Eccentric reducer at pump suction
Eccentric reducer at pump suction
(OP)
Hello to all
I have noticed using eccentric reducer at the pump suction for horizontal centrifugal pumps "Double Suction Split Case" for water pumping in HVAC application. Is this eccentric reducer required for all types of pumps like vertical centrifugal pumps and the end suction centrifugal pumps. Advices and comments are highly appreciated..
Thanks.
I have noticed using eccentric reducer at the pump suction for horizontal centrifugal pumps "Double Suction Split Case" for water pumping in HVAC application. Is this eccentric reducer required for all types of pumps like vertical centrifugal pumps and the end suction centrifugal pumps. Advices and comments are highly appreciated..
Thanks.





RE: Eccentric reducer at pump suction
There are many companies that absolutely require an eccentric reducer upstream of any sort of pump--I have not personally seen any data that supports this configuration, but culture is often a stronger force than science.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Eccentric reducer at pump suction
goto the McNally Institute website for sufficiently related articles on typical pump installations, etc.
good luck!
-pmover
RE: Eccentric reducer at pump suction
The eccentric reducer is only required on horizontal suction pipe. Reason as zdas04 said.
RE: Eccentric reducer at pump suction
By vertical pumps, I did not mean the vertical turbine pumps but the split case centrifugal pump mounted vertically, do we need to install the eccentric reducer for this type as well? thanks
RE: Eccentric reducer at pump suction
My personal belief is that eccentric reducers are not important, except in the most extreme cases.
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: Eccentric reducer at pump suction
RE: Eccentric reducer at pump suction
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: Eccentric reducer at pump suction
RE: Eccentric reducer at pump suction
What were the pump symptoms? eg Was it cavitation, decreased capacity, vibration?? Was the flow known to be two-phase? In two-phase flow I would agree that you should use flat-top eccentrics. Was it a start-up problem, where the flow was never able to reach a steady state? Did the pump run OK for a period and then gradually develop the symptoms?
I would be very grateful if you would write a paragraph or two describing these experiences so that I can watch out for these problems in future.
regards
Harvey
Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com
RE: Eccentric reducer at pump suction
I agree on you first half but when you mentioned about solids I think you just mean some minor solids in fluid.
When the fluid contains certain amount of solids, we call it slurry. For slurry pumping, solids settling is a major consideration far more important than air pocket. Most of the time the suction pipe is sized lower than the critical velocity that means solids will settle and slide at the bottom of the pipe. So bottom flush reducer is always required.
By the way, slurry pumps are designed solid enough to handle some air.
RE: Eccentric reducer at pump suction
bulkhandling (Mechanical) 9 Mar 06 14:08
"By the way, slurry pumps are designed solid enough to handle some air."
Just a small point - I don't really see any connection between "designed solid enough" and "handle some air". Air-handling is not a function how solid a pump is designed but a function of impeller geometry and volute design. However, I would agree that a slurry pump is more capable of handling "nuisanse air" entrained in the pumped product than a close-clearance clean product pump.
Naresuan University
Phitsanulok
Thailand
RE: Eccentric reducer at pump suction
For water pumps- flat side top or concentric- not as critical though.
Cheers,
Daniel
RE: Eccentric reducer at pump suction
Thanks once again....
RE: Eccentric reducer at pump suction
But when they are recommended (right, wrong, or otherwise), from what I recall, the position of the flat side (top or bottom) depends on whether you have a suction lift or an elevated supply.
RE: Eccentric reducer at pump suction
Another thing I do remember with double suction pumps is if you have an elbow on the suction side close to the pump, you should arrange the elbow so the flow does not cause an imabalance on the impeller.
This is not easy to explain in words but just think of the flow profile on the inside radius of the elbow compared to the outside radius. This is a known phenomenon and you should be able to find information on it.
RE: Eccentric reducer at pump suction
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