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Internal Seal Repairs Hydroelectric Pipeline

Posted: Monday 6th February 2006

When a pipeline springs a leak, sometimes the only practical way to solve the problem is to climb in and fit a repair seal internally. One solution, the Amex-10-Seal, is a low profile mechanical seal for internal repair of leaking pipe joints. A robust section of rubber that spans the joint is fitted using hydraulic expansion of stainless steel compression rings, thus eliminating the use of chemical adhesives and their associated hazards. The seal accommodates substantial joint movement, is abrasion resistant and each seal has an independently verified life expectancy of more than 50 years.

Exponents of the system, Planned Maintenance (Pennine) Limited (PMP) were recently appointed by AMCO Construction to carry out remedial works to a number of joints on a buried pipeline. The pipeline forms the penstock for one of Scotland’s newest hydro electric schemes at Kingairloch, which is located on the East side of the Morvern peninsula, 23 miles south west of Fort William.

Kingairloch Hydro Scheme has a generation capacity of 3.5 megawatts with a gross operating head of 143m. The scheme is located on the Kingairloch Estate on the Morvern Peninsula within the Abhainn na Coinnich river catchment. It includes a storage reservoir at Loch Uisge with water diverted from a number of tributaries of the Abhainn na Coinnich.

The penstock includes approximately 4500 m of buried pipe made up from approximately 3500 meters of 1200 mm diameter and 1000 meters of 900 mm diameter. The penstock pipeline is buried in a trench over upland terrain at variable gradients up to 50 % and is rated between PN 6 and PN 25. The pipeline had to be laid to very tight dimensional tolerances. Subsequently a number of the joints between sections of the pipeline did not conform to the specification.

AMCO Construction contacted PMP for a solution to the out-of-tolerance joints. They proposed using the Amex-10-Seal and their engineers used roped access skills to fit the seals from within the pipe. By completing all repairs internally, trenching and service costs were avoided. Yet the Kingairloch scheme presented PMP with very difficult working conditions. Roped access was required to reach down to pipe joints where the operating pressure approached 25 bar. Working from a removed section of the 900mm pipe, the PMP engineer was lowered to the location of each leaking joint, in order to carry out the preparation and fitting of the seals. In total 28 seals were fitted over a period of 2-3 months.

Paul Owen, site agent for AMCO, commented: ‘PMP did a good job. Their service was very effective with a rapid response.’

Lined Pipe Sealing

Again using Amex seals, PMP have also established a solution to hydraulic sealing in large and small diameter, close-fit lined pipes. In situations accessible by engineers trained in confined space working, the Amex-10-Seal can be fitted internally, to form a perfect seal between the PE liner and the host pipe. This allows the liner to be terminated at each side of points such as branch tees, valves, or joints between different pipe materials.

PMP have successfully used pipe end sealing technique in a project for Yorkshire Water, in which a ferro-concrete pipeline from Eccup Reservoir was lined using Enterprise plc’s ‘Subline’ method. The company installed Amex seals at transition points between the concrete pipe and new sections of ductile iron pipe, allowing mechanical couplings to be made, and also at washouts and at a man access tee.

Pipe end seals can be installed in any close fit PE liner, regardless of the lining technique, and are therefore suitable for use with familiar Rolldown, Swagelining and Subline methods.

Planned Maintenance (Pennine) Limited, formed in 1983, are specialists in joint repair and testing for man accessible pipelines. PMP also undertake penstock and valve repair, refurbishment or replacement, and reservoir surveys. For more information please visit

Vine Grove Works

Tel: +44(0)1706 836110
Fax:+44(0)1706 836111

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