Manitoba Hydro Kelsey Generating Station
Manitoba Hydro’s Kelsey Generating Station, a mammoth hydroelectric power provider, is one of the largest projects Di-Tech International has participated in. Paired with mechanical contractor PCL, sub-contractor Di-Tech International was responsible for the wire sawing and other select demolition tasks. The project focused on modifications to the draft tube of the turbine and the removal of the moody cone and embedded turbine components. Di-Tech divided the removal of the concrete with in the turbine into 4 phases. Over the course of 7 years, these 4 phases were repeated for 7 turbines at the Kelsey Generating Station, 1 turbine per year, and removing 400 tons each time within 5 weeks.
Below are the phases of removal and modification for each of the 7 turbines.
Cutting and coring on the main floor was enacted to allow pipe access, base removals, trenching, and floor openings through the 30-inch thick floor. This phase involved 2 working supervisors and 6 operators, who started the first few days utilizing numerous cutting methods. These methods included core drilling, chain sawing, and electric floor sawing.
Removing the stator frame via wire saw without damage to the anchorage points so that a new frame could be installed afterwards. Di-Tech cut under the existing frame to lift it from its anchors in the extremely confined space using a Plattner GS 9-15 wire saw. An inventive series of pulleys and interior pulleys allows the operators to cut in the confined space. New pockets were cut by the use of ICS 853 Pro Chain Saws.
Cutting a new access hatch in the 10-foot thick scroll case involved first coring 4 holes in the corners for the diamond wire to pass through with 2 exterior pulleys that would feed the wire back to the wire saw. This was repeated 3 times to complete and afterwards the concrete plug was removed in its 3 sections. A perimeter cut was then made to install a steel hatch, which would seal off the scroll case during the later phases of the project. Utilizing a wall saw after this was completed, operators made an inside perimeter cut 24 inches inward to recess the hatch, followed by the final cutting of chainsaws.
The main goal of this phase was the remove the embedded turbine components in the draft tube. The cutting area had a diameter of 24 feet at the top and 19.5 feet at the bottom, while also varying in thickness from 3.5 feet to 2 feet. A 2-inch thick steel plate made up the interior face of the draft tube liner and steel components were embedded throughout the draft tube’s liner. This would mean that there would have to be wire cuts through 2 feet by 4 feet steel blocks, increasing the difficulty of the task. 10 individual sections of the embedment were cut in lines, forming a decagon. Holes were cored at the end of each cut by the DM 406 H hydraulic drill with a 4.5-inch diameter for wire access 17.5 feet downwards. Lifting holes were also cored with Shibuya auto feeds, increasing efficiency and decreasing worker fatigue. The lifting holes in each 30-ton section would allow PCL to wrap each concrete section with feed chain for easy removal. While these holes were being drilled, the stator was removed to reduce the project time.
Afterwards, a slot was cut at the bottom of the embedment area to intersect with the access holes. This would gain access for operators to cut the new circumference of the draft tube, which consisted of 2 wire saws cutting at the same time in different locations. The first saw would be cutting 2-inch thick steel jacket or 2-foot by 4-foot steel block sides measuring 58 square feet, while the other would be cutting the 133 square feet backs, thus operating at an incredible pace.
Near the completion of the turbine’s modification and concrete removal, the profile of the draft tube floor was decidedly changed to increase water flow. This task required the Di-Tech’s Brokk 180 due to its small footprint and precision of removing the concrete around the reinforced steel.