PUMPS are usually operated with constant speed, head and flow. A pump is therefore designed for one particular of operation (duty point) and does not require a regulating device (guide vane). Ideally, the duty point coincides with the maximum efficiency of the pump.
TURBINES operate under variable head and flow conditions. In an MHP, flow must be adjustable to either accommodate to seasonal variations of the available water or to adjust power output according to the demand of the consumers. Adjustable guide vanes and/or runner blades (or nozzles controlled by a streamlined valve) regulate the flow
