8.2 Priming of Pumps: Self-Priming Types
293
8.2 Priming of Pumps: Self-Priming Types
The rotor work per mass unit, given by Euler’s formula, is independent of the fluid.
The corresponding pressure increase is proportional to the density. Density is about
1000 kg/m
3
with water. With air, it is about 1.20 kg/m
3
under atmospheric conditions.The ratio between them is about 800. If a pump features a 40 m water column
head, it yields 40/800 m = 50 mm water column in air. This pump can, with a rotor
running in air, raise water within the suction pipe by 50 mm. Normally, this does
not allow the water to reach the pump, which implies that the pump fails to be selfstarting. In order to start operation, the pump and the suction pipe have to be filled
with water. This preparation is called priming, which literally means making ready
for operation. This is normally done at the first operation of a pump when there is
a foot valve at the bottom end of the suction pipe. Even with a foot valve, air may
enter the suction pipe and the pump at standstill due to loss of tightness of the foot
valve. So, it is often necessary that air can be removed from the suction pipe. Jet and
water-ring vacuum pumps are sometimes applied with large pumps. Some pumps
realise the evacuation of the air themselves. These are called self-priming. Four
types are described below.
8.2.1 Side Channel Pump
This is the most classic self-priming pump (Fig. 8.4). It may be single-stage or
multistage. An open rotor with many radial blades turns between two stator walls.
One wall has an inlet port A, the other one an outlet port B, both near the shaft. At a
larger distance from the shaft, each wall features an incomplete ring-shaped channel
C or D, starting and deepening gradually at the place of the inlet port and becoming
shallower and disappearing at the place of the outlet port (the pump also functions
with one side channel). With a first operation, the pump is filled with water. By rotor
Fig. 8.3 Series connection of
inducer and impeller. (courtesy Sundyne)
293
8.2 Priming of Pumps: Self-Priming Types
The rotor work per mass unit, given by Euler’s formula, is independent of the fluid.
The corresponding pressure increase is proportional to the density. Density is about
1000 kg/m
3
with water. With air, it is about 1.20 kg/m
3
under atmospheric conditions.The ratio between them is about 800. If a pump features a 40 m water column
head, it yields 40/800 m = 50 mm water column in air. This pump can, with a rotor
running in air, raise water within the suction pipe by 50 mm. Normally, this does
not allow the water to reach the pump, which implies that the pump fails to be selfstarting. In order to start operation, the pump and the suction pipe have to be filled
with water. This preparation is called priming, which literally means making ready
for operation. This is normally done at the first operation of a pump when there is
a foot valve at the bottom end of the suction pipe. Even with a foot valve, air may
enter the suction pipe and the pump at standstill due to loss of tightness of the foot
valve. So, it is often necessary that air can be removed from the suction pipe. Jet and
water-ring vacuum pumps are sometimes applied with large pumps. Some pumps
realise the evacuation of the air themselves. These are called self-priming. Four
types are described below.
8.2.1 Side Channel Pump
This is the most classic self-priming pump (Fig. 8.4). It may be single-stage or
multistage. An open rotor with many radial blades turns between two stator walls.
One wall has an inlet port A, the other one an outlet port B, both near the shaft. At a
larger distance from the shaft, each wall features an incomplete ring-shaped channel
C or D, starting and deepening gradually at the place of the inlet port and becoming
shallower and disappearing at the place of the outlet port (the pump also functions
with one side channel). With a first operation, the pump is filled with water. By rotor
Fig. 8.3 Series connection of
inducer and impeller. (courtesy Sundyne)