Peristaltic pumps use compression to force fluids through tubing. A number of rotating rollers squeeze a flexible tube against a more rigid pump casing. As the roller moves over and past a point on the tubing, the bore of the tube expands to allow more fluid to enter. At least one of the rollers is in contact with the tubing at all times, therefore eliminating the need for valves to prevent backflow. The rollers, or roller carriers, are turned directly by the motor, the speed of which can be controlled to alter the flow rater or via a gearbox.
The primary parameters are the compatibility of the tubing material with the fluid to be transferred and its mechanical properties to maximize the service free interval. Some media can weaken or age tube material so a variety of tube materials are available. There is a compromise between higher pumping speed and tube life because of the stresses imposed on the tube by the rollers. Hence there is also a choice of tube sizes (internal diameter and wall thickness) and roller speeds (motor or gear box rpm controlled) to allow the selection of the optimum combination.
Gardner Denver peristaltic pumps have a maximum free flow rate of 3,000 ml/min, suction height of 8 mH2O and pressure height of 10mH2O.
A feature of Gardner Denver’s SR 18 and SR 25 series of peristaltic pumps is that the number of rollers doesn’t affect the flow rate. These compact, self-priming, dry-running and maintenance-free pumps have just two spring-load rollers. The volume of fluid, therefore, is not reduced between the initial pinch point and the final release point. Both series allow for the easy and quick exchange of tubing. The SR 18 series has a synchronous gear motor for smooth, continuous operations and the SR 25 series comes with the versatility of DC, AC or stepper motors. Both are designed for use in laboratory and analysis technology, the food industry and for hygiene and disinfection.
The peristaltic, or roller, pump was invented by Dr. Michael DeBakey, the world-famous heart surgeon, as a medical student in 1932. It was some 20 years later that it became a part of the heart-lung machine. Because the pump can deliver a continuous flow of blood, open-heart surgery became an important option for cardiac patients and physicians. This technology was developed further for applications in the chemical, medical, food and other industries, where abrasive and aggressive fluids must be pumped in a clean/sterile environment, allowing no cross contamination.