Bubble test on pump impellers
Bubble test on pump impellers
(OP)
I would like to specify a bubble test requirement to check performance on a critical pump first impeller.
I would like to know if there is any laboratory or univ doing this kind of test.
I would like to know if there is any laboratory or univ doing this kind of test.





RE: Bubble test on pump impellers
Naresuan University
Phitsanulok
Thailand
RE: Bubble test on pump impellers
Ok, on a bubble test we try to have visual access to this phenomena (usually with a transparent volute and with high frequency strobe light) and determine the areas, size and amount of bubbles that appear.
Sometimes a soft coating is applied to the impeller so that when the bubble implodes peel off this coating, being able to check the cavitation phenomena pattern
RE: Bubble test on pump impellers
RE: Bubble test on pump impellers
- your clear volute and standard one will not be identical and could result in invalid test results when applied to the real world parts.
Scipio is right - the standard test should be accurate for the majority of applications.
Check the Hydraulic Institute recommendations for more info.
Racing and bullfighting are the only real sports...everything else is just a game.
Bob
RE: Bubble test on pump impellers
So in short your money would be probably be better spent on improving your NPSHA. Stay away from low NPSHR impellers unless it is absolutely necessary. They generally have a more narrow window of smooth operation.
I have no experience with the coated impeller.
Regards checman
A side note: One of the most interesting things that we found with the test stand was that if you were able to create a vortex in the suction pipe you had to drastically change the operating condition to collapse it.
RE: Bubble test on pump impellers
As Ns and Nss increase 3% value becomes less useful until you reach the High Energy Suction area where 3% is useless because the impellers pass fluid with such high efficiency that they can be completely enveloped in super cavitation bubbles and still move a ton of water with reduced head still below the 3% value.
Incipient cavitation is present in most pumps in most installations, and visual detection of incipient cavitation does reveal how much incipient is occurring.
Good luck eliminating incipient cavitation, takes tremendous amounts of pressure to totally supress all cavitation, not possible in most situations, but it is possible.
Concerned about a problem, use an inducer, increase suction head, locate pump differently, etc.
I will check back, but am very busy to write more at the moment.
PUMPDESIGNER
RE: Bubble test on pump impellers
Any major hydraulics testing laboratory can probably do visual cavitation inception testing. In the USA the Penn State University Garfield lab, St. Anthony Falls lab and Alden Hydraulic Laboratory are probable candidates. In Britain and Germany, some possibilities are the National Engineering Lab and the Pfleiderer Institute, respectively.
A recent visual cavitation test at Pleiderer Institute is reported in Friedrichs,J. & Kosyna,G.,2002, "Rotating Cavitation in a Centrifugal Pump Impeller of Low Specific Speed", ASME J.Fluids Engineering, Vol.124,June, pp.356-362.
RE: Bubble test on pump impellers
St. Anthony Falls is good, nice guy runs it, enjoys his work.
PUMPDESIGNER