August 2017

A review of ventilation and gas management in underground mines

  • By B Robertson FAusIMM(CP), Consulting Mining Engineer and A Self MAusIMM, Principal, ACMC Pty Ltd

This is an excerpt from a paper to be presented at The Australian Mine Ventilation Conference 2017, which will be held in Brisbane from 28-30 August. View the program and register at www.austminevent.com.au.

During 2015 and 2016, the authors conducted a number of surveys, workshops and reviews of ventilation and gas management practices in Australian underground coal mines. The study was funded by the Australian coal industry’s research program (ACARP) with a brief to identify gaps in ventilation and gas management practices for current and future needs and to prepare a road map for change that would assist in delivering improvements.

The study found that despite many examples of leading practice, gas and ventilation management is not afforded the attention and priority that is warranted and that this must be remedied if future operational performance targets are to be achieved and the safety of the industry protected.

Background

Global underground coal mining history is littered with tragic disasters resulting from inadequate management of gas and ventilation. Australian incidences of fires, explosions and gas-related events in mines are a subset of this experience, including several in comparatively recent times. As a result of these disasters, much has been done to strengthen regulations, improve risk management competency and drive cultural change towards zero harm, with demonstrable success in injury rates. However, fatal incidents continue to occur and events such as the Pike River explosion in New Zealand on 19 November, 2010 starkly demonstrate that effective management of gas and ventilation in mines remains a critical issue.

In order to reduce the risks, hazard-specific management plans are used to facilitate the development and maintenance of effective and reliable risk control regimes. These have the potential to underpin successful management of mine risks provided they are effectively applied, regularly reviewed and continuously improved in light of changing conditions.

Project initiative

The safety performance of the Australian underground coal industry is illustrated in Figure 1. Data for this graph was obtained from annual reports of the regulators and the Minerals Council of Australia.

The graph shows the number of fatalities incurred since 1970 for NSW and Queensland, as well as more recent lost time injury (LTI) trends. The spikes in fatality data correspond generally with disasters involving fires and explosions. In addition to these disasters, there have been several ‘near miss’ incidents that could easily have resulted in multiple fatalities.

It is apparent that there has been a marked reduction in fatalities since the 1990s, corresponding with improvements in overall lost time injury frequency rate (LTIFR) results. This is as a result of application of improved safety management systems as well as progressive improvements in legislation following major disasters.

The NSW Department of Resources and Energy maintain a mining database of international fatalities (MacNeill, 2008). A review of the Australian data subset reveals that of the 918 registered underground coal fatalities in the dataset, 388 (42 per cent) were associated with gas and ventilation factors (eg asphyxiation, ignition, explosion, outburst). This high proportion, coupled with the fact that gas-related incidents have a high likelihood of producing multiple fatalities, provides justification for the highest vigilance in managing gas and ventilation in mines.

The Australian coal sector has seen dynamic changes over recent years with a rapid expansion phase and subsequent contraction that has strained management systems and, in particular, safety management systems. An intense focus on increasing production followed by reducing costs, coupled with a high turnover of staff, has raised concerns of erosion of safety management quality. A corresponding increase in the volume of reports referencing ‘red flag’ events (eg near misses, increased exceedance frequency and shortages of critical roles) has raised sufficient concern to warrant intervention. As a result, the ACARP Underground Research Committee determined that a study was required to identify the issues that needed to be addressed to strengthen controls in gas and ventilation management.

Study findings

Project scope

The objectives of the ACARP study were to:

  • identify gaps in ventilation practices for current and future needs
  • review and recommend changes to ventilation management processes that may be suboptimal, eg regulations, statutory responsibilities, management plans and guidelines
  • deliver a roadmap for change that would assist ACARP and industry stakeholders to deliver ventilation improvements.

The vision of the project is to improve ventilation and gas management to contribute to gains in these key performance factors:

  • safe mining
  • productive, low-cost mining
  • controlled and reliable mining conditions
  • coordinated and confident behaviours.

