Ten Allison-equipped Astra HD8 trucks make tunnel excavation duties productive, reliable and easier at the Nant de Drance and Linth-Limmern power plants.
The new construction of the pumped-storage power plant Nant de Drance in the canton of Valais calls for a fleet of robust, productive excavator trucks. The new underground hydro power plant is going to supply the future energy needs of Switzerland and its public transport system. Last spring, the construction consortium GMI (Groupement Marti Implenia)responsible for constructing the tunnel and power plant caverns, and processing of the excavated material, purchased six Astra HD8 (480 hp, 8x6, 48 tonne) trucks with Allison 4700R model fully automatic transmissions. They performed so well, a further order of four identical vehicles is due for delivery until April this year.
The Nant de Drance pumped-storage power plant, situated between two existing reservoirs in the Swiss/French border region between Martigny (Canton of Valais) and Chamonix will generate 600 MW by utilising the water pressure resulting from around 300 m of altitude differential. The plant is being built inside the mountain, at 1,700 m above sea level, with access via a 5.6 km tunnel. The construction consortium started work in January 2009 and will probably finish by 2017.
The 1 billion CHF (682 million Euros) project is being undertaken by Alpiq AG (formerly Atel), the Swiss Federal Railways SBB and the canton Valais with its electricity company FMV. The plant will cover consumption peaks of the Swiss Federal Railways, while ensuring a stable energy supply to the country's electricity network. During the night and weekends, when electricity demand is lower, the water in the lower lake will be pumped into the upper reservoir, where it is available for energy production when needed. The position of the two lakes is ideal: they are close, but with a big difference in altitude (2,205 m and 1,930 m above sea level).
Niklaus Zaugg, Mechanical Engineer, Groupement Marti Implenia, whose task it was to select and specify the trucks says, “Our site is 2,000 m above sea level and the access route in winter is impassible. For this reason, we work from April to November, 24 hour a day, on three shifts. It goes without saying, having strict deadlines to achieve our priority is to have absolutely reliable vehicles, which are productive and easy to drive.”
Astra's robustness and heritage in the heavy-duty dump truck sector combined with Allison's 4700R fully automatic transmission has fully met those needs. The transmission is specially designed to operate in the most difficult conditions, providing maximum driving comfort, uninterrupted power to the wheels and increased control of the vehicle at lower speeds. The transmissions, fitted to each of the 10 Astra HD8s, were ordered with integral hydraulic retarder, partly due to the slope of 12 per cent leading to the access tunnels, which often needs to be mastered with a fully-laden vehicle.
“The road to get to the landfill for the excavated material is very steep, and the automatic transmission's retarder simplifies operations a lot and provides extended brake life,” says Zaugg.
The transmission's torque converter, a fundamental component of Allison product, is a key contributor to reducing maintenance costs and providing unrivalled performance. Torque multiplication delivers superior vehicle startability on steep gradients, precise control under heavy load conditions and constant vehicle acceleration for safe operation on any type of terrain. With no requirement for a dry disk clutch – as found in manual and automated manual gearboxes – associated maintenance tasks are eliminated.
Another important consideration for the Swiss construction consortium was the change of drivers across the three daily shifts. As Niklaus Zaugg points out, “Our personnel working in tunnels are not used to driving all types of trucks, so it's very important to us that vehicles are easy to manoeuvre. Only fully automatic transmissions can ensure an operation free of bad surprises, like clutch failures resulting from wrong manoeuvres and subsequent downtimes for servicing. With Allison's automatics, our operators were able to drive the Astra HD8 from the very first day.”
“We are very satisfied with the trucks and by the premium service offered by Astra. Our new order just confirms it,” concludes Zaugg.
That's not all. One of the Astra HD8 trucks purchased by the Groupement Marti Implenia is presently being used on the construction site of another important Swiss power plant project, Linthal 2015, which will see the Linth-Limmern hydroelectric power plant optimised to generate 1,000 MW power. This investment totals approximately 2.1 billion CHF (1 billion 600 million Euro). Once completed, water will be pumped 650 m from the Limmernsee lake up to the Muttsee lake for electricity production.