Constructability Solutions for Temporarily Supporting 200’ Flare Stacks during Construction Modifications

A major challenge in process industries is the constant demand to keep up with environmental regulations, which often require modifications to existing equipment, structures, etc. Most major modifications require some type of a shutdown period, which impacts production and loss of revenue. Engineering constructability solutions are what minimizes these shutdown periods, while keeping facilities within regulatory compliance. These case studies examine the challenges and solutions on a project which involved an oil refinery adding new flare gas recovery (FGR) modifications to reduce emissions on five (5) different flares. These modifications required the bottom portion of existing derricked flare stacks to be removed and replaced with new stack tie-in sections designed to reduce emissions. The objective was to determine a way to accommodate the new FGR tie-in installations without having to perform a total removal of the flare stacks. Some of the challenges included qualifying the existing structures to support the dead load of the flare as well as temporary wind loads, maneuvering new steel through existing structures and piping leading to irregular geometries, and using temporary steel plate mat foundations, in lieu of concrete foundations, due to geotechnical concerns and limited excavation clearances. The solution involved a combination of hydraulic jacks, reinforcing existing derrick structures, and new additional support structures down to grade. The solution saved the refinery significant time and money in additional down-time had a flare removal been required. In order to develop the solution, three-dimensional laser scanning and structural modeling was employed and a unique deflection controlled hydraulic jacking process was developed.