The 2016 overhaul of the Navajo Generating Station’s Unit 2 is complete. Each winter, NGS completes either a major eight-week or minor four-week overhaul on one generating unit and all of the systems involved in its operation. The plant is currently in a three-year cycle of major overhauls.
The amount of work completed in this year’s 63-day, $47 million overhaul is amazing, says NGS Maintenance Manager Shayne Jones. “It’s pretty phenomenal,” he says. “At one point, we had close to 1,300 people out here working on the overhaul.”
In a major overhaul, one of NGS’s three 750-megawatt turbines and a generator is completely disassembled, inspected, repaired where needed and reassembled to specification. The boiler, boiler feed pumps, auxiliary turbines, precipitator and dozens of other pieces of equipment are torn down to their essential components and rebuilt like new again. In addition, all of the unit’s instrumentation is recalibrated to ensure accuracy and precision, and all ducts, fans, pumps, steam lines and valves are inspected and repaired to last until the next overhaul. This kind of maintenance has enabled NGS to run efficiently and reliably for 41 years.
“The reason we do overhauls is simple, really,” Jones says. “These units run 24/7/365. Many of the systems we cannot take out of service and perform maintenance when in operation. The only time we can do it is when the unit is offline.”
All of Unit 2’s pollution controls were inspected and serviced. This includes the huge electrostatic precipitators that remove 99.5 percent of the fly ash after coal is burned, the wet limestone scrubber that takes out 95 percent of the sulfur dioxide from flue gas, and its low-NOx burners that help prevent nitrogen oxide from being produced.
NGS overhauls at this time of the year provide a huge financial boost to the economies of Page, Arizona; the surrounding Navajo communities; the northern Arizona-southern Utah region; and the hundreds of Navajo men and women who return to do the work.
More than 95 percent of the temporary workers hired by main contractor Zachry Group were Navajo. “This would be my seventh year. Financially, it’s very important,” says Anthony Descheenie, a worker with Zachry Safety who is originally from Cornfields, Arizona. “Like all the other construction workers, I travel cross-country sometimes to look for work. I like it because it’s Navajo preference, and that’s good for my people here.”