A roller moves in and out of each slot radially and provides a seal against the wall of the case by centrifugal force. As the rollers pass the inlet port, the space between the rollers and the housing becomes larger and draws liquid into the pump. The fluid remains in spaces between and under rollers as it moves toward the outlet port. As the rollers near theoutlet port, the spaces become smaller due to the eccentric housing. Here the rollers are force inward toward the center the liquid is forced out the discharge port.
Roller pumps come in a wide range of pressure and capacity ratings.
Pump output varies from 1 to 35 gpm, depending on the length and diameter of the case, its eccentricity, and speed of rotor rotation. Roller pumps, constructed from different materials are available. But they are usually constructed with cast iron or corrosion resistant housings and rotors, and Viton, rubber, or leather seals. Consider compatibility between materials and the chemicals applied when selecting the pump. Nylon and teflon rollers are highly resistant to most agricultural chemicals, and are recommended for multipurpose sprayers.