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Draft tube installed at Nedre Røssåga

15 Aug, 2014

The upgrade of the Nedre Røssåga power plant from 1955 and construction of a new power station is Statkraft’s largest rehabilitation project this year. This summer a giant draft tube is being installed at the new power station.

During the period 2012-2016, a brand new power station will be built alongside an upgrade of the old station. The investment is NOK 1.7 billion and after completion Nedre Røssåga and Øvre Røssåga will be responsible for two per cent of the total electricity production in Norway.

So far, the project is proceeding according to schedule.

"In May, we completed the blasting work at the new power station, and in July and August the new draft tube will be installed. As far as we know, the tube is the largest ever to be used in Norway for a Francis turbine, and has the capacity to transport 105 cubic metres of water per second," says Project Manager Roald Nilsen.

The draft tube is the tube which conducts the water from the turbine down towards the outlet tunnel.

Handball pitch in the rock

The station hall, which has been blasted into the rock, is also very spacious. It is 40 metres long, 18 meters wide and the ceiling height is 44 metres. The dimensions are almost the same as an Olympic-size handball pitch.

Installation of the penstock will start this month. The penstock is at the end of the vertical shaft which conducts water from the inlet in the water reservoir down to the power station.

But that's not all. The spiral casing is on its way from the factory in China. The spiral casing is a snail shell-formed pipe which distributes the water flow into the turbine's guide vane. The installation at Nedre Røssåga is no mean feat; the casing weighs a total of 120 tonnes.

TBM drilling

Tunnel work is also ongoing. Whereas the outlet tunnel is being blasted in the conventional manner, the headrace tunnel is being excavated using a tunnel boring machine (TBM). It is the first time since the beginning of the 1990s that a TBM is being used in Norway.

"The machine is running smoothly and excavates about 125 to 150 metres per week," Nilsen explains.

A total of two million cubic metres of rock will be excavated during the project.