“We all know that the development operator in a coal mine has the most strenuous tasks than anywhere else in the pit, and due to the nature of the work there is more likely to be incidents where operators get hurt,” development maintenance coordinator Alan Bruce said in a presentation at the recent Roadway Development Operators' Workshop.
“As operator tasks become more repetitive while advance rates increase, the importance of ergonomics has become one of the most important issues in the design of continuous miners at Crinum mine.”
Consequently, supply cassettes, bolter control valves, work platforms, ventilation handling, mesh handling, dust, reach, noise and vibration were all considered in the design work for Crinum’s continuous miners.
Material supply cassettes
“When designing the cassette the ergonomic team went in with an open mind,” Bruce said.
Key points included in the design were to maximise the amount of supplies in the cassette; limit the amount of reaching and lifting required; the ability to load and unload the miner with two operators; colour code each cassette to know what supplies were to be loaded on it; connection of the chain slings to the Eimco jib; design of the jib to give maximum viewing while loading cassettes with the Eimco; partitions in cassette to separate supplies; and the loading of supplies and carting of supplies to the panel in cassette pairing frames and quick-detach system carry-alls.
The Crinum team assessed onboard ventilation to find a solution to operator frustration with the flex duct being awkward to handle and always catching on the rib or being squashed by the shuttle car.
A new duct was installed in 1997 at the front of the machine with a fibreglass transition piece to the rear of the machine resting on the top of the material cassette. “This proved to be a good concept with little trouble installing the flex duct in the vent tube. However, due to the size of the transition piece, vision across the machine was limited and the miner driver could not see where all his men were when manoeuvring so yet another design was required,” Bruce said.
In 1998 a complete new duct system was designed and manufactured to sit above the conveyor and terminated at the fantail joint. While this improved visibility the flexi duct could not hold its own weight.
After a few years Crinum decided to reduce the flexi duct diameter and flare the ends back to the original diameter.
In 2000 the last modification to the duct was made where the transition piece on the end of the onboard duct was a swivel gooseneck at the same height as the fibreglass tubes, which allowed the flexi duct to hold its own weight for the stretched length of 6m.
Originally at Crinum the roof mesh was carried into the panel on a multipurpose vehicle flat-top pod horizontally. The pod would be backed up behind the miner and the mesh unloaded and stacked manually.
“The ergonomic team came up with a design to carry the roof mesh into the panel on a MPV pod with bundles of mesh ties in lots of 20,” Bruce said.
“These bundles are carried in vertically on the side in the pod that has varying floor heights so that if the mesh rests against each other there will be one bundle higher than the rest to attach the purpose-built spreader bar which connects to the Eimco jib. The bundle is then carried by the Eimco and placed behind the miner in the rib where the continuous miner operators manually lift the sheets as required and bolt to the roof.”
Over the years Crinum has made two changes to the mesh weight – from 28kg to 24kg, then to 17kg. “This has stopped most of the injuries in the mesh handling area,” Bruce said.
In 1997 Crinum changed the position of the manual traction levers to a position up at the rib bolter controls to keep operators using the levers away from the rear of the miner where there was a pinch point area.
The installation of a cutter/conveyor isolator was also fitted in 2000 for maintenance work around the machine. Crinum also included electronic bolter controls but because the controls needed to communicate with the machine processor another flameproof enclosure was required – bringing total enclosures on the machine to six.
In 2004 a new version of electronic bolter controls was installed, operated by the machine’s CPU. “To do this the whole electrical system on the miner was upgraded to the Obelix system designed by Pempek and installed by Waratah Engineering. The system brought the six enclosures into one large enclosure.”
With hydraulic traction and one hydraulic pump Crinum removed three electric motors from the machine. By removing the motors and enclosures it has left the machine uncluttered and easier to maintain.
After some unsuccessful attempts at improving the hydraulics, it wasn’t until about three years ago that Crinum installed Rexroth KVA107 load sense piston pumps to replace the gear pumps on both sides of the machine.
Later Crinum installed a completely new hydraulic circuit using a Rexroth load sense pump, valves and filters to accommodate all the mining and bolting functions. The system had the first 24-volt Rexroth M4-12/15 flameproof solenoid load sense valves fitted to the entire circuit making the mining and bolting function use the same hydraulic valves.
These valves have a built-in flow control, load sense relief, spool monitoring and pressure transducers and can use proportional or black and white solenoids.
The hydraulic pump and drive motor is located on rubber mounts to reduce vibration and noise and two hydraulic track frame tanks have been joined to allow for fast cross-flow between tanks.
Electronic bolter controls
Specialist engineering companies and Crinum developed an “industry first” concept of installing electro-hydraulic controls on the continuous miner. The equipment incorporates a semi-automatic drilling and bolting process to improve the quality and consistency of the bolting cycle.
Push-button digital stations are now being used on all three of the miners with great success, Bruce said. Two of the machines have an operating screen mounted on either side where the set-up screen shows most of the parameters on one page.
The digital stations have pressure transducers to automate the bolters and record data for roof mapping. There is also an intrinsically safe counter on the feed circuit to record the position of the drill head on each rig to an accuracy of 0.3mm that is required for automation of the bolter and data recording.
According to Bruce, the digital stations offer many advantages, including consistent roof bolt installation, reduced operator fatigue and built-in diagnostics, and are capable of mapping the mine roof.
Further details on this story will appear in the September Australian Longwall Magazine.