Suction Pump Submergence
Suction Pump Submergence
(OP)
I am working on a problem with 'vortexes' forming in a MH . there are 2 18 inch HDPE suction lines to 2 different pumps. They are moving 5300 gpm down 2 18 inch bypass lines. The suction lift is 18 feet. Submergence is 5 feet. I have a graph to pull minimum submergence from and a calculator for the same. the graph is based on velocity and calculator is based on inside Dia. and Q. Would separating the suction lines help? Or do we need to increase submergence ? And do you guys have any other suggestions. Thanks
Richard A. Cornelius, P.E.
WWW.amlinereast.com





RE: Suction Pump Submergence
The last vortex problem I was involved with was large pumps (3000kW)consisting of 2 units installed in each forebay, one behind the other all in accordance with good practice and theory, after much hand wringing and hair pulling the problem was finally given to a hydraulic lab to analyse - to cut a long story short, the solution was to straighten the flow entering the forebay - this overcome the problem. This highlights the point that the inlet pipe / suction bell / submergence / location isn't always the cause of vortex formation.
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: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
The Hydraulic Institute has an equation for the vortex depth:
http://www.pumpfundamentals.com/help11.html
RE: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
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: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
https://www.bing.com/search?q=pump+inlet+vortex+br...
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: Suction Pump Submergence
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: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
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: Suction Pump Submergence
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Suction Pump Submergence
Little Inch, The pipes are cut at an angle. I will pass that on to the pump people for future reference . On this project it may be too difficult to get 3 24's into the pipe.
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
There's many things to try before you stick another pump in which might not make a big difference.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Suction Pump Submergence
Agreed, a vortex breaker of some sort should be fitted on each suction line also. The submergence will help with reducing vortexing somewhat. As suggested, the Hydraulic Institute has sketches on intake arrangements.
Changing suction lift may not be possible in this case ? If so, suggest adding a low NPSH booster pump ahead of the main pump for each pump run.
RE: Suction Pump Submergence
Cutting the slots would reduce the velocity at the bottom of the pipe and reduce vortex forming. I will pass that along also.
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
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: Suction Pump Submergence
As I think you know, the noise you're hearing is probably air going through the pump and not cavitating. Normally adding a bit of air reduces cavitation noise.
If you're getting cavitation without the vortex actually reaching the inlet then you're exceeding the lift capacity of the pumps.
In any event two pumps in parallel, assuming they go into the same header, are never truly equal, so one could easily be at a higher flow than the other.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Suction Pump Submergence
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: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
My assumption is that this is a temporary bypass pumping installation to repair a gravity sewer. There is no need for a permanent solution, just something that will work for several weeks. The flows should also be somewhat diurnal.
RE: Suction Pump Submergence
I would still go for slots equal to about 2 x the cross sectional area of the inner pipe or the same idea with a lot of holes drilled in it.
If this is a regular thing then maybe make up something which fits inside a 4' MH with strakes or guides to restrict swirl in the manhole section.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
RE: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
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: Suction Pump Submergence
RE: Suction Pump Submergence
This is a typical no data enquiry - lots of back and forth all based on the unknown ..........
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: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Suction Pump Submergence
Richard A. Cornelius, P.E.
WWW.amlinereast.com