As part of their continuous maintenance plan, Dampier Salt Ltd had planned to replace the corroded box beam of their A3 Radial Stacker in their Port Hedland facility. McDowall Affleck were appointed to undertake the 3D scan survey of the existing structure, design a new box beam to replace the corroded one and plan the replacement procedure in order to guarantee the global stability of the stacker following the removal of the corroded beam and allow the installation of the new structure in a safely manner.
The scope of work entailed a 3D Scan of existing structure, the planning of replacement procedure, detailed design of new box beam, replacement of supported structures with new stainless steel structures, shop detailing of new box beam and supported structures and local strengthening of existing structure at connection with new box beam.
We faced challenges of the As built information not being available, we had to minimise replacement time and impact on operations, avoiding triggering requirement for full review of stacker structure, plan a safe replacement process and avoid overstressing of structure during replacement process.
We managed to overcome this by having a 3D survey (point cloud) of an A3 stacker, detailed design based on accurate 3D scan, replacement process planned in detail, design a like for like beam to not affect relative stiffness and internal force distribution, review of foundations and cyclone tie downs capacity to support the structure during beam replacement. We needed structural analysis in temporary conditions and controlled release of energy during beam cutting via smart planning of cutting procedure and continuous monitoring of load in tie downs during beam cutting.
The replacement of the beam with a like for like structure did not alter the internal force distribution and avoided the requirement for a costly review of the remaining. With careful planning of the replacement process, this allowed Dampier Salt to successfully complete the works in the scheduled timeframe.