Crinum: Machine transformation

OVER the past 12 years BHP Billiton Mitsubishi Alliance’s Crinum mine has modified and built on its continuous miners to develop the optimum machine for its conditions, with the mine recently achieving its best year of development yet. ILN also reveals the Q&A session with Alan Bruce from the recent Roadway Development workshop.

Angie Tomlinson

Today, Crinum's machine of choice has evolved into the recently purchased ABM25s (slim) machine from Voest Alpine, which will be delivered to the mine at the end of October.

According to development maintenance coordinator Alan Bruce modifications to Crinum’s continuous miners began in 1997 with the transformation of three Joy continuous miners from 12CM30 to 12CM32.

Changes made to the model included the incorporation or addition of a supply cassette system, onboard ventilation, rib protection platforms, ergonomic design, the introduction of electronically controlled roof bolter controls, a new electrical system and a new hydraulic system utilising the 24 volt Rexroth flameproof solenoid valves.

One of the major obstacles with the original miners was it was not suited to Crinum’s wet conditions, so the first Joy 12CM32 was developed to include a centrifugal loading arm apron. While the CLA apron was added to overcome the water problem, it meant new engineering challenges for designers who had to reposition or resize the gathering head pivot, the cutter head frame, conveyor motors, rear bumper and insert plates to maintain the centre of balance to the machine.

The ventilation duct was also redesigned and moved to allow for a supply cassette system to be installed.

Ergonomics were also a major consideration for Crinum: “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,” Bruce said.

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.

Hydraulics was also a consideration for the mine two years ago. A 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 mining and bolting functions use the same hydraulics valves.

In an industry first, specialist engineering companies and the Crinum team developed and implemented a concept of installing electro-hydraulic bolter controls to the machines. The equipment incorporated a semi-automatic drilling and bolting process to improve the quality and consistency of the bolt installation cycle. The system will also provide data to geotechnical engineers about immediate roof conditions.

The roof condition data and bolter automation is operated through digital stations on the continuous miners. According to Bruce the digital stations offer many advantages, including consistent roof bolt installation, reduced operator fatigue, built in diagnostics and are capable of mapping the mine roof.

All the modifications over the years were included in the specifications to Voest Alpine for the new ABM25s . Next the mine will look at introducing the self drilling bolt when they become available, increase automation and improve roof mapping.

Question & Answers selection taken from sessions with Alan Bruce at ACARP's Roadway Development Workshops in Mackay, Pokolbin and Penrith last month.

Q: How much roof and rib support is installed at Crinum?

A: In good conditions there are 6 x 2100mm roof bolts installed per metre, with 2 x 1200mm steel rib bolts on the chain pillar side and 3 x cutables on the block side. When roof conditions deteriorate there are 8 x 2100mm bolts installed per metre.

Q: Why do the platforms on the ABM25(s) raise and lower?

A: Our ergonomist recommended that operators only move their head through a 15-degree arc in order to minimise pinching of the discs in the neck, and also required operators to be at suitable height level relative to the drills rigs.

The preferred operating height was above the preferred maintenance height, and to lift the machine components to 200mm to be above the work platform would have increased the overall machine height. We then decided to install a moveable platform which was raised for operation and lowered for maintenance, thereby putting the operators at the correct height and avoiding increasing the machine height.

Q: Where are the controls for raising and lowering the platform?

A: There is another valve bank situated beside the rib bolter controls to operate the platforms and the mesh handler.

Q: How far back from the face are the roof bolts installed?

A: The roof bolts will be installed at 2.6m from the face.

Q: The Joy Sumps Shearer addressed many of the ergonomic issues raised in your presentation – is there any benefit in revisiting that machine as a work platform?

A: The Sumps Shearer is no longer being considered for development by Joy, but I definitely believe it had potential.

Q: What sort of improvement do you expect from the new ABM25s?

A: The ABM25s is expected to give a 12% increase in development productivity.

Q: What other improvement initiatives are being considered with introduction of the ABM25s?

A: There are three different projects currently being undertaken. One is the ventilation-monorail system and its interface with the miner; the second is the supply cassette system, and the handling, carting and loading of supplies onto the miner; the third is the electrical requirements to run the machine, ie cable size and handling.

Q: Why have you fitted hydraulic traction drives on the CM?

A: To create room on the machine, that is two motors that are no longer required. Development and fitment of self drilling bolting systems are likely to require on-board chemical injection storage and pumps, and the space created by fitting the hydraulic traction units will allow retrofitting of SDB systems.

Q: You reported that you have just had your best year of development at Crinum – what performance rates were achieved, MPOH and metres overall?

A: Typically we achieved 3.5–3.75MPOH. I don’t have an exact figure but it was the most metres achieved in any one year and we only operated the three CMs on a part-time basis, rather than on a full-time basis as in previous years.