3.4.6 Peristaltic pump

Peristaltic pump

A peristaltic pump transports fluid by mechanically squeezing a space enclosed by a flexible element. The most usual peristaltic pump (flexible hose pump) operates by means of rollers or cams acting directly upon the hose containing the fluid, figure 3.46a. The number of rollers or cams vary depending upon the manufacturer, usually 2 or 3. A pump may be fitted with one or more hoses, sometimes as many as thirty. Peristaltic pumps are used in industries for slurries and mud with a high degree of fluid content and for aggressive chemicals or in laboratories for sterile applications and medical applications like heart lung machines.

Figure 3.46a Peristaltic pump (Hose pump)

In a peristaltic pump the pumped fluid is completely enclosed and cannot leak, assuming that the hose does not fracture as a result of the mechanical stresses imposed. Since such failures cannot be predicted it is necessary to replace hoses regularly as a preventive measure.

Peristaltic pumps can be used for all types of fluids and to some extent even gases. The suction capacity varies greatly for different designs. Pressure increases between 0.1 and 0.3 MPa are normal. The capacities vary from small metering quantities of 0.001 l/h up to flows of 10-100 m³/h.

Another type of peristaltic pump works by means of an eccentric rotor operating within a flexible elastometric element with the fluid trapped between the elastometric element and the pump casing. The rotation of the eccentric rotor transfers the fluid from the inlet to the outlet — figure 3.46b.

Figure 3.46b Rotary-peristaltic pump.
This pump is also glandless and leak-free, on condition that the flexible elastometric element does not fail as a result of the mechanical stresses. The elastometric element should therefore be replaced regularly to avoid unexpected failures. In order to select the correct elastomer and the correct pump casing material it is important to know the chemical properties and temperature of the fluid to be handled. Capacities range from 0.06 to 15 m³/h. Suction capacity 1-3 m. The pump supplies a strongly pulsating flow making it advisable to use flexible hoses to the suction and delivery lines. If fixed pipes are used some type of compensator should be fitted between the pump and the
pipe.