The Challenge: Andritz Hydro AB helping hydropower look to the future

The hydropower plant in Laxede on the river Luleälven was built more than 50 years ago. The turbines in two of the three units are now being refurbished and, for the first time, the runners will be replaced – a challenge taken on by Andritz Hydro AB. “This is the largest impeller we’ve replaced to date,” says Åsa Eklund, System Engineer at Andritz Hydro AB.

Hydropower currently meets about 16 percent of the world’s total electricity needs. For Sweden the figure is about 45 percent. Andritz Hydro AB is a highly respected company with more than 175 years of experience in turbine design. The Andritz Group is a global leader in hydraulic power generation and electro-mechanical systems and services for hydropower plants.

The majority of the hydropower plants along the Luleälv River, in the far north of Sweden, were built from the 1950s through to the 1980s. Many of them are now beginning to show their age and are in need of refurbishment.

The hydropower plant in Laxede, 100 kilometres from the mouth of the Luleälv River, is normally unmanned. But while refurbishment is underway, about 25 persons will be working at the plant. The water that normally flows into the facility to drive the runner in the unit that is being refurbished, has been diverted. The runner has been removed along with all other technical gear.

Gunnar Engström from Vattenfall is the project coordinator. He guides us around the site, where both Vattenfall employees and consultants are working. “This is a big project for us,” he says.

The second turbine will be replaced in 2015, while the third, which is much newer, is in full production.

The contract was signed with Vattenfall in 2011. Shortly afterwards, intense work started on calculations, design and manufacturing. The dismantling of the unit started in August 2013. Andritz Hydro AB has five people working at the site. Åsa Eklund from Andritz Hydro AB is responsible for technological matters.

“Even if you do careful studies regarding what to renovate, it is only when everything is dismantled that we can see exactly what needs to be repaired.” The runner, situated at the very bottom, will be completely replaced.

“The new runner has been designed by Andritz Hydro AB,” says Åsa Eklund.

In order for the work to be carried out as smoothly as possible, Andritz Hydro AB has chosen to use Superbolt tensioners from Nord-Lock to secure the blades.
“We began discussions with Nord-Lock about a year and a half ago, and after a couple of months’ work, we decided on the SB12 Superbolts.”

Andritz Hydro AB has previous experience of working with Superbolt nut-style tensioners and they are being used in the runner.

“However, this is the first time we’re using SB12 Superbolts,” she says. “But this is also the largest runner we’ve assembled so far – 6.5 metres in diameter.”

If they had worked with conventional bolts, she explains, the tools they would have needed for tightening the bolts would have been very large.

“This would not have been good from a work environment perspective, when people are working at a height of a couple of metres.” They can now manage with a normal-sized standard hand tool, barely one metre long.

“This means that more people can work on installation simultaneously and, consequently, the job is completed more quickly.”

Another benefit is that it is very easy to check how hard the screws have been tightened. “We can constantly and easily measure elongation to attain the right preload we have calculated.”

Åsa Eklund appreciates the collaboration with the Nord-Lock Group.

“Nord-Lock’s personnel are very service-minded. As an example, we needed advice on mounting an M375 Superbolt nut that would be fitted with stainless steel against stainless steel. Nord-Lock sent up one of its experts and we received excellent support.”

Inside the power plant, Magnus Ekman from Andritz Hydro AB is busy securing the blades on the runner using the SB12 Superbolt tensioners.

“It’s easier than working with regular bolts,” he says. “It’s simpler when there are several small bolts instead of one larger bolt.”

The units they are now refurbishing will be completed and back in service in May 2014. Work will begin on unit number two the following year.

“It feels really good to work with these bolts from a technical perspective, which means it’s good for the guys who install them, too,” says Åsa Eklund.

Facts: Andritz Hydro AB
About: Supplies equipment and services for new hydropower plants and refurbishes older plants.
Part of: The Andritz Group’s parent company is in Austria. The Head office is in Graz but the company and its various subsidiaries are represented in nearly every country in the world. Besides hydropower, the Andritz Group also operates in the pulp and paper industry, among others.
Total number of employees in Sweden: 320, of which 155 are in the Hydroelectric industry.

Business argument

This forms the basis of Andritz Hydro AB’s decision to choose Superbolt tensioners from the Nord-Lock Group.

  • Work environment: It is not necessary for us to use large and heavy hydraulic drivers.
  • Sustainability: We can guarantee a better work environment when and if service is necessary at the runner.
  • Safety: Superbolt MJTs can be safely utilized in confined and obscure installation conditions.

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