A cooling sleeve, also called a flow inducer sleeve, is a device used to make sure a submersible motor has enough water flowing over the surface of the motor to keep it cool.
In a water well installation the pump is surrounded by the well casing and the motor is mounted below the pump. As the pump draws in water from below, the water flows up the sleeve and over the surface of the motor and provides cooling for the water.
All borehole pumps installed in an open body of water required a cooling sleeve.