Baghouse #1 needed to be upgraded to meet current EPA standards. This included raising the elevation at which air exited the baghouse from its previous elevation of 93’-6” to 199’-0”. To accomplish this task, cupola ducts, twin manifold duct box trusses spanning 119 ft, and an exhaust stack 199 ft in height were designed to collect the exhaust at the top of the existing baghouse and transmit it to the required elevation.

Challenges
Nearly all of the steel was supplied by Nucor and the fabrication was performed by the Vulcraft division of Nucor in St. Joseph, Indiana. Because of this, Nucor viewed materials and fabrication as a much smaller cost than the erection of the structure. Thus, the most cost-effective solution required maximizing shop fabrication and minimizing field erection. To accomplish this, all elements of the new structure were designed such that large portions of the structure could be shop-assembled and shipped to the site whole. For the cupola ducts, each tapered duct consisted of two shop assembled box frames. For the manifold duct box trusses, shop assemblies included top, bottom, and side sections of each truss. For the exhaust stack, shop assemblies included vertical X-bracing panels, stair runs complete with handrail attached, framed platforms, and columns with pre-attached brackets and outriggers.

To minimize the amount of field assembly / steel mill downtime, the tapered cupola duct box trusses and manifold duct box trusses were assembled and sheathed on the ground prior to being lifted into place. CSD assisted the erector in determining centers of gravity and lifted weights for these picks, and designed special rigging and lifting frames necessary to lift these components into place over the existing Baghouse structure.