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Fire and explosion on Longwall No 1 Tailgate
at the Blakefield South Mine
5 January 2011
Published report prepared by the
Investigation Unit, Thornton
May, 2012 www.resources.nsw.gov.au/safety
Fire and Explosion on Longwall No. 1 Tailgate at the Blakefield South Mine
5 January 2011
Authors: Tim Flowers and Jennie Stewart, Investigators, Investigation Unit, Thornton
© State of New South Wales through the Department of Trade and Investment, Regional Infrastructure and Services (NSW Trade and Investment) 2011 Published by NSW Trade & Investment Report Date 8 May 2012 TRIM reference: 11/236 Disclaimer The information contained in this publication is based on knowledge and understanding at the time of writing (May 2012). However, because of advances in knowledge, users are reminded of the need to ensure that information on which they rely is up to date and to check the currency of the information with the appropriate officer of the NSW Department of Trade and Investment, Regional Infrastructure and Services or the user’s independent advisor.
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 i Contents Introduction
The incident that prompted this report
Location of the mine
The mine operator
The mining operation
Circumstances of the incident
Blakefield South Mine Ventilation
Overview of the ventilation
Ventilation at the time of the incident
Stone dusting at Blakefield South Mine
Evacuation of the longwall
Evacuation of the rest of the mine
Recovery of the mine
Remote sealing of Longwall No 1
Re-entry of Longwall No 1
Exhibits and samples taken
Condition of the longwall face
Sources of ignition
Coupling of lightning and the underground workings via a borehole
Conductive pathways through indirect coupling
Spontaneous combustion management plan
Faulty breathing apparatus
Employees at risk
Safety Management Systems
Systems of work
Positive actions by the mine
Actions of the Department
Mine reopens after work method reviews
Issues drawn to operators attention by the Investigation Unit
Safety Alerts released
Strategies to prevent recurrence
Glossary of Terms
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 iii Introduction The incident that prompted this report This investigation report sets out the events leading up to, and examines the possible causes of, an explosion underground at the Blakefield South Mine at 7.36pm on Wednesday 5 January 2011. Blakefield South Mine is operated by Bulga Underground Operations Pty Limited, known as Beltana Highwall Mining Pty Limited at the time of the incident.
There were 47 people working in the mine at the time of the explosion; all were evacuated safely from the mine. An underground fire was associated with the explosion and Blakefield South Mine was subsequently sealed. Blakefield South Mine was not able to be re-entered until 6 June 2011.
O ve r v i e w Location of the mine The Bulga Coal Complex is approximately 15 km southwest of Singleton, 1 km north of Broke and 1.5 km east of Bulga, in the Upper Hunter Valley of New South Wales. Bulga Underground Operations Pty Limited comprises the underground coal mines that form part of the Bulga Coal Complex.
Mining history Coal mining at what is now known as the Bulga Complex was started by the Broken Hill Proprietary (BHP) in 1982. It was then known as the Saxonvale Mine and was an open cut operation. In 1988 BHP transferred ownership of the mine to Elders Resources and the following year it was acquired by Oakbridge Pty Limited.
Oakbridge began underground coal mining in 1994 at the South Bulga Mine using the longwall method of mining. Coal was extracted from the Lower Whybrow seam. Longwall production at South Bulga Colliery ceased in 2002 after the extraction of approximately 30 million tonnes of coal from 13 longwall panels. 1 Beltana Highwall Mining commenced longwall operations in 2003. Blakefield South Mine began longwall operations in June 2010 in the Blakefield seam. Production operations at the Beltana Highwall Mine ceased as of August 2011.
Xstrata Coal, Bulga Complex Mining, 30 November 2011, http://www.bulgacoal.com.au/EN/Pages/default.aspx.
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 The operation
The companies At the time of the explosion Beltana Underground Operations Pty Limited was known as Beltana Highwall Mining Pty Limited. Beltana Highwall Mining comprised two underground longwall operations, the Beltana Highwall Mine and Blakefield South Mine.