Consultation

A range of initiatives were implemented in order to identify and prioritise the issues requiring attention. These efforts focused on engagement with those industry stakeholders with most knowledge and awareness of the factors involved and took the form of:

  • review of recent papers and reports
  • survey of selected cross-section of industry
  • workshop sessions to flesh out the more significant issues.

At the outset, a review of confidential submissions made by recognised industry experts at the request of ACARP was carried out. Individual surveys and group workshops delivered a broad representation of industry attitudes to ventilation safety.

The higher priority issues and initiatives captured in the study will be summarised in the full conference paper.

Future mines

The surveys and workshops focused more on current issues than future needs. In order to provide some context of the gas and ventilation requirements for mines of the future, reference was made to a survey prepared for the ACARP Roadway Development Task Group (Gibson, 2015), which contained predictions of future mining parameters as well as some ventilation requirements. Points relevant to this study are:

  • longwall panels will be designed up to 6-7 km in length, which is seen as the limit for two entry gate roads
  • three entry gate roads are desirable for ventilation capacity and gas management, but the ability to maintain adequate development float is a limiting factor
  • future longwall mines are projected to produce >6 Mt/a run-of-mine (ROM)
  • ventilation and egress are considered significant challenges for long panels
  • better ventilation systems are needed for gas control on high production faces
  • monorail mounted ventilation systems are considered desirable to assist rapid development, but add complexity
  • respirable dust control requires good ventilation close to the face, appropriate pick selection and cutter head speed, dust suppression at the face, dust screens on cutter/bolter miners and dust scrubbers
  • legislated respirable dust levels will continue to reduce
  • there will be limitations placed on the use of diesels due to concerns regarding diesel particulate matter (DPM)
  • heat management will be an issue for most Queensland mines, requiring increased ventilation, use of chillers or spot coolers, possibly reduced working times and lower powered hydraulic pumps.

It is observed that many of these aspects are already in evidence at current higher performing mines. It is likely that even higher levels of output than those indicated will in fact be targeted in the next ten years, requiring significant improvements in gas and ventilation services to maintain compliance. In particular, if automation of longwall and development systems achieves the aspiration levels currently targeted, then ventilation will become a major constraint without step change improvements. In addition, mines in general are progressing ever-deeper, which normally brings more hostile environmental conditions.

Recommendations

Based on the findings of the study, a number of recommendations were made and an actions roadmap was prepared, suggesting accountabilities and priorities. A final report was submitted to ACARP (Robertson and Self, 2016). There is a need for collaboration between stakeholders to agree on commitments, implementation roles and timing. A summary of the recommendations follows, with expanded results and recommendations to be published in the full paper.

Management

Whilst there are differences in the legislation governing coal mining practice in Queensland and NSW, it appears that operators in both states are able to successfully work with their existing regulations, suggesting that there is not an immediate need for major reform. However, there are a number of issues that warrant adjustment to increase clarity of purpose and to remove ambiguity. Avenues are open to communicate with the regulators to resolve such uncertainties. Harmonisation of state legislation remains a desirable but challenging goal.

The ventilation officer (VO) is a key statutory official at mines and has a large responsibility in assuring safety. However, it is apparent that in many instances, the ability of the VO to fulfil the obligations
of the role are compromised by a number of factors.

The tragic confirmation of a number of coal worker’s pneumoconiosis (CWP) cases in Queensland highlights a management systems failure. Whilst investigations are still in progress it is clear that a major overhaul of dust hazard management is required.

Ventilation Control Devices

Ventilation Control Devices (VCDs) are regulated in both states but the survey identified a need for some improvements in relation to fitness for purpose. It is proposed that functional requirements analysis be conducted on surface and underground VCDs, as well as fan infrastructure, to identify design and regulation changes that would improve designs.

Specific hazards

Initiatives were identified for a number of specific hazards: spontaneous combustion, outbursts, heat management and lightning strike. Whilst there are existing, mature controls for spontaneous combustion and outburst hazards, the scale of risks and cost-effectiveness of controls for these hazards warrants ongoing improvements.

Heat risk is mainly confined to central Queensland mines, but expected increases in exposure with depth and intensity calls for best practice controls to be implemented. The risks of lightning strike are poorly understood and controls are weak.

