dismantling 26' id ductwork and Chimney Repairs

The 700' tall reinforced concrete chimney at NRG Energy's Oswego Generating Sta. was designed to service (6) oil-fired boilers.  After the Units 1 thru 4 boilers were removed from service, GCI was contracted to remove the 42’ long unsupported span of 26’ Ø insulated ductwork extending from the boilerhouse to the concrete chimney. 

With the duct spanning from the boilerhouse roof 175' above grade, supporting the duct for sectional dismantling was not feasible.  Adjacent structures created additional obstructions and severly restricted access, further complicating the project.    

Gibraltar's rigging expertise, scaffolding ability and experience working at heights inabled GCI to offer an innovative and cost-effective work plan to safely lower the duct to grade for disposal. 

The dismantling operation involved (3) separate lift operation, starting with the removal of an expansion joint section.  This was necessary to provide sufficient clearance allowing the duct to be rotated prior to lowering into the narrow alleyway between the building and chimney.

The duct was lowerered as a single 42' long section, weighing approx. 60-tons and the 3rd operation involved cutting a 24,000 lb stiffener ring free from the liner duct within the chimney and lowering it to grade.  

Some additional project highlights include:    

  • The use of a 600-ton crane at a 120' radius to lift and lower the 60,000 lb. duct section.

  • Requirements for Engineered Lift Plans and a sub-surface soil investigation; which ultimately led to the need for soil upgrades.

  • Demoltion and salvage of the duct section at grade.  

  • The installation of a 30’Ø steel blank-off plate at the steel liner.

  • The installation of a metal closure panel on the breeching opening in the concrete shell.
  • The installation of a 28’Ø steel blank-off plate on the abandon ductwork at the roof.