Rotary Lobe / Piston Pumps (aka "rotary piston" - In German), popular for high viscosity ("non Newtonian") liquids, often need suction stabilizers, of the Flo-Thru type to ensure uninterrupted filling. Rotary Lobe Pumps have improved performance, use less power, and produce smooth flow when connected to pulsation dampeners. Though relatively pulseless Tri and Bi Lobe Pumps show pulsation from the compression in the lobe root of the rotary pump. As rotary lobe pump use is often for high viscosity pulsation dampeners with only one connection cause pressure pulses because of the energy required to force reciprocation up & down a "T" branch. All these recommendations are for "Flo-Thru."
Lobe pumps are used in a variety of industries including pulp and paper, chemical, food, beverage, pharmaceutical, and biotechnology. They are popular in these diverse industries because they offer superb sanitary qualities, high efficiency, reliability, corrosion resistance and good clean-in-place and steam-in-place (CIP/SIP) characteristics.
Rotary pumps can handle solids (e.g., cherries and olives), slurries, pastes, and a variety of liquids. If wetted, they offer self-priming performance. A gentle pumping action minimizes product degradation. They also offer continuous and intermittent reversible flows and can operate dry for brief periods of time. Flow is relatively independent of changes in process pressure, too, so output is constant and continuous
Lobe pumps are similar to external gear pumps in operation in that fluid flows around the interior of the casing. Unlike external gear pumps, however, the lobes do not make contact. Lobe contact is prevented by external timing gears located in the gearbox. Pump shaft support bearings are located in the gearbox, and since the bearings are out of the pumped liquid, pressure is limited by bearing location and shaft deflection.
Lobe pumps are frequently used in food applications because they handle solids without damaging the product. Particle size pumped can be much larger in lobe pumps than in other positive displacement types. Since the lobes do not make contact, and clearances are not as close as in other Positive displacement pumps, this design handles low viscosity liquids with diminished performance. Loading characteristics are not as good as other designs, and suction ability is low. High-viscosity liquids require reduced speeds to achieve satisfactory performance.