Barnhart was contacted by a power plant with an emergent need for a high-capacity structural support for its scrubber units. Significant degradation of the steel in the outer walls of the vacuum chambers in the scrubbers had been discovered, which could have led to a total collapse. Having the units down meant the plant was eager for a support method to allow for safe repairs and to start the units as soon as possible.
Barnhart devised a system utilizing a Modular Lift Tower (MLT) to support the vertical load in the event of a structural failure of the scrubber outer walls and/or support steel. The team developed a distinctive MLT configuration, including “piggyback” vertical bents to improve stability as typical horizontal bracing was not an option because of site constraints.
Barnhart’s concept delivered a self-supporting MLT placed in a tight and congested footprint. This stable system did away with the use of guy wires or additional bracing from adjacent structures. MLT bents were used as vertical shoring columns. Multipurpose girders were used to span across from bent to bent and a combination of pull-up gantries and 200-ton hollow-core jacks provided an uplift capacity of 600,000 pounds.
Another challenge was the need to support each scrubber at multiple attachment points. In total, the crew connected to 12 radial lift points around the circumference of each scrubber. This was accomplished using slide beams with custom-fabricated offset links. Once the MLTs were erected, the plant safely began repairs by fitting and welding cladding sheets. The MLT system also allowed the plant to operate the units while completing repairs, greatly reducing downtime. After all repairs were completed, Barnhart quickly and safely demobilized.