Cavitation Influence on the Operation of a Pumping Station Rig with Variable Speed Pumps

To analyse duty points dropdown when centrifugal pumps run with cavitation on their suction side, experiments were conducted on a pumping station (PS) rig, where up to three variable speed driven pumps can run in parallel-coupling. The PS rig is equipped with insufficient measuring devices, like most urban PS-s. The duty points shifting was assessed with respect to pumps' performance curves. A comparison was made with respect to duty points obtained for a regime free of cavitation, after changing the suction pipe (from DN40 to DN63). Global recordings were available, namely a pressure head inside the PS-unit, and the total discharge flow rate at the PS exit. Duty points for each pump were derived using a sensorless control approach and the affinity laws. For the pumps running at nominal speed, the fully cavitating and the incipient cavitating regimes were proved by the NPSH available at the pump inlet, with respect to the NPSH required by the pump. The fully developed cavitation starts way below the 3% head dropdown limit.