Articles & Case Studies

Rotary lobe pumps for the transfer of flocculant in water treatment system

Posted: Tuesday 30th June 2020

A manufacturer of mobile water treatment systems was in urgent need of two positive displacement pumps for one of their new units. It was important that the pump had a gentle pumping action to ensure that the flocculant was not damaged during transfer.

The installation involves a Dissolved Air Flotation (DAF) system, this is fed by mine water that is high in suspended solids and dissolved solids. A flocculant is created to remove the solids from the water, the DAF unit then removes as much of the flocculant as possible. However, not all the flocculant can be removed by the DAF and some remains that is then separated by a secondary filtration system.

The required pumps are positioned between the DAF and the secondary filter, a standard centrifugal pump would damage the flocculant before it can be fully removed due to the shear force, that is why a shear sensitive positive displacement pump is required.

A flow rate of around 70 to 80m³/hr and a pressure of 4 bar is required from each pump for the water treatment system to function correctly. We therefore selected 2 of our LB-M/125 horizontal Rotary lobe pumps complete with gear box and 22Kw motors. These pumps will each produce a flow rate of 76m³/hr at 4 bar. The gear box reduces the operating speed to 428RPM to ensure a slow and gentle pumping action.

Due to the lobe design, the LB-M series is excellent at handling both high viscosity and low viscosity liquids and solids without causing damage. It creates minimal pulsations as the flow is smooth and continuous, pulsations can be an issue with other pump types. These pumps are also self-priming and reversible which provides flexibility should the installation change or the pumps be required for a different process at a later stage.

The LB-M lobe pumps make maintenance simple for engineers as a removable stainless steel wear plate is installed. This is a sacrificial part that wears first to protect other components such as the pump casing, the plate is then replaced, and this is far more cost effective.

To provide further flexibility for the engineers on site, the motor installed is suitable for operation by frequency inverter and fitted with PTC sensors for protection. This allows the customer to control the motor speed and therefore reduce or increase the flow rate as required. We ensured both pumps were manufactured in 4 weeks as per the customer’s request, they now have robust and reliable pumps for their water treatment system.

For more info visit or phone +44 (0) 1773 302 660

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August 2021

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