resonace at vane pass frequency
resonace at vane pass frequency
(OP)
I have a couple of 500 hp vertical pumps. Wastewater application, they are series centrifugal pumps. The pumps vibrate excessively readings are above 1.0 in/sec at 3 times turn speed. They have 3 vane impellers. Bump test indicates a natural frequency of the pump bearing case at 3 times turn speed.
How do I go about stiffening the pump case to change the natural frequency, or what would be the alternatives to stiffening.
How do I go about stiffening the pump case to change the natural frequency, or what would be the alternatives to stiffening.





RE: resonace at vane pass frequency
RE: resonace at vane pass frequency
C. Hugh (www.Hatch.ca)
RE: resonace at vane pass frequency
RE: resonace at vane pass frequency
RE: resonace at vane pass frequency
RE: resonace at vane pass frequency
Thanks
electricpete
RE: resonace at vane pass frequency
You can try to balance the system in place (if your situation allows it). Perform a balance with the pump operating normally. If vibration reduction is possible, hydraulic unbalance is probably the problem. You can further check this hypothesis by checking balance on the pump when dry (probably on a balance stand or other fixture) and comparing the result to the wet case. Assuming that the shaft was balanced to begin with, the dry balance should now be off by the amount of weight and angle that you added for the wet case.
If this is the case, you can elect to leave the balance weights in place, or see if the impeller can be remade to tighter tolerances.
RE: resonace at vane pass frequency
Asami, T. etal, Analytical Solutions to H_infinite and H_2 Optimization of Dynamic Vibration Absorbers Attached to Damped Linear Systems, Transactions ASME, Journal of Vibration and Acoustics, Vol. 124, April 2002, pages 284-295.
All the equations, though mind-bogglingly lengthy, are at least in comprehensible BS form rather than the usual PhD form. vanstoja
RE: resonace at vane pass frequency
Also current issue of magazine has an article in their website on changing mass: http://www.sandvmag.com/
Changing the Effective Mass to Control Resonance Problems, Richard Smith, keywords: effective mass structural resonance, 0105smit.pdf, 4 pp, 53 KB.