John Day Dam team works on fixes big and small

After Main Unit 7 began leaking oil, the design team at John Day Dam began looking for a better solution than pinning the turbine blades. Previous solutions meant disassembling the turbine to replace the O-rings used to seal the oil into its chamber, a four-month job. (Corps of Engineers photo)

After Main Unit 7 began leaking oil, the design team at John Day Dam began looking for a better solution than pinning the turbine blades. Previous solutions meant disassembling the turbine to replace the O-rings used to seal the oil into its chamber, a four-month job. (Corps of Engineers photo)


By Diana Fredlund, Public Affairs Office

Big equipment often means big challenges, but less expensive, smaller-scaled solutions to problems often spring from teams looking at those big challenges. Turbines can be two stories tall, which can pose big challenges for the engineers and maintenance staff responsible for keeping them humming.

John Day Lock and Dam, located about 100 miles east of Portland, Ore., houses 16 turbines in its powerhouse. A study determined that up to half of them could be pinned and the powerhouse could still efficiently generate hydropower. (Corps of Engineers photo)

John Day Lock and Dam, located about 100 miles east of Portland, Ore., houses 16 turbines in its powerhouse. A study determined that up to half of them could be pinned and the powerhouse could still efficiently generate hydropower. (Corps of Engineers photo)

The John Day Dam, located about 100 miles east of Portland, Ore., on the Columbia River is capable of producing 2.2 million kilowatts at peak production; enough to meet the electrical needs of two cities the size of Seattle, Washington.

One of the last Columbia River dams built by the U.S. Army Corps of Engineers, the John Day Dam was completed in 1971 with 16 Kaplan turbines in its turbine gallery. Kaplan turbines use variable pitch blades.  Similar to a fixed blade propeller, a Kaplan turbine can adjust the angle of the blade as it travels through the water – which dramatically increases the operating range of the unit and allows the unit to operate more efficiently.

Introducing more moving parts into a piece of equipment under load – such as water pressure – increases the likelihood that something will go wrong. Engineers call it fatigue failure. Kaplan turbines have a lot of moving parts under load, any one of which can malfunction.

“Turbines operate in harsh environments, with continuous blade adjustments under large loads. With so many moving parts, fatigue failure is always a design consideration,” said Kellen Shide, a mechanical engineer with the Corps’ Hydroelectric Design Center. “In addition, these units are nearing the end of their design life, which means they’ve been operating for 40, 50 or 60 years. The maintenance staff does a great job of monitoring the turbines and keeping them operating reliably.”

In recent years, engineers and mechanics have seen linkage failures in some of the Kaplan turbines. As the water turns the propeller, it spins a set of large magnets past coils of copper wires, called a stator. If a linkage to one of these turbine blades fails, it prevents the whole propeller from functioning properly. There is tremendous vibration and the generator must be shut down to prevent damage to other generator components. As the Kaplan units age, maintenance staff and engineers have seen linkage failures increase.

About two years ago, Main Unit 11 in the John Day turbine gallery experienced a linkage failure. Historically, the only way to repair linkage failures was to disassemble the whole turbine and repair the blade; no small job for maintenance staff and engineers.

“Replacing a Kaplan turbine means the unit would be taken out of service for a year or more and cost millions of dollars. Unstacking, or disassembling, a unit is also a massive undertaking,” Shide said. “We needed to ask, can a repair allow the unit to continue functioning?”

Corps of Engineers graphic image

Corps of Engineers graphic image

HDC completed a regional Kaplan repair study in 2009 that reviewed Kaplan turbines in Portland and Walla Walla districts. “The study found that pinning a turbine blade would allow the unit to operate, but the blades are then in a fixed position, decreasing the operating range and flexibility,” Shide said. “An analysis of the situation found that no more than half of John Day Dam’s turbine units could be operated with blades in a fixed position. After that point the power grid loses too much flexibility and units would need to be repaired back to variable pitch blades.”

Pins are used to lock the blades in a fixed position. The HDC study showed that pinning the blades at 29 degrees was the best compromise between power production and favorable fish passage configuration, Shide said. “This allows the unit to continue operating. It isn’t a permanent condition; if needed we can go back later and repair a unit.”

