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The starting of vacuum pump or pump group belongs to light load starting for prime mover, and there will be no problem when starting in general. However, for some large units, due to the inertia of the unit, it is difficult to start, and there is a large starting current when starting. If you do not pay attention to the starting mode, it will damage the power grid or motor. Therefore, enough attention should be paid to the starting characteristics of different types of pumps.

(1) Zero flow start characteristic of centrifugal pump

Under zero flow condition, the shaft power of centrifugal pump is small, which is 30% ~ 90% of the rated shaft power. Therefore, the starting characteristic of centrifugal pump is zero flow starting (i.e. valve closing start). After the pump reaches the rated speed, the discharge valve can be adjusted to the flow rated point.

(2) Large flow starting characteristics of axial flow pump -- full open valve starting

Under zero flow condition, the shaft power of axial flow pump is high, which is 140% ~ 200% of the rated shaft power, and the minimum power is at high flow rate. Therefore, in order to reduce the starting current, the starting characteristic of shaft power should be large flow start (i.e. full open valve start).

(3) Starting characteristics of mixed flow pump -- full open valve starting

Under zero flow condition, the shaft power of the mixed flow pump is between the above two pumps, which is 100% ~ 130% of the rated power. Therefore, the starting characteristic of the mixed flow pump should be that between the above two pumps, start with full open valve.

(4) Starting characteristics of vortex pump -- full open valve start

Under zero flow condition, the shaft power of the vortex pump is high, which is 130% ~ 190% of the rated shaft power. Therefore, similar to the axial flow pump, the starting characteristic of the vortex pump should be large flow start (i.e. full open valve start).