Coal, Emissions

Managing the Plant: Cumberland Fossil Plant

Issue 4 and Volume 106.

Editor’s Note: This is the initial installment of “Managing the Plant,” a new Power Engineering feature where we will interview a power plant manager to identify key strategies, initiatives and programs being used to improve efficiency, reduce cost, and enhance overall plant performance..

Cumberland Plant Manager Leonard ‘Bud’ Hancock.
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TVA’s coal-fired Cumberland Fossil Plant is located on Barkley Lake, about 80 miles northwest of Nashville, Tenn. Construction began in 1968, with commercial operation in 1973. The plant consists of two 1,300 MW units, both relying on identical B&W once-through supercritical boilers and cross-compound ABB/Alstom steam turbines. TVA installed limestone scrubbers for SO2 control in 1994, low-NOx burners in 1998, and is currently installing SCRs that will go into service in 2003/2004. In 2001, Cumberland set several plant operating records: electricity generation, 18.7 million MWh; equivalent forced outage rate, less than 3 percent, a 70 percent improvement over 2000; and heat rate, 9,678 Btu/kWh.

“To be a successful generating plant in today’s environment, I’m convinced you have to engage the employees in the business,” says Cumberland plant manager Leonard “Bud” Hancock, who admits the mind shift hasn’t come easily. “We’re constantly looking for indicators that will enable us to tie employee actions to plant performance.” One such indicator Cumberland has successfully exploited is the loss on ignition (LOI) metric for its fly ash.

Cumberland marketed 150,000 tons of fly ash in 2001, and expects to market much more in 2002. The marketability of fly ash, of course, depends on a plant’s ability to produce fly ash with minimal carbon content. At Cumberland, the limit is 1.5 percent LOI. “To keep our entire workforce focused on this issue,” says Hancock, “we control chart LOI every day, and we e-mail this control chart to every employee every day. If the LOI is trending upward, everyone in our engineering, operations and maintenance departments knows what specific actions need to be taken to turn things around.” For example, the first thing done at Cumberland is to use acoustic guns to analyze the coal pipes and determine if there is a problem with the grind size from the pulverizers. As a side benefit of controlling LOI, Cumberland has reduced slagging conditions, improved heat rate, minimized combustion imbalances in the furnace, and reduced tube wastage and slag falls.

Cumberland derives a lot of benefits from what it calls System Teams, which are cross-functional teams (e.g., engineer, maintenance planner, operator, engineering aide, coal handler) that focus on optimizing the performance of systems with the greatest potential impact on plant reliability. Water quality is extremely important for the supercritical once-through boilers. Cumberland switched to an oxygenated feedwater program in 1997 and almost immediately noted reduced deposit build-up. “I didn’t believe that would happen when we first switched,” acknowledges Hancock. Cumberland relied on the differential pressure between the first pass and the second pass as the performance indicator for the deposit build-up; the differential consistently dropped over time, and the deposit reduction was validated during a subsequent outage by taking tube samples. “We haven’t acid-cleaned the boilers since the switchover, and we shouldn’t need to for quite awhile,” says Hancock.

Predictive tools, such as infrared, oil analysis, vibration analysis, acoustic monitoring and motor analysis, are essential in the System Teams approach. The System Teams determine the best predictive tools for determining the health status of a particular system, and then draw on the talents of Technical System Analysts (TSA) who specialize in using a given predictive tool.

If the infrared specialist, for example, picks something up during a routine route inspection, he develops a report detailing the problem and its potential fix. The report typically includes not just the infrared photo, but a regular digital photo as well to aid in evaluation. “The report is e-mailed not just to that System Team, but to all the System Teams,” says Hancock. “The System Team will then generate a corrective work order, and depending on how emergent the situation is, and what the risk is, we can address the problem immediately if necessary.”

Benchmarking guides Hancock’s management of the plant. For example, based on a system Hancock has seen at other fossil and nuclear facilities, Cumberland will be switching to an eight-week rolling work schedule for maintenance by June. Maintenance work won’t get into the schedule unless advance planning is completed and approved. When implemented, all maintenance work in a given week will have to be coordinated through a “work-week manager,” a position that will alternate between a shift supervisor and a maintenance supervisor. “A pitfall that I’ve seen over the years is the constant re-deployment of maintenance forces, a reactive system that isn’t very effective,” says Hancock. “The eight-week rolling work schedule should move our culture away from such a reactive approach.”

A similar approach extends to outage planning. TVA has a readiness process that requires scope lockdown by 36 weeks prior to outage. “That’s challenging,” says Hancock, “but we’re almost there.” During outages, Hancock assigns supervisors to both 12-hour shifts. These individuals can resolve anything right then so there are no holdups in the schedule. Cumberland’s craft people are intimately involved in coordinating outage work with outside contractors, such as Day & Zimmerman NPS. “When we were doing some horizontal reheater work during a recent outage, our boilermakers helped the contractor supervisors devise a better welding plan, identify modifications that didn’t show up on the drawings – basically serving as the local technical expert,” states Hancock.

Hancock points to human performance as his biggest challenge. “I never realized how much of a responsibility management has in driving human performance, in helping reduce the chances of people making mistakes,” says Hancock. Simple improvement techniques can be implemented immediately, such as developing good operating and maintenance procedures and requiring their use; conducting good pre-planning in all functional areas, not just maintenance; and conducting effective pre-job briefings related to safety and the work process. “Anytime there is an event at Cumberland,” says Hancock, “we look at it from a human performance perspective. For example, if we have a boiler leak, is there a human performance element for why this tube failed? If we maintain what we did outside the human performance area, we’ll stay at our current equivalent forced outage rate. The way we’re going to get better is by focusing on the human performance factors.”

Hancock is proudest of the long-term vision employees developed at Cumberland: to be the number one plant in the industry by being employee-driven. Cumberland’s guiding objectives are to ensure the safety of the workforce and the community; and to provide reliable power at a competitive price while protecting the environment. These words will lead Cumberland for years to come.