Serving Whitman County since 1877
Serving Whitman County since 1877
Activity hums at Lower Granite Dam, with an annual maintenance project wrapping up, replacement of original strainers and a backup generator, and a large-scale turbine repair project in the preparation stage.
In July, crews started going through all six power generating units at the dam, part of annual maintenance which also includes an in-depth overhaul of one unit - No. 6 this year.
For each of the wide circular units, workers perform a slew of tasks, such as setting and re-setting switches, draining and purifying oil, recalibrating sensors and testing functionality.
On the No. 6 unit, they took it further. Beginning in July, workers de-watered the turbine and took much of it apart, including the hydraulic governor – the device that monitors the speed of a generation unit – and various sensors which operate like a breaker in a house.
To take water out of a turbine, workers first put a bulkhead, like a valve, in front of and behind the turbine and pump the water out.
The No. 6 tasks were completed Aug. 8 when the crews moved onto finishing the yearly maintenance on the five others. All will be complete by the first week of September.
At full capacity, each single unit can power all of eastern Washington with the exception of metropolitan Spokane.
In addition to the general maintenance work this summer, three of the original exciters are being replaced, along with the dam’s original strainers and backup generator.
Andritz Hydo – an Austrian contractor with an American base of Charlotte, N.C. – is changing out three of the six exciters, which are the pieces which put electricity into the generator.
“It takes a little electricity to make electricity,” said Bob Lustig, Chief Maintenance Officer at the dam.
Three of the exciters were replaced two years ago. This year the final three are being switched out. All six of the small-closet sized boxes were original to the 1975 dam.
The strainers being replaced for the first time at Lower Granite are steel-housed, and are used to filter twigs and other debris from the water used to cool the plant.
The backup generator will be retired in favor of a new one this year as well.
“The dams were really well-built, stout structures,” said Lustig. “We do this to make them last another 30 years.”
All the while, the contractor has arrived on site for the fall’s turbine cavitation repair project.
Cavitation involves building a new, clean surface for turbines and turbine walls, to combat the nicks and scratches of years of use. The work will be done by Hydro Consulting and Maintenance Services, Inc., of Spokane.
“It’s putting on a new coat of paint, except it’s metal,” said Stephen Doherty, Public Affairs Specialist with the Walla Walla District, U.S. Army Corps of Engineers.
While the turbine being worked on is shut down, the others will take up the slack.
It is common for turbines to be shut on and off as the Bonneville Power Administration adjusts the amount of electricity being generated at each dam.
During normal operation, the power generation units – which each house a turbine – can be turned on and off within seconds, as hydroelectric power is used as a checks-and-balances mechanism on the power grid. Since the hydroelectric system has to be balanced – and there is no ability to store power in the system – oftentimes the units are shut down to account for excess power from other sources, such as the coal plant in Boardman, Ore. and the Hanford nuclear plant, near Richland, Wash.
Garth Meyer is a former Whitman County Gazette reporter.
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