Published in the June 2010 Australian Longwall Magazine

The Mandalong mine, which is located near Morisset, south of Newcastle in New South Wales, started longwall mining in January 2005. Its recoverable reserves are estimated at 102 million tonnes.

The mine’s new high-production longwall face is only 150 metres wide (most longwalls average 300m) mainly due to potential subsidence issues associated with mining under the local properties and water courses.

This in turn has increased the need for high productivity and performance in development to ensure longwall continuity.

Mandalong operates a Sandvik ABM-20, dating back to 1992, and four ABM-25s, delivered in 2004 and 2005, with all machines overhauled between 2007 and 2009.

One of the main issues with miner bolter performance is consistency, as variation in the operation of the machine during cutting cycles can deliver notably varying roadway conditions.

According to Mandalong development electrical engineer Bruce Davies, the uneven shape of the floor being produced by the continuous miners was a significant safety and operational issue.

“We were experiencing a large proportion of slip/trip/fall injuries in our development sections and the quality of the road surface was very uneven,” he said.

“For a number of years, we’d been aiming to have all our operators mining a consistent roof and floor horizon.

“We’d been attempting to do this through different procedures and increased training, but with limited success.

“Because of this, we decided to trial Sandvik’s Autocut feature on one of our ABM-25s.”

Mandalong engaged Sandvik to assist its site engineers to implement the Autocut feature on one of its ABM-25s.

This resulted in immediate improvements in safety, Davies said, with Autocut assisting in reducing the incidence of slip/trip/fall injuries due to the improved floor horizon. As well as the safety improvements and subsequent cost savings from reduced repair costs there have been other benefits.

“Autocut has significantly improved the quality of the travelling roads for worker transport and shuttle car movements, and improved the workplace for belt moves,” he said.

“We’re also getting cost savings through reduced machine damage – such as wheel units and SMVs [specialised mining vehicles] – due to the floor improvements.

“Coal sizing has been improved with Autocut, resulting in improved coal flow and reduced slabbing, plus we’ve seen a slight improvement in the rib conditions and because it’s an automated process, the miner driver is now freed up to assist with bolting. We have also seen a significant cost saving, due to the decreased need for roadway maintenance.

“The great advantage of Autocut is that the ‘people part’ of the operation is removed, so that the same cycle is cut every time and we are getting more consistent cycle times.”

The project won the Mandalong operation this year’s Centennial Productivity Innovation Award, presented at an annual two-day conference for the entire Centennial group.

This conference allows each business segment to present how it is going to improve its business productivity through the use of technology.

Following the success of Autocut on the first ABM-25, a second unit has since been fitted with the system.

The Autocut sequence involves the cutter being programmed to travel through a pre-determined set of coordinates, including pauses for shuttle cars, as well as interlocking with other machine functions, such as conveyor and auto-TRS (posi-set). This cycle is infinitely variable and the technology is easily transferable to existing ABMs and MB600 series machines.

Other advantages include smoother machine operation, shearing proceeding up and down at a set rate, and cutter and loader motor currents being smoothed out.

One of the most significant advantages of the Autocut system is the consistent improvement in productivity. Since installing Autocut in the two ABM-25s, Mandalong has twice broken weekly development records and in February this year broke its monthly development record.

“We are confident that with this system, we have plenty more records to break,” Davies said.

“In successfully implementing this project, we had a lot of valuable assistance from Sandvik engineers Duncan Edwards and Greg Smith, which helped with its success.

“However, probably the biggest driving force has been the acceptance by crews, their interest in the system, and the better results and floor horizons that have been consistently achieved.

“Good feedback from our operators has allowed us to refine the Autocut function to make it even more successful.”

Sandvik Mining and Construction Australia’s engineering/product line support manager for underground soft rock mining, Duncan Edwards, says Autocut was developed to bring about process improvement in mining applications through greater consistency.

“Traditionally, floor-to-roof cutting is used and is carried out according to a predefined set of limits,” he said.

“However, with Autocut the focus is on machine set-up and operator interface at the start of the cut to enable the use of the more consistent roof-to-floor methodology.

“This ensures consistent horizon control, and also allows production to match bolting to relieve belts and transfers, and improve overall productivity.”

In addition, coal can be sized at the face to enhance output and cycle cutting times are more consistent.

The Autocut system has provided considerable improvements in safety, operating costs and substantially improved productivity. The system has now been in operation for six months and the improvements have been sustained.

The marked improvements delivered by the Autocut system have attracted the attention of Sandvik’s global management, with Lars Josefsson (Sandvik Mining and Construction president) travelling to the site on his recent visit to Australia to witness first-hand the success of Mandalong’s development team.