Rotary pumps have limited chemical resistance so that they can accommodate the requirements of the gear materials and casing. Highly accurate rotary metering pumps are therefore expensive because of their tight pump tolerances and motor requirements. Roller or peristaltic-type pumps eliminate some of the problems presented by gear pumps by using a set of rollers that squeeze a flexible tube in a circular pump housing. The fluid trapped in the section of the tube squeezed off by the rollers is forced through the tube as the rollers rotate. For the pump to provide accurate flow, the rollers must squeeze the tube down completely to prevent recirculation, placing significant stress on the tubing.
Peristaltic pumps can accurately meter very low flows down to fractions of a milliliter.
These pumps require no valves and have a seamless, sterilizable flow path in which the fluid never contacts the pump. They can handle some particulates and are easy to maintain. They are not suitable for high pressures, however, and tubing life presents some concerns. Tubing selection requires a balance between flexible materials with long life and materials that provide adequate chemical resistance. As the tubing wears and loses its flexibility, the accuracy of the pump in metering applications also degrades.