine. I'm not sure about your data collection experience, but if this is a new skill you are acquiring, my advice is to ask an experienced person to verify the reliability of the data. All analysis steps and recommendations depend on reliable data.

But I could be totally wrong.

Regards- Ali M. Al-Shurafa

RM
@Registered Member posted:

Sometimes, the data collected is not a good representative of the condition of the machine. I'm not sure about your data collection experience, but if this is a new skill you are acquiring, my advice is to ask an experienced person to verify the reliability of the data. All analysis steps and recommendations depend on reliable data.

But I could be totally wrong.

Regards- Ali M. Al-Shurafa

Yes this is a new skill that I am trying to acquire.I am using Adash vibrio 4900m which is a basic version . I had seen some tutorial videos and acquired the data from machine. Unfortunately I don’t have anyone to guide me. Here I have posted NDE (H) but  I have taken measurements from other points to NDE(V) and NDE(A) . Is there any VPF limit chart so I would be able refer .

Thankyou

RM

Now you need to be a maintenance guy, process guy, analyst and jack of all trades. Rule of thumb, overall vibration levels above .3 in/sec/pk or 8 mm/sec/pk is a rough running machine.

Low amps and reduced flow cause vibration, this is most likely due to little to no flow in the pump, the water is churning inside of the pump causing high G values in your time waveform 80 g's pk to pk! Normal values for time waveform should be 3-4 g's pk to pk. Have seen restricted flow on pump inlet, incorrect pump sizing, broken discharge pipe all cause low flow/low amps.

Worn clearances inside the pump or broken discharge check valve can cause reduced flow, I suspect the flow problem caused the pump to fail

Dave

RM
@Registered Member posted:

Now you need to be a maintenance guy, process guy, analyst and jack of all trades. Rule of thumb, overall vibration levels above .3 in/sec/pk or 8 mm/sec/pk is a rough running machine.

Low amps and reduced flow cause vibration, this is most likely due to little to no flow in the pump, the water is churning inside of the pump causing high G values in your time waveform 80 g's pk to pk! Normal values for time waveform should be 3-4 g's pk to pk. Have seen restricted flow on pump inlet, incorrect pump sizing, broken discharge pipe all cause low flow/low amps.

Worn clearances inside the pump or broken discharge check valve can cause reduced flow, I suspect the flow problem caused the pump to fail

Dave

Thank you sir for your valuable comment  .when the pump was dismantled the pump wearing and wear-plate was damage .This worn out parts lead to vibration which eventually failed the pump?The impeller retainer bolt was damage and impeller was touching the casing while dismantling.We had run vertical pumps with worn out plate  nothing has happened ,the flow would reduce gradually but never experienced such drastic failure is it because the pump is installed horizontally .

RM

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