The Limmern pumped-storage plant excess power created during off-peak periods can be saved or converted into valuable peak-load energy. Axpo was engaged for the planning and construction. With more than 6000 employees, Axpo is the largest Swiss producer of renewable energy and an international pioneer in energy trading and in the marketing of solar and wind power.
For Axpo, the Limmern pumped-storage plant of Kraftwerke Linth-Limmern AG became one of the most important expansion projects of recent years in the area of renewable energy. A total of 2.1 billion Swiss francs was invested. The Limmern pumped-storage plant has an output of 1000 MW, and in effect it acts as a giant battery in the middle of the Swiss Alps.
In this project the topic of safety was implemented holistically, starting as early as the planning stage. Find out below how this power station was protected against falls, and the challenges which had to be overcome.
The challenges
The Limmern pumped-storage plant was installed underground inside the rock, and is now able to pump the water from the Limmernsee reservoir back up to the Muttsee reservoir, which is located 630 metres higher, in order then to reuse it for power generation as required. The Muttsee reservoir, which used 250,000 m3 of concrete in its dam wall, can hold 23 million m3 of water.
Both in the Muttsee dam wall and in the lower-lying Limmernboden dam wall, inspection patrols must be performed regularly to identify possible cracks or other changes in the structure. Routine checks also have to be performed on other measurement instruments in the dam walls. These indicate possible movements, and report them to the control centre in the valley below. If these deviations are outside tolerance, then in the worst case an alarm is triggered and appropriate measures are taken to protect the population.
Because of the routine and safety checks, it is necessary to access the interior of the dam walls. A number of danger areas exist in high dam walls such as the Limmernboden dam wall (maximum height 146 m). These areas have to be protected against falls.
The principal danger here is inclined descents. The Limmernboden dam wall has steps with an inclination reaching 52 degrees. For additional hold, some of these have a handrail on one side only. The danger of slipping or sliding is increased here by an adjacent drainage channel which takes away seepage water.
There is also the challenge that runs of steps approx. 20 metres long are then followed by a platform only a few metres in length, before the next set of steps commences. If a fall were to occur here, this would have severe consequences for the person in the danger area. A fall from such a height would be unstoppable.
For this reason, a fall protection system is absolutely essential. These safety solutions have to protect the service technicians and workers when accessing these steeply inclined inspection route sections. Last but not least, the delivery of the materials required for building the hydro-electric plant and installing the safety solution was hampered by the location of the dam wall at around 1800 m above sea level, and by its accessibility only via a tunnel roughly 3km in length.
TAURUS as fall protection within the Limmernboden dam wall
In order that the service technicians and maintenance personnel can move in safety on the steep steps between the inspection routes, the TAURUS rail safety system was installed. However, development of a reliable safety concept in advance was the top priority. The Taurus system provides protection along the handrail for the steps, preventing a fall downwards or into the adjacent drainage channel.
The TAURUS-GLEIT-A31 slider, specially developed for the TAURUS ALLROUND, allows protected and unobstructed movement along the system. In general, TAURUS ALLROUND protects ascents and descents in this area, and even transitions represent no challenge for the safety system made of aluminium rails.
Thanks to the short lanyard and the slider’s space-saving integrated energy absorber, the anchor point always runs close to the person positioned in the danger area. Amongst other things, this prevents the danger of falls.
The fall protection system is installed on the concrete wall of the steep tunnelled stairs between the inspection routes of the dam wall. It uses standard components: the TAURUS-RAIL-10, BEF-21, 2-component mortar, and 16 millimetre threaded rods. The TAURUS-BEND provides simple and effective onsite adaptation of the rails to the structures actually present in the dam wall.
4 advantages in favour of TAURUS
- Reliably prevents falls, through the installation of the fall protection system along the handrail for the steps, and the use of a short lanyard.
- Protected movement along the steep ascents and descents, thanks to the robust rail system.
- Continuous protection, because the rail system also protects the transition from a vertical to a horizontal plane.
- Great flexibility, thanks to the onsite adaptability of the aluminium rail.
Summary
Thanks to the TAURUS ALLROUND rail system, it has been and will in future continue to be possible to ensure the safety of the service technicians and maintenance personnel of the Limmern pumped-storage plant. While the pumped-storage plant sustainably increases security of power supply in Switzerland, the TAURUS fall protection system ensures that fall risk is eliminated and thus protects the safety of the workers onsite.
If you want to know more about fall protection systems for hydro-electric plants, simply contact us. Our experts will be pleased to help and advise.
Photo rights: Axpo Holding AG
