Australian Paper committed to an ambitious upgrade and construction programme at their Maryvale Paper Mill in the Gippsland district in south east Victoria.
The projects ... the Pulp Mill Project was to cost an estimated $300 m and the Wood Yard upgrade an additional $30 m.
“Crane and rigging hours were a significant component in the activities – over 44,000 hours with cranes ranging from 3 tonne mini crawlers to a 400 tonne hydraulic All Terrain mobile ... and two Tower Cranes,” said Garry Hilton, Senior Supervisor at BOOM’s local depot in Morwell.
The specific lift that won the award was the installation of an interconnecting conveyor on the wood chip stacker reclaimer machine in the new Wood Yard.
The connecting conveyor, a total of 97.5 m long with a weight of 101 tonnes, had to be lifted and placed on top of two Stacker Towers 30 m high.
“The designers of conveyor system had provided assembly procedures but no details were available for lifting methods as this was the first time a conveyor system of this type had been built in Australia,” explained Garry.
Lift points, lift lugs and slinging techniques had to be developed by BOOM.
The support structure for the middle of the conveyor was not self supporting and required two cranes to hold the legs while three cranes lifted the conveyor above and into position for securing.
Request for lift plans
BOOM’s office at Morwell in Victoria was asked to prepare two lift plans for lifting the conveyor in one section 97.5 m long and another plan for lifting in two sections ... either way a precision job,” said Garry.
An additional option was a three piece lift but as it required cranes to hold suspended loads overnight and crews to work 24 hour shifts it was not the preferred option. Understandably, the site safety group raised concerns with working at night. Ultimately this method, attractive because it enabled lifting shorter lengths, was ruled out,” he added.
To lift the conveyor in one 97.5 m length would require four cranes in the 300 tonne class ... and with it the risk of deflection beyond tolerances of 250 mm. Cost issues and weather also had to be considered.
“We presented what was in our view, the best procedure ... to lift the conveyor in two sections.
“One section of 69.5 m weighing 73 tonnes required three large cranes plus two cranes lifting and holding the supporting legs in position with a sixth crane lifting the tension bracing.
“We estimated the lift could be placed and secured within twelve hours which allowed for all canes to be de rigged.
“Then the final lift, on another day, being a 25 m section weighing 28 tonnes, lifted by two cranes,” said Garry.
It was by far the best outcome ... and successfully completed without incident.
“There were a number of issues, some complex, which included Planning and Risk Control,” said Garry.
They included a lengthy list of activities requiring extensive precision, engineering capabilities based on extensive crane experience. For example:
Weather: Monitoring weather from a week in advance, particularly as to wind and rain and interpreting the affects at the site.
Ground surface: Soil testing, as the site was reclaimed land and understand how loads could be handled..
Time constraints: Having cranes ready and completing lifts in daylight hours.
Overloading of cranes: This was possible when the conveyor sections were lifted onto the support legs - which were in turn supported by cranes. Any possible overload effect was likely to be on the support leg cranes.
Support legs matching the conveyor: As it turned out, prior test lifts showed the support legs were pre assembled in the wrong way, preventing completion.
Structural failure of the conveyor: Distortion beyond tolerances was possible throughout the mid air lift phase – BOOM riggers were lifted by scissor lifts in unison with the conveyor lift to report on the possibility of distortion throughout to the lift.
Conveyor stability during crane unloading: This was a critical process as there was the possibility of the conveyor tipping away from the tower.
Crane cost control: Minimising crane sizes and thus costs to ensure a cost efficient outcome for Australian Paper.
It was a complex lift with the possibility of a mishap in many areas if pre planning and engineering processes were not ‘spot on’ and based on practical experience.
“The whole lift programme was a great example of BOOM’s ability to pre plan, develop well engineered process and lift with absolute precision.
“It was a great team effort and we are very proud that such an excellent outcome was achieved ... and then recognised by our peers the Lift of the Year judges,” concluded Garry.
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BOOM’s successful Garry Hilton, Senior Supervisor at the Morwell depot in Victoria accepts the Winner’s Award for category A – Lift for cranes over 60 tonnes, presented by the publisher Michelle Grady, publisher of Construction Contractor magazine.
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