Vibration Monitoring 2

[sshep]

My Friends,

We have some large pumps (3000 rpm, 1.5MW drive) operating in parallel which are experiencing vibration problems. The monitoring consists of single point vibration measurements on the inboard and outboard bearings. Maintenance is concerned about vibration readings which often exceed 20mm/s, and believe that there are process reasons for high vibration. I can hear some slight cavitation, and there does seem to be a relationship between vibration and flow.

I am looking for a resource by which I can become educated about vibration. I can tell that I am working with people who are also out of their league because they speak of vibration "amplitude" in units of "mm/s" (velocity).

Can anyone point me to a "vibration for dummies" level resource to become educated on this subject. I will continue to look online and at API, but I think some of you will know alot about this subject and can help me figure out how to make a diagnosis of cause for high vibration readings.

best wishes,
sshep

 

[srfish]

Hi,

One sourcce is "Flow-Induced Vibration" by Robert D. Blevins.

 

[micalbrch]

What about this?

 

[MJCronin]

"monitoring consists of single point vibration measurements on the inboard and outboard bearings."

It seems to me that you have a minimal vibration monitoring system for a large and expensive piece of equipment

Bently Nevada (now owned by GE) is a leader in this field

http://en.wikipedia.org/wiki/Bently_Nevada

http://www.ge-mcs.com/en/bently-nevada.html

 

[ScottyUK]

And Emerson-CSI are their biggest competitor (miles behind in market share, nice hardware though). Their "When the turbine trips" link is my idea of hell: the machine rings me and wakes me up to tell me it has tripped.




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If we learn from our mistakes I'm getting a great education!

 

[JLSeagull]

Perhaps inlet head pressure too low, temperature high, tight rotating turns etc. could cause suction flashing. Cavitation and flashing could share similar features.

 

[tgmcg]

You need to get a spectrum analyzer on there. If the seemingly flow-dependent vibration occurs at a specific frequency or across a range of frequencies in the lower frequency range, then it may be cavitation.

I would also suggest taking a close look at NPSHA vs NPSHR.

Better to have a specialist evaluate this as this is not a subject quickly learned and some prior experience in interpreting the vibration data is essential.