Kelly Earthmoving uses Epiroc hammer mounted on spider excavator to tackle challenging quarry project

At a large quarry in the Midlands, Kelly Earthmoving has delivered some enabling works associated with the installation of a cable-suspended conveyor that will span nearly 1 kilometre across the quarry.

Kelly Earthmoving was brought on to the site due to their experience and specialist capability. The Irish company undertakes a variety of specialist work across the country. The company, headed by Gerry Kelly, offers specialized services to their clients. 

"We already undertake rock breaking and cutting for our existing clients," Kelly explains. "But this project has seen us extracting and breaking far more rock than we have ever done on a single job. It's been a tough but enjoyable project to be involved in but also one that has been hard on the equipment."

The project has seen the Kelly team on site for 12 months working on two separate sites. The terminal anchor point for the suspended conveyor system has been excavated and construction of a large concrete foundation is underway. This left the team working almost at the top of the quarry and adjacent to an existing haul road. The team had already created a working platform to allow the civil contractor to construct a piled wall which released the area required to construct the suspended conveyors deflection tower.

Once completed, the Kelly team were back on site to create a 33 degree ‘slot' through the upper quarry benches to accommodate the conveyor's cable catenary profile.

From the upper platform, Kelly formed a slope down through the mudstone and rock to where a second working platform was broken out and levelled. At this point, the team encountered the very hard rock that the quarry is famous for.

"We had a number of options for the removal of the rock head," Kelly explains. "We looked at sawing sections out, but the rock was littered with enough fractures that allowed us the quicker option of using hydraulic breakers instead."

While some of the exposed rock was easy to remove, the company found that the material below wasn't, and ended up breaking a number of hammers and countless chisels in the process.

"It was getting beyond a joke. Every couple of days we were breaking a chisel or sometimes more," Kelly explains. "Our usual hammers were struggling with the hard rock so we decided to look at investing in something more reliable and productive to complete the job. Coyle Equipment Services has been supporting us on this project from their new, purpose-built depot in West Bromwich, so on the advice of William Coyle we used an Epiroc MB 1200 hammer as a replacement for one of our existing tools. And to be fair, we have been very impressed with the Epiroc breaker's reliability and performance."

Carefully driving a path through the rock, the 12 tonne, 157hp Menzi Muck wields the Epiroc MB 1200 hammer with ease despite it being designed for the larger 15-26t carrier range.

"The Menzi is just a massive powerpack," Kelly explains. "It will push out over 200 litres per minute with the Powerline pump, far more than the Epiroc breaker requires."

Lift capacity even at its full 6-metre reach is over 4 tonnes, making the Menzi an ideal hydraulic attachment carrier. Carrying a hefty 120mm diameter chisel, the MB 1200 delivers between 340 and 680 blows per minute which, according to Kelly, is more than capable of taking apart the rock.

Fitted with Epiroc's AutoControl system, the hammer is able to detect pressure on the chisel. It also detects when the chisel breaks through the material to protect it from blank firing and causing potential damage to the percussion chamber.