Pumped hydropower stations provide a sustainable source of energy, generating during the day and pumping water back to the storage reservoir at night. The pumping station is crucial to the operation of the plant, so when one of the 13-tonne (14.3-ton) pumps at a remote Norwegian site needed to be repaired, the operator called on Sulzer’s engineering expertise.

Located between Bergen and Oslo, the Skarje Pumping Station was put into operation in 1987. Three Ahlstrom pumps are situated 150 meters inside a mountain and deliver water to a reservoir 100 meters above using 2.8 MW motors. Each pump is a 3-stage vertical column design and they have been operating reliably for nearly 35 years. However, the remote location of the pumping station means that during the winter months it is inaccessible due to heavy snowfall – an issue that remains until spring. As a result, the operator was keen to achieve a timely repair when one of its pumps required an overhaul.

The design of these pumps allows for some leakage past a mechanical seal, but after decades in service, one of the pumps had a significant leak that was overwhelming the return pipework. The maintenance team at the hydropower pumping station removed the equipment from service and dismantled it, with the aim of replacing the seal.

During this process, they discovered that one of the spider bearings was also damaged and that additional support would be needed to complete the repairs. The team contacted Sulzer to see what could be done to restore the pump so that it could quickly resume operations.

The dismantled pump was transferred to the local Sulzer service center where further investigation continued. One of the first discoveries was that the drive shaft, which is split into two sections, was bent. Discussions with the operator resulted in an agreement that trying to straighten the shafts may not be the best solution. At 175 mm in diameter and up to 5.5 m in length, the best solution for perfectly straight shafts would be to install new ones. On the positive side, the impellers were in excellent condition, especially after so long in service.

Having decided to manufacture a new set of driveshafts, Sulzer could source the OEM drawings and all the machine tools necessary to complete the process in-house. Sulzer’s service center in Finland has taken on the role of Ahlstrom experts and was able to provide all the necessary knowledge and equipment to complete the repair of the driveshafts.

Paul Berry, Technical Manager Sulzer Pumps Norway, explains: “The size and weight of these shafts posed a considerable challenge, especially in finding a lathe and grinding machine that could handle them. The fact that we already had the drawings meant we could streamline the manufacturing process without having to reverse engineer the dimensions.”

In the meantime, the damaged bearing housing was metal sprayed and machined back to OEM dimensions. Once the new shafts were ready, the pump was reassembled in Norway, with all new bearings, seals, and wear rings. When the roads to the hydropower pumping station became clear again, the pump was returned to the site and recommissioned.

Paul Berry concludes: “In Norway, hydroelectric power accounts for more than 95% of the national supply, and for the pumped storage systems it is essential that the pumps are kept in optimum condition. To support customers, our local service centers can deliver turnkey overhaul projects enhanced by our pump design and manufacturing capabilities. For this operator, we have ensured their hydro facility will continue to operate efficiently for years to come.”

Sulzer is a global leader in fluid engineering. We specialize in pumping, agitation, mixing, separation and application technologies for fluids of all types. Our customers benefit from our commitment to innovation, performance and quality and from our responsive network of 180 world-class production facilities and service centers across the globe. Sulzer has been headquartered in Winterthur, Switzerland, since 1834. In 2021, our 13’800 employees delivered revenues of CHF 3.2 billion. Our shares are traded on the SIX Swiss Exchange (SIX: SUN).

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