What is a cooling casing and when should it be used?

During operation of the electric submersible pump, the flow of the inlet liquid laps the external surface of the electric motor in order to cool it. When the size of the well does not allow to obtain the minimum speed for maintaining the motor properly cooled (as reported on our technical documentation) the electric pump can be inserted inside a casing that is narrower than the well to increase the speed of the liquid flow which laps the outside surface of the electric motor.