Pump suction streamline

[iceland1]

Hi,

I need to run a 2000cubic meter/hour capacity pump thats located on a barge moored at a quayside. The suction inlet is 30" and is located on the bottom of the barge which is at 7m draught,i.e 7m below the suface of the sea. There is limited clearance between the suction and the sea-bed and there is sediment on the bottom that i want to avoid taking into the system. To make a decision if i can run this pump i need to know how far the streamlines of flow into the suction line will extend from the intake twoards the sea bed. Any guidance or refeneces on where to start would be appreaciated.

 

[abeltio]

This reference is excellent.
Pump Handbook
by Igor Karassik, William C. Krutzsch, Warren H.Fraser and Joseph P. Messina (Editors) 2nd Edition
Mc-Graw Hill Book Co.
ISBN 0-07-033302-5
There is a chapter dealing with clearances around pump intakes.
HTH

saludos.
a.

 

[PUMPDESIGNER]

Pump Handbook is indeed a good source.

One thing you should do is install "anti-swirl" guide vanes in the intake structure/pipe.

The higher the Ns of the pump, the more likely the water in the intake will begin to "twist" as it enters the intake structure. To eliminate this twisting or swirling motion of the water install guide vanes in line with the flow so that there is no obstruction to flow but the vanes will resist any swirling in the water as it approaches the impeller/propeller.

Perhaps too late now, but if the intake were belled before breaking the plane of the bottom of the hull, then you cause more volume to come from the sides instead of from straight down.

Now that it is all over with and the boat/intake is built, why not test either by real test or by CFD? Hard perhaps, but there is no easy way to calculate this so testing has always been the final authoritative source on intakes such as you describe. The factors that would have to be included in any analyses using pure math formulas are type of impeller/propeller (Ns), intake size and shape, the actual shape of the intake end bell (if you have one), and the multitude of smaller items such as salinity, temperature, surface roughness of the intake structure, etc. There are far too many variables to accurately predict by simple formula. CFD would be your only hope.


PUMPDESIGNER