Dry work on Severn Bridge

Laing O’Rourke and its partners, Munters and Faber Maunsell have successfully completed a main cable de-humidification system on centre spans of the Severn Suspension Bridge.



The project, for the Highways Agency, is the first operational main cable de-humidification system in the UK. It involved wrapping the Severn Bridge main cable in a polymer based material to create a homogenous seal and installing a de-humidification plant room within the bridge. The plant then drives dry air into the main cable to reduce the level of humidity in it and suspend or delay the progression of corrosion of the cable strands.

To wrap the cables, the polymer based material was spirally wound onto the main cable and heat shrunk in position creating a seal between each spirally wound section and a tight fit onto the main cable itself.


The de-humidification system was designed and installed by humidity specialists Munters, working closely with Laing O’Rourke and the project consultants, Faber Maunsell to provide reliable plant and equipment for 24/7 operation and real time monitoring.