Which pump can be started against a closed discharge valve?

Centrifugal pumps are designed to move fluid through the application of centrifugal force, which is generated by the rotation of the pump impeller. This characteristic is crucial when considering the ability of a pump to be started against a closed discharge valve.

When a centrifugal pump starts with a closed discharge valve, the pump can initially build pressure due to the impeller's action, leading to a rapid stop if the valve does not open quickly enough. This behavior is different from other pump types. For instance, axial flow pumps and gear pumps typically require fluid movement to lubricate and cool the components. Starting these pumps against a closed discharge can result in damage or overheating. Submersible pumps, while often capable of handling some degree of pressurization, generally function best when they have a flow path available.

Thus, centrifugal pumps are favored in scenarios where they may encounter closed discharge valves during startup, despite potential risks associated with cavitation or system pressure spikes if the discharge remains closed for an extended period. This operational flexibility is crucial in many water treatment processes, where system dynamics can change rapidly.