Thordon Bearings’ brake cups are being supplied to Hydro-Québec, the largest hydropower company in Canada, as part of a decade-long turbine brake system overhaul program.
The Burlington-based bearing and seal specialist is providing the brake cups to its Canadian distributor RMH Industries, an integrated company specialising in mechanical and hydraulic repair and machining of oversized parts. RMH Industries has been manufacturing and repairing brake blocks for Hydro-Québec since 2020.
Repairing brake blocks
Forty-eight Thorseal brake cups will be delivered for installation to the Manic-2 station (the Jean-Lesage generating station) in Québec, after previously supplying them to the Churchill Falls, NL station. While Manic-2 deliveries continue, Thordon is also supplying the first cups for the Bersimis-2 station.
Each brake block is generally made up of two to four pistons, depending on the size of the power plant
One hydro-turbine typically has 8-12 brake blocks. Each brake block is generally made up of two to four pistons, depending on the size of the power plant. The cups are a critical component of the pneumatic/hydraulic braking system, because they ensure a seal is maintained for the pistons that are used to slow and stop the turbines.
Potentially catastrophic failure
The hydro-turbines typically weigh hundreds of tons and if the braking system were to fail, the thrust bearing could be subject to excessive load, leading to wiping and potentially catastrophic failure.
The brake blocks are also used to lift the turbine, and if low quality seals result in significant leakage, this operation cannot be performed. The brakes are located under the turbine, making them difficult to access. The dimensions of the cups can vary considerably. For the Manic-2 power station, the Thorseal self-lubricating polymer lip seals are 152mm (6in) in diameter with 177-203mm (7-8in) lip.
Oil-lubricated alternatives
Thordon’s Thorseal brake cups are made from a proprietary elastomer that has no shelf life
Ryan Edmonds, Business Development Manager for Hydro Power at Thordon Bearings, notes that unlike slightly cheaper rubber cups, Thordon’s Thorseal brake cups are made from a proprietary elastomer that has no shelf life or degradation of properties over time.
“The Thorseal material will not crack, so it eliminates the risk of slow wind down that can damage fragile babbitt sleeve bearings,” he said. Thorseal brake cups provide long wear life with no need for periodic replacement due to their internal lubricant that reduces drag more effectively than oil-lubricated alternatives.
Operating mechanism bearings
Operators of many other hydro facilities around the world are considering brake system refurbishment programs, said Edmonds. “Saving a few thousand dollars on low-quality cups is not a wise investment when the catastrophic consequences of failure could result in extensive downtime and tens of millions of dollars in repairs.”
Thordon Bearings designs and manufactures a complete range of high-performance, long-lasting hydro-turbine bearing system designs that require no oil or grease, including turbine guide bearings, wicket gate and operating mechanism bearings, and radial or axial shaft seals.
