New Rotork actuators go beyond the limits

New Rotork actuators go beyond the limits of old to achieve reliable river gate operation.

New Rotork valve actuators have been installed at an important river gate and weir to improve river level control and secure more reliable automatic operation.

Bedford Sluice on the River Nene at Northampton is the main control structure before the Northampton Washlands, an environmentally sensitive amenity area supporting a wide range of outdoor sport and leisure activities. The four radial gates on Bedford Sluice regulate the river flow through the City of Northampton to prevent flooding and maintain water levels for nearby facilities including the River Nene Navigation, the Nene Whitewater canoe course and a rowing club.

Operation of the radial gates was literally beyond the limits for the actuators that have been replaced. Fitted with mechanical limit switches, they could not cope with the exceptionally long stroke required to fully operate the gates. External limit switches were therefore installed to operate directly on the gate stems, but these had proved to be less than 100% reliable and on occasions had caused damage to the installation by failing to stop the gates in time.

The new IQ intelligent electric actuators installed by Rotork have replaced mechanical limit switches with a Hall Effect magnetic pulse system that accurately measures and controls the stroke without the restrictions inherent in gears and switches. The system converts the actuator's output centre column rotation into an electronic signal, which is compared to position limits programmed and stored within a secure, non-volatile memory, removing any chance of a mechanical failure.

Working for the Environment Agency, Rotork has carried out all aspects of the actuator modernisation project. Rotork's specialist Site Services Department designed and fabricated new adaptation and installed IQ40 intelligent actuators. Exeeco, a Rotork projects and services company, carried out the electrical installation including connection to a telemetry link and associated panel modifications. In this way, work on all four gates was completed in a period of only four weeks. As part of the customised installation, the actuators' handwheels have been removed and replaced with special adaptors for a hand-held hydraulic power pack. In the event of emergency operation during power failure this will enable the gates to be moved as quickly as possible.

The new actuators are controlled from a level sensor positioned a short distance upstream of the installation. Signals from the level sensor trigger sequential operation of the individual gates in order to achieve accurate river level control under all ambient conditions. The computerised programme is linked by telemetry into the Environment Agency ARTS supervisory system, based at the main monitoring and control room at Peterborough. Under normal circumstances, operation of Bedford Sluice is fully automatic, but the actuators are programmed to transmit an alarm in the event of any malfunction, to facilitate immediate remedial action.