Pump Cavitation
Pump Cavitation
(OP)
If a pumps is dead headed, how would you determine the time it would take to cavitate? How this time compares to reality? Could it cavitate inmediately?
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RE: Pump Cavitation
cavitation is a function of flow into the eye of the impeller.
Running against a "dead" head can cause numerous other problems: high temperature within the pump case, high levels of vibration, broken pump stafts, bearing failure, seal failure, noise - to name a few of the problems.
Suggest you look at the following site for more info.
http://www.mcnallyinstitute.com/index.html
Naresuan University
Phitsanulok
Thailand
RE: Pump Cavitation
note also that 'immediate' effect of cavitation is loss of power/head accompanied with noise, vibrations, etc.
but for pump itself (regarding the damage inflicted), cavitation is a long term process with cummulative effects, which may or may not be connected to loss of power/head characteristic for fully developed cavitation!
RE: Pump Cavitation
RE: Pump Cavitation
RE: Pump Cavitation
"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein
RE: Pump Cavitation
RE: Pump Cavitation
My understanding of this is that it is not an increase of NPSHr in terms of a requirement to avoid cavitation as the NPSHr requirement drops with decreasing flow but a head (pressure) requirement to get the water onto the impeller blade/s due to a mis-match of the flow into the impeller eye at the reduced flow. However, you would read the NPSHr curve as the head requirement for the duty /flow.
I think you will also find this is true for all centifugal pumps - it is not usually shown due to the fact it is not normally tested for standard production pumps and, in most cases is really unnecessary as well as misleading due to the fact that operating in the region of reduced flow introduces other problems not associated with NPSHr/a.
Naresuan University
Phitsanulok
Thailand
RE: Pump Cavitation
RE: Pump Cavitation
I've been around a few pumps that were mighty noisy, with gravel-y banging like severe cavitation when running with a severely restricted discharge (for required system testing). Mostly pumps with a few blades.
What you are hearing is the noise generated by the mis-match of the inlet flow onto the impeller blades -not cavitation. Coupled to this could be internal recirculation which introduces other problems including noise and localised cavitation in some cases.
Naresuan University
Phitsanulok
Thailand
RE: Pump Cavitation
By the way, cavitation is the formation AND subsequent collapse or implosion of gas bubbles in a liquid due to dynamic action.