The Mica station is one of BC Hydro’s largest generating stations. It currently operates with four generating units delivering a total output of 1805 MW.The station was designed to hold six generating units, but only four were installed when the facility was constructed in 1977. A $700- $800M expansion project will install the two remaining generating units, adding another 1000MW of power generation capacity.
The two new turbine hall cranes, designed to work in tandem to provide synchronized lifts up to 1150 tons, are the largest ever delivered by Konecranes in North America. The massive double-girder cranes are cab-operated with radio backup, spanning 76ft over the turbine hall on an 800ft existing runway. Inverter-driven and AC powered, the cranes feature a PLC-based control system that monitors a load restriction path and the control synchronization system. The cranes will operate inside an underground chamber. Access to the turbine hall is via a 400ft tunnel.
According to Joseph Botros, Konecranes regional sales manager, a unique feature of this project is the challenge presented by installing the cranes – a challenge where Konecranes Nuclear Equipment & Services’ proprietary technology developed for installations in the nuclear industry gave them a substantial edge in winning the order.
“Normal installation inside the underground facility using mobile cranes would be problematic –they wouldn’t fit in the limited headroom without removing ceiling supports,” said Botros. “Working with Konecranes Nuclear Equipment & Services we were able to utilize a brand-new technology they developed, and patented, in 2010 to make this challenging installation inside the cavern without removing ceiling supports or, most importantly, disrupting power generation.”
Originally designed to complete complex installations at nuclear facilities, the patent pending Jacking Tower is delivered by tractor-trailers and assembled inside the cavern to the required height. The Jacking Tower rests on a base that allows for even load distribution, which is one large advantage over mobile cranes, whose tires have a very small footprint. Another advantage of the KNES Jacking Tower is the presence of a jib arm that can be utilized to raise and lower smaller loads. The Jacking Tower not only has the ability to remove all components from under the crane rather than above it also installs the cranes from below.
The Jacking Tower was developed by Konecranes Nuclear Equipment & Services’ in-house engineering group in New Berlin, WI, and is the only one of its kind in the world.
“This technology was used for the first time in September, 2010 at the Indian Point Nuclear Power Station in New York for a cask-handling crane installation, where spent fuel rods are removed in casks,” said KNES spokesman Mike Yoder. “The Jacking Tower saves time, money and lowers risk because it is seismically qualified – in the event of an earthquake, it cannot come down. In the nuclear world, it’s all about risk management. If you can somehow diminish the risk, you can set yourself apart from competitors,” he continued.
According to Owen Williams, BC Hydro’s project manager, Konecranes Jacking Tower technology and its ability to install from below was a real advantage in the underground location.
“Konecranes had an elegant way of replacing the existing cranes with new ones which allowed us to install new cranes while having a limited impact on the operating generating station,” he said. “It is important to note that our generating station will continue to provide approximately 15% of BC Hydro’s total power generation output during this project. The installation will create a fundamental constraint on this work, but the solution that Konecranes proposed made us feel that the risks were being managed well.”
Konecranes protected areas load-path technology was a large part of the technical solution that allowed the new, heavier cranes to operate safely on the original runway. PLCs ensure that when the synchronized cranes lift a rotor to transport it to the maintenance bay, the trolleys are not allowed to leave the centerline of the span. Trolley motors shut down if they are outside a certain range. By keeping the load in the center, it ensures that the weight is distributed over all of the wheels, to prevent excessive loading on the runway.
