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Ropeway With Nord Industrial Gear Units

by editorial staff WORLD OF INDUSTRIES


Located at an altitude of 2,100 metres, Tignes is one of the highest villages in Europe. Connected to the Val d’Isère, it is one of the most luxurious skiing regions in the French department of Savoy. When modernising the ropeway on the Grande Motte, the Swiss company Garaventa, which specialises in ropeway construction, relies on the reliable and low-maintenance industrial gear units from Nord Drivesystems.

The Société des Téléphériques de la Grande Motte (STGM) operates a total of 44 mountain cableways, from simple ski lifts to cable cars. The ropeway to the Grande Motte is one of the most important ones. It starts at an altitude of 3,038 m at the mountain station of the underground funicular from Tignes and ends at 3,454 m in the glacier area of the Grande Motte. At 3,656 m, this glacier is one of the highest peaks in the region and lies at the heart of the Vanoise National Park. Due to being well developed and its extraordinary location, skiing is possible here into summer. For ambitious mountaineers, this is also an ideal starting point for mountain and glacier tours. Snow depths between six and ten metres attract up to 20,000 holiday visitors to the Grande Motte.

A second life in high mountains

After two years in construction, the ropeway started operation at the Grand Motte on Christmas Eve in 1975. Since then, it has been transporting up to 1,010 people an hour in each direction at a length of 1,696 m and a maximum inclination of 55 %. In spite of meticulous maintenance, the harsh alpine weather conditions with ice, snow, storm and rain, as well as 30,000 runs a year take their toll on this engineering masterpiece. After more than 40 years, an overhaul of this important facility became necessary. Although the safety of ropeways is particularly strictly monitored, time did not pass without leaving a trace on the drive technology and the cabins. Maintenance costs and effort increased while the passengers’ comfort was no longer up to date.

From 2016 to 2018 and after a carefully thought-out planning phase, the ropeway was overhauled, technically modernised and equipped with new cabins in three project stages. A central point of the project was the refurbishment of the complete drive technology using a Nord drive system. In addition, bearer and pulling ropes were replaced. The Doppelmayr/Garaventa Group is responsible for this project. The technology and market leader in ropeway construction has already implemented over 15,000 ropeway systems worldwide and is also very familiar with the special challenges of retrofitting old facilities. The restored ropeway was specially designed by Garaventa to withstand the extreme weather conditions in high alpine terrain.

New cabins with panoramic view

Each of the two ropeway cabins carries 100 people. The Swiss cabin specialist CWA has not only equipped them with the required travelling comfort inside: As a special highlight, they have an open observation deck on the cabin roof. This way, up to 20 people can enjoy the stunning panorama view during summer. 80 people can travel inside the cabins. It is thus the world’s largest ropeway with an observation deck. The observation decks are dismantled in winter. Depending on weather conditions, the ropeway can reach a maximum speed of ten metres per second. In this case, the entire distance is covered in five minutes.

Immense forces are safely absorbed

When it comes to ropeways, the safety of people is paramount as lives can quickly be put at risk in the event of malfunctions. For this reason, certain technical calculations are based on a five-fold safety margin. The bearer rope balance weight is 150 t per track. In other words, each of the four bearer ropes must bear a weight of 75 t. Due to the exposed location and the extreme weather conditions, a hydraulic damping system, which can absorb the forces occurring when ice drops off the ropes can also be activated for the balance weights. A 46 t pull rope balance weight ensures the correct tension of the pull rope loop. The 49 mm thick bearer ropes weigh 13.5 kg per metre. Ice may double or even triple this weight and increase the cable diameter up to 240 mm.

Optimally matched drive technology

For this ropeway project, Nord Drivesystems supplied Garaventa AG with two ready-to-install industrial parallel gear units as well as pre-assembled couplings and flywheels supplied by KTR Systems GmbH. Nord Drivesystems’ strengths include not only particularly high speed and flexibility in project implementation but also the very compact design of its Unicase housings that up to size 15 allow for high torques of up to 250,000 Nm in relation to the frame size. The compact design was especially important because there was limited space in the existing buildings of the Grande Motte ropeway. For this reason, interfacing connections had to be relocated individually and peripherals designed accurately to match the given dimensions of the safety enclosure.