The project staff assisted contractors who pinned Main Unit 11’s ailing turbine blade, using one of the eight allowed turbine pinning opportunities available to them. “Pinning a unit is still a big job, but it allowed us to get the unit back into service in about four months – much quicker than if we’d needed to restack or replace it,” said Rob Lewis, John Day Dam’s maintenance chief. “Main Unit 11 is up and running again, helping us generate hydropower.”

Another situation that could be solved by pinning the blades began concerning John Day Dam’s maintenance staff: oil leakage.

“Machines need oil to lubricate moving parts, but at a hydropower dam oil can’t reach the river,” Lewis said. “To keep oil away from flowing water, the turbines use an O-ring to seal the contained space. The high pressure on the O-rings can cause the seal to degrade over time and leaks can occur, but replacing the O-rings to stop a leak means disassembling a unit, taking it out of service for months. We needed to find a better solution.”

Pinning the blades could solve the problem since there is no need for lubricant if there are no moving parts. “That was a consideration, but we knew we could only pin eight turbines – why would we use such a big fix for a small leak? If in response to oil leaks we exhaust the number of units we can pin, what happens when we have a linkage failure in another unit? There had to be a better way,” Lewis said.

The design team, made up of John Day Dam maintenance and mechanic personnel and HDC engineers, began brainstorming possible solutions.

“We asked ourselves – what is the bottom line? Keeping oil from leaking anywhere, but especially into places where it could reach the river,” Lewis said.

Work crews installed a bypass pipe that transports oil back into Main Unit 7’s containment chamber. Over time O-ring seals can weaken, but when it happens now, this oil management system will keep the lubricants away from the river and back in the container where it belongs. (Corps of Engineers photo)

Work crews installed a bypass pipe that transports oil back into Main Unit 7’s containment chamber. Over time O-ring seals can weaken, but when it happens now, this oil management system will keep the lubricants away from the river and back in the container where it belongs. (Corps of Engineers photo)

Environmental compliance is one of the Corps’ most important mandates. “One drop of oil in the water is too much,” said Ken Duncan, Portland District’s environmental compliance coordinator. “The Corps has a strong program whose goal is to see no oil reach the water. We work to ensure our containers and our practices are the best they can be. If any spills do occur, we work to stop the leak and clean the spill, coordinating with state and federal water agencies to ensure everyone is aware of our situation.”

With the environmental mission clearly in focus, the design team came up with a relatively inexpensive way to remedy the oil leaks. “The pressure forces oil to find the path of least resistance – and we know that will always happen,” Lewis said. “When the oil leaks past the O-ring, we found a way to block all the paths it could find to the river. The team devised a way to place a vent tube at one of the leak points; the vent tube transports any leaking oil back into the containment chamber. It remains in a closed area that doesn’t allow it to reach other equipment, the floor or the river.”

Best of all, the repair costs less than pinning the unit and leaves that option available for a future linkage failure that might occur elsewhere. “Pinning the unit to stop an oil leak would work, but it reduces the flexibility in the system,” Shide said. “This is a much better solution.”

The oil management solution was installed in Main Unit 7 at the John Day Dam nine months ago, and Marshall Waddington, John Day Dam power plant mechanic, is keeping an eye on the results. “The unit has been back in service since August 2013. We have not detected any leakage since then. This solution proves to be a viable option to a performing a complete teardown of the unit.”

Lewis is proud of the solutions the team developed. “Our design team started looking at the big picture when it came to maintaining this big equipment,” Lewis said. “We could have pinned Main Unit 7 to keep the oil from leaking and called it ‘job complete.’ Maybe that would be complete, but we would have lost a chance to proactively find a better fit. Together we found a solid, relatively inexpensive repair that allows our turbines to continue doing their job – generating low cost, reliable electricity.”

 

Main Unit 7 design team members

Greg Hicks, John Day Mechanic
Jeff Phillips, John Day Mechanic
Charles Davidson,  John Day Mechanic
Marshal Waddington, Mechanical Worker in Charge, John Day
Jesse Alsup, John Day Mechanical Planner
David Mackintosh, John Day Mechanical Engineer
Kellen Shide, Hydroelectric Design Center Technical Advisor
Rob Lewis, John Day Maintenance Manager