Reciprocating positive displacement

Reciprocating positive displacement pumps may have adjustment of the length or frequency of the stroke as another control feature. These may be solenoid or pneumatic devices that can be operated off a flow controller, as shown on Figure 3.21(d). 

Figure 7.4. Performance of several kinds of pumps, (a) Comparison of small centrifugal and turbine pumps (Krista and Annett, 1940). (b) An axial flow pump operating at 880 rpm (Chem. Eng. Handbook, 1973). (c) An external gear pump like that of Figure 7.12(e) (Viking Pump Co.), (d) A screw-type positive displacement pump, (e) NPSH of reciprocating positive displacement pumps.

Figure 21.12 Reciprocating positive displacement pump operation...

As the viscosity of a liquid increases, the maximum speed at which a reciprocating positive displacement pump can properly operate decreases. Therefore, as viscosity increases, the maximum flow rate through the pump decreases. 

Table 21.3 Common failure modes of reciprocating positive-displacement pumps...

Vetter, G. and Schweinfurter, F. (1989) Computation of Pressure Pulsations in Pumping Systems with Reciprocating Positive Displacement Pumps, in Proc. 3rd Joint ASCEIASME Mech. Conf. San Diego, Pumping Machinery, pp. 83-89. 

Reciprocating positive displacement machines exist in versions such as piston pumps, membrane pumps, piston compressors, and membrane compressors. These machines achieve the highest pressures and the pumps are additionally able to reach a high conveying precision. The main reason for these features is the leakproof discharge chambers (operating areas of the positive displacement machines). 

Drive Technology for Reciprocating Positive Displacement Machines... 

Figure 13.9 Drive technologies for reciprocating positive displacement machines (a) crankshaft with stroke adjustment with the eccentric radius s(r) (b) spring-cam drive with stroke adjustment (A) (c) linear drive s(A) ...

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