Hi all

Just another confirmation needed that the diagnosis is correct. I've been analysing this thermal fluid pump for a while now, its had high readings before but now they started increasing again. I suspected internal mechanical looseness within the pump but i'm only basing it on the DE H reading as its the highest (a number of synchronous running speed harmonics are dominating the spectra data). the time-wave form shows signs of impacting so that would partially confirm my suspicions, however we put a new motor on two months ago, had it laser aligned and it ran great. low readings. the readings this month have started to pick up and i'm wondering if the vibrations from the pump would create vibrations through and into the motor too?  I am fairly new to this so this might be a basic error. I've attached pictures of all the spectras to show you guys what is happening. 

Motor is a Brook crompton 55kw 2960rpm.

Centrifugal Pump KSB Horizontal volute casing pump, single-stage pump size 100-250

Attachments

Images (18)
Original Post

James

1. The vibe data are very hard to read. Can you re-post different color font  It was not clear to me which graphs apply to the pump vs. motor

2. Why did you replace the motor 2 months ago? 

3. You said it ran fine great with low levels for a while...and now levels are up. Can you overlay data when levels were low and the high levels now?

4. Does he pump run at one particular flow rate and close to the BEP?  

5. Are you noticing any possible looseness at the mounting feet?

6. Did you notice any unusual wear at the coupling?  and what type of coupling do you have?

Regards

Jim P

ivibr8 posted:

James

1. The vibe data are very hard to read. Can you re-post different color font  It was not clear to me which graphs apply to the pump vs. motor

2. Why did you replace the motor 2 months ago? 

3. You said it ran fine great with low levels for a while...and now levels are up. Can you overlay data when levels were low and the high levels now?

4. Does he pump run at one particular flow rate and close to the BEP?  

5. Are you noticing any possible looseness at the mounting feet?

6. Did you notice any unusual wear at the coupling?  and what type of coupling do you have?

Regards

Jim P

Hi Jim P

1. It does say at the top of each sepctrum the name of what it is (motor or pump) and the orientation. however if it is still not clear i can change it. 

2.we changed the motor because the DE bearing was making an audible screech, grease would make it stop for about 30-60 seconds and then it would come back. i wasn't getting any useful vibration data off it to suggest a bearing fault but we decided to replace it just to be sure. 

3. I am guessing when you say overlay you mean like a waterfall diagram. unfortunately i can't do But i can attach a spectra of when it was low.

4. yes it does but im not sure if that is the pumps BEP i am guessing so but ill find out for certain.

5. no they all seem good.

6. its a spider/jaw coupling. when we changed the motor the coupling was worn so the new coupling has been installed. 

Attachments

Images (1)

That last post shows quite a bit of change since January which helps.  You don't show any HF data so it is not clear if you have rolling element bearing defects also. It certainly appears, as Irshad suggested, some looseness within the pump.  See this URL   https://www.mobiusinstitute.co...amp;sTitle=Looseness

You can have looseness transmit through the coupling but comparison between the pump and motor reading should show where the main problem lies.  As is often the case, many issues with equipment can be more than one problem.

Regards

JP

I would make a few checks before taking pump for repairs that may not be needed. Check the following:

1) Loose coupling hub on shafts

2) Shaft end-gap or coupling hub gap is too close

3) Motor and pump base (including bearing support) bolts are tight

4) Pump suction and discharge pipe supports and hangers are in good condition and not loose or impacting

5) Temperature change may affect hot alignment

Laser alignment does not necessarily mean that coupling was assembled correctly or that it hasn't loosened or that alignment has not changed!

Walt

dear 

how about axial reading for pump and how about phase measurement ???to take right decision for case you need to do full measurements like ( spectrum in three axis ( V-H-A , and one measurement for high freq like Enveloping and if we check for big  vibration problem Like  ( unbalance , looseness , misalignment ) should be do phase measurement, and prefer to displace the waveform as gs Unit 

best regards  

Walt Strong posted:

I would make a few checks before taking pump for repairs that may not be needed. Check the following:

1) Loose coupling hub on shafts

2) Shaft end-gap or coupling hub gap is too close

3) Motor and pump base (including bearing support) bolts are tight

4) Pump suction and discharge pipe supports and hangers are in good condition and not loose or impacting

5) Temperature change may affect hot alignment

Laser alignment does not necessarily mean that coupling was assembled correctly or that it hasn't loosened or that alignment has not changed!

Walt

Thanks Walt

After consulting with the company that laser aligned it, they mentioned that the had a lot of difficulty aligning it because the mounting base plate which is concreted in has broken some of the concrete, allowing excessive movement. this may be the reason why i am seeing both the increase in looseness through the asset and not just the pump. we are going to look at ways to solve this to increase the stability. many thanks for your help.  

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