On the river Weaver in Cheshire, the Dutton sluice site consists of eight large sluice gates lifted by Rotork actuators. The water level in the river determines when to open or close the sluice gates and navigation is closed to river traffic if the water level is too high.
The site is a key measurement point and the level monitoring needs to be very accurate. Consequently the level of the river is now measured by four instruments. The first two are ultrasonic sensors (for redundancy) mounted in stilling tubes. These tubes are required in order to reduce loss of echo issues from weather and surface conditions. However the tubes can require substantial engineering to install, and generally they need continuous on-site maintenance to prevent blockages, or repairs to keep measurement errors to a minimum.
Even with this stilling tube installation, the scada maintenance engineer has commented, “In recent years we have experienced issues where either one or both of the ultrasonic sensors loses echo or drifts, causing level sensor failure alarms to be sent out.”
As a result, the Canal & River Trust (CRT) has installed two other devices alongside the ultrasonic sensors, as test instruments. Designed and manufactured by VEGA, the radar level sensors Vegapuls WL61 are unaffected by weather or surface conditions and were simply mounted on a unistrut adjacent to the stilling tubes. CRT has compared the data from both sets of instruments over several months and found that there was no drift with the WL61 water radars since installation.
“Whilst we have seen occasions where the water level on one or both of the ultrasonic units rises and the radars have not,” commented the engineer. “As far as I can see, the WL61 radars provide more reliable data than the ultrasonic devices. My concern with the ultrasonic sensors is that drift could create nuisance alarms and result in staff call outs.” There are also the ongoing maintenance requirements associated with the stilling tubes. “I do not have these concerns with the WL61s. In addition, I have confidence in the support from VEGA should an issue arise with any of the instruments at a later date.”
As the engineer summed up, “I am pleased with the quality and performance of the VEGA radar level sensors. We will be installing these in place of the ultrasonic sensors at the other River Weaver sites and in other CRT sites as we replace older equipment.”
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