High achiever

CRINUM’S report card would read something like: “Over-achiever who consistently works hard to meet self-set high standards”. Its longwall, located in central Queensland and owned by BHP Billion Mitsubishi Alliance, has consistently rated amongst the top of its class.

Angie Tomlinson

Published in September 2005 Australian Longwall Magazine

Since the wall kicked off in 1997, Crinum has never failed to appear in the top six producing longwall mines in the country.

Much of this success has been put down to the workforce’s fondness for high operational standards. Plus, with longwall operations superintendent Keith “the general” Weise at the helm - a self-professed lover of “standards” - the operation is looking good.

“We have had visitors from the States and they have said they have never seen a longwall with such high operational standards – it’s a real feather in the cap,” Weise said.

Crinum produced 4.1 million tonnes in the 2005 financial year, against a forecast of 4.16Mt. Crinum has peaked at 5Mtpa, but wasn’t able to reach the lofty target this year due to the last block mined being pulled short because of a major 20m reverse fault. This resulted in an additional relocation.

The mine extracts the full Lilyvale seam at an average height of 3.4m. While the mine has enjoyed good results, the going hasn’t always been easy, with weak strata conditions. The Lilyvale seam is highly cleated, with the top 700mm of the seam particularly cleated. The cleat has a significant impact on the strength of the coal, with an average mass coal strength of 3-4Mpa.

The roof ranges from 5-20Mpa. It consists of mudstone laminated with some weak sandstone, and is very weak in the immediate roof area. Crinum frequently operates in areas of low roof strength (less than 10Mpa) in the bolted horizon. These areas require substantial secondary support.

Periods of weighting conditions have been experienced on the longwall, in the past attributed to size and proximity of the Corvus sandstone, vertical and horizontal stresses exceeding immediate roof strength in places, and continual face stoppages.

“It is now believed the Corvus sandstone plays a lesser part in this weighting problem. However, the weak, friable and unsupportive nature of the coal seam contributing to face spall and roof slabbing exacerbated by face stoppages may play the largest role in these weighting conditions,” Weise said.

The main remedy to dealing with the difficult strata conditions is a detailed longwall hazard map. The map gives the crew warning of where it will run into weak zones and where additional secondary support needs to be installed in the gateroad.

Crinum also utilises the Geoguard Shield Monitoring System to monitor the performance of the longwall supports. It enables rapid detection of face weightings, periodic weighting intervals and maintenance problems.

Support performance is transmitted to geotech Kim Beasley, who is able to monitor when a weighting cycle is coming onto the face. It also serves as a maintenance tool, displaying which roof support may be in need of repair or might have a problem. “We can see from watching the Geoguard that a particular chock may not be performing as it should – the geotech gives a print-out to the mechanical coordinator who rectifies the problem,” Weise said.

To counteract the challenging geology, Crinum - in conjunction with Hydramatic Engineering – is also undertaking a cutting-edge project on roof mapping.

Crinum mine has a life of ten-plus years, with operations moving from Crinum South to Crinum East and finally to Crinum North. The Crinum South operation has a life of three years before operations will be transferred to Crinum East in August 2007. Crinum East has a mine life of seven years. Development will move to the new area within the next six months. Crinum management has opted to relocate to Crinum East solely because of the massive fault at longwall 15. Rather than perform stone drivage through the fault, the longwall will be relocated and works will be developed off the Gregory Crinum highwall.

Weise said management was considering going from the current 270m face to a 300m face at Crinum North.

Like a few of its forward-thinking longwall counterparts, Crinum is aiming for full automation of the face. The mine has just ordered a DBT EL3000 shearer –identical to Beltana, which has achieved excellent results from the automation of its machine. The new shearer – to replace the current EL1000 - will be commissioned on longwall 15 with delivery in late-2006.

With cutter motors that have 650kW of power each, Crinum’s EL3000 packs total installed power of 1600kW. The shearer features DBT’s most advanced automation available, including the Navigator 2, featuring state-based automation. The Crinum order is the second brand new EL3000 DBT has sold in Australia. DBT has also performed upgrades to shearers at Newlands, Dartbrook, Broadmeadow and Kestrel to bring components to EL3000 standards. Crinum currently achieves 95% shearer availability, but will look to at least 97% with the new shearer.

Accompanying the new shearer at longwall 15 will be a new DBT PF6 panline. The new panline will have the benefit of being able to replace the sigma section and pantec without having to replace the whole panline. Crinum will carry over its existing 156 Joy 2-leg 900t shields to the new areas.

Crinum’s longwall moves have been made easier with the aid of Mine Technical Services (MTS), which has been awarded a contract to supply skilled manpower for longwall relocations for the remainder of Crinum South. MTS performs much of the pre-installation, including installing the AFC and BSL prior to the move.

The longwall has a capacity of 3500 tonnes per hour; the trunk conveyor has a capacity of 4000t/hr.

On the maintenance front, Crinum has a 12-person longwall crew that contains four tradespeople, giving the mine the ability to do preventative maintenance. Crinum utilises two four-hour maintenance windows between shift changes.

Like most Bowen Basin mines, Crinum makes...click here to read on.