Up- Thrust in Vertical Turbine Pumps
Up- Thrust in Vertical Turbine Pumps
(OP)
If the discharge piping is full of liquid, during start up, can a thrust balanced Vertical Turbine Pump go in up-thrust?
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Up- Thrust in Vertical Turbine Pumps
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RE: Up- Thrust in Vertical Turbine Pumps
http://www.peerlessxnet.com/documents/tibs/TIB-8_T...
The downthrust increases with differential pressure.
The upthrust increases with velocity.
So we can see on a steady state basis that low flow / high dp favors downthrust and upthrust only can exceed downthrust for high flow low dp.. far to the right of BEP toward runout.
During startup, the curve would need to be adjusted for speed. The consideration favoring upthrust is where the differential pressure does not build up quickly. The most common cause as you mention is air anywhere in the system (not just the pump). But I would venture to say it's not the only cause. For these specific pumps there are three thumbrules given where momentary upthrust may occur during start(at least that's logical reason they would require driver to accomodate momentary upthrust)
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(2B)+(2B)' ?
RE: Up- Thrust in Vertical Turbine Pumps
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(2B)+(2B)' ?
RE: Up- Thrust in Vertical Turbine Pumps
To minimize the upthrust, the pump startup procedure should include starting the pump with a partially closed discharge valve. After a few seconds, the valve can be fully opened because the discharge pressure will be fully developed.
See the attachment, pages 56-57.
RE: Up- Thrust in Vertical Turbine Pumps
http://turbolab.tamu.edu/proc/pumpproc/P22/06.pdf