tva logoTennessee Valley Authority
TVA River Neighbors
November 2006

 

On the job

Outage crews get down and dirty

You never know when the call is going to come. Sometimes the phone rings in the middle of a cold winter night. Or right after work on a sweltering summer evening. But when the call comes, Machinist Foreman Denny Paul and the rest of the “greasy bellies” are ready to spring into action.

image of TVA employee

TVA Machinist Foreman Denny Paul inspects the Chickamauga Unit 1 generator rotor for potential problems during a recent scheduled outage.

Paul and his counterparts are members of the outage crews that are sent from TVA’s Power Service Shops to power plants all across the Valley — many times to conduct scheduled repairs, but also to respond to emergency situations. Machinists wear their vocational nickname proudly, according to Paul: “The term ‘greasy bellies’ refers to the fact that we’re used to maneuvering in extremely tight places. A lot of times, we do our work lying down — using our hands and feet to crawl in and out of machinery.”

The machinery they’re working in and around is designed to produce electricity — in this case, from hydropower, the force of water as it passes through generating units at TVA dams. Hydro is particularly important to TVA’s mix of generating sources since it’s clean, inexpensive, renewable, and capable of coming online almost instantly to respond to peak power demands.

TVA has 109 conventional hydro generating units, including four pump turbines at Raccoon Mountain. In an ongoing effort to upgrade generating equipment, slightly more than half of these units have had turbines replaced fairly recently; the remaining turbines may have been in service for as long as five decades.

Given their age, it is no surprise that TVA’s hydro units are occasionally down for repairs. Most outages are for planned maintenance, but sometimes the unforeseen occurs and a unit is forced offline until emergency repairs can be made.

In either case, Paul and other outage crew members are ready to respond.

Pre-planning for scheduled outages begins several years in advance. About two weeks before a unit is taken out of service, things really start to happen. The necessary tools and equipment are brought to the site. Crews are assembled with the skills and training needed for that particular project. Trucks are unloaded and trailers are set up close to the powerhouse. An elaborate “lay-down plan” ensures that tools are precisely where they need to be, positioned in the order in which they will likely be used — all with the intention of maximizing efficiency.

On the day the outage is scheduled to begin, plant technicians take the unit out of service. They isolate, shut down, and tag all electrical and mechanical components. They depressurize the hydraulic system and make sure that all electrical safety grounds are in place. After going to great lengths to make certain everything is completely safe, says Paul, “all that’s left is for us to start grabbing wrenches and tearing that thing down.”

The disassembly process alone may take close to a month. Next comes the maintenance and repair phase, followed by unit reassembly. Testing is the last step before startup and return to service.

Forced outages are a different matter, says Paul. Without the benefit of pre-outage planning, instinct and experience take over. “When you get the word that a unit has tripped off, you grab everything you think you might need and get there as fast as you can.”

Since these unanticipated outages may occur at times of heavy demand for electricity — and because having to turn to other generating sources is more expensive — there’s a premium on getting units back online. Even with this sense of urgency, however, Paul says that there are greater concerns that override any other consideration. “We pride ourselves on three things,” he says. “We do it safely, we do it quickly, and we do it right.”

Mike Thompson, Lead Outage Manager in TVA’s Hydro Production organization, echoes that sentiment: “Our crews will work through the night, if necessary, to analyze a problem and repair a component. But as anxious as we are to get a unit back online, there’s no way we’re going to compromise when it comes to safety or quality. Yes, you could say that ‘the clock is ticking.’ But it never ticks loudly enough to overshadow those primary considerations.”

Every project is unique, with its own set of challenges. Each power plant has equipment that differs from that at other plants — and a single location may feature various models and manufacturers.

The massive scale of the repair work is part of the challenge, says Paul. “Some of the components we work on weigh from 150 to 250 tons, so you have to make a lot of heavy lifts. The most important thing is to pay attention at all times because the environment changes constantly. A piece of machinery can swing or drift against a wall when you’re moving it. A component can be in a different position than it was the last time you walked through an area, so now there’s a big open hole where there was a solid surface just a few minutes ago. We’re extremely thorough in our planning and constantly mindful of following established safety procedures; our lives literally depend upon it.”

Environmental protection is important, too. “It can be tricky if the job involves a lot of oil that must be transferred from the unit. We are extremely careful with solvents, and we always use oil-containment kits if there’s even the possibility of a spill. Our goal is to prevent even one drop from getting into the water.”

Thompson has a great appreciation for the people that do this kind of work: “Sometimes, it takes a 40-pound wrench. Other times, it requires six 100-ton-capacity hydraulic jacks. But what it almost always takes is great care and attention to detail. Denny and our other outage crew members are dedicated individuals who do a terrific job under challenging circumstances.”

It’s all about making the best possible use of the water, says Thompson. “The things we’re doing are designed to improve efficiency and availability. We are interested in providing multiple benefits to Valley citizens from the way we operate the reservoir system and that includes getting the maximum value out of every drop of water.”

Paul takes a great deal of personal satisfaction in his work, as evidenced by this succinct self-assessment: “It’s a good quality machine when we get done with it.”

At the end of a job, there’s no greater reward for outage crew members than hearing a unit start up and run, says Paul. “After all those days and nights of hard work, the sweetest music in the world is what we refer to as that ‘60-cycle hum.’”

 

 

           
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