Oykel Viaduct
In early 2007, TI Protective Coatings embarked upon an ambitious restoration project for Network Rail, in a remote location in the Scottish Highlands. The structure; UB 302/151 Oykel Viaduct, carries the single track Far North Line over the River Oykel between Culrain and Invershin stations. The bridge is situated within a Special Area of Conservation due to Pearl Mussels and Atlantic Salmon. The site also borders an expansive Site of Special Scientific Interest, the Kyle of Sutherland Marshes.
The viaduct consists of 6 spans; 3 masonry arch spans on the Invershin East bank, with one spanning over the A836 Trunk Road, the 4th at 74m in length is a steel lattice girder designed viaduct with 2 levels of integrated walkways embedded within the bridge; with 2 further spans on the Culrain West bank. A pedestrian walkway was constructed on the north side of the structure in May 2000. The bridge consists of 6,000m² of steelwork, requiring 240 tonnes of abrasive and 5,000 litres of paint to complete.
The structure is a Grade 2 listed structure, built in 1867 for the Sutherland Railway Company; it is now owned and maintained by Network Rail Scotland with the pedestrian walkway being operated by the local Highland Council.
T.I. Protective Coatings provided a full Grit Blast and Painting program, Masonry repairs and Steelwork repairs; including the removal of the existing track level walkway and the installation of a new walkway during possessions.
They divided the central 74m steel lattice girder span into 5 phases due to the wind loadings imposed upon the structure. Wind speeds were monitored continuously and innovative encapsulation engineering controls were installed to reduce the loadings.
Unsound paint and corrosion was removed by Grit Blasting using copper slag abrasive in accordance with RT98 and BS7079:Part A1 to achieve a surface standard of SA 2½; suitable for the application of an approved Network Rail Paint Specification. Mechanical Preparation allowed areas where it was not practical to Blast clean to receive the required standard of preparation.
The 3-Coat Paint System selected was able to continue to cure at low temperatures; this was vital considering the remote location of the structure in the Highlands, and the timing of the works, between January and May 2007. As temperatures fell to -15°C during the daytime; Heaters and Dehumidifiers had to be introduced. A Stripe Finish Coat was applied to increase the aesthetics; a variation to the specification but felt to be best practice. All of the work was overseen by an in-house T.I. Protective Coatings ICORR Level 2 Paint Inspector.
Commenting upon the project; T.I. Protective Coatings Managing Director, Graham Moor had this to say: “Whilst on-site we were successfully audited by the Network Rail Paint Inspection team; with some exceptional feedback regarding our approach to the contract and the level of quality. The project has also been put forward by Network Rail Scotland for a National Restoration Award and we also received letters of thanks from members of the local council & the community.”
The project was completed on the 31st May 2007; with the protective paint systems service life of 25 years; T.I. Protective Coatings have ensured this engineering marvel is expertly finished and now superbly suited to its breathtaking surroundings for many more years to come.
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