A positive displacement pump operates by trapping a fixed amount of fluid from an intake pipe and then displacing that trapped volume into a discharge pipe. Lobe pumps utilize intermeshing 4-wing helical lobes mounted on parallel shafts. The shafts are rotated by gears with a maintenance friendly design (no complicated timing gears to worry about). As the lobes un-mesh on the intake side, they create a cavity with an expanding volume. Your sludge or slurry flows into the cavity and is trapped by the lobes as they rotate. The sludge or slurry then travels around the interior of the casing in the void between the lobes and the housing segments. The pumped material does not pass between the lobes. As the lobes begin to mesh on the discharge side, the lobes force the sludge or slurry through the outlet port under pressure. The capacity of material being pumped can be changed by varying speed of the pump.