Sulphuric Acid Interpass Tower

Vessel in excess of 200,000lbs, large diameter ducting, stair tower and platform structure.


Lopes Limited was awarded the contract to design and build a new Sulphuric Acid Interpass Tower and remove the decommissioned unit at the Vale Smelter. The timeline was aggressive with less than 12 months from beginning of fabrication to commissioning of the unit. Strategy involved maximizing in-house shop fabrication; shipping the vessel to site in ten large sections. All welds in the shop and the field were subject to complete LPI as well as X-rays in several locations. The vessel was also braced and fit-up meticulously to maintain circularity tolerances required for acid-resistant brick lining. Almost 200’ of large diameter ducting and the stair tower structure were also fabricated and installed by Lopes forces.


There is no shortage of obstacles on any project and with a tight schedule, there is no time to waste. The entire foundation had to be hoarded due to an exceptionally cold fall. The 110’ tall scaffold structure was erected, hoarded, and heated to allow welding to progress without delay during the winter months. A removable temporary roof was also devised to keep the weather out and the heat in. Crews put in remarkable efforts battling bitter cold to keep ahead of schedule. All work was sequenced to maximize efficiency allowing up to 50 tradesmen to work on-site simultaneously in a safe and productive manner. With winter once again closing-in, maximized crane lifts and coordinated waste disposal paired with focus and determination had demolition work completed prior to the arrival of prohibitive weather.

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  • Sulphuric Acid Interpass Tower
  • 27’-0” Diameter x 82’-3” Tall Vessel (bottom 45’ brick-lined mild steel; upper portion 316 Stainless)


  • Destination: Copper Cliff, ON, Canada
  • Vessel in excess of 200,000lbs, large diameter ducting, stair tower and platform structure
  • Brick-lined lower portion including self-supporting brick dome
  • Extensive piping requiring welding of exotic metals (Alloy 20 & Saramet 35)
  • 8,000ft3 of ceramic packing installed in vessel (27’ diameter x 14’ deep)
  • Demolition and removal of old tower, ducting and piping
  • Project successfully completed safely, on-time, and within budget