A Guide to Submersible Bore Pumps

Borehole pumps are a form of multistage submersible centrifugal pump that may be buried to great depths. They're usually made to fit into narrow holes called boreholes, which are bored deep down to draw water from water tables or aquifers.

Boreholes are typically narrow (just over 4") due to the depths to which they are bored, and pumps are offered according to borehole size, capacity, and pressure. Submersible Bore Pumps are usually longer than normal pumps of comparable capacity to compensate for the limited space in which they can be mounted.

Borehole motors are normally filled with non-toxic water or oil for bearing lubrication, with a mechanical seal for sealing. A cable gland separates the cable from the motor.

The diameter of the cable is determined by the depth of the borehole. Because there is a voltage loss as cables stretch, the cable diameter must be raised once they reach a certain length in order to transmit enough power to the motor.

How does a Borehole Pump Work?

A motor drives a shaft, which in turn drives one or more impellers in the unit. The engine is at the bottom of the pump, while the pump is placed above it. In contrast to other pump designs, the pump intake is in the centre of the unit and the discharge is at the top.

The first impeller draws fluid into a suction strainer, where it is sent to the diffuser. If the pump has a single impeller, liquid flows around the non-return valve before exiting the pump. Liquid continually enters a suction casing, then discharge casing across numerous impellers, before passing around the non-return valve and exiting the pump if the design is of multi impeller construction. Impellers are usually of closed or semi-open axial design if handling sand.

Designs

Pump impellers can have a single stage or a multistage design. High flows at medium heads are possible with some single stage designs, such as our PR Range (up to 160M). The pump's single impeller is made of technopolymer, which allows it to float and manage 300g/m3 of sand when water is extracted from bodies of water with high sand content. In most cases, units can only hold up to 50g/m3 of sand.

Unless equipped with a floating impeller design, multistage designs are unable to accommodate such large amounts of sand and are utilised for delivering smaller flows at high pressure.

Cast or pressed metal might be used in the construction. The Cast design eliminates welds that can be harmed by seawater, resulting in thicker sections that are more durable and capable of accepting small particles that might otherwise destroy pressed pumps.

Solar-powered motors can be wound to run on direct current (DC) or three-phase motors. Borehole motors driven by three phase electricity are generally preferable in isolated locations and villages because they are significantly easier to maintain with limited expertise and tools. Due to their nature, DC motors can be difficult to maintain, and expertise is sometimes insufficient.

Cooling Shroud / Sleeve

Borehole pumps are available in both vertical and horizontal configurations. A cooling sleeve is necessary when the motor is mounted horizontally or in an open body of water to ensure that the motor is cooled when the fluid velocity falls below the minimum requirement.

The device guarantees that water velocity is increased past the motor, which provides the necessary cooling and prevents the motor from overheating.

Applications

Borehole pumps are commonly used for drainage, irrigation, drinking water supply, reducing groundwater in mines, and construction excavations. They're also utilised to provide seawater to oil rigs, where the vertical distance between the pump and the platform might be over 50 metres.