Pumps reciprocating pump

Kurbel-pumpe,/. reciprocating pump, -welle, /. crankshaft. 

The piston is driven in and out of a solvent chamber by an eccentric cam or gear. On the forward stroke, the inlet check valve closes, the outlet valve opens, and mobile phase is pumped to the column on the return stroke the outlet valve closes and the chamber is refilled. Unlike syringe pumps, reciprocating pumps have an unlimited capacity, and their internal volume can be made very small, from 10-100 p. The flow rate can be varied by changing the length of stroke of the piston or the speed of the motor. Access to the valves and seals is usually fairly straightforward. 

Positive-displacement pumps—reciprocating pumps problems can be classified into the following categories ... 

Pumps Centrifugal Vertical mixed flow Vertical axial flow Gear pumps Reciprocating pumps... 

Like all high pressure pumps, reciprocating pumps provide due to their periodically fluctuating displacement a pulsating flow. 

Performance data for rotary pumps is given in several forms. Figure 6.21 shows a typical plot of the head and capacity ranges of different types of rotary pumps. Reciprocating-pump capacity data are often tabulated, as in Table 6.26. 

Depending on the principle of operation, we shall distinguish four categories of pumps pneumatic pumps, syringe-type pumps, reciprocating pumps and hydraulic amplifier pumps. The principles of operation of these four types are different and will be described briefly. 

Two major types of pumps are used in LC llie screw-driven syringe type and the reciprocating pump. Reciprocating pumps are used in almost all modern commercial chromatographs. 

There are multiple types of pumps utilized for HPLC however, this discussion will focus on reciprocating pumps since most commercial instrumentation is equipped with this type of pump. Reciprocating pumps are widely used, because they have many qualities desirable for HPLC, including the ability to generate high pressures and reproducible gradients. This type of pump uses a piston to... 

Table 21.3 lists the common failure modes for reciprocating-type, positive-displacement pumps. Reciprocating pumps can generally withstand more abuse and variations in system demand than any other type. However, they must have a consistent supply of relatively clean liquid in order to function properly. 

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