Tried and tested power packs in a Unicase housing

The two-stage Maxxdrive industrial parallel gear units from Nord Drivesystems in the second largest size 14 are characterised by a high power density, quiet operation and top reliability. Large rolling bearings ensure high axial and radial load capacities and a long service life. These drive technology heavyweights also offer a modular, flexible design as well as wide range of mounting options. This makes the robust parallel and right-angle gear units in one-piece Unicase housings ideal for a great number of heavy-duty applications. For example, Nord has already fulfilled many projects for complete drive systems based on industrial gear units, for heavy-duty operation with motors and drive electronics for tasks including conveyor technology, pumps and agitators.

Daniel von Rickenbach, the sales manager of the Swiss Nord subsidiary Getriebebau Nord AG considers the project in Tignes an important reference: “Our industrial gear units are convincing in practice on the Grande Motte and supply best performance data. In passenger transport, this application thus proves what we already know from use under significantly harder physical conditions in conveyor systems in mining and cement industries: Industrial gear units from Nord Drivesystems are the first choice if absolute reliability and safe operation are required.”

Safety for all eventualities

The particularly high safety demands on products implemented in ropeway technology are a vital factor. For this reason, the ropeway is equipped with a redundant drive system in a mirrored configuration. The drive axis protrudes on both sides of the large central 2,800 mm diameter cable pulley driving the pulling rope. Both sides are each connected with an identical drive system. Each of the two air-cooled 600 kW strong main drives is connected to the drive side of a Nord industrial gear unit via a torsionally flexible claw coupling with brake disc. The brake disc provides additional centrifugal mass. An additional brake disc is mounted on the drive axles on the opposite side of the housing of the industrial gear unit. The four brake discs are each equipped with a spring-operated, fast-acting service brake. In case of a power cut, for example, the drive axes can be slowed down quickly but gently via the operating brakes as hard braking should be avoided whenever possible. The brake discs’ high inertia supports the gentle braking process and prevents danger and inconveniences for the passengers. In normal operation, drive shafts are braked by the drive’s frequency inverter.

Equipped with multiple evacuation options

A torsionally flexible coupling with electrically insulating, flexible buffers establishes the connection to the drive pulley on the respective output side of the industrial gear unit. With this coupling, the respective drive can be disengaged for maintenance and overhaul inspection. Then the ropeway can continue to operate with half load at full speed or at half speed with full load.

The same applies for a special operation, in which the second drive chain stays engaged and rotates without load. In normal operation, the drives share the load.

When starting up with an acceleration of 0.3 m/s2, the maximum torque at the cable pulley is 135 kNm while in operation it is 110 kNM. Two spring-applied safety brakes on the drive pulley can lock it at a standstill. A hydraulic emergency drive is available and can be switched on for an evacuation run. This drive then engages in a gear rim on the drive pulley. An emergency power generator provides the necessary energy. The gear unit is then also rotated. If the cabins fail to be moved back to the station in case of a malfunction, a simple rescue ropeway is ready at the top station on each side of the cable. This is then hooked in and can be moved up to the cabins by a diesel-driven winch for evacuation.

Successful commissioning and test phase

Damian Zenklusen, Project Manager for Engineering Special Ropeways at Garaventa, carried out the modernisation project with his team: “In the initial phase of operation, vibration levels and gear oil have been analysed. The results show that the industrial gear units and the complete drive system work perfectly and as intended. The mechanical components are of high technical quality.”

“This is our claim: to always realise the best solution for the customer, both technically and economically.” Daniel von Rickenbach confirms. Jean-Dominique Maurin also draws a positive conclusion: “Garaventa builds the best ropeways in the world. The ropeway is an infrastructural centrepiece for opening up the Grande Motte for skiing and mountain tourism. This is why highly reliable technology is indispensable. The result of the retrofit meets all our expectations. The new electromechanical components, especially the drives and gear units, work absolutely economically and reliably.”

Source: Nord Drivesystems

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