An Enerpac Strand Lift system capable of safely positioning huge loads to accuracies within fractions of a millimeter is being employed by VDM Group in constructing Australia’s largest-ever magnetite mining and processing operation.
CITIC Pacific Mining’s $US4 billion Sino Iron Ore project in Western Australia involves 12 of the biggest iron ore processing mills ever built, which are manufactured in China and transported in sub-assembly form for precision positioning onto their bearings 21 metres above the ground.
It is the first time iron ore processing mills have been fabricated in a factory in China and transported internationally, travelling by sea and road for rapid assembly at a destination more than 7,000 km distant and in the process achieving huge time savings over on-site fabrication.
The initial six pairs of 800 tonne ball mills and 1,400 tonne autogenous mills are being installed by VDM Group using the Enerpac precision lifting technology over an one year programme extending from January this year until end of January 2011, as the huge project builds up to an initial target capacity of 27.6 million tons a year from a resource of more than two billion tons of measured indicated and inferred magnetite ore. More mills may be added later as the site 100 km from Karratha grows to become one of the world’s biggest iron ore developments. The project, owned by China Metallurgical Company, will employ 10,000 workers to build it, 800 to run it and involve extensive technology transfer, with Chinese and Australian design teams developing the mills that will process the magnetite ore into fine concentrate and produce value-added products that will help pave the way for the magnetite industry in the state. (See box following).
The Australian and International Enerpac Integrated Solutions team worked with CITIC Pacific previously in constructing the Beijing Olympics Birds Nest Stadium. The partnership employed Strand Lift technology that draws on Enerpac’s worldwide prestressing and post constant tensioning technology as well as heavy lifting expertise that was used in the lifting from the ocean floor of the 10,000 tonne Russian submarine Kursk.
The powerful PLC-controlled synchronous Strand Lift heavy lifting systems hoist loads of thousands of tonnes where access is restricted, overhead space is limited or maximum stability is required. Applications range from mining, energy and petroleum sites onshore and offshore, through to the placing of weapons systems in submarines, positioning machines in tunnels and erecting bridges and viaducts.
The Sino Iron Ore Strand Lift System specified by VDM Group for CITIC Pacific and MCC Mining involved four 444tonne 37 Strand, Strand Jacks, with Recoiler and Palm Tree Control Systems positioned on the prefabricated steel structures above the position to which the ball malls are delivered by road from the Cape Preston wharf to the mill site at Cape Preston concentrator area in Western Australia’s far northwest. The mills travel overnight for several nights at about 1 km an hour on multi-wheel transporters before being placed beneath the Strand Lifting equipment for raising 6 metres clear of the transporters, then lowering 6 metres for positioning onto the mobile transporter that is driven laterally into position on rails after the multi-wheel transporter is removed.
The mobile transporter subsequently transports the mills laterally to a position adjacent to the foundation towers on which the trunnion bearings are located, where the Strand Lift System operating from another prefabricated jacking towers lifts and lowers them into their final position. The strand lift can raise and lower at speeds up to a metre every nine minutes, with one-person control of the many steps involved from a PLC screen synchronising the action of the jacks.
The jacks involve large capacity, hollow core hydraulic cylinders, dual locking cylinders and especially designed clamping wedges. The cluster of cylinders (each of which can be of up to 1,000 tonnes lifting capacity) are positioned directly above the load to draw it securely upwards on multiple wire rope strands governed by an integral locking system. The precision lifting system –suspended from a fixed, stable surrounding framework gives complete control at each stage of the lift, with the hydraulically actuated and PLC controlled lifting and locking system able to secure the load in any position
“Accuracy is critical in all phases of the operation, none more so than the positioning of the huge mills onto their bearings. The lifts required very accurate and stable technology that could operate reliably in conditions including extreme heat, frequently well over 40 deg C, as well as the possibility of frequent winds,” said Enerpac Integrated Solutions Manager Mr Colin Chapman. Mr Chapman and Enerpac Technical Support Engineer Ray Paasila assisted the engineer controlling the first Strand Lifts undertaken by the VDM Group.
“VDM Group invested a great deal of time and energy into fostering the teamwork that paid off during the lift. They travelled to Europe to train on the technology and worked closely with Enerpac and Enerpac Global Integrated Solutions Specialist, Mr Antonia Lopez Pasteur, who came to Australia for the first lift,” said Mr Chapman.
“The teamwork all paid off during the first lift, when, during the positioning over the bearings, we lowered the mill to within 0.6mm of the target position as required by the mill manufacturer people on site. This is quite a marvellous achievement considering the mill is nearly 800 tonnes and we had to contend with winds we estimated at about 10m/s at the top of the mill foundation.
“Setting down the mill onto the thrust blocks was the most delicate part of the whole operation. There is only 0.5 mm clearance on each side between the thrust blocks and the groove in the trunnion of the mill.
“The CITIC Pacific and Monadelphous people involved asked us to adjust the mill position with four ancillary manual jacks by 0.1 mm at a time. VDM Group demonstrated tremendous skill by lowering the mill in steps as small as 0.2 mm as the mill approached the target position, far surpassing original specifications required.
“Then the on-site team raised the trunnion bearings to make contact with the trunnions at both ends to support the mill. The cradles were then lowered down and then preparation was made to move the mobile transporter out of the way.
“It was an enormously intricate process, requiring extraordinary precision, preparation and teamwork. It was an outstanding achievement by all involved.”