Enhancing Operational Efficiency of Inlet Screws

Anglian Water was facing challenges with their inlet screws, which consumed between 4,000 and 5,500 kWh per day due to reliability issues. These screws were manually operated to mitigate these issues, leading to higher energy consumption. Each screw operated continuously, using soft starters for 24 hours a day.

Project Initiation

Anglian Water approached IDS to explore the benefits of altering the control strategy for these inlet screws. The goals were to reduce startup current and torque, minimise energy consumption, ensure a return on investment, decrease the number of revolutions and stops and achieve a smoother flow into the works.

Project Logistics and Installation:

• Delivery and Setup: IDS arranged for two 200kW IP54 ABB ACS880-37 Ultra Low Harmonic freestanding variable speed drives (VSDs) to be delivered to the site. These drives were positioned opposite the Motor Control Centre (MCC).
• Infrastructure Modifications: Mains and motor cables were rerouted from the starter sections to the drives on a cable tray over the panel. Existing soft starters were replaced, and the panels were adapted to convert to Direct on Line (DoL) feeders for the VSDs.
• Integration: An isolating signal splitter was installed to interface with the new VEGA level controller. Each VSD received inlet well level signals to manage the on-off and duty assist, controlled by the VEGA level controller.

Project Installation and Commissioning:

IDS collaborated with Anglian Water to install two 200kW Ultra-low harmonic freestanding cabinet-built variable speed drives in the MCC. New mains and motor cables were installed and existing panels were modified to accommodate these changes. A VEGA level controller was also installed to optimise the control of the screw pumps, achieving lower revolutions and extended component life while reducing energy consumption.

Enhancing Operational Efficiency of Inlet Screws

Efficiency and Financial Benefits:

The installation of VSDs reduced the kWh consumption from 4-5.5 thousand per day to approximately 1 thousand. Additionally, the operating hours were reduced from 48 to 20 hours per day across both screws. This not only extended the life of the components but also enabled Anglian Water to identify and utilise the most efficient screw more effectively.

Project Completion and Review:

The collaboration between IDS and Anglian Water led to a project that was completed without delays and within the budget. The project goals were met efficiently, with the IDS team providing support and ensuring that operations continued safely and without interruption. The risk of potential challenges such as storm flooding and equipment issues was well managed, and thankfully, none of these risks materialised.

This project demonstrated the exceptional capability of variable speed drives and the benefits they offer. Through strategic planning and effective collaboration, Anglian Water was able to significantly enhance their operational efficiency and reduce energy costs, demonstrating a successful partnership and technical execution.