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Working blind 340m underground

Newcastle’s Wheeler Cranes were recently engaged at a local hunter valley mine site to do something out of the ordinary when it comes to the use of all terrain mobile cranes.

An early morning call to wheeler Cranes supervisor Peter Beveridge, from long-time customer and friend Simon Montford owner of Civil Sydney, started the ball rolling on something Wheeler Cranes rarely does with all terrain mobile cranes.

“Simon explained the task was to remove soil material from the bottom of a new vent shaft at one of the local Hunter Valley mine sites. The challenge was the soil and sludge was 340m below the surface,” said Beveridge.

A site inspection and meeting were arranged with the Mines Construction Project Manager. During the site inspection it was identified that the task had already been undertaken by another company utilising a Lampson pin jib crawler crane on dry hire, with a clamp shell being lowered down the shaft.

“The fact that there was information and video evidence already available, gave me confidence that we could proceed with our Liebherr LTM 1250 6-1. The next challenge was finding the right size clamp shell or grab that would suit the capacity of our cranes line pull,” said Beveridge.

“After a few initial enquiries with some local stevedoring companies we found that there were no suitable clamp shells or grabs available locally. But following a recommendation from Newcastle Stevedores GM James Griffiths, I got in touch with Bulk Cargo Services in Brisbane we hired a 4m3 touch grab which I thought would be suitable for the task,” he said.

Obviously, there were a number of significant challenges and risks to consider prior to starting says Beveridge.

“My initial thoughts and calculations were based around grab weight 3.5t and material weights of 1.4t per cm with a combined weight of approximately 9.1t when the grab was full. This allowed me to use a single part line from the cranes 425m second Winch with a line pull of 105kn.

“I wasn’t overly confident with my calculation for the material being based around coal material weight – 1.4t per cubic meter, but I submitted this to site for review as part of our lift plan. There were no concerns mentioned or raised from site regarding the calculation of the materials, but I was still a little sceptical,” said Beveridge.

“I thought what if it’s wet would the material it be heavier. If we send the Grab bucket down and it ends up exceeding the cranes line pull then we would be in a lot of bother which got me thinking how we could minimise the risks. During my time with Eglo Engineering and Lampson, I roamed around the country putting Lampson Transi-Lifts and Manitowoc 4100 & 4600 ‘ringers’ together and we were using two winches in the hook block reeving in some models.

“I had thought of using the two winches on the Liebherr LTM 1250 6-1 but put these thoughts to the back of my mind until I started discussing and planning the task with our 250 operator Tim Archer. I mentioned my concerns to Tim and right away he said, ‘why don’t we use the 2 winches’, I looked at him and said ‘Great idea- Déjà vu’,” said Beveridge.

Tim Archer and Josh Redman Wheeler Cranes Rigger on the 250, mobilised the crane to site and set the crane up with the two winches rigged on a Friday afternoon. The touch grab arrived from Brisbane on Saturday morning which allowed enabled work to start, says Beveridge.

“The first time the grab was lowered down the vent shaft it came back up empty. Tim suggested we change the rigging as he couldn’t get a feel to see if the grab was engaging or locking. We added a few heavy shackles into the rigging and lowered the grab back down for the second time and when winched it up, it was as full as a boot – over flowing and wet but with the two winches in play we were more than happy to see the grab full.

“Tim got the crane into a rhythm and his skills as an operator really shined for this task considering he was working blind 340m ‘down under’,” said Beveridge.

Three days later the task had been completed with around 110 cubic meters of materials removed which allowed the miners underground to resume work.

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