Rotary lobe positive displacement pumps tend to be fairly easy to clean in place (CIP). However, many applications benefit from a circumferential piston (CP) style of rotary PD pump. Because of their tight-clearance design, CP pumps can often provide for lower required inlet pressure, higher pressure differential, and high viscosity product handling.

Due to its tight internal clearances, it can be a challenge to adequately CIP a CP pump. Rotors can be removed, but as we mentioned in Part 1, there are costs and risks involved.

The outside of the rotors and pumping cavities can be exposed to cleaning easily with simple pumping rotation.

Two more challenging areas to clean are the rotor nut cavity and the seal area. The key to cleaning these areas is to flood them with CIP solution. For CIP solution to reach them, it must travel through a tight path, or 'dead-leg', where product can be trapped.

Choosing a pump design that minimizes the length of dead-leg to reach the affected area increases your ability to CIP the pump.

Some pump designs have been modified to allow for more flow to the seal area. However, drilling holes also allows for more product slip, reducing efficiency. Choose a pump that was designed for CIP, with shorter inherent paths to the seals and rotor nut.