Beltana Highwall Mining operated in the Lower Wybrow seam.
Bulga Underground Operations is managed by Bulga Coal Management Pty Limited which in turn is managed by Xstrata Coal.
Bulga Underground Operations is one of the Xstrata Coal group’s coal mining operations.
Xstrata Coal is the world’s largest producer of export thermal coal and a significant producer of premium quality hard coking coal and semi-soft coal. With headquarters in Sydney, Xstrata Coal has interests in over 30 operating coal mines in Australia, South Africa and Colombia and an exploration project in Nova Scotia, Canada 2 The colliery holder was identified as Bulga Coal Management Pty Limited, a joint venture of Saxonvale Coal Pty Limited and Nippon Steel Australia Pty Ltd. The ultimate holding company, of Bulga Coal Management Pty Limited is AZSA Holdings Pty Limited.
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 The mine operator Bulga Underground Operations is the nominated mine operator under section 17 of the Coal Mine Health and Safety Act 2002 and operates the mine on behalf of the Bulga Joint Venture (BJV).
Bulga Underground Operations is 68.25% owned by Xstrata Coal through its various management and ownership companies. It is managed by Xstrata Coal NSW on behalf of the Bulga Joint Venture. 3 Bulga Underground Operations is a wholly owned subsidiary of Bulga Coal Management Pty Limited.
The ultimate holding company of Beltana Highwall Mining Pty Limited was Oakbridge Pty Limited.
The mining operation Blakefield South Mine has been developed over the last five years with Longwall No 1 (LW1) starting production in June 2010. The longwall is 325 metres wide and is representative of a trend for ever wider longwalls. It was intended that after the completion of LW1, the next wall would be 405 m wide. Large quantities of air are passed through the longwall to remove dust and gas. Bulga Underground Operations had installed two ventilation shafts in Blakefield South Mine, each with three fans. The mine operated a forcing/exhaust ventilation system (more commonly referred to as a push/pull ventilation system) with Ventilation Shaft No 1 pushing air into the mine and Ventilation Shaft No 2 pulling air out of the mine. Normally air is pulled through the mine only.
The push/pull system of ventilation is designed to reduce the pressure difference between the mine air along the longwall face and the surface so that, theoretically, the absolute pressure along the face is the same as the surface absolute pressure. This reduces the likelihood of the goaf atmosphere that is high in methane (CH4), and therefore inert (note that the atmosphere in the goaf of LW1 contained 80 to 90% CH4 at the time of the incident), 4 mixing with oxygen drawn from the surface or being drawn from the goaf out into the mine workings.
Reducing the available oxygen diminishes the risk of two unwanted scenarios from occurring: the development of an explosive atmosphere in the goaf and spontaneous combustion.
Note: The ventilation of the mine is discussed in greater detail in the section titled Blakefield South Mine Ventilation.
Blakefield South Mine is also the world’s first longwall mining operation to use an 11 kV powered armoured face conveyor (AFC) in a hazardous zone, defined by section 3 of the Coal Mine Health and Safety Regulation 2006. The greater width of the longwall combined with increased power to the shearer requiring greater power to drive the AFC.
LW1 utilises 158 x 2.0 m wide 1270 tonne yield load powered roof supports. The AFC was the most powerful in the world (when operating) with: a 400 kW crusher, a 600 kW x http://www.xstratacoal.com/EN/Operations/Pages/CoalOperations.aspx Readings of the goaf atmosphere taken by gas monitoring from the gas drainage wells.
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 1550mm wide beam stage loader (BSL) and two 1600 kW x 1100 mm AFC drives (upgradable to 3 x 1 600 kw). The shearer has 1000 kW rated ranging arms, 860 kW cutter motors and 150 kW mega drive haulage. 5 Figures 1 and 2 below show longwall roof supports and a longwall shearer similar to the roof supports and shearer that were in use on the face of LW1.
