Burgess-Limerick’s 2010 Reducing Injury Risks Associated with Underground Coal Mining Equipment study uses injury statistics provided by Coal Services for all incidents in New South Wales during the three years to the end of June 2008.

The most common incident type involved workers receiving strains while handling gear such as bolting supplies, mesh and ventilation tubes.

There were 176 strain injuries during handling activities associated with continuous miners and bolting machines.

Burgess-Limerick noted most mines were reducing the manual handling risks by loading consumables and other equipment into a container pod then loading this onto a CM using either a load haul dump attachment, a jib or a “racker system”

“Providing storage for drill steels, dolly and bolt plates near bolting rigs further reduces handling of these items,” he said.

New continuous miners feature integrated mesh carriers and research is underway to use a polymer spray on the roof instead of mesh.

Burgess-Limerick said none of the sites visited during the study “satisfactorily controlled” the risks with handling vent tubes, as highlighted by a recent case in Queensland where a worker fell from an LHD bucket while trying to separate ventilation tubes.

“Reductions in the length and weight of the tubes and adding webbing handles to fibreglass vent tubes are positive steps,” he said.

“Miners which have a flexible vent ducting (elephant’s trunk) bring additional handling risks.

“The height-adjustable platform implemented on some Sandvik miner bolters may reduce handling issues associated with mesh and vent tubes.

“Vent tube handling risks may also be reduced through the use of flexible ducting and a monorail system.”

Overall, the most safety incidents occurred during bolting with 332 recorded in the three-year period.

With plenty of upward stretching required during bolting there were 70 cases of strains, often to shoulders.

Burgess-Limerick said shoulder load could be decreased by reducing the reach distance needed to access the drill pots.

“This reach distance varied considerably across continuous miner models observed.

“Redesign of platforms and bolting rig controls has been undertaken to improve access, and mast-mounted drill rig controls and rotation of the drill pots also reduce injury risks.”

Cable bolting to overcome tough geological conditions also increases the risks involved with handling and inserting these bolts.

Burgess-Limerick said Sandvik had proposed an integrated bolt handling system to address these risks, allowing cable to be fed from the rear of the continuous miner and under the platform to the bolting rig.

Handling cable was identified as the most common cause of injury associated with continuous miners with about 32 each year in NSW.

The injuries vary from minor shoulder strains to serious back injuries.

Handling continuous miner cable also presents a high risk of injury from previous biomechanical analysis .

The provision of a monorail along with the use of a hydraulic cable reeler attached to an LHD are some measures to reduce cable handling risks, but scientific research into the development of automated bolting is ongoing.

“When this is feasible, the introduction of automated bolting will result in a marked decrease in injury risk through the elimination of a range of hazards,” Burgess-Limerick said.

“Automation of continuous miners and shuttle cars is also being investigated by the CSIRO with ACARP funding.

“Although this may be further away, once automated bolting is achieved, non-line-of-sight remote control will also be a feasible means of removing pedestrians from the vicinity of the continuous miner to a large degree.”

Injuries while bolting

There were 175 bolting injuries involving a worker being struck, whether it be by falling materials such as rock, coal, steel plates and bolts, or by high-pressure hydraulic fluid from damaged hoses which notched up 31 cases alone.

Being caught in between moving parts of equipment resulted in 69 bolting injuries with the most horrific resulting in the amputation of a left forearm when it became entangled in steel rib mesh and a drill steel.

A lot of the causes of these bolting injuries stemmed from failure to correctly operate bolting controls or unsafe positioning by the operators.

It is possible for workers to accidently bump control levers with the battery, lamp cap cord or the self-contained self-rescuers on their sides, and in some cases falling rock or bolts can also bump a lever into operation.

Metal guarding of the controls provides protection against such events, but Burgess-Limerick said care was required to ensure the guarding did not increase the reach distance to the levers or cause difficulties operating them.

The ergonomist has previously found that shape coding of the lever knobs to enforce the relationship between the knob shape and its operating function can reduce selection errors.

“Consequently it is important to ensure that the relationship between shape and function is standardised, and that a means is provided to prevent shaped handles being placed on the incorrect lever,” Burgess-Limerick said.

The movement of a control lever and its related function has been subject to various studies and findings in a bid to minimise inadvertent operation.

A definite safety measure identified is that mines ensure their bolting rigs underground share consistency in control operation.

With many finger injuries recorded during bolting operations, there are various safety measures already in place at Australian coal mines.

“These include the use of a ‘panic bar’ to isolate the bolting rig before placing drill steel and bolts, fitting of ‘keeper plate’ to drill mast, rubber insertion warning plates between head plates of adjacent bolters, guarding to prevent access between rigs, and guards on gripper jaws, spacers between top plate and intermediate plate, rubber ‘early warning’ guards and requiring two-handed operation for full power operation,” Burgess-Limerick said.

Crush cones were presented at the 2006 NSW mining safety conference as an innovation with the aim of reducing the risk of entrapment between timber jack and drill mast.

Hydraulic fluid injection, slips and trips

The substitution of hosing with stainless steel piping wherever possible is a key tactic to cut down the risks of a possible fluid injection injury, with dangerous injuries coming from just tiny pin-prick holes in the high-pressure hoses.

Falls or slips from CM platforms result in about 20 injuries per year in NSW.

Burgess-Limerick said the probability of slips and trips while working on a platform would be decreased by ensuring that the platforms are a single level.

He added that handrails were justified for all platforms no matter their height, while noting that improvements to platform lighting and kickboards around platform edges were “worthwhile”

“Flameproof fluorescent lighting has been provided and advances in LED lighting technology are promising for improvements to equipment lighting and for continuous miner platforms and bolting rigs in particular.”

The revised handbook of the study, which was funded by the Australian Coal Association Research Program, is freely available here: http://burgess-limerick.com/download/d10.pdf

Industry monitors for the project were Xstrata’s Dave Mellows, Centennial’s John Hempenstall and Peabody’s Peter Brisbane.