Underdog – This package of scope is the “crown jewel” on the $500m Prominent Hill Mine Expansion. OZ Minerals through ICN conducted an expansive search for suitable contractors so that they could ensure that this important structure was in the right hands. Most of the highly regarded and largest fabrication firms in the country were considered for this work, but OZM chose Bowhill Engineering to put their trust in! Why you might ask, well we’ll leave that to our client to explain.
Coordination – This structure due to the scale of the highly loaded mechanical equipment that it’s designed to support had to be robust and built to the highest standards. Each specific piece of mechanical equipment has loads that need consideration before design could be 100% finalized. With steel supply lead times at an all-time high, the circumstances created a difficult juggling act. Bowhill worked in with their suppliers to be very flexible with OZM through the designers, prioritizing components that could be completed and delaying those elements that were affected by the absence of critical information, this was purely for the good of the project. This approach avoided over engineering, and minimized delaying the whole project even though the equipment specifications took longer than programed.
Erection surety – This structure is of large scale, the methodology chosen to erect was bold and necessitated a large crane and significant set up and planning. The Prominent Hill site is remote, it’s 700km north of Adelaide so getting a 900t crane to site comes at a premium. Any nasty surprises on site would be prohibitively expensive and a risk that required significant rigor in management. The 450t – 22mx22mx20m h module, complete with much of the mechanical equipment, is hoisted 40m from the ground to land on 4 raker columns each 2.5m diameter. Whilst the site works is not in Bowhill’s scope, the process requires that the brave riggers and welders scale the structure and complete a full site butt weld of the 4 columns at 40m high!
Safety in design – As explained above, the safety of the erection crew is of paramount importance and many novel solutions were uncovered. Temporary access to the weld splices were provided via steel access platforms that were fixed to the columns, tapered alignment guides in the joint ensured that alignment and root gap were accurate to shorten fitup time and to keep people away from crush zones.
Accuracy – the scale of the structure made full shop assembly impractical, however because the accuracy was so important, it was decided to do a partial assembly and full point cloud laser scan which was transposed over the 3D model to identify the true asbuilt accuracy. This gave the whole team confidence that the fitup on site would go smoothly. “Could you imagine if we sent all the elements up to site and something didn’t fit! The cost to program as well as commercially would be horrendous. It’s not the sort of structure that you can just slot the holes and fit it up, it’s got to be of the highest precision” Jeremy Hawkes MD Bowhill Engineering.
