Multiple-head pumps

To reduce the amplitude of the pulses, some manufacturers have proposed the use of multiple-head pumps, also named multiplex pumps, in which the same motor powers the several heads which are out of phase. From Fig. 9a it can be seen that, with a sinusoidal drive pump with two heads 1S0 out of phase, the amplitude of the pressure pulses will not be changed. The flow-rate will be doubled and the flow profile will be a rectified sinusoid. With three heads 120° out of phase, the pulses are partially damped, as shown in Fig. 9b. The maximal pulse amplitude is 13.3% of the maximal flow-rate if the distance travelled by the piston is the same for the three heads. In this instance the average flow-rate is 95.5% of maximal flow-rate, which is a considerable improvement. 

An example of a complete continuous process with a multiple head metering pump suitable for liquid detergent manufacture is provided in Figure 14.4a. This... 

When two or more pumps operate in series, the total head-capacity curve is obtained by summing up the pump heads at each capacity. Series pumping is most effective when the system head curve is steep. Multiple pumps in... 

As soon as the mobile phase reaches the first coil unit, the two phases interact to establish the hydrodynamic equilibrium where one phase with less wall surface affinity is split into multiple droplets which oscillate synchronously with the coil rotation. While continuous pumping of the mobile phase keeps breaking this equilibrium state at the head end of the coil, the two phases can quickly react to restore the equilibrium by readjusting their relative volumes in each coil unit. Thus the stationary phase pushes newly introduced excess amounts of the mobile phase toward the tail end of the coil. 

Self inducing agitators have been on the market for many years These communicate the low pressure region behind the blades with the head space Figure 15.4a) or a gas supply source via a hollow shaft and therefore use some of the input shaft energy to draw in the gas. Often they have multiple blades, sometimes curved like a centrifugal pump impeller,... 

Answer by Author A criterion for NPSH computation reliability is its repeatability when using a wealth of data. A three-thermocouple redundancy per measurement and the multiplicity of test runs pinpointed the temperatures selected. Then, by using equivalent vapor pressures, and by judiciously establishing pump inlet head losses, no erroneously-negative values of NPSH were realized. Since related suction specific speed values were neither imaginary nor infinite, and, because no hypothetical approaches were necessary to calculate their real values, the NPSH values were deemed reliable. 

The IPL must be capable of detecting and preventing or mitigating the consequences of specified, potentially hazardous event(s), such as a runaway reaction, loss of containment, or an explosion. A single IPL may address the multiple causes for that hazardous event and, therefore, multiple event scenarios may initiate action of one IPL. For example, high pressure in a vessel could be caused by either a pump dead-heading into it or by external fire. For both cases the vessel s pressure safety relief valve counts as a valid IPL. 

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