I was wondering if anyone out here some good articles on the subject of vane pass in centrifugal pumps that you could share.
Speaking from my own personal experience, when vane pass is present the pump is operating in an unstable area of the pump curve. At least 75% of the time it is due to suction issues, the other 25% is resonance of base/pump, loose bolts, or discharge related hydraulic problems. You will need a pump curve for your pump
pressure readings on suction and discharge
temperature of product
motor hp and rpm
specific gravity and viscosity of product
Knowing these parameters will allow us to better assist you resolving your vane pass issue
Depending upon the exact design (Specific Speed, which essentially defines the geometry) the minimum unsteadiness at vane-pass may occur right at BEP or a bit to one side or the other. The specific speed also determines how steeply the unsteadiness increases on either side of the sweet spot.
At flows below BEP the unsteadiness will tend to be steered back into the pump leading to pumpset vibration. At flow above the BEP there's more of a tendency to dump the unsteadiness out the discharge, which will cause piping vibration. So, pump vibration and piping vibration do not necessarily track together.
Acoustic resonances in the system can cause a significant increase in unsteadiness. These effects depend upon sound speed, and could thus vary with temperature. Also if you have marginal NPSHA- NPSHR a bit of vapour formation can dramatically increase unseadiness at vane-pass frequency.
For "researchy" type info look for articles by U Bolleter and Elmer McKay.
Hi Alan ----
Somewhere back in the archives of the Vibe Institute - I believe in early eighties - there was a wondeful article published in the Vibe Institute Journal entitled "Vane Passing tones in centrifugal pumps" extremely well written paper, that addresses what is really a pretty complex subject.
As pointed out by others, there many possible causes of excessive vane pass vibe in a centrifugal pump, and all should be evaluated using whatever info and data is available.....however in my experience, by far the most common cause of excessive vane pass is improper location of the impeller (this is especially true when dealing with shrouded impellers) relative to the diffuser in the casing. This mislocation can be axial OR radial. If the hydraulic data checks out, then such geometry errors are about the only other choice. Wear in the diffuser and/or impeller vanes should not be ruled out either. Feel free to contact me if you want to discuss further. I think you have my contact info.
There is some good information in a thread about two years back. Go to http://maintenanceforums.com/eve/forums/a/tpc/f/3751089011/m/5891058304.
The Foiles paper appears to have been there at one time or another but seems to have been withdrawn. He is a regular contributor to the forum so perhaps he will repost.
John from PA
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