PUMP Impeller

By

Er. Laxman Singh Sankhla B.E.Mech., Chartered Engineer

Jodhpur, India Mail ID: laxman9992001@yahoo.co.in

Pump ImpellerImpellers are circular devices with curved blades that stir the fluid in a centrifugal pump. Impellers fit tightly on the shaft and are usually pressed on or off. Although there are several ways an impeller can be held in place on the shaft, the most common method is with a key and keyway.

An impeller is the most critical part of a centrifugal pump because its size, shape and speed determine pump capacity.

There are three different types of impellers:

1. Open impellers are blades mounted on a shaft with just enough backing or "shroud" to maintain the rigidity of the blades,

FIGURE 2.4 OPEN IMPELLER

2. Semi-open impeller have a shroud completely covering one side of the blades,

FIGURE 2.5 SEMI-OPEN IMPELLER

3. Closed Impellers have shrouds covering both sides of the blades with a central hole (eye) on either one or both sides to allow fluid to enter the impeller.

FIGURE 2.6 CLOSED IMPELLER

Single suction impellers (Figure 2.7) allow fluid to enter only one side of the impeller, A problem with such an impeller is that an imbalancing thrust can be generated in the direction of suction. This can be a serious problem in high volume or high discharge pressure pumps and is often resolved with a double-suction impeller.

Double-suction impellers (Figure 2.8) allow fluid to enter both sides o the impeller, and the thrust generated on one side of the impeller is countered by the thrust generated on the other side.

FIGURE 2.7SINGLE-SUCTION IMPELLER

FIGURE 2.8DOUBLE-SUCTION IMPELLER