When one hydroelectric plant operator took an environmental stance against water pollution, it went cold turkey on its use of grease in its plants.
Grease is a common lubricant on bronze bushings, ensuring that the bronze bushings can move easily since the coefficient of friction is reduced with grease. However, since grease needs to be reapplied regularly, large amounts of grease are applied in a hydroelectric plant that uses bronze bushings.
With the environmentally-conscious decision to remove grease from its operations, the hydroelectric plant company, which currently manages a portfolio of diverse renewable energy assets, had the satisfaction of knowing that it was improving the water quality on the various waterways on which it operates in the US.
However, the decision significantly affected the wear of its bushings, particularly its wicket gate bushings, since bronze bushings immersed in water show considerable wear without the application of grease.
The bushings showed rapid wear and there was considerable wear on the wicket gate stems — the cylindrical shafts or journals to which the wicket gates are attached and that run inside the wicket gate bushings, describes the engineer that has been managing the company’s hydroelectric plants for several decades.
“Composite materials were offered as a solution, promising low friction and a reduced wear of the stems,” he says of the company’s first attempts to overcome the problem of wear on unlubricated wicket gates.
“The first composite materials that were used to replace the bronze in the 1980s had some problems, from seating problems to water swell that caused wicket gates to seize,” he notes.
Then in the early 2000s, the company introduced Vesconite Hilube wicket gate bushings, and experienced little swell, good resistance to abrasive wear and high strength.
The company continues to use Vesconite Hilube wicket gate bushings where it is the contractor on hydroelectric plant maintenance projects.
“The avoidance of emitting lubricants in the waterways is based on State regulations,” says the engineer.
The acceptable limits and reporting duty vary from State to State but the head office of the renewable energy company in New York has taken the stance of avoiding all emissions, he says.
Since the company employed Vesconite Hilube wicket gate bushings (also known as guide vanes) in the 2000s, their use represents some of the longest test cases of Vesconite Hilube in this application.
The engineer notes that the environment and lubricant is ordinary river water, the quality of which varies considerably.
“In hydro plants that are located on a dam with a large storage reservoir the water is usually clean because sediments settle out,” he says.
“In ‘Run of the River’ plants, the reservoirs are small, and, at high flows, there is not enough time to eliminate the sediments,” he comments, noting that the abrasive content varies naturally from river to river, but also seasonally as the peak flow seasons churn up more sediments.
The engineer notes that the wear rate of the wicket gate bushings and stems is affected by this, and the duration of operation between repairs varies.
“There is a vast reduction in wear from the Vesconite material compared to bronze in all cases,” he states.
The company that runs many hydro projects, as well as wind, solar, distributed energy and other projects, aims to operate a high-quality clean energy portfolio responsibly.