Paris Energy Center
Owned by Viva Alamo LLC
Operated by NAES Corp
260-MW, gas-fired, 2 × 1 7EA-powered combined cycle located in Paris, Tex
Plant manager: Mark Vest
Trolley system streamlines replacement of collector rings
Challenge. Paris experienced a hard ground on the generator collector shell leads in October 2015. As part of the outage, collector rings were removed, sent to a shop for machining, and then reinstalled. Last step involved heating the rings to allow them to reposition themselves onto the shaft of the rotor.
The process proved ineffective on the first try because the lengthy crane travel time allowed the rings to cool down before they could be moved from the heater to the collector end of the shaft. Result: The collector shell wouldn’t slide into place after reinstalling the rings.
Next, plant personnel tried applying source heat to get the rings hot enough to slide into place. But the installation failed again, this time resulting in material defects that required the collector ring assembly be returned to the shop.
Upon inspection, the shop deemed it necessary to open the fit by one to two mils to allow smoother installation. This resulted in 15 days of downtime, during which the plant could dispatch only at partial load (1 × 1).
Solution. Learning from the first trial, a maintenance technician designed and built a trolley system to accommodate reinstallation when the rings returned. The trolley consists of a chain-fall hoist suspended from a set of rollers that travel along an I-beam rail (Fig 1). The heavy-duty legs are bolted to the concrete ground to provide stability during lifts (Fig 2).
This system allows staff to remove the rings from the heater—an industrial oven designed to heat metal—and convey them to the collector end in a fraction of the time it took using a conventional crane (Fig 3). The rings remained hot during reinstallation and a consistent temperature was maintained across them. The need for a crane was eliminated.
Results. Thanks to the proactive, creative thinking of Maintenance Technician Bud Browning, Paris Energy Center was able to expedite collector-ring reinstallation, reduce outage scope dramatically, and achieve substantial cost savings in shop time and crane support.
Brent Brady, maintenance manager
Bud Browning, maintenance technician