The maintenance team at Leland Olds Station, a coal-fired power plant near Stanton, N.D., cares deeply about keeping the plant running and providing people with electricity—especially in the dead of winter. That's why, in 2009, we began looking for a better gearbox to use on the plant's coal conveyors.
Located four miles southeast of Stanton on the Missouri River, the plant is owned by Basin Electric Power Cooperative, one of the largest electric generation and transmission cooperatives in the United States. It generates and transmits wholesale, bulk electric power to 2.8 million customers in nine states (Figure 1).
Figure 1. The two-unit, coal-fired Leland Olds Station power plant near Stanton, N.D., generates and transmits about 669 megawatts of wholesale, bulk electric power to 2.8 million customers in nine states.
When the 222-megawatt Unit 1 at Leland Olds Station went online in January 1966, it was the largest lignite-based power plant in the Western Hemisphere. Unit 2, a 447-megawatt unit located adjacent to Unit 1, began commercial operation in December 1975. In 2007, construction began on a $410-million project to install a wet limestone scrubber to remove sulfur dioxide emissions.
In general, the plant consumes about 3.3 million tons of lignite per year from North American Coal Corp.'s Freedom Mine in Beulah, N.D. The plant also uses about 230,000 gallons of water per minute—most of which is released back into the Missouri River. The plant's boilers produce 1005 °F steam, which spins Unit 1's 290,000-hp turbine and Unit 2's 590,000-hp turbine at 3600 rpm.
Leland Olds Station is the only power plant in North Dakota that uses a "v-slot" coal-unloading system. This v-shaped hopper and enclosure automatically unloads six rail cars at a time. It takes about one hour to unload a 60-car train (Figure 2).
Big Coal = Big Electricity
Figure 2. A trainload of lignite waits to be unloaded at the Leland Olds Station. The plant uses a v-shaped hopper and enclosure to automatically unload six rail cars at a time and takes about one hour to unload a 60-car train.
Originally, chain cases were used on gearboxes serving the plant's conveyors, but due to issues with grease and improving plant cleanliness, the maintenance department switched to belt drives. However, we found the change from chains to belts added too much tension and overloaded the bearings in the gearboxes, and that's when the maintenance headaches began (Figure 3).
For years, we've been playing musical gearboxes on these conveyors. We would take a failing gearbox off and replace it with our spare, and hope that we could fix the gearbox before we needed the spare somewhere else on the line. Most of the time, we were scrambling to make these things work and keep the conveyors running.
Extra time was also needed to realign belts after a gearbox was installed, which is a critical job, requiring skill, time and effort. These change-outs were also complicated because of where the gearboxes are located—in confined, hard-to-reach spaces with not much room to work.
This was a big deal for us and the plant because failing gearboxes threatened our ability to generate power. While we never did lose generation, we had to sweat it out a few times to get the job done. We knew this was not a good situation, and we needed to do something about it.
Combining Reducers, Motors, Pulley and Shafting
Consequently, we called in a trusted distributor to help find a reliable solution. Craig Taylor, manager of Motion Industries' branch in Bismarck, N.D., had been a frequent visitor at the plant, and had helped our team with several other projects. Taylor was familiar with the failing gearboxes, and recommended Baldor's Dodge Quantis right-angle, helical bevel gear reducer.
"We've had good success using Dodge Quantis gearboxes in other applications over the past six years," explains Taylor. "They have a good service record, so there was no question about what Leland Old Station's conveyors needed."