Actuators enable automatic flood defence plan

Rotork electric valve actuators are being used throughout an innovative river level management automation project performed by the Environment Agency in the Anglian region.

Rotork electric valve actuators are being used throughout an innovative river level management automation project performed by the Environment Agency in the Anglian region.

The ambitious project, designed to improve flood protection in Norfolk and Suffolk, involves automating manually operated sluice gates at river weir and bypass channel locations throughout the area and linking them by telemetry to centralised control rooms.

Traditional manual operation of these sluices could be labour intensive, time consuming and inefficient, as Environment Agency M and E Flood Defence Engineer Ivan Nicholls, who is project manager for the automation scheme, explained: "In many cases it could take a long time even to reach the sites, some of which are in remote locations with poor access.

Also, especially at night, they can be potentially hazardous, demanding the despatch of two men per visit for safety reasons".

"Operating the sluices manually provides a relatively crude adjustment, usually fully raising or lowering the gate, which may not always suit prevailing or subsequent river conditions.

Electric actuation, working automatically in response to a signal from an upstream level sensor, introduces the ability to raise or lower the gates in small stages at frequent intervals, and therefore react with far more accuracy to changing river conditions".

"However, the lack of a mains electricity supply at some locations was a fundamental complication demanding a well thought out solution before the automation scheme could proceed.

Our enquiries revealed that Rotork manufactured a suitable actuator for this type of application which would operate from a DC stored energy source.

We were therefore able to design an entirely self-contained package, including all the control elements, running from a bank of batteries that are kept charged by wind and/or solar power.

The first site to be modernised, on the River Yare at Keswick Mill near Norwich, was commissioned in 1999".

The plant installed at Keswick Mill is typical of all the battery-powered sites, although it is unusual in having both solar panels and a wind turbine generator.

Four solar panels and the turbine are used to charge the 48V batteries for actuator operation, while one solar panel is dedicated to the 12V control and telemetry system.

A Milltronics ultrasonic level sensor and controller communicates with the actuator via a 4 to 20mA analogue gate positioning signal.

In order to maximise energy preservation, the plant is normally "asleep", waking every hour to check its status and make any adjustment to the gate position before closing down again.

By making only small adjustments at hourly intervals the system is able to react accurately and sympathetically to the status of the river, without the danger of over-compensating for changes in the water level.

Real-time data from the site are transmitted to the Environment Agency's Anglia Region telemetry system control rooms at Peterborough and Brampton, and can be accessed at other control rooms.

Downstream from Keswick, the multiple gate weir at Trowse is one of the sites where the Environment Agency has been able to install the latest Rotork IQ intelligent electric actuators, due to the availability of a mains power supply.

A Mitsubishi PLC with MMI (man machine interface) touch screen control panel is utilised for mains powered sites, enabling the control system for all actuators on the site to be housed in the same sized compact cabinet as the single gate battery-powered sites.

At Trowse the introduction of the automatic river management scheme has been blended in with an impressive new housing development, built on the site of a derelict printing works.

Further automated sites include Hellesden Mill at Norwich on the River Wensum and Glevering Mill near Woodbridge on the River Deben.

At all the sites the Environment Agency has carried out the civil and mechanical work whilst the equipment design and installation has been performed by Dabbrooks (Eng) of Great Yarmouth.

Rotork's recent announcement of a DC version of the IQ intelligent actuator introduces the ability to standardise on the IQ for all future sites, whether mains or battery powered.

With this in mind, Ivan Nicholls has recently negotiated a framework agreement with Rotork for the Environment Agency Anglian Region.

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