Published in September 2006 Australian Longwall Magazine
The Grasstree longwall will mine the relatively low German Creek seam extracting at heights between 2.3-2.7 metres on a 300m face with longwall blocks ranging from 1.7-3.9km.
According to Grasstree longwall co-ordinator Scott Barwick the operation was “designed as a high capacity, low seam mine that will consistently produce in excess of five million tonnes a year”
The mine is serviced via a shaft/winder system, including a personnel and equipment shaft (main intake), development coal production shaft (main return) and emergency egress shaft (second segregated intake).
The mine’s 2-leg 1152t rated roof supports with PM4 support control system, PF5 1242mm AFC with new PMCD control system and 400kW BSL and crusher have all been supplied by DBT.
The Eickhoff shearer features 1.85m Kennametal drums, 750kW cutter motors and 2 x 90kW AC haulage. The shearer has a maximum haulage speed of 39 metres per minute and max cutting speed of 21.5mpm.
The operation will also utlitise a 600m Macquarie Manufacturing monorail.
The electrical package has been supplied by Ampcontrol and includes a 6.25mva 3300/1000 v IP66 transformer, 7 outlet IP66 pump DCB, 8 outlet FLP P66 combined face DCB and control and monitoring enclosure and Ampcontrol voice communications and iMAC face lockout system.
The Longwall Hydraulics pump station is track-mounted and has a maximum flow of 1140 litres a minute. “We identified during flow studies that at 21 metres a minute cutting speed on the shearer we required approximately 1000 litres per minute to keep the supports up with the shearer,” Barwick said.
The pump station will be positioned in the middle gate road six pillars outbye.
To control gas Grasstree has pre-drained the panels using well-proven medium radius drilling (MRD) techniques and in-seam pre-drainage. They have also utlised post drainage goaf bore holes and ventilation and tailgate sealing strategies.
Coal extraction has started in the lowest part of the seam at 2.3-2.4m.
Transportation and installation was performed using FBL10 LHD’s with CHT 50 Chariots, Eimco 936 and MH-40 loaders.
“This was a long way to transport the equipment which presented several challenges, especially when we were in the process of upgrading several conveyors and trying to install a longwall,” Barwick said.
During the installation and commissioning phase of the project the Grasstree team experienced only one first aid case during the complete installation, a great achievement according to Barwick for a largely inexperienced crew over an extended period of time.
“This is a credit to all those who carried out this installation and all the support staff that assisted,” he said.
The Grasstree team is made-up of a mix of experienced and inexperienced miners. Since 2003 the mine has grown from 16 employees to more than 230.
A comprehensive recruitment program was used with a initial database to sort applicants; telephone interviews; psychometric and aptitude testing; leadership exercises and face to face interviews conducted by an assessment centre; reference and absenteeism check and lastly; a coal board medical and physical capability test.
“We recruited 12 crews to cover a 7 on, 7 off production roster, and a four on, three off for the maintenance and supply crews. Our objective is to be the best longwall mine in the group and our personnel are our best asset,” Barwick said.
According to Anglo, the use of a 7 on, 7 off roster has helped attract workers to the mine and giving families the ability to live on the coast and travel to the mine for their time on.
