Bradley Lifting Corporation has manufactured a 68 US ton lifting beam for Duke Power’s Oxford hydroelectric generating station in Conover, North Carolina, USA. The new lifting beam is part of a project to replace two ageing cranes with a single gantry crane. The crane is used to lift the main flood gates that regulate the water level in Lake Hickory, which eventually feeds into Lake Norman near Charlotte, North Carolina. The previous procedure required a gang to climb out on top of the dam and manually attach the crane hooks to lifting eyes on the gates. Weather conditions and darkness often made this task dangerous and although no accidents ever actually happened, there were a number of people who felt that it was only a matter of time.
With the new lifting beam, an operator just has to enter the climate-controlled crane cab and lower the beam to attach to the gate. As Bradley’s chief engineer Scott Swaltek explains, an automatic latch, which alternately cycles with the vertical crane motion, allows a set of lifting hooks to swing into the existing lifting eyes for attachment.
To prevent corrosion, all structural steel members were sand blasted and coated with epoxy paint. All hardware, pins, and exposed metal surfaces were manufactured from stainless steel. Because the new gantry crane could only be rated at 75 US ton, Bradley engineers used a truss design to reduce the weight of the lifting beam to less than 7 tons.
A smaller lifting beam, rated at 40 US ton, was also manufactured to lift the false gates which sit upstream of the main flood gates. These gates allow the main flood gates to be removed for repair without draining the lake. Because these gates are no higher than the height of the main flood gates and are stacked on top of each other, at times, the false gate lifting beam can be completely submerged under water when it is being attached to these gates. Previously, divers had to be hired to attach the crane hooks to the false gates.
The customer has future plans to automate the crane so it can be controlled remotely from one operating station somewhere along the network of dams on the river system.
