Pumps pressure pulsations

The large variety of displacement-type flmd-transport devices makes it difficult to list characteristics common to each. However, for most types it is correct to state that (1) they are adaptable to high-pressure operation, (2) the flow rate through the pump is variable (auxiliary damping systems may be employed to reduce the magnitude of pressure pulsation and flow variation), (3) mechanical considerations limit maximum throughputs, and (4) the devices are capable of efficient performance at extremely low-volume throughput rates. 

Note Do not use a commercial back-pressure device for this test, as this may dampen the true pressure pulsations arising from the pump. 

FIGURE 8 Example of HPCL pump power up, flow accuracy, and pressure pulsation verification document, as part of either an OQ or PQ protocol. Courtesy of PerkinElmer LAS, Shelton, CT. 

Pump Flow Accuracy and Pressure Pulsation Tests 7... 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

The pumping rate is controlled by piston retracts or by the cam rotating speed. The main drawback of this type of pump is sinusoidal pressure pulsations which lead to the necessity of using pulse dampers. 

The pulsation amplitude for different pump speeds have been computed at three testpoints (TP 1, TP 2, TP 3). The computation indicates, that nearly over the whole speed range the pressure pulsations remain below 3 %. At a speed of 45 rpm the pulsation amplitudes pass a maximum which indicates an acoustical resonance (Fig. 6)... 

Vetter, G., Schweinfurter, F. Computation of Pressure Pulsation in Pumping Systems with Reciprocating Positiv Displacement Pumps. 3rd Joint ASCE/ASME Mechanics Conference, San Diego, 1989, 83 - 89. 

Vetter, G., Seidl, B. Pressure Pulsation Dampening Methods for Reciprocating Pumps. Proc. 10th Int Pump Users Symp., Houston TX, USA 1993, 25-39. 

To further minimize possible pressure pulsation, the pumps can be installed together with a pulsation dampener mounted at the discharge. Pulsation dampeners are air pressurized or spring loaded to ensure a smoother product flow in the process line. Slow rotational speed of the pump s crankshaft also helps to minimize pressure pulsation. 

The major operating problem of piston pumps is dissolved air and the formation of bubbles in the eluent. Bubbles in the pump heads cause pulsation of volume flow and pressure pulsation. Bubble formation and cavitation problems are promoted at the inlet check valve because the minimum pressure in the system is reached here. For this reason the eluent must be suitably degassed. This can be done online by a membrane degasser, by pearling helium offline through the eluent or by the use of an ultrasonic bath. 

Figure 3.1 Experimental set-up for the partial oxidation of polyolefins9 pressure reduction valve (1), needle valve (2), rotameters (3), slide valve (4), reciprocating pump (5), pulsation absorber (6).

Figure 9.7 Methods of pressure generation (a,b) reciprocating pumps/compressors, (c) multistage centrifugal pumps, (d) Pulsations in volume flow produced by above pumps.

Figure 9.30 Pressure pulsations produced by a triplex piston-pump in an installation equipped...

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. 

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