Massive Mesa A stacker delivered in record time

The 250 tonne machine - which was commissioned in February - is the height of a fifteen-storey building. It is not only one of the largest stackers in operation in the Pilbara but one of the largest stackers of its type in the world.
It can be seen from up to 10 km away, creating something of a landmark in the area.
The Tenova SEMF joint venture - which consists of Tenova SPA and SEMF Pty Ltd - was responsible for all detailed mechanical, structural, electrical and software design as well as stacker fabrication and delivery. HWE Mining had overall responsibility for designing and constructing the mine which is scheduled to produce 25 million tonnes of iron ore a year.
The mine comprises an ore handling and train loading plant, with the stacker creating a stockpile above the train loading plant. The stockpile is approximately the diameter of the MCG, 45 metres high and contains 300,000 tonnes of iron ore.
According to Tenova SEMF’s James Manners - who project managed the fabrication and assisted with the supervision of the assembly of the stacker - what was also especially remarkable about the stacker’s rapid turnaround is the fact that it the first of its kind.
“What’s better still is that it was designed and fabricated in Australia according to Australian standards, a rarity these days with the majority of stackers designed and manufactured overseas.”
Tenova SEMF attributes the rapid 16-month turnaround to five key factors:
• Design through to fabrication was done in 3D
• Pre-ordering steel prior to completion of detailed design
• Trial assembly in workshop of major components
• Correct sequencing of components’ delivery
• Working closely with the head contractor in the assembly phase
SEMF’s principal structural engineer, Bob Dunbabin, said, “Everything from design through to shop detailing was done in 3D. This not only enabled the design team to get the complex geometry of the machine right the first time but allowed our fabricators, Haywards, to base their fabrication and shop detailing on our 3D design model.
“This increased understanding of the complex design geometry assisted in eliminating errors in manufacturing, contributing significantly to reducing overall turnaround time.”
This is the first time Tenova SEMF has designed such a large-scale project entirely in 3D.
Aware that deliveries of steel can take up to 14 weeks, uncut lengths of heavy duty steel from Japan were pre-ordered before the stacker design was complete.
“Because the machine was designed and developed in 3D, the drafting package provided us with a bill of materials very early in the piece, allowing us to identify which items had long lead-times and what we should order ahead of time,” said Manners.
“What this meant was that we received the steel right on schedule for fabrication.”
Manners said receiving the shipment on time was a significant coup given that there was a major steel shortage in Australia at the time.
Trial assembly of the major components in Haywards’ workshops also contributed to reducing the overall turnaround time of the project.
It enabled Tenova SEMF to examine different ways of pre-assembling parts of the structure to ascertain the quickest and easiest method of erection and to eliminate potential problems. This would lessen the amount of actual time on site, reducing OHS risks and on-site costs.
Once trials were complete the stacker was dismantled and sent by truck to the Pilbara for final construction.
“Pre-assembly in the workshops certainly paid off. Usually stacker alignment is difficult in the final assembly and especially so for a stacker the size of Mesa A. However, we were able to achieve alignment to within 4mm without any adjustments,” said Dunbabin.
Correct sequencing of components’ delivery to the Pilbara mine site, also contributed to achieving a tight turnaround.
“It was vital that we matched component delivery to the actual erection sequence of the stacker which wasn’t easy given the complexity and size of the project and the fact that we had twenty trailer loads of components driven to North-West WA,” said Manners.
“Getting it right was also important as cranage costs are enormous (up to $30,000 per day) and any delays as a result of error can cost head contractors thousands in unnecessary expenses.”
All up, the major assembly lifts of the stacker took just two weeks.
“HWE pre-assembled the machine on the ground into large components.  This minimised any work at heights. Had assembly of Mesa A happened in a more piecemeal way, it would have taken significantly longer to erect,” said Manners.