SafeWork SA inspectors were called in to investigate following a fire at the mine site’s underground magazine during the change of shift.

The magazine’s deluge system activated automatically and the Emergency Response Team (ERT), along with the magazine keeper, attended the scene and confirmed that the fire was extinguished.  No one was injured in the fire.

The SafeWork SA inspectors investigated the fire and the Mine Operator engaged a forensic fire investigator to identify the most likely cause.

During the SafeWork SA investigation it was discovered that several of the blasting cartridges were damaged and had leaked a black substance from the casing.

A Safety Data Sheet for the cartridges identifies that the explosive composition may auto-heat when exposed to humid conditions. The humid conditions of the underground mine may lead to the generation of heat caused by the exothermic decomposition and subsequent reaction of the explosive compositions.

The most probable cause of the fire was found to be due to the auto-heating of the explosive substances leaking from damaged cartridges causing ignition of the explosives or the carton.

SafeWork SA is warning mine and quarry operators to:

• Ensure explosives are within their recommended shelf life. Where explosives have expired, have clear and actionable plans in place to destroy them safely and as soon as reasonably practicable.
• Store explosives in accordance with the temperature and humidity requirements in the Safety Data Sheet or Technical Data Sheet.
• Ensure blasting cartridges are stored in cartons that are closed and sealed.
• Damaged explosives should be quarantined away from other explosives and destroyed as soon as reasonably practicable.
• Explosives users should ensure that they have whole of life plans in place for explosives and security sensitive ammonium nitrate (SSAN), including clear plans to deal with out of specification explosives such as those that are expired or damaged.

Further links:

• Mining and quarrying