ECS weeds out any blockage risks at Black Dyke Intake

ECS Engineering Services has updated two Brackett Green® drum screens at Black Dyke Intake in conjunction with Ovivo. The works were carried out on behalf of the Environment Agency to reduce any risk of blockage at the site. This was a key concern as the intake forms a key component of the Ely Ouse To Essex Water Transfer Scheme, which diverts large quantities of water to reservoirs in Essex.

Located at Feltwell in Norfolk, Black Dyke Intake receives water from the River Ouse via a cut-off channel. Collected water falls 90 feet into a series of underground tunnels and pipelines until it joins the River Stour, with water passing through numerous pumping stations and eventually into Essex reservoirs.

Due to its important role in this infrastructure, it is imperative that Black Dyke Intake does not suffer blockages. Consequently, the installation features two large Brackett Green® drum screens to filter weeds and algae from the intake to reduce any chance of blockage. However, after a long service life, it was clear that the two screens required an update and overhaul.

Bracket Green® drum screens are, as the name suggests, large drums that feature filters installed around the circumference. Water flows into the drum and out through the panels, with weeds and algae collected in the filters. The drum rotates, with a wash water system removing the debris from the filters. The result is a screened flow of water that then falls into the tunnel complex.

Phil Anderson, ECS Project Manager, explained ECS’ involvement: “We were contacted by the Environment Agency to join the project as a principal contractor. Each of the drum screens was located in an 8-metre-deep chamber and would require partial disassembly within a confined space. Additionally, each one is quite sizeable, so cranage was needed to carry out the work. A new motor and gearbox were also required.”

First of all, ECS isolated the chambers and utilised an over pumping system to keep them dry. In conjunction with Environment Agency Fisheries, any fish in the chamber were carefully removed by tipping bucket and released in the nearby river. With the fish gone and the chamber dry, ECS removed any debris. Fixed scaffolding was then installed to allow three tier access.

Disassembly could now begin in earnest. The filters and chains were removed before the screen was split in two, with the main head, weighing approximately five tonnes, lifted by crane out of the chamber. A new top head was then installed and integrated into the original half screen. Modified chains were added along with 52 new filters.

To ensure the continued reliability of the powertrain, a new motor and gearbox were installed. By replacing both with modern equivalents, the efficiency of the drum screens was improved, unlocking long-term energy savings for the operators.

The wash water system was also reintegrated to remove debris from the screens. As part of this, all seals were replaced and the installation could now remove debris with increased proficiency. After testing and commissioning, the drum screens could continue to capture weeds and algae from the water flow to reduce any risk of blockage.

Phil concludes: “We are a framework contractor for various water authorities throughout the UK due to the fact we can provide a complete electromechanical service. Our experience working within confined spaces – illustrated by our multiple Royal Society for the Prevention of Accidents (RoSPA) Gold Awards – plus a proven track record with the Environment Agency meant this project could be completed efficiently.

“With the overhaul now complete, the risk of blockage is reduced, the efficiency of the powertrain is improved and the future reliability of the installation is secured.”