Cavitation
Cavitation
(OP)
Hi
We have a purified water storage tank, volume 2000L and the pump starts to cavitate when the level drops below 1500L.
Could someone give information on how to solve this problem or a prodecure to follow to rectify this problem
Thanks
We have a purified water storage tank, volume 2000L and the pump starts to cavitate when the level drops below 1500L.
Could someone give information on how to solve this problem or a prodecure to follow to rectify this problem
Thanks





RE: Cavitation
- increase NPSH available and/or
- decrease NPSH required.
You can increase NPSH available by:
- increase elevation difference between vessel and pump
- decrease pressure drop in pump suction line (e.g. by increasing pipe diameter, reducing line length, number of elbows etc. or reducing the flowrate)
- increase pressure in vessel (not possible when vessel is open to atmosphere)
You can decrease NPSH required by:
- installing another pump with less NPSH required
A procedure you could use is as follows:
1) find out what NPSH required of current pump is
2) calculate NPSH available (= pressure in vessel + elevation difference at low liquid level - pressure drop between vessel and pump suction, all expressed in same units as NPSH required (e.g. meters of liquid))
3) check whether you can increase NPSH available so that current pump can still be used. How to increase the NPSH available (by increasing vessel elevation or pressure or decreasing pressure drop in pump suction) depends on specific circumstances at your plant, and on whether NPSH available is significantly reduced by (excessive) pressure drop in suction
4) if it is not possible to increase NPSH available sufficiently, see whether you can obtain other pump with lower NPSH required
RE: Cavitation
RE: Cavitation
Hope this helps.
saxon
RE: Cavitation
All of the above comments are good, however, you should ask yourself, what has changed in the process ?????
Has the transfer pump been rebuilt recently ? Was a higher speed electric motor installed ?
The NPSHr for a 3550 rpm motor is typically twice that of a 1750 rpm motor on the same pump
Sometimes, the wrong impeller is used, the impeller was installed with a "ding" or dent or a misalignment could push the operation into the unstable range
Another source of "cavitation" is an increase in the liquid temperature.....is the liquid being strored at a higher temperature ?
Just my opinion.....
GIVE US MORE DETAILS !!!
MJC
RE: Cavitation
1. Check suction strainer blockage- clean and reinstall
2. Location of pump suction wrt tank inlet and layout of the suction line, vortex breaker(as suggested by sexon)
3. Suction velocity (line size)- High velocity can cause air entrapment.