A lobe pump, or rotary lobe pump, is a type of positive displacement pump. It is similar to a gear pump except the lobes are designed to almost meet, rather than touch and turn each other.

Lobe pumps are similar to external gear pumps in operation in that fluid flows around the interior of the casing. … 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.

While rotary lobe pumps and progressive cavity pumps are types of positive displacement pumps, the design of each unit results in several operational differences. A rotary lobe pump is typically able to move material more consistently – efficiently handling viscous liquids, pastes and abrasives.