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Vertical Hollow Shaft Motors

What Are Vertical Motors For?

First developed in the early 1920s by engineers from a small LA-based motor company called U.S. Electrical Motor, vertical shaft motors are a unique solution to the efficiency issues and the high cost that was associated with using horizontal pumps to tap into groundwater supplies. Originally, the above-ground pumps were used for irrigation in dry but otherwise agriculturally favorable climates such as California. They had right angle gear configurations and were powered by internal combustion engines.

Putting an electric motor on top of a pump eliminated the need for a mechanical gearbox (to provide torque) and external thrust bearings (for additional pump thrust). Less equipment meant a lower cost, a smaller size, easier installation, and fewer parts. The vertical pump motors also operate about 30% more efficiently than horizontal motors and are more durable and reliable for the pump application because they are specifically designed for the job and were also designed to withstand a wider variety of environmental conditions. Under these conditions, farming in California was able to flourish.

This innovation helped California become the top farming state in the United States despite its seasonal rainfall and dry summers. Today, vertical shaft motors are used for many applications, including turbine pumps, axial flow pumps, mixed flow pumps, and propeller pumps.

Solid Shaft Motors and Hollow Shaft Motors

Vertical pump motors come in two varieties with different construction features: either a solid shaft or a hollow shaft. A key difference between the two is the way that the motor is mounted on the pump; the solid shaft variety are attached to the pump shaft by externally mounted coupling while the hollow shaft variety are connected to an integrally mounted drive coupling.

Overall, hollow shaft motors have many advantages over their solid counterparts. No adjustable coupling is required for the VHS motor, so there is a reduced cost involved due to having fewer parts to purchase, repair, or replace. Additionally, impeller adjustments are made easier with the VHS’s single part coupling and convenient access to the top of the motor. Finally, VHS motors also have a lower profile, so no adjustable coupling is required in the discharge head and they are not as susceptible to reed critical frequency or vibration problems.

If you are looking for a pump motor that will make installation and upkeep easy and be similarly easy on your budget, then chances are that a vertical hollow shaft motor is what you are looking for.

Choosing the Right Vertical Hollow Shaft Motor for the Job

To get started, some unique features of a vertical motor that you will want to know include the specifics of the motor coupling type, bore requirements, and if it requires a non-reverse ratchet to prevent the motor from spinning backward if the impeller is inundated with water when the motor is off.

In addition to horsepower, speed, enclosure, input power, and frame size specifications that are associated with all induction motors, VHS motors also specify thrust requirements. The thrust capacity of the motor has to exceed the sum total of its axial forces. This includes the weight of its rotor, the pump line shaft and impeller, and the dynamic forces that are required to lift the liquid to the surface.

When it comes to thrust, you have three options: a normal thrust motor, a medium thrust motor, or a high thrust motor. A horizontal motor is considered a normal thrust motor and is best for general applications where little to no external thrust will be applied to the motor bearing.

A medium thrust motor, also called an in-line pump motor, is designed for a specific operation and considered a definite purpose motor. The impellers are mounted directly on the motor shaft, and the thrust bearing is usually located at the bottom (that way, the rotor thermal growth does not impact the impeller clearances). The motor shaft and flange run-out tolerances are required to be tighter than normal because the impeller performance depends upon close tolerance with the pump housing.

A high thrust motor can be highly customizable per the manufacturer, but they commonly offer thrusts as high as 100%, 175%, or 300%, and the thrust bearing is usually located near the top.

How can we help?

If you require assistance to select the right motor for your job, you should never hesitate to contact a professional here at Telco. We are happy to answer any questions you may have about picking out the right vertical hollow shaft motor based on your needs.