Submersible pumps, as the name suggests, are specifically designed to be submerged in the liquid that is pumped. These specialized pumps are used in industrial and commercial applications and in homes and schools.
Submersible pumps were first built in Europe and were more commonly seen during the 1950s in the U.S. Some initially doubted the reliability of submersible models, believing that they would struggle to work in a fully submerged application. However, the first models were successful, and the pumps gained popularity in the 1960s. During this same period, the pumps were fitted with a guide rail, which assisted in removing the pump when it needed repairs. As an increasing number of firms saw the benefits of submersible pumps, the technology’s popularity grew. Now the pumps are significant components in many modern pumping stations and other applications.
Fitted with waterproof cables that supply power directly to the motor, the system is constructed so that the motor and the turbine bowl are directly attached to each other. Therefore, a submersible pump is a complete unit with the motor and mechanical and electrical controls enclosed within a frame and cover.
To function effectively, the pump must have a significant volume of fluid running through it at any given moment. This maintains the correct temperature and prevents the system from overheating. In some cases, this cooling cannot occur because the pump may not be completely submerged. In these situations, a shroud with a closed top can be fitted and will assist in directing the liquid into the pump.
A submersible pump operates similarly to other turbine pumps. However, changes to how the motor starts are required because the pump needs additional overload protection. This protects the longevity of the pump and ensures that the power is shut off immediately if the motor stalls or the impeller becomes jammed. The absence of a shut-off mechanism could cause damage to the motor windings.
Submersible pumps are available in a range of sizes, determined by the application for which they are intended. Smaller models can be used in homes or light commercial settings and usually have a power consumption of 0.75 kilowatts (kW) to 2.2 kW, accommodating solids up to a maximum of 55 millimeters (mm) in diameter. For heavier duty applications, such as in construction and industrial applications, larger pumps are available, and these can typically handle waste and solids up to 65 mm in diameter.
Submersible Pump Applications
Submersible pumps are available in different sizes to suit many applications. They can either be installed as a single unit or as a dual system.
In industrial applications, installing two pumps together is generally the preferred option because it provides a degree of redundancy if one unit stops working. This type of installation reduces the degree of wear and tear on the individual pumps and offers greater capacity if required.
A main benefit of submersible pumps is their ability to be positioned below ground level without causing any access issues. Therefore, they can be installed in many environments, including:
- Deep wells
- Areas that are prone to flooding
- Areas in which a traditional pump motor could become damaged by contaminated water
- Settings in which a quiet pump is necessary
- Areas with limited space
- Agricultural applications
Submersible pumps can also be used in-line in pipelines to boost flow—fitted horizontally within the pipe instead of vertically. They are ideal for use in this type of environment because they operate in virtual silence, and the motor and electrical components are enclosed to prevent damage from the fluid.
While submersible pumps have a wide range of uses, some situations exist in which they are not the ideal choice, including:
- Excessively high temperatures
- Corrosive environments
- Abrasive fluids
- Fluid that contain excessive diameter solids
Each submersible pump system is designed to suit a specific range of applications. This allows the system to be as simple or complex as required and appropriate to the needs of the environment.
The control system directly manages the level of the liquid within predefined parameters, and this starts or stops the pump when the liquid reaches the preset level. Generally, three different controls exist within a pump, and these turn the pumps on or off and provide an alarm if the fluid exceeds a defined level.
Within a dual pump system, the controls will usually alternate between the two pumps. This type of multiple pump system will also feature an override, which is used to start the second pump if the flow rate cannot be accommodated by a single pump or if the first pump fails.
The development of the submersible pump has resulted in a highly efficient and safe piece of equipment. Once installed, these pumps are reliable and will last for many years. They offer an ideal solution when an electric pump is required in an environment that is submerged in fluid or lies below ground level.
Domestic Submersible Pumps Best PracticesFor additional guidance, this list can help ensure the safe operation and installation of domestic submersible pumps.
- Thoroughly read all the installation information provided in the manual.
- Check the pump to make sure it is not damaged prior to use.
- Check the voltage of the pump.
- Check the size of the sump so the float switch can freely operate.
- Connect to an appropriately protected power supply.
- Make a note of the pump type before fitting it in the sump—easier if the pump fails and is underwater.
- Fit a non-return valve if possible so the pump does not work harder than necessary.
- Make sure the float switch can move unrestricted.
- Make sure the pump filter is cleaned regularly.
- Lower the pump with the power cable.
- Place the pump on the bottom of the sump. Keep it slightly raised to reduce the chance of the filter blocking.
- Use a discharge hose that is smaller than the pump connection.
- Allow water to freeze around the pump.
- Allow heavy objects to fall on the pump or stop the float switch’s operation.
- Leave the top of the sump open or uncovered.
- Lay the pump on its side.
- Operate or move the pump while it is connected to the power supply.
- Use the pump to empty swimming pool water if people are in the pool.
- Use the pumps to move hydrocarbons (for example, petrol, diesel or fuel oils).
- Allow the pump to run dry.