A Tale of Two Upgrades
Melton Hill and Fort Loudoun Dams Get Life Extensions
Outside Lenoir City, Tennessee, two Tennessee Valley Authority hydroelectric dams built 20 years apart are getting new leases on life.
Melton Hill Dam, a two-unit generating site, and Fort Loudoun Dam, a four-unit generating site, are undergoing outages to upgrade to more environmentally friendly turbines that will extend the operating life of the plants.
It’s no easy task. Hydro outages typically take a long time to complete, primarily due to the refurbishment of oversized components, which can take three to six months, not including shipping time.
The team at Melton Hill are a study in perseverance.
Unit 1 underwent an extended outage for repairs and maintenance, including the replacement of the turbine original to the plant.
This particular outage is called a Hydro Life Extension because the turbine upgrade, combined with other system maintenance, adds 40 years of operating life to the plant.
The original turbine, which looks like a gigantic boat propeller, was upgraded to a new fixed-blade design. The original design had blades that adjusted up or down based on water flow.
The new design will use less water and, because the blades don’t move, it removes the potential for oil leaks, making it more environmentally friendly.
“These blades are huge, weighing 16,592 pounds each, and must be cured hanging to get it right,” TVA Melton Hill plant manager Eric Hamby said.
The outage was originally planned for 400 days, but global supply chain impacts from the pandemic affected the outage timeline.
Because the blades are upgraded every 40 years, this is a specialty item that only a few hydro equipment companies manufacture across the nation and around the world.“Once we’re back online, we’ll be providing 40 megawatts to the people of the Valley – which can power approximately 23,400 homes,” Hamby said
A 30-minute drive away, Fort Loudoun Dam is more than 360 days into a 510-day outage on Unit 1, which is also going through a Hydro Life Extension, including upgrading the turbine to a fixed-blade design.
Similar to the Melton Hill crew, the Fort Loudoun team has encountered pandemic-related supply chain issues. This time on the smaller components.
“Things are going reasonably well,” said construction manager Pam Fleming. “We are struggling with hardware issues because of lack of supply availability. In order to stay on schedule, we’ve had to use some old components as stand-ins to conduct fit-up until the replacements are available. In addition, we are continuing to receive new and remanufactured items onsite for reassembly as they are being returned from the Power Service Shops and other vendors.”
One critical work task that has to be performed for unit reassembly is the static vertical alignment of the various unit components. This work uses auditory micrometer equipment to detect the sound of static contact noise along the center wire in the hydro unit.
“The wire must be perfectly centered within the unit structure, hanging plumb and free,” said Mike Thompson, QA support at TVA Fort Loudoun Dam. “The goal during this test is to hear just the faintest static sound when the micrometer makes contact between the wire and the various unit components. So, the lower the volume, the closer the unit components are to being perfectly aligned with the center wire.”
With the reassembly process underway, Fort Loudoun Unit 1 will once again be in operation this fall with 35.5 megawatts back on the grid, providing power to approximately 20,700 households across the region.
“We were able to provide lessons learned from the Melton Hill outage to the Fort Loudoun Unit 1 outage, which has been a more efficient process. I’m proud of the Fort Loudoun team for staying on task and continuing to work toward a successful outage completion,” said Hamby, who’s also the plant manager of Fort Loudoun.
This summer, as part of its 90th anniversary activities, TVA is hosting public tours of select TVA dams. Learn more at tva.com/90.