Case: Enhancing Pontoon Bridges in the Bayou State: Constant Tensioning System
Many of Louisiana pontoon bridge systems are being converted from a single point of contact device (e.g. electric driven split drum logging winch) to a centralized hydraulic operated winch system that is PLC controlled and separated by pipe runs exterior to the operator house into two opposing winch devices that maintain cable tension at all times to keep the wire rope clear of the water.
The customer sought an inexpensive means to convert at least five Pontoon Bridges to a hydraulic winch system that would fulfill the following needs:
- Simplify operator control.
- Reduce safety hazards to the operator and maintenance concerns for the State.
- Maintain wire rope clear of the water during entire period of operation and while open or closed.
- Ensure that during and after testing of the new system, that the old system could still be connected and operated in an emergency.
The concept produced by SIT utilized two opposing winches in near proximity to the Operator house, but on opposite sides of the pontoon bridge that controlled the position of the pontoon by imparting a pulling action at one end of the pontoon and a constant tension drag on the opposite end. The wire rope was run through two new positioned sheaves to maximize the pulling forces on the bridge, yet allow the wire rope to run alongside the pontoon clear of the water when the bridge was fully open. This ability removed any need to run wire rope through sheaves located on the far side of the water way and allowed the winches to exert direct forces on the pontoon bridge at all times.
Hydraulic power for the winch system was provided by centralized hydraulic power unit using redundant electric motor/pump combinations for back up.
Remote control of the hydraulic power unit and winch system was provided in a shelf style operator console with joy stick functional control and touch screen system feedback display. This control system provides an automatic function of creep speed, ramping speed, and full speed based on the position of the bridge in the canal.
It’s safe to say SIT exceeded all project requirements. The system has proven itself in high wind and high water/current situations, and aids in operator control of the waterway and roadway.