Hi There,

Have anybody experienced reverse flow in a running pump? I have been told by plant operator that once he finished unloading first compartment and remove the empty suction hose to next compartmnet there was product flowing back through pump suction and cause spill. Pump was unloading product from truck to above ground tank with 15meter height when this happened. Pumpe can make 16 meter head. Please somebody tell me how this back flow is possible while the pump is running?? Never heard of check valves?

Nothing new under the sun. Centrifugal pumps may experience reverse flow in event of sudden power cut to the pump driver and where the check valve fails (or it's not present at all) .
The pump speed reduces quite rapidly (low inertial force of rotating parts) until the pump is not capable to overcome the system head. It's at that point the flow direction reverses and passing from discharge to suction side.Vacuum pumps