Submersible pumps are linear positive displacement pumps that are fully submerged in the fluid they are pumping. They are powered by an electric motor situated right above the pumping element. The motor shaft extends down into the well and connects directly to the rotating impeller of the pump. Some key features and components of these pumps are discussed below.
Motor
The electric motor is the power source for the submersible pump. It is air-filled and hermetically sealed to prevent fluid ingress. Motors for submersible pumps are typically continuous duty types made of corrosion-resistant materials like stainless steel. They come in single or three-phase varieties with power ratings ranging from fractional to several horsepowers. Properly sizing the motor to the pumping requirement is important for performance and efficiency.
Impeller
The impeller is the rotating part of the Submersible Pumps that increases the pressure and flow rate of the fluid. Common impeller designs include semi-open, closed, and multi-vane. Impeller selection depends on factors like viscosity and solids content of the fluid. Impellers made from corrosion-resistant metals like brass or stainless steel are able to handle most industrial liquids.
Pump Casing
The pump casing houses the motor and impeller assemblies. It has inlet and discharge ports as well as internal passages to guide the fluid into and out of the pump. Case materials can be cast iron, steel, stainless steel, bronze or polypropylene depending on the application. Centrifugal pumps usually have cylindrical or volute-shaped casings while positive displacement pumps incorporate specific internal geometries.
Power Cable
An insulated power cable running inside the shaft connects the submerged motor to the power source on the surface. Cable jackets are made from oil-resistant and cut-resistant rubber or thermoplastic elastomers. The cable may be armored for additional impact protection in some applications. Intake screens are provided at the bottom of the cable entry to prevent debris ingress.
Applications
Submersible pumps are widely used in water and wastewater systems, irrigation, desalination, petroleum production and several industrial processes due to their durable and versatile design. Some common applications are discussed below:
– Water Supply: Used for raw or potable water withdrawal from rivers, lakes, wells and distribution in municipal water networks.
– Dewatering: Employed for draining water from open pit mines, construction sites, basements during flooding and more.
– Wastewater: Used for transferring sewage, sludge and effluents in municipal treatment plants and pumping stations.
– Irrigation: Installed in agricultural wells to discharge pressurized water through pipes and irrigation systems such as sprinklers.
– Desalination: Employed in desalination plants to transfer pre-treated seawater and brine between various stages.
– Oil Production: Used as down-hole pumps in oil extraction to boost reservoir pressures and recover higher percentages of crude.
– Industrial Processes: Installed for liquid handling in a wide range of industries including power, food processing, dairy, chemicals and refineries.
Advantages and Limitations
The key advantages of submersible pumps include their compact design occupying less well space, priming not being required, and the ability to handle solids and gases in the fluid better than vertical installations. However, certain limitations include higher capital cost compared to some alternatives, and requirement of professionally installed power cables for safe long-term operation. Proper pump sizing and selection along with periodic maintenance are also important for optimizing performance.
Submersible pumps have proven to be versatile and reliable machines for a variety of water and process pumping duties. Their robust construction allows implantation in some of the toughest applications across different industries worldwide. With continuous technological advancements, these units will continue to gain more applications in the coming years.
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