For residents of Canada's Yukon Territory, a remote region with an unforgiving climate and average winter temperatures below zero degrees, reliable electricity is essential.
The 1,800 people in and around Watson Lake, just north of the Yukon's border with B.C., rarely experience power failures. Their local utility, Yukon Electrical Co. Ltd. (YECL), averages just six power outages per year, usually affecting small areas and lasting an average 15 minutes.
A six-person staff at Watson Lake maintains a power station rated at 4 MW peak capacity, along with 25 kV distribution lines running 15 miles east and west from the city. The majority of the electric power comes from a Caterpillar 3606 diesel generator set, installed in 1985 and now just beyond 100,000 hours of operation.
During 13 years of continuous base load service, the in-line six-cylinder 3606, rated at 1,650 kW at 900 rpm, has achieved 94 per cent availability. The six per cent downtime includes all shutdowns for maintenance, service and top-end and major overhauls. Of the four unscheduled outages during the genset's life, two were caused by generator failures.
The engine, coupled to a 1,500 kW Ideal fully synchronous generator, carries the bulk of loads typically ranging from 1,000 to 3,000 kW. Typical daily peak loads are 1,800 kW in summer and 2,200 kW in winter, and the typical annual peak is 2,700 kW.
Intermediate, peaking and backup capacity are supplied by a 650 kW Caterpillar 3512 diesel, a 1,000 kW Caterpillar 3516 diesel, another 300 kW diesel-powered unit, and two 650 kW Caterpillar 399 diesels. Together, these units meet the territorial government's requirement of 100 percent emergency reserve capacity.
A century of service
Reliable service has been a hallmark of the YECL since it was founded in Whitehorse, the territorial capital, in 1901. YECL is a wholly-owned subsidiary of Alberta Power Ltd., in turn owned by ATCO Ltd., based in Calgary, Alberta. With 45 employees, a total 14.2 MW of capacity and 1997 sales of $31 million, YECL supplies 14 communities in a service area with 13,000 customers spanning 186,000 square miles.
The company purchases power from Whitehorse-based Yukon Energy Corporation and operates eleven isolated small generation plants, nine in the Yukon and two in northern British Columbia. Watson Lake is the largest generating station, and the smallest is at Swift River, Yukon Territory, with 65 kW capacity.
Dave Hill, Watson Lake plant supervisor, credits the plant's reliability to the longevity of the 3606 engine, proactive maintenance by mechanic Pat Lund and senior operator Joe Suffesick, and a close partnership with the Whitehorse branch of Finning Power Systems, a Caterpillar dealer. Finning provides technical support and performs all overhauls.
The Watson Lake power plant was built in 1985 to accommodate the 3606, which was too tall for the previous plant. The other five generator sets were moved to the newly constructed plant.
The 3606 was installed at Watson Lake as a prototype, but since then the 3606 has been a production engine, the smallest member of Caterpillar's 3600 series.
In continuous service, the brake specific fuel consumption is measured at 3.9 liters per kW/hr.
The Watson Lake unit has delivered the manufacturer's recommended 20,000 hours of operation between top-end overhauls and 40,000 hours between major overhauls. Inspections performed at major overhauls have proven the quality of maintenance at the Watson Lake plant.
At 40,000 hours, all pistons and cylinder components were replaced, the pistons with current-production units representing two generations of design upgrades since Caterpillar introduced the 3600 engine family in the mid-1980's.
Also, at 80,000 hours, the crankshaft was removed, check-ed for deflection, Magnaflux inspected for defects in the journals, and pronounced fit for service up to 100,000 hours, and possibly beyond. In addition, the engine's original front and rear main seals remain intact, something Lund attributes to negative crankcase pressure (0.75 inches of water), which helps evacuate contaminants from the crankcase.
Automated operation
"Our goal is to get the best possible fuel economy, reliability and component life from the equipment," says Lund, who has maintained the engine since it was installed. "All our maintenance and operating practices are aimed in the position."
In typical base load service, the 3606 operates at 75 to 95 per cent of full rated load. A PLC-based automatic control system brings an additional unit on line when the 3606 reaches 100 per cent load and sheds a unit when the load drops to 95 per cent.
Heat recovered from the 3606 engine's jacket water warms the 2,400-square-foot power plant and office building, a 1,200-square-foot vehicle garage, and a neighboring 864-square-foot building leased by ATCO subsidiary Frontec Corporation.
The power plant runs unattended except from 8:00 a.m. to 5:00 p.m. weekdays when Lund and Suffesick are on duty. Both the power plant and distribution lines are electronically monitored and alarmed. The alarm system is configured to signal on-call utility staff in case of a line fault, engine/generator fault or building fire.
The engines are continuously monitored for overspeed, low oil pressure, high coolant temperature, high oil temperature and high crankcase pressure. An abnormal trend in any of these parameters triggers an alarm and notification of on-call plant staff by telephone and radio. A severe abnormality activates the 24-volt DC safety shutdown system. In the event of a shutdown, the control system automatically brings the necessary standby capacity on-line.
Protecting uptime
Unscheduled shutdowns have been rare at Watson Lake. "We perform planned maintenance regularly based on the manufacturer's recommendations and our own experience," says Lund. "We perform all maintenance on time, no exceptions, and have done so for 13 years. In the long run that has helped us to get remarkable life out of the original engine components and to run the plant unattended the majority of the time."
At regular intervals, Lund orders two separate oil analyses, one from Finning Power Systems and the other from an independent laboratory. He compares the results as a cross-check and uses the data to track components wear and oil condition. Oil analysis has helped Lund extend the normal oil-change interval to 2,400 hours, with oil filter changes at 1,200 hours. Oil is changed earlier if the analysis indicates a drop in the oil's total base number (TBN) to less than half the new-oil value.
Lube oil for the 3606 is a zinc-free, high-detergent formulation with high capacity to suspend dirt particles and high lubrication and cooling factors.
In daily operation, Lund and Suffesick read and record critical engine parameters four times per day. They inspect valves at 2,400 intervals and adjust as necessary. Finning Power Systems' technicians visit semi-annually for checkups that include visual inspection, valve and injector adjustment, vibration testing, combustion pressure and exhaust temperature measurement, and generator inspection.
Aside from modifications to update to current production pressure, the 3606 engine remains as originally installed. At the 80,000-hour overhaul, plant staff replaced the original governor with a current model Woodward 2301 electronic governor capable of isochronous speed control. In 1993, the original equipment helical rear train was changed to the current spur gear design.
"Special credit for this plant's success belongs to Pat Lund and Joe Suffesick," says plant supervisor Hill. "They are solely responsible for the long-term serviceability and good maintenance record of the 3606 and all the units in the plant."
Looking ahead
The 3606 remains the heart of the Watson Lake power system as the YECL plans to accommodate three to five percent annual growth demand. Plans may include the addition of another large generator set to replace the older Caterpillar 399 units.
Meanwhile, Watson Lake residents, night after night, remain assured of reliable heat and lighting throughout the long and difficult Canadian winters. ET