In a recent bridge construction project, a work crew required a method to accurately and securely position concrete formwork. The contractor’s primary concern was keeping the large concrete forms level during positioning. Thern, Winona, Minn., provided the solution with six winch systems configured for simultaneous operation to concurrently lower the formwork while keeping them level during the move. These winch units were custom built to user specifications to provide the accurate control needed for the operation. Designed for two-part rigging, each winch provided 30,000 pounds load capacity and 100 feet of travel.
Crews enjoyed the high level of load control afforded by the economical helical-spur gear sets of these Thern winches, and to facilitate simultaneous operation, all six winches were controlled by a single 460-volt, three-phase, variable frequency drive control system, eliminating the hassle of controlling multiple units individually.
The crew positioned the winches on pre-made sleds located above the concrete deck. Using a system of directional sheaves, they connected the winches to the forms below and carefully lowered them via six-point rigging back to the ground. Winch brake motors maintained constant positive load control during the operation providing maximum load security. The operation was a success due to the versatility, reliability and performance of Thern power winches tailored specifically to the needs of the project.
Lift & Access is part of the Catalyst Communications Network publication family.
