Chris Wilkinson, managing director, Mining Consultancy Services (Australia).
Australian underground longwall mines face the same opportunistic challenge in the current international coal market as all other coal mines in Australia and around the globe – produce as much safe coal as possible! All options and opportunities are eagerly weighed up to increase longwall production rates to take opportunity of the all-time high coal prices over the last three years and the further spike in prices evident during negotiations early in 2008.
Longwalls are recognised money spinners, but the “pulse” of a longwall mine is determined by development rates. Generally, throughout Australian longwall mines development float is marginal or non-existent, and various efforts and techniques are employed to reduce the possible negative and restrictive effects it could have on longwall production levels.
Good development rates and a healthy float ahead of the longwall reduce pressure on the entire operation and eliminate inefficiencies which are typical to development constrained operations. It eliminates the risk of longwall production outages due to hold-ups by development and reserve sterilisation caused by truncating longwall panels caused by development shortfalls.
“Just-in-time” completion of development panels for the installation of longwalls doesn’t allow any margin for error, increasing risk profiles and putting unnecessary strain on the operation.
Operations with a marginal or negative float typically introduce an additional development unit or units to create longwall inventory. This significantly increases development cost above initially motivated operational expenditure (and capital expenditure in some cases), with factors of between 130% and 200% of initial development capacity typical.
On the contrary, keeping development units to the minimum assists with the following:
- Alleviates pressure to recruit and retain skilled underground miners (especially in the current market conditions);
- Reduces total ventilation requirements;
- Smooths peak capacity requirements and operational limitations on conveyor and coal clearance systems;
- Reduces quantity of diesel equipment required for men and material transport and operational support; and
- Reduces requirements for other infrastructure and services.
A proactive approach is key in achieving a healthy development float and sustaining it. In the current volatile market with typically high turnover of personnel at all levels, it is imperative to build a framework of management and operating systems which will assist in maintaining production and process continuity despite the change of personnel.
Improved process-based management systems will ensure optimisation and full utilisation of the existing systems, and reduce dependency on additional or upgraded infrastructure and systems to achieve improved results.
A concentrated and formalised effort is required to focus on improvement of development rates (metres per operating hour) and operating hours through implementation and measurement of the following:
- Improved management systems to increase uptime and reduce the most significant delay of panel extension time;
- Greater emphasis on mining and engineering standards through a formalised approach to manage and control standards and setting the base for improved performance in the panel;
- Focused approach to improve availability and reliability of production equipment in the panel to further improve uptime;
- Emphasis on skills and targeted training of development personnel, supported by the resources required to sustain skill levels in a volatile market with high turnover levels; and
- Application of new technology where applicable and economically justifiable.