Figure 1: Typical longwall face showing chocks and AFC http://www.joy.com/en/Joy/Products/Longwall-Systems.htm Complete Longwall Systems Brochure Figure 2: Longwall face Beltana Highwall mine showing shearer and longwall chocks Photo by M. Freeman, 24 April 2010 http://www.excellenceawards.org.au/2010_finalists/2010-finalist-37.html Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 I nve s t i g a t i o n It was determined on 13 January 2011 that the incident would be investigated by the Investigation Unit. On 14 January 2011 the Investigation Unit Manager, Steven Millington and Investigator Tim Flowers attended the mine.
The mine was sealed at this time and no inspection of the scene would be possible until the mine had been safely recovered. The investigation concentrated on interviewing all relevant witnesses and appropriate people in management, and collecting documents to begin the process of identifying the cause(s) of the explosion.
On 6 June 2011 the mine, excluding LW1, was successfully reventilated after one earlier failed attempt (on 15 February 2011). The longwall was remotely sealed from the surface via boreholes drilled from the surface to intersect LW1 gate roads at predetermined points. A combination of fly ash and Rocsil (a brand of rapid expanding fire resistant antistatic foam) 6 was pumped down these holes to seal LW1 from the rest of the mine. Once the atmosphere in the mine was rendered safe it was possible to inspect the mine, and in particular, the electrical apparatus leading into the mine.
Once the development headings had been reventilated work began on the reventilation of the longwall gate roads. This was undertaken via a number of stages whereby the mine’s rescue teams would enter through the seals, then advance a number of cutthroughs before erecting a further seal so that the outbye seal could be fully breached.
This process concluded in December 2011.
To date the longwall has not been recovered.
One of the mine’s rescue teams was able to access the longwall face as far as the tailgate and reported surprisingly little damage down the length of the face. The team collected some articles from the tailgate area and a dust sample; otherwise the face area and the tailgate have not been thoroughly inspected or examined.
The incident At 7.36pm on Wednesday 5 January 2011 an explosion occurred in the vicinity of LW1 tailgate at the Blakefield South Mine.
The underground crew working at the LW1 panel that evening consisted of a longwall crew supervisor/deputy, shearer operator, production fitter/maintenance supervisor, technician/electrician, bootend attendant, mechanical technician, longwall operator, electrician/technician, electrician and an electrician/technician.
At the time of the explosion LW1 was stopped for maintenance. Three of the 10 crew members were having a meal break at the crib room at 17 cut-through. Five of the crew were repairing flight bars on the AFC at the maingate. A production fitter/maintenance supervisor was two thirds of the way along the wall at No 130 support marking loose bolts.
Wilson Mining Services, Rocsil Foam Rapid Cavity Filler, (9 March 2011) http://www.wilsonmining.com.au/Rocsil.htm.
Investigation Report Blakefield South Mine Fire and Explosion – 5 January 2011 The force of the blast knocked the production fitter/maintenance supervisor off his feet.
The overpressure created by the blast was still of sufficient strength when it passed the maingate, some 325 m away, to require the workmen to brace themselves. The pulse from the explosion could be felt all the way to the Mains crib room and at the entry to Maingate 2 and Maingate 3 some two to three kilometres away.
The following is a description of events that occurred at the time of the explosion by the
crew supervisor/deputy and the production fitter/maintenance supervisor:
The production fitter/maintenance supervisor felt his ears pop at about 7.30pm.
“I felt … a change in pressure and then I felt like a shockwave hit me and then a really loud crack … it sounded like it was right next to my ears,” he told investigators. “And, then the shockwave did knock me over, probably a bit over a metre, knocked me back towards the maingate. “ Blinded by the dust, he was only aware of an unusual odour.
“Something which was really different was the smell. It smelt like gunpowder, kind of like cordite after you shoot. It’s a real distinctive smell and I’ll never forget that smell.” Unsure of what had happened, the man ran for the maingate while the deputy called out to see if he was injured.