By Carroll McCormickMachinery and Equipment Maintenance
Electricity means money and Hydro-Québec’s Beauharnois hydroelectric generating station is making its share of both this year: It generated a record 1,182,706 MWh in July 2011, thanks to all 38 generating units running. As well,...
Electricity means money and Hydro-Québec’s Beauharnois hydroelectric generating station is making its share of both this year: It generated a record 1,182,706 MWh in July 2011, thanks to all 38 generating units running. As well, 60% of this year’s scheduled maintenance jobs had been completed by March, its Unit 20 was back in service after refurbishment and, of course, Mother Nature has provided lots and lots of water.
Extracting this kind of performance out of a generating station is no paddle on a duck pond though. Located 40 km southwest of Montreal on Lac Saint-Francois and the Beauharnois canal, the kilometre-long generating station is the fourth-largest of Hydro-Québec’s 60 hydroelectric generating stations.
Construction on the Beauharnois station began in 1929, but its age alone is only part of the story of what makes it uniquely challenging to operate. With an installed capacity of 1,911 MW, it is more than nine times bigger than the next largest hydro station of its vintage. Its installed capacity is 507 MW greater than all of its 19 octogenarian and nonagenarian contemporaries combined.
The commissioning of the generating station was strung out from 1932 to 1961. The smorgasbord of unit types installed over the decades requires a lot of specialized knowledge to operate and maintain.
Ginette Vaillancourt, facilities engineer, Beauharnois, gives a taste of the generating station maintenance team’s daily bread: “The quantity and the wide variety of equipment in the generating station make it very challenging. There are Francis and propeller-type turbines and several different unit manufacturers. For example, we have turbines and generators manufactured by Westinghouse, General Electric, Canadian Allis-Chalmers, Dominion Engineering Works, Alstom, Voith, Oerlikon and English Electric. There are different designs, configurations and different technologies to consider: old and new, modernized and semi-modernized, digital and analogue.”
Mechanics, electricians, civil workers and operators total about 150. Technicians, engineers, managers and administrative staff bring the generating station’s population to about 200. To keep staffing levels up and reduce the irretrievable loss of knowledge as old hands retire, Hydro-Québec hires post-secondary graduates and sometimes pairs staff with experienced mentors.
“On-site coaching is sometimes used as an alternative or in addition to in-class training,” Vaillancourt says. Hydro-Québec also arranges training on topics such as generating units, speed-control systems, cranes and safety codes.
Scheduled maintenance includes familiar-sounding tasks such as routine and visual inspections of accessible parts for sparks, leaks and unusual noises. Permanent monitoring systems track variables like vibration, stator and bearing temperatures, oil levels, pressure, flow and air gap.
Once a year, every unit is shut down for four to five days of routine maintenance and servicing. This includes verifying oil leaks, oil sampling, analysis of generator and turbine bearings and hydraulic systems, and verification of wear on exciter brushes. These tasks do not generally require disassembly or the use of a platform in the area of the runners (turbine blades).
On six- and 12-year schedules, every unit – usually three a year – is taken out of service for four to five weeks worth of more extensive maintenance tasks. “Furthermore,” Vaillancourt adds, “two units are usually out of service most of the year for major refurbishment or modernization work. We take advantage of these major shutdowns to perform extensive maintenance work on them.”
Refurbishment work requires taking units out of service for 40 to 60 weeks. “A major rehabilitation project has been under way here since the beginning of the 1990’s. It includes stator winding replacement and turbine runner replacement, major civil work, modernization of exciters, digital retrofit or replacement of speed governors, installation of monitoring systems and measurement instruments, etc.,” Vaillancourt says.
The maintenance team at Beauharnois is well equipped to do most repair work. Its machine shop is kitted out with gear like lathes, moulding machines, vertical and horizontal band saws, drill presses, bench grinders and a hydraulic press. The welding shop has some of this gear, plus a combined bending-punching-shearing machine and combined bending-shearing machine. In-house welders, in addition to doing small jobs, can also repair cracks and cavitation damage (pitting due to exploding air bubbles in areas of low pressure) on the runners.
Machining of some parts, like servomotors, specialized or robotized welding and tricky on-site boring tasks are carried out by a machine shop brought in from elsewhere in the Hydro-Québec system. Machining of heavy parts, like bottom rings, head covers and vane rings, and manufacturing and machining of turbine runners, stator rewinding and major civil works are outsourced to other companies.
Beauharnois uses the Maximo computerized maintenance management system (CMMS) to track all this maintenance work. About 8,600 pieces of equipment are entered in the Maximo software. There are roughly 8,700 coded items, including basics and common spare parts that are currently used, and specialized or strategic parts, both in store or to order.
Beauharnois follows what could be loosely referred to as a maintenance playbook: the Maintenance Management Concept used throughout the Generation Division of Hydro-Québec. It takes into account things like the expected services of the generating station, applicable laws, rules, regulations and commitments; maintenance specifications in condition assessment standards and maintenance analysis guides; and systematic, conditional and corrective maintenance planning, equipment condition assessment and maintenance assessment.
“This helps us optimize maintenance: do the right maintenance action on the right equipment at the most appropriate time,” Vaillancourt explains. This kind of organization and planning allows the maintenance team to accomplish 85% of its planned maintenance, maintain an average forced outage rate as low as 1% and an operating factor of about 85%, all the while carrying out the 40- to 60-week-long major refurbishments or modernization on two units a year.
In recent years, good practices have been improved and include the following: refined maintenance planning in weekly meetings to coordinate and schedule maintenance tasks; doing as much maintenance as possible between January and March to minimize the water spillage that occurs when units are taken out of service at other times of the year; and putting all available resources onto the unit that is out of service to minimize the duration of outages.
Water spillage is a concern inherent to the location of the Beauharnois generating station. A hydroelectric dam with a reservoir behind it does not lose water if a unit is not operating. The water just sits there. Beauharnois, on the other hand, is a run-of-river facility. It does not store water. It is a strictly get-as-can-get proposition: every litre of water that is not spinning a runner is a litre lost to the downstream side of the generating station. There is great motivation, then, to keep unit uptime as high as possible.
“This makes it a real challenge to perform maintenance while maintaining a high operating factor and a low forced-outage rate,” Vaillancourt states. “Our main goal is to take the right maintenance actions on the right equipment at the right time, and to offer maximum availability to meet hydraulic and market demands while maintaining equipment long-term reliability. This is what our business is all about.”
Carroll McCormick, senior contributing editor, is based in Montreal. He is the recipient of several awards for his articles in Machinery & Eq