Why does the centrifugal pump close the pressure to start?
Therefore, the operation rules of multistage centrifugal pumps require that the inlet valve be opened before opening, and the outlet valve is closed. However, the export valve closed time can not be too long, because at this time the medium in the pump cycle, the medium temperature gradually increased, easy to cause mechanical seals, due to lack of lubrication friction and wear or damage.
The motor power is selected according to the rated flow of shaft power points plus 15 to 25%, if the outlet valve is fully open to start, the pump flow may deviate from the amount of fixed lot, pump efficiency also reduces a lot, resulting in shaft power greater than the motor power caused by tripping even burned electric machine.
The flow is zero (i.e. off dead) minimum, the highest lift power; with the outlet valve opening increases, flow increases, the lift, power and efficiency are increased, the maximum value (usually in the vicinity of the highest rated flow point)
