The pumping industry was revolutionized with the creation of the vertical pump motor in the early 1920’s. This allowed for electric motors to be attached to the top of a pump, and the impacts were impressive. The installation process was simplified, and because it required fewer parts, was then less expensive. The efficiency of the pump motors increased by 30%, and because vertical pump motors are purpose specific, they are more durable and reliable than their horizontal counterparts. Vertical pump motors are generally classified by their shaft type, either hollow or solid.
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Both types of pump motors are explicitly designed to operate vertical turbine pumps, and they typically have a P-base mount without feet. The construction features of vertical pump motors influence their application and maintenance needs.
The most obvious difference between the two types of pump motors is that one has a hollow shaft, which changes its construction features from that of a solid shaft. In hollow shaft pump motors, the pump head-shaft extends through the motor shaft and is joined at the motor’s crest. An adjusting nut is located on the peak of the head-shaft which streamlines the regulation of the pump impeller strength. A steady bushing is often installed to stabilize and center the pump shaft in the motor shaft. When started, the pump shaft, motor shaft, and steady bushing rotate concurrently, resulting in a mechanical stability comparable to that of a solid shaft motor. Vertical hollow shaft pump motors are the most commonly used motor for deep-well pumps, but they are also being selected for any pump operation that requires easy adjustability.
Vertical solid shaft pump motors are connected to the pump shafts near the bottom end of the motor. The shaft extension typically has a circular keyway to pass on pump thrust, and a radial keyway to transmit torque. The lower end coupling of the pump motor and the pump shaft is seen more often in tanks and shallow pumps, rather than deep-well operations.
The type of shaft determines the type of coupling, whether it will be externally mounted, or an integrally connected motor-pump system. Numerous manufacturers sell both hollow shaft and solid shaft pump motors in all of the most common high thrust versions.