Issues with Centifugal Pump under vacuum on the suction side.
Issues with Centifugal Pump under vacuum on the suction side.
(OP)
Hello. I've used the forum several times in the past for information, but just recently decided to join.
I have a Gould's 3196 1x1.5-8 that is under vacuum on the suction side of the pump (-15 to -20 in hg). The pump is supposed to pull the water out of the tank and feed some nozzles that spray down on a filter belt. The issue is that we are getting very little flow the through the nozzles and the tank is filling up. As a result, the excess water is being pulled in to a vacuum pump and overloading it. The gauge on the discharge is reading 4 psi and does begin to raise when discharge valve is closed. When the suction line is opened and closed, nothing changes on the discharge gauge, it reads 4 PSI. There is no notable build-up or wear in the pump bowl or impeller. Impeller clearance is correct. With vacuum off the tank and the tank full of water, no leaks were noted on the pump seal or suction line. One small leak was noted on a recirculation line that goes from the pump discharge back to the tank. Any other ideas as to what to look at?
Thanks in advance.
KDUN
I have a Gould's 3196 1x1.5-8 that is under vacuum on the suction side of the pump (-15 to -20 in hg). The pump is supposed to pull the water out of the tank and feed some nozzles that spray down on a filter belt. The issue is that we are getting very little flow the through the nozzles and the tank is filling up. As a result, the excess water is being pulled in to a vacuum pump and overloading it. The gauge on the discharge is reading 4 psi and does begin to raise when discharge valve is closed. When the suction line is opened and closed, nothing changes on the discharge gauge, it reads 4 PSI. There is no notable build-up or wear in the pump bowl or impeller. Impeller clearance is correct. With vacuum off the tank and the tank full of water, no leaks were noted on the pump seal or suction line. One small leak was noted on a recirculation line that goes from the pump discharge back to the tank. Any other ideas as to what to look at?
Thanks in advance.
KDUN





RE: Issues with Centifugal Pump under vacuum on the suction side.
RE: Issues with Centifugal Pump under vacuum on the suction side.
Where is the vacuum gauge located, you need to measure the vacuum at the pump inlet.
Have you checked the total flowrate thru'the nozzles
Can you post a curve.
How can closing the inlet valve not result in a change of discharge pressure.
Is this a new or existing pump installation.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Issues with Centifugal Pump under vacuum on the suction side.
RE: Issues with Centifugal Pump under vacuum on the suction side.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Issues with Centifugal Pump under vacuum on the suction side.
RE: Issues with Centifugal Pump under vacuum on the suction side.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Issues with Centifugal Pump under vacuum on the suction side.
RE: Issues with Centifugal Pump under vacuum on the suction side.
Is the inlet pipework clear - no blockages when the unit is operating.
For a unit that was operating the normal checks would be
Direction
Impeller loose
Inlet blocked
Vacuum higher than design increasing inlet head and reducing discharge head.
I am unable to open the pump curve on my phone, will try later on my comp.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Issues with Centifugal Pump under vacuum on the suction side.
It sounds like there is not enough net positive suction head for the pump to work. This could be caused by not enough pressure in the feed tank or by a blockage in the piping.
RE: Issues with Centifugal Pump under vacuum on the suction side.
Like a pump curve we can open, a diagram of the set up, some flow data, pressures and head at different locations.
Details of this mysterious recirculation line. How is flow or pressure controlled??
What pressure does the nozzle need?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Issues with Centifugal Pump under vacuum on the suction side.
A pump that was operating ok previously and which now doesn't is usually something straightforward, although at times can be difficult to track down.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Issues with Centifugal Pump under vacuum on the suction side.
With nothing really to go on, my only suspsicion is that your flow through the pump is higher than you think and for some reason a lot more flow is going back through the bypass. This would equate well with the small rise in pressure when the discharge valve is shut as then the bypass would have 100% of flow instead of maybe 80%?
Down at the end of the curve you might have only 35ft differential head instead of 55 at your base flow rate.
Try isolating the re-circulation line and see what happens....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Issues with Centifugal Pump under vacuum on the suction side.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)