Lobe Pump

obe 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 service-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.

Rotary pumps also offer superior CIP/SIP performance. Once in line, they can be cleaned without being removed. Depending on the application, it is a good idea to check with the manufacturer to make sure if a particular lobe pump meets both 3-A requirements.

As a general rule, rotary pumps require very little maintenance. Some manufacturers offer pumps that allow for seal servicing and maintenance with the pump in line.

How Lobe Pumps Work

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.

1. As the lobes come out of mesh, they create expanding volume on the inlet side of the pump. Liquid flows into the cavity and is trapped by the lobes as they rotate.

2. Liquid travels around the interior of the casing in the pockets between the lobes and the casing -- it does not pass between the lobes.

3. Finally, the meshing of the lobes forces liquid through the outlet port under pressure.

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 PD types.  Since the lobes do not make contact, and clearances are not as close as in other PD 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.  Reductions of 25% of rated speed and lower are common with high-viscosity liquids.