Rotork valve actuators assist Severn Trent's improved water quality programme

Rotork IQT intelligent electric actuators for quarter-turn valves are a central feature of a filter improvement project at the Severn Trent Ogston water treatment plant in Derbyshire.

The plant was first opened in 1946 to treat water from the adjacent Ogston Reservoir, now distinguished as where round-the-world record breaking yachtswoman Ellen Macarthur first learnt to sail.

Norwest Holst Construction Ltd has carried out the complete upgrade of twelve rapid gravity filters at Ogston, including the fitting of Tetra block filtration flooring, replacing the old sand and gravel media with an improved sand and anthracite formula and installing a new clean backwash water main. The project also involved fitting new butterfly and plug valves with Rotork IQT actuators in virtually all areas of the plant to automatically control the filtration and backwashing sequence of operations. The actuators are connected to refurbished PLCs and linked to a new master MCC (Motor Control Centre) that runs the plant, treating up to 40 ml/day (megalitres a day) for consumers in the surrounding areas.

Kevin Rodenby, Norwest Holst's M & E Supervisor on the project, appreciates features of the IQT actuators which assist the commissioning and running of the new plant. "Rotork's hand-held, non-intrusive setting tool is especially helpful in simplifying and speeding up commissioning, eliminating the time-consuming effort of removing electrical covers." he said. "Quick and easy to follow setting instructions are clearly displayed on the actuator's indication screen, which also provides local valve position and status information."

IQT actuators also incorporate on-board data loggers where commissioning settings, historical operational data and valve operating torque profiles are stored. This information can be downloaded over the non-intrusive link for analysis and review using Rotork IQ-Insight PC software to maximise plant utilisation and eliminate the threat of unexpected breakdowns.

The IQT actuators operating filtered water outlet and backwash water inlet valves are factory fitted with the Rotork CPT (Current Position Transmitter), enabling partial valve movements to be controlled and indicated in response to an analogue current signal from the MCC. CPTs were also retrofitted to the only actuators retained from the original plant?- Rotork AQ units on the forward rinse valves  enabling them to be included in the new control regime and eliminating the need to replace them.

Ogston is the latest in a programme of water treatment plant upgrade projects, undertaken by Norwest Holst Construction Ltd and utilising Rotork actuators, designed to bring improved water quality to users in the Severn Trent Water area.