Pumps
DOE-HDBK-1018/1-93
POSITIVE DISPLACEMENT PUMPS
Figure 20 Diaphragm Pump
Positive Displacement Pump Characteristic Curves
Positive displacement pumps deliver a definite volume of
Figure 21
Positive Displacement Pump
Characteristic Curve
liquid for each cycle of pump operation. Therefore, the
only factor that effects flow rate in an ideal positive
displacement pump is the speed at which it operates. The
flow resistance of the system in which the pump is
operating will not effect the flow rate through the pump.
Figure 21 shows the characteristic curve for a positive
displacement pump.
The dashed line in Figure 21 shows actual positive
displacement pump performance. This line reflects the
fact that as the discharge pressure of the pump increases,
some amount of liquid will leak from the discharge of the
pump back to the pump suction, reducing the effective
flow rate of the pump. The rate at which liquid leaks
from the pump discharge to its suction is called slippage.
Rev. 0
ME-03
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