Changes in Pump Performance with Adjustments in Pump Lift.
Changes in Pump Performance with Adjustments in Pump Lift.
(OP)
I have a one stage mixed flow deep well pump which uses a closed impeller. In our last performance test, we were 0.10 of a pound low from our acceptable limit. I instructed the that the pump lift be adjusted from 5/8" to 3/16". Past performance tests have shown that an icrease of 0.75 lb has occured when this is performed. This adjustment did increase the discharge pressure by 0.50 lbs. My question is are there any papers, articles, etc. that show that this is the case (or not)? What I have read indicates that there is no effect if the impeller is a closed impeller. I believe that what they mean is that there is no negligible affect, however for a 16,000 gpm pump operating at a discharge head of 60 feet, an incrase of 0.50 lb in discharge head in this instance is significant and affects operability. I made sure that the test method was correct, and that the precision test gauges were in cal.





RE: Changes in Pump Performance with Adjustments in Pump Lift.
With enclosed impellers you do not have an end clearance per say. You have wearing ring clearance instead. It appears that your wear rings are worn to a point they should be replaced. By lowering the impeller you are most likely increasing the insertion of wearing rings and that gives an addition pressure drop which decreases the slippage past the rings. You may also be inserting areas of the wear rings that do not have the same amount of wear because they where not in close proximity to its mating ring which also decreases the amount of slippage. You must be careful because sudden changes in discharge pressure or other service conditions may cause the impellers to contact the bowls causing a major problem and or a more expensive repair. The design clearances are there for a reason.
Regards checman
RE: Changes in Pump Performance with Adjustments in Pump Lift.
RE: Changes in Pump Performance with Adjustments in Pump Lift.