Queensferry Crossing cable cleaning found to have beneficial effect

Engineers responsible for the Queensferry Crossing have expressed cautious optimism at the results of recent tests of methods to mitigate against ice accreting on the bridge’s cables and towers.

The trial of the prototype cable cleaning machine in November 2021.
The trial of the prototype cable cleaning machine in November 2021.

Laboratory tests have confirmed that cleaning the cables has a beneficial effect, however the extent of this is yet to be quantified. Further testing will be carried out over the months ahead. The stay cables on the north tower of the Queensferry Crossing were cleaned between September and November 2021. The central and south towers were left uncleaned so that a comparison could be made.

Cleaning of the cables was followed up in December by laboratory tests at the Jules Verne Climatic Wind Tunnel in Nantes, a specialised research facility which can replicate the specific combination of weather conditions that cause ice accretion. Cleaned, soiled, new and damaged sections of the high-density polyethylene pipes that encase the Queensferry Crossing’s cables were exposed to freezing temperatures, wind, sleet and snow inside a 6,000m2 wind tunnel.

Cleaning was found to be the best performing option for mitigating the build-up of ice on the cables, and icephobic and omniphobic coatings were shown to reduce the build-up of ice on the concrete tower.

Chris Tracey is South East Unit Bridges Manager for BEAR Scotland, which maintains the Queensferry Crossing. He said: “We won’t know for sure until we experience another incident of ice accretion on the bridge itself, however these test results give cause for cautious optimism that cleaning may have a beneficial effect.

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“Further tests are required to measure the extent of this effect under a wider range of conditions, and we will continue to monitor the cables closely on site.

“Tests of specialist coatings on the concrete tower also showed promising results, however further work is required to verify these results and to identify how these coatings might be used in practice.

“Ice accretion is not a problem unique to the Queensferry Crossing, and we hope that the research and development carried out here will ultimately be of wider benefit."​​​​​​​​​​​​​​​​​​​​​