These pumps have a set of rotating gears, flexible impellers, screw rotor or vanes connected to a driven shaft. Therefore most of these pumps incorporate a mechanical seal, packing or lip seal along the shaft at its back end in order to keep the fluid from leaking along the shaft. There are a few models, which are magnetically coupled and thus seal-less. Another type which is seal-less is the Peristaltic which uses a rotating roller assembly to compress a hose over a given arc length. These pumps are very reliable in pumping medium to thick liquids which typically are not handled by Centrifugal pumps and in applications where medium to high discharge pressures are needed at low flow rates. Varying the motor speed easily controls their output. Most units include some sort of built in relief valve, but those that do not must have one installed into the piping to prevent a dangerous over pressure condition. Not recommended for liquids with fine abrasives or thin non-lubricating liquids like water that will accelerate pump wear. Typical Positive Displacement Rotary pumps include helical gear, spur gear, lobe, progressive cavity, peristaltic, flexible impeller and sliding vane to name a few.
Categories within Rotary Pumps - Gear, Flexible Impeller, Screw