The Thames Water Ring Main, formerly known as the London Water Ring Main, plays a critical role in supplying drinking water in the capital. Originally built between 1988 and 1993, the structure forms a 50-mile ring of 2.54 metre diameter concrete pipe. Primarily, this is used to transfer drinking water from water treatment plants in the Thames and Lea basins into the city.
The main ring lies between ten and 65 meters below ground level and passes through 21 wells that serve as supply, storage and pumping stations. One of these pumping stations is Battersea Shaft.
Battersea Shaft consists of a large 30-meter-deep vertical shaft, containing six pumps that can supply multiple areas of London with drinkable water. However, increasing development in the city has made it necessary to remodel and replan the network to supply this new demand.
Due to rapidly increasing development in London, predictions suggest that there would be a significant shortage of drinking water capacity in the coming years. To accommodate a growing — and increasingly thirsty population — the station required additional pumping capacity. This necessitated new equipment in the form of a pump, pump motor and variable speed drive (VSD).
With guidance from a team of experts, it was decided to replace one of the 30 mega-litre per day pumps with a new 45 mega-litre per day option, the largest possible power within the physical limitations of the environment.
However, the real challenge of this replacement was due to the constant demand of drinking water in the capital. To minimise disruption, the pump needed to be replaced without stopping operations. This necessity had a major influence on the design and construction of the pump, and the overall project itself.
It was decided that only the pump that needed to be replaced would be taken offline, enabling the rest of the system to continue operating as normal. However, to achieve this, detailed planning of the pump’s removal, installation and commissioning was required.
Pump supplier Bedford Pumps supported this entire process. Through the company’s close relationship with motor manufacturer, WEG, the team was able to replace the pump without having to resort to cuts in the supply to the London water network.
For this application, WEG engineers, along with Bedford Pumps, decided the best option was a water-cooled motor design.
The existing pump and motor had extensive fault detection instrumentation and a monitoring system. Therefore, the same range and functionality was installed in the new pump. In addition, due to the uniqueness of the location, the replacement of any wiring between the electrical equipment and the pump was invasive and required downtime, so all new instrumentation had to be selected to be compatible with the existing wiring, which further complicated the motor selection process.
For this application, WEG chose a 450 kW master line water cooled induction motor. These motors are said to stand out for the flexibility of their electrical and mechanical functionalities, as well as being easily customised, making them interchangeable with already existing motors.
For the Battersea Shaft Pumping Station, WEG committed to achieve 96% efficiency performance. Following completion of the project, during testing this figure was not only achieved but exceeded with a greater margin.
Following completion in January 2020, the pump is now fully commissioned and in full service. What was notable, is that designing the new equipment to work with existing infrastructure, together with detailed construction planning, massively minimised the installation period for the project. That, crucially, avoided pumping station outages.