Three connection methods between water pump shaft and electric motor

1. Fixed connection

Fixed joins are becoming increasingly common. In this arrangement, there is no coupling between the shafts of the water pump and the motor; the water pump casing is flange mounted and mounted on the motor and water pump flanges with a tight fit. The impeller of the water pump is mounted directly on the shaft of the electric motor. For this arrangement, care should be taken to ensure that the deflection or axial play of the motor shaft plus the tolerances of the machine must not cause contact between the water pump casing and the water pump rotor. The material of the motor shaft must be compatible with the liquid being pumped.

If the impeller of the water pump is positioned by a nut, the direction of the nut thread must take into account the direction of rotation of the motor. A coaxially connected high-pressure water pump with an unbalanced design can produce excessive axial thrust, which will affect the load-bearing capacity of the motor bearings. Installing some form of water slinging plate on the motor shaft to prevent liquid leaking through the water pump seal from entering the bearing is very practical for fixedly connected water pumps.

2. Direct connection

Water pumps are often directly coupled to electric motors. Where coaxial connection is not possible, most connections use flexible couplings. A flexible coupling allows slight misalignment between the motor and pump shafts, with their axes either at an angle or parallel but offset. Some older flexible and rigid couplings produce substantial axial and radial loads on the motor bearings. With the development of flexible disc couplings, these earlier couplings have been phased out because shaft misalignment can generate severe additional loads.

Flexible disc couplings are capable of transmitting very high torques without requiring large dimensions and with only minimal axial and radial loads due to misalignment.

3. Flange motor

Flange-type motors can keep the motor and water pump housing concentric, and the connection method is simple. This structure is usually installed vertically, with the motor placed on top of the water pump, and the water pump supports the weight of the motor. The shafts of the water pump and the motor are connected in a conventional manner, or direct connection can be used. In addition, as the connection method of the water pump, this structure also needs to consider the axial force. If the water pump itself does not have a thrust bearing, this thrust must be considered when selecting the motor.

As a further development of the flange motor, the vertical hollow bushing motor is used. This structure uses a variable length hollow bushing to connect the water pump and the motor. The water pump shaft passes through the center of the motor shaft hole, and the motor's torque is transmitted to the water pump shaft through the coupling assembled on the motor shaft end. The weight of the water pump shaft and impeller, as well as the axial thrust generated by hydraulic power, are borne by the bearings of the motor.

Source: Internet

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