Explosion in truck cabin from air-conditioning system

What happened?

On 11 January 2021, a serious accident occurred while a mine worker was driving a truck in an underground mine. There was an explosion in the truck cabin causing serious burns to the worker's face, hands and chest. Fortunately the worker's eyes were protected from the blast by safety glasses.

The force of the blast dislodged some of the windows of the truck's cabin and these were blown clear of the truck. Figure 1 shows the deformation to the metal filter access panel for the air-conditioning (AC) system and Figure 2 shows a window lying where it was ejected by the blast.

How did it happen?

While the investigation is still ongoing, the findings of the investigation to date indicate that:

the AC was charged with a refrigerant containing propane and isobutane (hydrocarbon) instead of compliance with the original equipment manufacturer (OEM) requirement which stipulates the use of R134a refrigerant
the AC was not certified for the use of the hydrocarbon refrigerant
personnel servicing and charging the AC did not hold Queensland Gas Work Licenses for working with hydrocarbon refrigerant
the release of hydrocarbon refrigerant from the AC into the cab created an explosive atmosphere which was ignited by an unidentified source.

A similar incident occurred in 2014 when a drill operator in a coal mine suffered burns to the face, hands and torso in an explosion after hydrocarbon refrigerant leaked from the AC system and ignited.

Key issues

Deviation from OEM Guidelines

Equipment not re-engineered

Personnel unlicensed for hydrocarbon refrigerant

Recommendations

The Site Senior Executive must ensure that:

they inspect all refrigeration plant and equipment including AC units on mobile plant to verify compliance with OEM guidance with regards to refrigerant(s)
any refrigeration plant and equipment charged with refrigerant(s) not specified by the OEM must be immediately quarantined from use
if an alternate refrigerant is used, the refrigeration system must be inspected and certified for the use of that alternate refrigerant. In the case of hydrocarbon refrigerants, this is certified by the Petroleum and Gas Inspectorate
any refrigerants may only be charged or drained by persons that are specifically licensed for those refrigerants.

Investigations are ongoing and further information may be published as it becomes available. The information in this publication is what is known at the time of writing.

We issue Safety Notices to draw attention to the occurrence of a serious incident, raise awareness of risks, and prompt assessment of your existing controls.

References and further information

Guidance on Queensland Gas Work Licences can be found at https://www.business.qld.gov.au/industries/mining-energy-water/resources/safety-health/petroleum-gas/gas-work-devices/licences-authorisations

Authorised by Trevor Brown - Deputy Chief Inspector – Mineral Mines & Quarries

Contact: Mark Desira, Inspector of mines (Chemical and Occupational Hygiene) , 0467 808 736 QldMinesInspectorate@rshq.qld.gov.au

Issued by Resources Safety & Health Queensland

Safety: This information is a guide only and is issued to promote safety through experience. It is not to be taken as a statement of law and must not be construed to waive or modify any legal obligation.

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