Goaf gas management

Three topics are covered in this group: – gas monitoring, goaf management and inertisation.

Operators currently have access to a range of gas monitoring systems that service current requirements but are characterised by inherent weaknesses, including: accuracy, range, costs, time delays, cross sensitivity and durability. Other ventilation environment parameters, eg velocity, pressure, temperature, dust and diesel particulates, are not currently well served with remote sensors. The management and interpretation of data captured by these sensors relies on appropriate and timely human oversight. New technologies that would support a step change in environmental monitoring are evolving, such as fibre optic gas detection.

There is a wide variation in the understanding and management of goaf atmospheres and there are also inconsistent approaches to management and few guidelines. Key risk areas are the longwall tailgate corner, pressure control around the goaf and goaf sealing. Similarly, there are shortcomings in the way that inertisation is applied in practice. It is recommended that guidelines for best practice management be developed for these issues.

Self escape

Self escape capability is central to post-incident emergency plans and all mines maintain suitable facilities and training. However, it is noted that a number of self escape elements could be substantially improved. The study recommends a review of the design of primary escape ways and changeover stations, strengthening of backup escape options and provision of the capability to assess conditions following an incident.

Planning

In order to be fully effective, ventilation planning must be carried out systematically and integrated with mine planning and production scheduling. A suitably structured ventilation planning system will address not only design issues, but importantly: fitness for purpose, risk management, financial implications, implementation and compliance. There is a case for a best practice ventilation planning guideline to be made available. Ventilation surveying and modelling are important elements of a ventilation planning system that need to be correctly conducted.

A robust gas drainage design and operations capability has been developed in Australia, but its effectiveness is sometimes compromised by short-term financial decision-making or planning failures. Gas drainage planning should form part of the ventilation planning system and be subjected to similar controls as ventilation planning. As for ventilation planning, there is a case for a best practice gas drainage planning guideline to be made available.

Implementation

In 2016, ACARP agreed to support an extension to the original project to enable a number of the recommendations to be carried out by the authors. These are:

  • guideline for management plans
  • scoping study for next level gas monitoring
  • draft standards for surface and underground VCDs
  • improved design for mine fan installations to survive explosions
  • evaluation of knowledge bases for spontaneous combustion and outburst management
  • guideline for goaf management
  • guideline for inertisation
  • evaluation of status of borehole camera surveillance
  • guideline for ventilation design
  • guideline for gas drainage design
  • guideline for ventilation surveys and modelling
  • guideline for heat management.

A number of other recommendations have been canvassed with appropriate stakeholders who are at different stages of analysis and implementation.

Conclusion

A survey of a cross-section of industry stakeholders identified a number of shortcomings in current gas and ventilation practice in Australian coal mines and confirmed that intervention is needed to strengthen control and confidence. Attention was given not only to current concerns but also the need to lay a solid platform to successfully meet the needs of future higher performance mines.

Eighteen critical topic areas were identified and evaluated. For each of these areas, issues requiring attention were identified and recommendations proposed to deliver improvements. Whilst there are a number of recommendations calling for research or new technology innovation, the bulk of recommendations relate to improvements in day-to-day practices. Consequently, a number of the recommendations call for the development of guidelines for best practice. This is considered necessary to lift standards and achieve more consistent performance.

Acknowledgements

The authors acknowledge ACARP for funding this study and especially the members of the Underground Technical Committee for having the awareness and conviction to challenge current practice. Many individuals have made contributions to the study by way of surveys, workshops and referenced papers, for which the authors are appreciative.  

References

Gibson G, 2015. Industry Survey – Establishing the Functional Requirements of an Integrated Roadway Development System, Report prepared for ACARP Roadway Development Task Group.

MacNeill P, 2008. International Mining Fatality Database, April [online]. Available from: www.resourcesandenergy.nsw.gov.au/miners-and-explorers/safety-and-health/incidents/international-mining-fatality-review [Accessed: 22 March 2016].

Robertson B and Self A, 2016. Ventilation and Gas Management – Underground Coal Mines, ACARP Report C25001.

Feature image: adamziaja/Shutterstock.com.

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