Canned motor pumps with isolated motors are recommended for pumping liquids with a high concentration of solids (above 10%). This design separates the liquid in the motor section from the solids present in the process stream. The motor cavity is filled with a clean liquid that is compatible with the process stream. An auxiliary impeller, located on the rotor assembly, circulates this liquid through a heat exchanger where it is cooled before it re-enters the motor.
A throttle bushing, lip seal, or mechanical seal is used to keep the process fluid separated from the liquid in the motor. To ensure that no solids enter the motor section of the pump, a clean liquid is introduced as makeup volume through the motor section and then travels through the throttle bushing, lip seal or mechanical seal into the process flow. The makeup flow rate will vary depending on what type of device is used to separate the motor from the pump.