News: Maintenance inspection on track at Laurel River Dam
Story by Mark Rankin
LONDON, Ky. – A team of U.S. Army Corps of Engineers Nashville District electrical and mechanical engineers is conducting a two-year required maintenance inspection at the Laurel River Dam.
A group of electrical and mechanical engineers from the Wolf Creek power plant are performing the maintenance inspection which consists of setting the head and tailgates, draining the penstock, examining the generator turbine, and wicket gates and inspecting the electrical and mechanical components of the generator.
The dam was scheduled for shutdown in late October and early November to allow maintenance workers time to inspect and make repairs if required to components.
“Inspecting the penstock takes time and safety is first,” said Wolf Creek Power Plant Superintendent Chris Marlowe, in charge of the maintenance.
Greg Haste, senior mechanic at the Laurel River power plant said after the team reviews safety measures bolts and panels are removed on the penstock housing.
Matting is laid to prevent slippage on the surface and scaffolding is placed inside the scroll case. Scaffolding allows mechanics easier access the large wicket gates for workers to gain access to inspect and collect clearance measurements from readings from various areas.
Water is charged through a tube from 250 feet below the surface of the reservoir water, it enters an 18 foot steel-lined tube called a penstock.
“The penstock is an intake structure that provides water flow from the reservoir to the turbine,” said Haste. “The water is directed through slots on the inner diameter of the scroll case and it falls through the turbine, causing it to spin.”
Jonathan Sims, a journeyman mechanic working inside the penstock explained one of the key elements of his job is taking measurements of the wicket gates.
He said water entering the turbine flows through a series of louvers, called wicket gates, which are arranged in a ring around the turbine inlet.
“The amount of water entering the turbine can be regulated by opening or closing the wicket gates as required. This allows the operators to keep the turbine turning at a constant speed even under widely varying electrical loads,” said Sims. “Maintaining precise speed is important since it is the rate of rotation which determines the frequency of electricity.”
The turbine is coupled to an electric generator by a long shaft. The generator consists of a large, spinning "rotor" and a stationary generator "stator". The outer ring of the rotor is made up of a series of copper wound iron cells or "poles" each of which acts as an electromagnet. The stator is comprised of a series of vertically oriented copper coils nestled in the slots of an iron core. As the rotor spins its magnetic field induces a current in the stator's windings and generates electricity.
Once the water passes through the turbine it enters the draft tube. The draft tube is larger diameter steel outlet tube which slows the water before it exits the dam on the downstream side.
Marlowe said the inspection is going well and will take at least two weeks.
The period allows the crew plenty opportunity to examine specific areas and provide proper maintenance which extends the life span of the generator.
“We are pretty good at doing these types of jobs,” said Johnny Lee, a journeyman mechanic. “We have plenty of experience inspecting areas, looking for damages and making repairs.”
Marlow said the maintenance operation is routinely simple however there are many moving parts in the process.
Each maintenance element requires a few hours and attention to detail.
Omissions, minor mistakes and failures could cause millions of dollars for rate payers.
The team performing the work: Jason Greene, journeyman electrician, Jonathan Sims, journeyman mechanic, Joey Murray, Eric Guffey and Pam Reams, maintenance workers, Johnny Lee, journeyman mechanic, and Greg Haste, senior mechanic.
Laurel River Lake is an artificial lake built in 1977 by the U.S. Army Corps of Engineers on the Laurel River, a tributary of the Cumberland River, in the Daniel Boone National Forest.
The 282-foot high dam was built between 1964 and 1974.
The Corps manages the operation of the dam and recreational facilities around the reservoir while the lake is managed by the Forest Service as part of Daniel Boone National Forest.
Laurel River Lake’s drainage area is 282 square miles, 19 miles long and has 206 miles of shoreline.
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