Flooded suction

By flooded suction we mean the liquid pressure on the inlet side of the pump. Flooded suction can be created by gravity if the liquid level is above the centerline of the pump shaft. The centrifugal pump then receives the liquid via an inflow from a higher point. Flooded suction is also possible when several pumps are installed in series.

Flooded suction for dry prime BA pumps

Dry prime BA pumps with their own vacuum system are designed to quickly draw liquids and to overcome suction lift. However, vacuum assisted pumps are not designed for flooded suction. Below we have come up with a number of installation tips and respond to your frequently asked questions.

For which mobile pump applications can you expect a flooded suction?

• Cleaning storage tanks, underground mining, ship engine rooms, booster stations and pumps in series installations.

Which fittings should I install in the pipework when there is a flooded suction?

• We recommend to install gate valves and non-return valves to prevent liquid leaks during pump repairs or cleaning work.
• Take the correct measures to prevent pump damage due to water hammer.

What is the maximum pre-pressure on a standard BA pump?

• The maximum pre-pressure with a vacuum assisted pump is 2 mwc (0,2 bar).

What if the pre-pressure on the BA pump is higher than the permitted value?

• Check the maximum allowed pressure of the pump casing, the flanges and the pipes.
• Modify the float box of the vacuum system in accordance with the information in the float box modification instructions.

Flooded suction vs suction lift

From a pumping point of view, flooded suction is in many cases preferable when compared to suction lift. With flooded suction, the pump does not have to make any effort to suck in the liquid and therefore does not lose any head on the suction side. Another advantage of flooded suction vs suction lift is the lower risk of downtime (most pump failures are caused by suction problems).