Reciprocating pump

While the foregoing examples have dealt with applications on centrifugal pumps, the same sort of analysis can be made for reciprocating pumps, reciprocating compressors, or other rotary users hke cooling-tower fans. 

Compressors and pumps (reciprocating) Conveyors (heavy duty)... 

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

Vacuum pumps reciprocating piston type decrease the pressure to 1 Torr rotary piston down to 0.001 Torr, two-iobe rotary down to 0.0001 Torr steam jet ejectors, one stage down to 100 Torr, three stage down to 1 Torr, five stage down to 0.05 Torr. 

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. 

API Standard 674, Positive Displacement Pumps—Reciprocating, June 1995... 

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

Constant-flow systems are generally of two basic types reciprocating piston and positive displacement (syringe) pumps. Reciprocating piston pump can maintain a liquid flow for indefinitely long time. 

Type of pump Reciprocating, piston-type metering pump... 

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. 

From the last shown elution method, it is clear that the pump is a very important accessory for high-pressure liquid chromatography. There are three main types of pumps used in modern chromatographs membrane pumps reciprocating piston pumps syringe type pumps constant pressure pumps... 

The flow of the SCF under pressure is maintained by long-stroke piston pumps, reciprocating piston pumps, or membrane pumps which deliver the mobile phase in liquefied form. The fluid is then heated to supercritical conditions before entering the column. Pressure and flow rate must be kept as constant as possible in order to maintain constant conditions for separation and to achieve a stable baseline in the chromatogram. Oscillating pumps can therefore have three heads, which deliver at different times, or a pulsation dampener in order to minimize pulsation. 

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. 

Low voltage motors used in the oil industry usually have modest starting times, since the majority of their driven machines are pumps. Reciprocating compressors and ventilation fans can have reasonably long starting times. It is therefore not normally necessary to provide special relays to detect the stalling condition. 

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