Optimize Pump Intake Design with Formed Suction Inlets

Vertical wet pit pumps have been frequently used for cooling tower type pump intakes requiring the need for a vertical transition from the shallow cooling tower basin to the deeper pump pit. Given the sensitivity of approach flow condition toward the wet pit pumps, cooling tower type pump intakes tend to have a large intake footprint and higher submergence depth. Over the past several years, it has been found that the use of formed suction inlet (FSI) can result in a more compact and economical pump intake with substantially reduced intake footprint and may also result in a lower submergence depth. The US Army Corps of Engineers Type 10 FSI is commonly used as it offers several advantages such as improved approach flow hydraulics in high cross flow conditions, less sensitive to the skewed velocity distribution at its entrance and also has excellent subsurface vortex suppression capabilities. This paper presents the results of hydraulic design related to two cooling tower pump intakes; one uses traditional vertical wet pit pumps and the other uses vertical pump with a FSI. Both intakes have similar application requirements and pump capacities. Model results confirm that the use of the FSI results in the reduction of the footprint of the intake structure by 38% and a more than 5-ft reduction in submergence requirements. In addition, physical sump model testing on the pump intake with FSI is briefly described.