Canada’s Yukon Territory is a remote region with an unforgiving climate. With average winter temperatures below zero degrees, reliable power is important. Yukon Electrical Co Ltd (YECL) operates a 4 MWe plant at the town of Watson Lake. The plant, based on a Caterpillar 3606 diesel, has just reached 100 000 hours of operation. Over this period, the plant has achieved 94 per cent total availability.
The engine carries bulk loads ranging from 1 to 3 MWe. Typical daily peak loads are 1.8 MWe in summer, and 2.2 MWe in winter. The typical annual peak is 2.7 MWe.
The downtime includes all routine maintenance shutdowns. Over the period of operation, there were a total of four unscheduled outages, two due to the generator, two due to the engine.
The 3606 was installed at Watson Lake as a prototype. The 3606 has an 11 inch bore, 11.8 inch stroke, and 110.8 cubic inch displacement. In continuous service, the brake specific fuel consumption is 3.9 litres per kW/h.
At 40 000 hours, all pistons and cylinder linings met the reusability guidelines, and were reinstalled. At 80 000 hours, the pistons and cylinder linings were again found to be suitable for reuse, but were replaced anyway. In addition, at 80 000 hours, the crankshaft was removed, checked for deflection and defects, and pronounced fit for continued service.
In addition, the engine’s original front and rear main seals remain intact after 100 000 hours of operation. This has been attributed to negative crankcase pressure of 0.75 inches of water, which helps to evacuate contaminants from the crankcase.
In typical base load service, the 3606 operates at 75-95 per cent of full-rated load. An 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.
The power plant and distribution lines are electronically monitored and alarmed, the alarms being configured to signal on-call utility staff.
The engines are continuously monitored for overspeed, low oil pressure, high coolant temperature, high oil temperature and high crankcase pressure.
Pat Lund, one of the three operators at the plant, said: “We perform planned maintenance regularly, based on the manufacturer’s recommendations and our own experience. We perform all maintenance on time, no exceptions, and have done so for 13 years. In the long run, that has helped us get remarkable life out of the original engine components, and to run the plant unattended the majority of the time.”
One technique that has been adopted to extend maintenance periods has been to send oil off to two separate laboratories for analysis. This allows the operators to track component wear and oil condition. This has helped the plant extend the normal oil change interval to 2400 hours, with oil filter changes at 1200 hours.
Apart from modifications to update to current production components, the 3606 engine remains as originally installed.
YECL plans to accommodate an estimated growth of three to five per cent annually in power demand. To do this, it intends to replace the older gensets with another large unit.