Howard wrote:

Paul:
    Cavitation is a phenomenon resulting from restricted suction..... a pump
with a restricted outlet will not cavitate.... it will stall..... a
different phenomenon, and not  harmful to a pump as cavitation is.   Actual
cavitation results in greatly increased wear and will literally eat away at
the metal in a pump......   I believe there is a confusion of terms
here.......In cavitation water goes to vapor under suction....  basically
the same thing as happens when a vapor lock occurs in a car.

                                                                H.W.

That is interesting Howard. I did not know there was a distinction.
In that light I don't know whether the Mazda pump is stalling or
cavitating. Since it is a closed loop, pressurized system how can
you tell?

Paul Lamar

Bill Freeman wrote:

I believe Howard is correct.  Cavitation is when the local water pressure
gets low enough to cause the water to flash into vapor.  Since this is a
VERY local condition, as the vapor bubble moves, it suddenly reaches
conditions where it cannot exist as vapor and very quickly changes back
to liquid.  The bubble collapsing causes extremly high local pressures and
can literally pick out chunks of metal locally.   This occurs at dirrerent
pressures
for different water temperatures, but for a particular case, it is nearly or
completely a constant temperature process.  Can be VERY damaging to
impellers.   If a pump cavitates heavily for any extended period, expect the
impeller to be destroyed.  I have seen bronze impellers destroyed in chemical
process service in a few weeks due to moderate cavitation because they
were using the pump in inappropriate pressure/flow conditions.

Stalling would occur if the fluid were prevented from exiting the pump and
was forced to recirculate,  from the "outlet" portion of the pump back to the
"inlet portion, sort of evening out the pressures throughout the pump, roughly.

Bill
Long EZ builder & pilot
mechanical engineer

 
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