Ihave been facing a problem with sea water circulating pump (vertical pump).Although, there is no high vib. and no high amp. there's sound of Impact. It has been appeared for sometimes and suddenlly disappeared.
RPM:355
Motor NDE BRG:1.6 mm/s rms this is highest reading.
The quistion is what kind of plot analysis should I use?

cavitation?

Jonesy may be right, you should probably try to associate pump head with the noise. How is this guy mounted? I assume in a pit of some kind. Can you get a level indication on the pit? can you look in and see any vortices in the sea water?

Vibration analysis at the upper bearings or bushing may not get you much. If you can get an accel down the barrel it would be better, but may not be possible.

Could it be a check valve flapping? Does it sound like rocks in the flow?
What type of analyzer do you use?

By chance, is this a hollow shaft motor where the pump shaft passes up through the motor shaft? I have seen these run without issue, even though the pump shaft was not centered in the motor shaft bore.

Plot analysis type? A thump is a thump.

Our long term vertical pump sporadic thumping experiences:

1. Broken pump flange - mid span of a 16' casing, wasn't noticed in vibration or performance. A mechanic was in the pit working on another issue when he noticed some water coming out from the flange. Half of the bolts were broken.

2. Inlet Screen was wrapped around the impeller. When the screens were checked - none were missing 8-)

This message has been edited. Last edited by: CBM Novice,