In the early 1920s, California’s agriculture industry was booming, and as the demand for the Golden State’s homegrown products increased, growers had to expand their operations, which, in turn, meant an increased demand for the state’s most valuable resource – water.

The climate of central and southern California is ideal for agriculture; the only ingredient missing is the rain. California’s rainfall is seasonal – dry during the hot summer months, and wet for only a few months in the winter. There wasn’t enough water in reservoirs, lakes and rivers to meet the irrigation demand, much less the drinking water demand.

One solution was to tap the ground water supply. To do so required above-ground, horizontal pumps with right-angle gear configurations, and powered by internal combustion engines. Many were using ditch pumps that would send the water only a short distance.

The system worked, but end-users became increasingly frustrated with efficiency issues and higher costs associated with equipment losses. For instance, the ditch pumps used up bearings very quickly because of all the downward pull on the shaft. The farmers voiced those frustrations to pump manufacturers, who, in turn, looked to motor makers for some help in finding a solution.

The solution came in 1922 when engineers from U.S. Electrical Motors – a small Los Angeles-based motor company – developed the first vertical pump motor. Called the Vertical HOLLOSHAFT, the motor revolutionized the pumping industry, and made it possible to irrigate vast areas of cropland, helping to make California the nation’s top farming state despite its limited water resources. (In 1924, U.S. Electrical Motors would introduce another revolutionary product – the push-button starter for induction motors.)

Putting an electric motor on top of a pump solved three critical issues facing customers – convenience, cost and reliability.

A Matter of Convenience

By marrying a motor with a vertical pump, you eliminate the need for the mechanical gearbox, which provides the torque for a horizontal motor. Less equipment means easier installation and more space. Another added benefit is that a vertical motor makes it much easier to align the motor shafts with the driven equipment, which means less vibration.

Cost Considerations

In addition to the cost savings from having fewer parts, vertical pump motors operate at a much higher efficiency than horizontal motors, due to the elimination of the gear box. Vertical motors like the HOLLOSHAFT also handle more pump thrust, which eliminates the need for external thrust bearings.

Two Designs Types

Vertical motors are specifically designed to drive vertical turbine pumps. There are two types of vertical pump motors – solid shaft and hollow shaft. The solid shaft is coupled to the pump shaft by use of externally mounted coupling, while the hollow shaft allows the pump head shaft to extend through the motor shaft and connect to integrally mounted drive coupling.

Some of the advantages of hollow-shaft motors:

Ease of impeller adjustment – access at top of motor, coupling is one part with a gib key, and pump-adjusting nut supplied by pump supplier.

Fewer parts – no adjustable coupling is required, and less cost.

Lower profile – no adjustable coupling required in discharge head, and less susceptible to reed critical/vibration problems.

All induction motors are specified by horsepower, speed, enclosure, input power, frame size and mounting. But vertical motors require additional information:

  • thrust requirements,

  • solid shaft (VSS) or hollow shaft (VHS),

  • VHS coupling type and bore requirements, and

  • is a non-reverse ratchet required?

The magnitude and direction of the thrust are determined by the pump and the dynamics of the liquid flow. Even when a system is designed for thrust in one direction, transient conditions will sometimes temporarily change thrust direction. Thrust then is defined as either up thrust or down thrust.

The motor’s thrust capability must exceed the sum of the axial forces from the weight of its rotor, the pump lineshaft and impeller, plus the dynamic forces required to lift the liquid to the surface.

Normal-thrust motors are used in general applications where there is no or very low external thrust applied to the motor bearing. It often is a footless horizontal motor with a P-flange and drip cover.

Medium-thrust motor usually are called in-line pump motors, this is a definite purpose motor. The pump impellers are mounted directly on the motor shaft. Since the pump impeller performance depends on close tolerance with the pump housing, the motor shaft and flange run-out tolerances must also be tighter than normal. The thrust bearing usually is located at the bottom so that the motor rotor’s thermal growth does not affect the impeller clearances.

With high-thrust motors, 100-percent, 175-percent and 300-percent thrust are common. They usually are available as solid-shaft and hollow-shaft versions, and the thrust bearing usually is located in the upper end.

Vertical motors are electrically similar to horizontal motors, but are mechanically different, because of the unique cooling requirements. Generally, enclosures are designed to handle a wider range of environmental conditions than those designed for horizontal motors. Where footless requirements are needed, it is common to use vertical motors, due to the many application advantages to the driven equipment.

Today, vertical pumps have a wide variety of applications around the world including:

  • Turbine pumps are used for municipal and industrial water supplies, processing and circulating water applications. They vary in output capacity from 10 gpm to more than 25,000 gpm.

  • Axial-flow pumps often are used to supply water for municipalities, cooling, irrigation purposes, and for pumping out ponds or areas having excess amounts of water.

  • Mixed-flow pumps are used with cooling water circulation, storm and drainage sewers, irrigation projects and municipal aqueduct or canal pumping.

  • Propeller pumps are found in effluent pumping, flood control and reclamation projects.

A great example of the how the vertical pump motor continues to help California fight the water war is the Delta-Mendota Canal/California Aqueduct Intertie project. Nearly completed, the Intertie, or short canal, is a 500-foot underground canal and pumping station that will move water from the state-controlled California Aqueduct to the federally controlled Delta-Mendota Canal. The linking of these two canals is expected to improve water supply reliability in a part of California hardest hit by dry conditions.

The canals are linked via two 108-inch-diameter pipes, with a pumping capacity of 467 cubic feet per second. Making this possible are four, 1,000-HP Titan Vertical HOLLOSHAFT Motors.