Two concrete towers stand 20m above the ground on either side of the mouth of Dartford Creek. Two steel gates, each 30m across and weighing over 160 tons each, suspended at high level between the two concrete towers. This is the UK Environment Agency’s Dartford Barrier flood defence system in Kent, England.
Like a huge guillotine at the creek mouth, one gate may be slowly lowered on its supporting chains onto the river bed to block the flow of water. The the second gate may be slowly lowered to rest onto the top of the first gate.
Just a couple of years ago, the control system was starting to show its age. As part of a large upgrade to the barrier, its associated control system was overhauled. The original control system was a completely hardwired based relay system that was over 30 years old.
Qualter Hall, who provides an attractive ‘one stop shop’ for a multitude of engineering solutions, decided to call ProSoft Technology because it was a reliable, cost effective solution that was endorsed by Rockwell Automation.
Two Rockwell Automation ControlLogix redundant PACs are inside each of the 20m towers to control the opening and closing of the barrier, but much of the equipment the control system spoke to was PROFIBUS or Siemens based. Two PROFIBUS Master communication modules (MV156-PDPMV1) from ProSoft Technology were installed inside the ControlLogix PACs to facilitate communication from the Rockwell Automation processors.
Fibre optic cables were installed between the two towers, as part of the control system overhaul. While the cable links were being constructed, ProSoft Technology 802.11 Industrial Hotspot radios served as the communication link.
“The wireless link was then used as an automatic fallback connection should fiber optic connection be lost. The ProSoft Technology equipment was selected for its flexibility and support of the spanning tree protocol (RSTP)”, said Andrew Garwood, senior contracts manager in the controls division of Qualter Hall, Barnsley.
ProSoft Technology’s solutions helped ease the engineering work by making it possible for the ControlLogix system to communicate as one single protocol. The system now allows data to be reviewed quickly, centrally and remotely, providing convenience when accessing diagnostic information.
