Électricité de France (EDF) has announced plans to outfit more of its operations with Thordon’s SXL polymer radial shaft seals, following the successful implementation of this technology at one of its key power plants.

La Rance Power Plant, situated in Brittany and operated by EDF, is one of the world’s largest tidal power stations. With 24 turbines boasting a peak output of 240MW and an average of 57MW, the facility’s annual power output is about 500GWh.

The plant’s original shaft seals – made of an ultra-high molecular weight polyethylene (UHMWPE) and carbon graphite material – required replacement due to their poor longevity and performance, explained Axel Swanson, Thordon Bearings’ Business Development Manager – Hydro, Pump & Industrial.

“We knew from experience that SXL seals not only perform substantially better than UHMWPE and carbon seals, but they significantly reduce leakage rates and extend the wear life far beyond the original installations. Thordon SXL shaft seals have a typical wear life of more than 15 years.

“For the EDF plant we came up with an improved radial seal design that would fit into the existing housing. Thanks to our industry-leading expertise in hydro turbine seals and bearings, EDF was convinced the new SXL segmented seal was the right solution for this application. Initial trials were a huge success,” said Swanson.

During the retrofit process, the outdated seals were replaced with Thordon’s SXL segmented shaft seals, facilitated by the company’s authorized distributor for France, Wenex Equipements SA. The SXL seal is unlike traditional shaft seals in that the elastomeric polymer material used is specifically designed to optimize performance and reduce operational costs.

“The SXL segmented shaft seal has several unique features that make it a perfect match for EDF’s needs,” said Laurent Le Trouher, Wenex Equipements’ Area Sales Manager. “Installation and replacement of all seal components can be carried out without removing the shaft. The main advantages of an SXL shaft seal over the carbon type, are reduced leakage, extended wear life, design flexibility, and a very robust material. Carbon-based seals can be brittle and break easily during installation. The SXL seal, however, lends itself to installation and operational simplicity. It is also easily maintained.”

Thordon’s segmented seals can be tailored for shafts of up to 3.9m (12.7 feet) in diameter, with operational parameters closely mirroring those of carbon graphite or phenolic seals. They can be designed for use in either radial or axial sealing systems.

Le Trouher welcomed EDF’s decision to invest further in Thordon’s products. “After being in service for one year, the utility has expressed its satisfaction with the performance of the new Thordon SXL seals and ordered a second set.”

When the La Rance facility, located on the estuary of the Rance River, in Brittany, France, opened in November 1966, it made headlines as the world’s first-ever tidal power station. It remained the world’s largest until 2011, when South Korea’s Sihwa Lake Tidal Power Station started operations.