Canadian Overhead Handling has installed the first of two 136t gantry cranes at Hydro-Québec’s Beauharnois power house, on the St Lawrence River, southwest of Montréal.

The second gantry is under construction at COH’s facility in Québec and is expected to be commissioned by October 2003.

The Beauharnois power house dates back to 1932. The gantry cranes are supplied as part of the final stages of a major rehabilitation programme that began in the early 1990s.

The cranes will be used to service the stop logs and 74 water intake gates on the 1km-long dam, handle the hydraulic trash grab and clamshell mud bucket and hoist the departure transformers from the ground level to the dam deck 28m up.

COH supplied the gantries to Hydro-Québec, the Québec government owned hydro-power company, as part of a C$7m (US$4.5m) turnkey project. Technical specifications of the project were written by consulting engineer SNC-Lavalin.

The gantry hoist house, sitting 18m above the dam deck, shelters a twin hook 136t main hoisting machinery and two separate, open winch type, 3t secondary hoists. The hoist house is serviced by a low headroom 3.2t Stahl SH hoist.

Below the hoist house, straddling the main hooks, a 25t auxiliary trolley rolls on a separate set of girders. This design allows the hook to cantilever 14m past the upstream gantry travelling rail.

Except for the Stahl house maintenance unit, all hoists are designed and fabricated by COH, a subsidiary of the French company Reel. All the gearboxes for the open winch hoists and trolley and gantry travel drives are of COH own design and fabrication.

All the machinery is run with Marathon motors controlled by ABB ACC601 hoist and ACS601 horizontal translation AC variable frequency drives. The main and auxiliary hoist motors can operate at up to 150% torque capacity for short periods to pull out a stalled gate in the dam.

A Modicon PLC system, designed and programmed by COH software engineers, controls an array of functions and interlocks.

The PLC is coupled to input/output modules by a fibre optic network, reducing the amount of wiring between the modules and main panel, and between the back plates in the main panel itself.