Intelligent valve actuation at Severn Trent Water’s “beacon project”

Severn Trent Water’s Minworth sewage treatment works, which serves around 1.75 million of Birmingham’s population, is undergoing a major modernisation project that will improve the quality of the water put back into the River Tame and significantly upgrade the work’s facilities, improving the quality of the 1bl (one billion litre) daily treatment capacity.  The £145 million project is being handled by an alliance comprising Severn Trent Water, North Midland Construction Nomenca and Biwater, with Pick Everard as consultants. It will create one of the world’s most efficient and technologically advanced large scale treatment works.

Tony Wray, chief executive officer of Severn Trent Water, has praised the scheme as a “beacon project”, adding that the 30-strong supply chain should be proud of the numerous achievements at Minworth.  As a member of this supply chain, Rotork has supplied over 250 Profibus network-enabled IQPro intelligent electric actuators for valve control throughout the new and refurbished plant areas.

Many of the actuators are installed on the new eight-lane inlet works, the new 22 primary settlement tank island and the enlarged activated sludge plant.  In all areas Rotork IQPro multi-turn actuators operate penstocks to control the flow through the works, whilst on the activated sludge plant, IQTPro direct drive quarter-turn actuators are also installed on the air flow control valves that regulate the introduction of air into the treatment tanks.

The actuators are linked on fully redundant Profibus field networks to Allen Bradley PLC platforms at intelligent motor control centres (iMCC’s) throughout the site.  These interface with the site’s Rockwell SCADA system, which is accessible at local HMI terminals at key site locations.  Feedback from sensors throughout the plant is used to automatically operate the actuators to account for fluctuations in flow, caused, for example, by storm conditions, and to enhance the efficiency of operations. The software for the SCADA system has been written by Saftronics Controls and the whole network has been designed to provide extended information and historical trending for energy management and condition monitoring.

Assisting this function, data loggers in the Rotork actuators store a commissioning ‘footprint’ of valve operating torque and a torque curve for all subsequent valve operations.  This data can be downloaded and analysed with Rotork IQ-Insight software in order to identify and plan valve maintenance requirements.  The technology assists the optimisation of plant utilisation and eliminates the need for over-cautious maintenance scheduling.

As a further assistance to maintenance, all the actuators utilise Rotork’s ‘bumpless’ Profibus interface module, which enables individual motorised valves to be disconnected without disrupting communication with the other devices on the network.

The new Rotork actuators join hundreds that are already installed at Minworth.  Most have been fitted  during previous modernisation programmes at the site and supplied through the long-standing framework agreement that Severn Trent Water has with Rotork.