Significant operating and economic benefits can be realized by replacing a poorly functioning or damaged oil-lubricated turbine guide bearing with a water-lubricated design (Figure 1), as part of a well-planned hydropower refurbishment or overhaul project.

1. Endesa replaced an oil-lubricated turbine guide bearing at its Prada plant with the water-lubricated design shown here. Courtesy: Thordon Bearings

“Future maintenance is simplified because the water-lubricated bearing allows the shaft seal assembly and the turbine guide bearing to be arranged in an uncomplicated and compact arrangement,” said Greg Auger, Thordon’s business unit manager for Hydro & Clean Power. “The seal assembly can be easily accessed, the oil sump and lubrication system will be replaced with a simpler water supply system, and the bearing itself can be quickly inspected or replaced, in case of damage, by renewing only the non-metallic bearing insert in a matter of hours.”

There is, of course, an important environmental aspect too; there is no danger of leaking oil into the river, eliminating any pollution risk at its source.

Water-lubricated bearings have been used successfully in practice around the world since the earliest installations of hydro turbines, utilizing wooden blocks or staves to support the turbine shafts, then evolving to rubber, and eventually utilizing advanced synthetic elastomer materials. Thordon’s water-lubricated bearing technology is suitable for Francis or Kaplan turbines in vertical or horizontal configurations, assuming that careful thought is given to critical design considerations.

“The conversion of turbine guide bearings from oil to water lubrication is a technically and economically feasible solution,” said Auger.

Thordon Bearings is a pioneer in the development of premium bearing and seal systems for water-lubricated applications (Figure 2). With several recent conversions completed, the company has demonstrated that a well-engineered water-lubricated design can eliminate the risk of turbine oil leakage, as well as solve ongoing maintenance and repair problems associated with older equipment.

2. The shaft seal may be located below or above the turbine guide bearing, depending on whether a water-lubricated or oil-lubricated bearing solution is used. This image shows a Thordon SXL segmented shaft seal being installed. Courtesy: Thordon Bearings

The company continually works with customers worldwide to identify opportunities to incorporate water-lubricated bearings into planned rehabilitation projects. During a recent six-month period, Thordon supplied water-lubricated bearings for installations at hydropower stations in Austria, Bulgaria, Canada, the Czech Republic, France, India, Italy, Spain, Sweden, and the U.S.

Endesa, Spain’s largest utility, has converted eight existing power stations to Thordon’s water-lubricated solution. The first conversion, in 2010, involved a Voith Kaplan vertical turbine at the Lleida plant. That was followed by a similar project at Endesa’s Termens hydro plant in 2012. Two similar conversions were completed at the company’s Prada plant. The first Prada vertical turbine—a Francis type with a 500-millimeter shaft running at 600 rpm at 300-meter head—was converted in 2015, followed by a second unit in 2016.

—Edited by Aaron Larson, POWER’s executive editor.