Types of Submersible Pumps and some of their Uses

Pumping equipment is ubiquitous and is used for all manner of purposes. Some of the more common uses include transporting crude oil from wells and drilling platforms to distant refineries and distributing natural gas and drinking water to homes and businesses. It is also essential for numerous routine production tasks across a wide range of other industries. In most cases, the equipment used forms an integral part of a pipeline system. However, submersible pumps are an exception. They rely for their operation on a source of mechanical energy, generally an electric motor or an internal combustion engine. Consequently, unique design features are necessary to enable these devices to operate whilst immersed in water.

There are essentially two ways a manufacturer can ensure the motor or engine will not be affected by contact with extraneous liquids. The first is to ensure that, during the pumping operation, the motor is located at a sufficient distance above the liquid’s surface. This design principle is employed by a variety of the submersible pump commonly known as a vertical spindle or sump pump. The motor is mounted on the end of a tubular column that extends above the waterline in these units. The column houses the motor’s drive shaft that provides the rotational energy to the submerged unit’s impeller. These semi-submerged units cost markedly less than a fully-sealed, underwater model. Furthermore, eliminating the need for watertight seals also avoids the attendant risk of leakage due to continuous wear and tear.

Typical industrial uses for these units include handling slurries and fluids containing abrasive solids, but these submersible pumps can also be of value in the home. Homes with basements built on low-lying ground are often subject to regular flooding that, unless controlled, could damage their foundations over a sufficiently long period. These vertical, spindle-driven devices are commonly employed as sump pumps. Once installed, they remain on standby and inactive until a sensor or float mechanism detects that a preset water depth is present. At this point, the device activates automatically, draining the floodwater, transporting and discharging it at a suitable location outside of the premises.

In the second type of submersible pump, all mechanical components, including the motor, are contained in a combined housing that can be completely immersed in the liquid being pumped. In these units, fluids are prevented from entering and causing damage to the motor in one of two ways. As mentioned earlier, the first option is to protect the power unit by fitting watertight seals to the driveshaft. While these seals are highly efficient, their lifespan is limited. Therefore, users should check them at intervals and replace any showing signs of wear and tear to avoid costly repairs.

The submersible pump offers the advantage of being self-priming, so it can remain submerged between uses or even permanently if required. Also, they require less energy than surface-mounted models because the surrounding head of liquid forces water into the pump’s inlet. The close coupling between impellers and motor also helps prevent cavitation. On the domestic scene, these devices are used to power fountains and other decorative water features. Households that have installed a borehole also rely on these units to transport water to the surface and distribute it as necessary.

Not surprisingly, the industrial applications for submersible pumps are far more numerous. In contrast to most domestic models, these units are generally required for heavy-duty tasks and must, therefore, be more robust and powerful. For a start, they are one of the mainstays of the world’s petroleum industry, where they are used to extract the highly viscous crude oil from wells that can often be as deep as 4 000 feet or more. They are also an invaluable means to transfer slurries such as sewage, handle wastewater and feed water to irrigation systems on arable farms.

On occasions, submersible pumps must handle corrosive or abrasive liquids that tend to corrode or erode their seals. Such tasks call for units with an alternative design that dispenses with the need for seals. Instead of being driven directly by a shaft-mounted motor, the impellers in these models are turned by electromagnetic forces. The absence of a driveshaft eliminates any need for seals. Although sharing a common housing, the motor is isolated from the pump chamber and impeller.

A top-quality product guarantees top performance, which is why so many South African companies and individuals chose to purchase their submersible pumps only from Prochem.


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