Do I Need A Dewatering Pump?

12 Jul, 2021

What is a dewatering pump?

As the name suggests, dewatering pumps typically find use at mining locations, construction sites, tunnels, and other places to remove water and maintain a certain dryness level.

Essentially, dewatering is the process of removing ground or surface water so that the natural groundwater table level goes down, ensuring safety, speed, access, and other benefits for workers.

Construction sites may require dewatering before digging, and drilling commences for building foundations or underground structures. At mining sites, dewatering helps conduct mining effectively. In addition to drawing water, the process can also help in various other ways, such as removing issues related to fluid movement that can destabilize the entire operation.

Your dewatering efforts require a well-suited, reliable pump that can remove water without disruption under challenging ground conditions.

The various types of dewatering pumps include centrifugal, positive displacement, submersible, and airlift pumps.

Centrifugal

In a centrifugal pump, a rotating impeller sucks the air out of the hose, allowing water to reach the pump due to atmospheric pressure. In such pumps, a process of priming has to take place before actual use. For example, a new pump or a pump that has been shut off for a long time often runs out of pressure. Priming is the process of building in enough pressure in the pump by rushing water back into the pump and forcing it out.

A self-priming centrifugal pump is a specialized one. The design allows a vacuum to be created at the impeller eye to remove air from the suction line continuously. However, self-priming pumps have a suction lift limit. Hence, it is crucial to consider cavitation calculations before procuring one.

Positive Displacement

A positive displacement pump works by making trapping a fixed amount of fluid and then making it move by forcing (displacing) it into the discharge pipe. As opposed to centrifugal pumps, positive displacement pumps are constant flow machines. They can, theoretically, produce the same flow at a given speed (rpm) irrespective of the discharge pressure.

These pumps can handle highly viscous fluids. Rotary and reciprocating are two classifications of displacement pumps. While rotary pumps operate via rotation of the pumping element, reciprocating pumps use a constant back and forth motion.

Airlift Pumps

The airlift pump or sump pump uses compressed air to lift water. When compressed air mixes with water, the air being lighter in density rises quickly. Due to fluid pressure, the water moves in the direction of the ascendant airflow and goes put.

Airlift pumps find a use for handling sewage, oil, or sludge in tunnels and excavation pits. The efficiency of an airlift pump depends on the submerged length (Hs) in relation to the geodetic head (Hgeo) and the airspeed difference between the fluid and air. The greater the difference, the lower the overall efficiency of the pump.

Submersible

Submersible pumps have operational advantages. These pumps submerge directly into the water for immediate use, eliminating the need for priming and saving time. Submersible pumps are usually quiet, lightweight, and portable.

Their pumping action takes place without a suction pipe, and the water around helps keep the motor cool. Cavitation issues are rare. Submersible dewatering pumps are suitable for dirty water mixed with mild abrasives.

Here are a few suggestions before you buy a dewatering pump. Always remember to select a pump that is neither too small nor too large. A less than optimal pump size can flood out, while a large one would face motor heat-up issues. Pumps also face cavitation issues.

Simply put, cavitation occurs when a dewatering pump does not get a full supply of flowing water. A flooded inlet is crucial to maintain enough suction pressure. Therefore, it is vital to ensure that the suction line size is equal to, or greater than, the size of the inlet port.

For your dewatering pump to perform well, it is important to know the required pressure. Every pump will have a minimum Net Positive Suction Head (NPSH) requirement for continuous flow. You'll have to compare the available NPHS (NPSHa) to the net positive suction head required (NPSHr) when selecting a dewatering pump. NPSHa must be more than NPSHr, ideally between 1-1.5 m safety margin to prevent the risk of suction cavitation.

High capacity dewatering pumps or flood pumps range above 35 HP.

These pumps typically operate in any position, even in partially submerged conditions. Such pumps find use in disaster or emergency applications, construction sites, and wellpoint applications for lowering groundwater levels.

A smaller dewatering pump of 5HP or even 10HP can take care of numerous applications related to construction, mining, utilities, industrial, marine, and more.

Dewatering pumps from Piranha Pumps

Our industrial dewatering pumps have undergone rugged construction with the finest quality components. Our pumps are available in various models from 3/4 hp to 45 hp with flows to 1800 gallons per minute and heads to 450 feet. We design and manufacture our dewatering pumps for dependable performance.

Our pumps can perform with challenging applications such as mine dewatering, power plant sumps, construction site dewatering, and industrial mill sumps. So whether you're a contractor or a waterfront homeowner, our dewatering pumps are sure to exceed your expectations.

Our range begins from 0.75 HP to dewatering pumps of 5 HP, 10HP, and beyond up to 45 HP.

Piranha dewatering pumps come with the following unique features:

Designed to transfer water or water with light suspended solids
Operation for high volume or high head applications
Available with corrosion-resistant coatings
Customizable with float switch and control accessories
Ready for any of our flotation platforms

Piranha Pumps has been in business since 1961 as a representative for various pump manufacturers. In those years, the pumping industry was still evolving, even as newer technology started finding ways. As time went on, we found the public was missing out on various novel technological advances in pumps and dredging equipment. Piranha Pumps then transitioned into a manufacturer for pumps and now boasts an inventory of over 75 different pumps and pumping systems.