WA’s Director of Dangerous Goods and Petroleum Safety recently issued a safety bulletin on the suitability of dry chemical powder fire extinguishers when transporting explosives and other dangerous goods.
Both the Australian Code for the Transport of Dangerous Goods by Road and Rail (ADG) and the Australian Code for the Transport of Explosives by Road and Rail (AEC) require transport companies to carry dry chemical powder (DCP) fire extinguishers when transporting dangerous goods.
The bulletin noted that there have been two incidents in Western Australia in the past two years where DCP fire extinguishers have not effectively extinguished a brake or tyre fire on a vehicle transporting ammonium nitrate (AN).
In both cases, these were the only type of fire extinguisher carried and the fire reignited shortly afterwards. The vehicles involved had been regularly serviced and well maintained.
In the first incident, the driver used all four DCP extinguishers on the vehicle. When the fire reignited, an exclusion zone was set up around the vehicle to let the fire burn itself out – fortunately without further incident.
In the second incident, after the use of two DCP extinguishers, passing motorists assisted the driver in effectively extinguishing the fire by providing two foam fire extinguishers and water.
Although DCP fire extinguishers are effective, they do not remove the heat from metal and rubber, which can lead to reignition.
DCP extinguishers contain a very fine powder that acts as a blanketing agent preventing access to the oxygen required to support the fire.
However, it does not remove the heat from the medium (e.g. tyre or brake), thus reignition is possible when there is a break in the DCP coverage.
In light of these recent incidents, the Department of Mines, Industry Regulation and Safety has recommended to the National Transport Commission (NTC) that vehicles transporting security sensitive ammonium nitrate (SSAN) carry water-based fire extinguishers in conjunction with DCP fire extinguishers.
It is strongly recommended that companies transporting SSAN, explosives and other dangerous goods: