The existing exhaust stack was comprised of four separate pieces. Three original carbon steel sections were topped by a relatively new stainless-steel portion. The lowest section of the stack, located below the roof level, was determined by non-destructive examination and analysis to be salvageable. The middle two sections of carbon steel stack were replaced with new stainless-steel portions due to extreme corrosion. The top section of the existing stack was salvaged, but the ladders and platforms were reconstructed from stainless steel.
To minimize the risks associated with working at height, the decision was made to fully assemble and dress the new stack at grade, then lift the stack to its final position as a single unit. With this in mind, Rally worked with a fabricator to construct new stack sections off-site, reinforce the salvaged components of the original stack on-site, then erect the new stack assembly. Laser scanning aided in the alignment of mating flanges and braces.
Rally was responsible for the structural and mechanical engineering of the new stack, in addition to the planning and scheduling of many aspects of the EPCM process.
This project went straight into detailed engineering with a compressed schedule of three months for engineering, fabrication and construction. Rally issued one Mechanical material requisition for the pre-fabricated stack sections and one Civil / Structural CWP for the on-site work.