Pipe maintenance descent for Conjet robot
By Lindsay Gale17 August 2010
The 12 MW Glenlee hydroelectric power station is one of six such facilities that make up the 106.5 MW Galloway Hydro-Electric power scheme in the south west of Scotland. Built in the mid 1930s, this is comprised of a 60 km network of lochs, dams, tunnels, aqueducts, pipelines and rivers that connects the six power stations in a cascade system that reuses the water several times for power generation.
At Glenlee, water is gathered in Loch Clatteringshaws and then flows through a 6 km (3.7 mile) tunnel to a portal control valve above the power station. From here, it plunges down 125 m (410 ft) through a 570 m (1,870 ft) steel penstock to the station's 6 MW turbines.
The penstock required cleaning and repainting - this had not been carried out since it was installed in the 1930s, and Scottish Power Generation Ltd brought in Falkirk-based specialist contractor Concrete Repairs Ltd to do the work. CRL believed that high pressure water jetting could be applied to the job, and in turn recruited Perthshire-based N.E.T. Waterjet Ltd to carry this out.
N.E.T. purchased a Conjet 324 Robot and fitted it with the optional Hammelmann rotor head instead of the standard hydrodemolition lance. The flange-bolted expansion joints and butterfly valves in the penstock were removed to provide the robot access at several points. The machine has been working a single shift, seven days a week, and has averaged a cleaned area of 200 m2 (2,150 ft2) per shift, with a best area of 320 m2 (3,440 ft2) in a single shift. CRL follows along behind the robot to give the cleaned pipe a two-coat glass flake epoxy coating from a purpose built gantry that travels down the inside of the pipe.
Waste water and debris is collected by CRL in a sump in the turbine house of the power station, from where it is then pumped into tankers for off-site environmental treatment and disposal.