SubscribeRotork electric actuators are used in a variety of valve automation applications to help to maintain and improve the Environment Agency's management of the UK's rivers and countryside.
Projects often involve Rotork’s specialised Site Services Department for the design and fabrication of valve adaptation and associated services, as these recent examples illustrate.
Installation of Rotork IQ actuators heralds secure operating future for Victorian tidal gateway
The gateway – essentially two locks in one – at South Ferriby on the Humber Estuary maintains the water level and helps to prevent silting in the River Ancholme whilst allowing the passage of ships and boats. In past times the river, which runs in two intertwining ‘Old’ and ‘New’ channels – the result of considerable engineering work – was an important route for transporting cargo from rural communities to industrial towns. Today, although the majority of traffic is for pleasure, the river is a significant environmental asset and land drainage channel.
The lock, a Scheduled Monument, was built in 1843 to a Sir John Rennie design and virtually all of the operating machinery that has been modernised dates from that time. Eight gearboxes open and close flood gates and ebb gates within the main lock chamber by means of chain drives whilst a further four gearboxes operate valves – colloquially known as “cloughs” – in the lock walls to allow water in and out of the lock.
Rotork was awarded the contract for Phase One Works as part of the Environment Agency framework agreement for valve actuators, with an expanded scope of work relating to the additional site activity required. This involved dismantling and refurbishing the twelve original hand operated gearboxes, the re-manufacture of any worn out parts, design and fabrication of adaptation and pedestals for the new Rotork IQ electric actuators and all site electrical installation and commissioning work.
The IQ actuators are individually operated by a hand-held plug-in pendant which enables the lock keeper to observe and accurately control the position of the gates and the water level in the lock. Previously, looking into the lock and hand winding the gearboxes at the same time was not possible, making single-handed operation of the lock difficult as well as laborious.
The successful completion of Phase One Works at the South Ferriby tidal gateway modernisation project has secured the future operation of the lock. Senior Lock Keeper Alan White explains: “Motorising the flood gates, ebb gates and cloughs enables us to operate the lock’s functions more safely and with better accuracy for the continuing benefit of the river and its environments. Also, with approximately one thousand boats using the lock during the April–to–October season the task will be far less arduous than when it was all done by hand.”
New Rotork actuators go beyond the limits of old to achieve reliable river gate 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.
Rotork actuators at the centre of Environment Agency’s 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. 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 & 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 48 volt batteries for actuator operation, whilst one solar panel is dedicated to the 12 volt control and telemetry system. A Milltronics ultrasonic level sensor and controller communicates with the actuator via a 4 to 20 milliamp 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 is 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.