What is surprising is that solutions to low utilization are well known but not successfully implemented in Australian longwall operations. The reasons for this are discussed.
Are US longwalls more productive than comparable Australian longwalls?
We compared a ‘US composite’ longwall to a ‘Australian composite’ longwall. The composites were based on 19 US mines and 13 Australian mines. In 2000, the US composite produced 4.8Mt compared to 3.6Mt for Australian 5-day composite and 4.5Mt for the Australian 7-day composite.
The composites cannot however be meaningfully compared due to the fact that they work different numbers of days per week and have different shear sizes. The US composite worked mainly a 6-day week whilst the Australian composite worked a 5 or 7-day week. Australian mines also had larger shear sizes. To meaningly compare the mines output was standardised to assume that they operated 5 days per week and cut shears of equal size.
When operating time and shear size is standardised the US composite produced 4.3Mtpa versus 3.6Mtpa for the 5-day Australian composite. This represents a revenue loss of $23 million per year. For 7-day mines this represents some $188 million, (i.e. the US composite produces 9.5Mtpa versus 4.5Mtpa for the 7-day Australian composite.) Clearly Australian longwalls are less productive than US longwalls.
How do we account for the productivity gap?
There are two major ways to explain the productivity gap: US longwalls have faster cutting times (ie greater number of shears per operating hour) or they have higher utilization.
We modelled the relative impact of cutting rates and utilization using U_GAP. (U_GAP is a software program which models the utilization of a longwall based on key parameters such as shear size, total longwall production, time taken for longwall moves, number of available days per year etc.)
Using U_GAP we estimated that 5-day and 7-day composites have a utilization rate of 51% and 41% respectively. Our research shows that best practise utilization is around 61% thus 5-day and 7-day mines are suffering from a 10-20 percentage point short fall in utilization! In contrast the US mines approximate best practise utilization.
What are the causes of low utilization?
Before talking about the causes of low utilization it is helpful to think about the solutions. In most industries, utilization can be improved by the implementation of the basic techniques that underpin Total Quality Management (TQM), Reliability Centred Maintenance (RCM), Total Productive Maintenance (TPM), Continuous Improvement, Six Sigma etc. These techniques include statistical process control and problem definition, pareto charts, fish bone diagrams etc.
Why haven’t these techniques been successfully implemented in Australian longwalls?.
Utilization improvement programs have two things in common: they require a ‘future’ orientation and detailed analysis of problems (ie delays). But the nature of longwall operations almost precludes such a future orientation and detailed analysis.
Longwalls, by virtue of their complex geotechnical environments, are subject to more delays than the average manufacturing plant. For example, a ‘best practise’ manufacturing plant would expect a utilization of around 90-95% whilst ‘best practise’ utilization for longwalls is 60-70%. The difference is significant. In an average week (ie 7 x 24 operation), a plant manager would expect the plant to be down between 9 and 17 hours per week versus 50-67 hours for a longwall manager. For the plant manager, downtime is an unusual occurrence, while for the longwall manager it is regular or usual.
As delays are more common longwall managers spend more time responding to them and they respond to them in a particular manner. They focus on fixing the problem rather than preventing the problem from occurring. As a result often no permanent fix is put in place and therefore the problem is likely to occur again. There is simply no time to do the detailed analysis required – as soon as one breakdown is fixed another occurs or at least managers are expecting it to occur.
In conclusion, we believe that for Australian mines to match the productivity of US mines they must achieve best practise utilization. One important step in achieving such best practise is the successful implementation of process improvement techniques that are typically underpin the methods described above.
* This topic was the subject of a paper Baird gave at the AJM Longwall conference in Queensland in March.
