Lifting blind at 340m underground

WORKING BLIND 340M UNDERGROUND

A Liebherr LTM 1250 6-1 all terrain delivers on a complex underground lift. Cranes & Lifting speaks to Wheeler Cranes regarding the complexities of lifting at 340 meters underground.

Two winches on the Liebherr LTM 1250 6-1 and planning, were key to a successful lift.

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 a project requiring Wheeler Cranes to consider utilising an all terrain crane in a way it wouldn’t normally consider.

“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 coal, soil or sludge materials were 340m below the surface,” said Beveridge.

A site inspection and meeting were arranged with the Mines Construction Project Manager 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 lowered down the shaft.

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

“After a few initial enquiries with some local stevedoring companies, we found that there were no suitable clamp shells available locally. But following a recommendation from Newcastle Stevedores GM James Griffiths, I got in touch with Bulk Cargo Services in Brisbane and 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 the clamshell weight of 3.5t and material weight of coal 1.4t per cubic meter with a combined weight of approximately 9.1t when the grab was full. This would make suitable to use the single part line from the cranes 425m second winch with a line pull of 105kn.

“I wasn’t overly confident with my calculations for the material being based around coal material weight of 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 engineering regarding the calculation of the materials, but I was still a little sceptical,” said Beveridge.

“I questioned what if it’s wet or of a different density would the material be heavier, if we send the clamshell bucket down and it ends up exceeding the cranes line pull when full, we would be in a lot of bother. This got me thinking about how we could minimise the risks.

“During my time with Eglo Engineering and Lampson, I spent several years traveling around the country putting Lampson Transi-Lifts and Manitowoc 4100 & 4600 ‘ringers’ together and on some occasions two winches were utilised in the hook block reeving of the crane configuration.

“This got me thinking about using the two winches on the Liebherr LTM 1250 6-1 but I 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 main 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 along with others mobilised the crane to site and set the crane up with the two winches rigged on a Friday afternoon. The clamshell arrived from Brisbane on Saturday morning which allowed work to start, says Beveridge.

“The first time the clamshell was lowered down the vent shaft it came back up empty. Tim suggested we change the rigging as he couldn’t get a feel through the crane’s reactions to know if the grab was engaging or locking.

“We added a few heavy shackles onto the rigging and lowered the clamshell back down for the second time and when we winched it back 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 clamshell full and weighing in and around our original estimations.

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

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

“It’s very rewarding when a plan comes together, I thank everyone who helped or contributed to bringing the resources together for us to complete this project safely. As usual, the Liebherr didn’t miss a beat,” said Beveridge.

The winches needed to manage a combined weight of 9.1t.