Fixed connection is more and more common, there is no coupling between water pump and motor.The water pump housing is flanged and mounted on the flange of the motor and water pump with a tight fit. The impeller of the pump is mounted directly on the shaft of the motor. For this arrangement, care should be taken to ensure that the motor shaft yaw or axial turbulence plus machine tolerances do not cause contact between the pump housing and the pump rotor.
Pumps are often directly connected to the motor. In the case where the pump and the motor cannot be coaxially connected, most of the connections are made with flexible couplings. Flexible couplings are used to allow a slight axial misalignment between the motor and the pump shaft (the axes of the two are angled or parallel)
The flanged motor keeps the motor and the pump housing concentric and the connection method is simple. This type of structure is usually installed vertically, with the motor on top of a water pump that supports the weight of the motor. The shafts of the water pump and motor are connected by conventional methods, and direct connection can also be used. In addition, as the coupling method of the water pump, this structure also needs to consider the axial force, if the water pump itself does not have the thrust bearing, must select this electric motor must consider this thrust.