Switchloading is defined as `when a flammable or combustible liquid is to be filled into a vehicle tank compartment which had previously contained a liquid having a lower flash point'.
This situation is most likely to arise, but not limited to, when a combustible liquid such as diesel is pumped into a tank that has previously contained petrol. While the tank may have been emptied of its liquid contents, it is likely to still contain flammable vapours that could ignite.
Work health and safety requirements
The WHS Act requires persons conducting a business or undertaking (PCBUs) in particular those in control of workplaces to take all necessary steps to ensure that safe systems of work are implemented, maintained and supervised, and that persons undertaking them are provided with adequate information and training to ensure their safety.
The WHS Regulation, clause 351 provides more specific obligations to manage the risks to health and safety when handling hazardous chemicals at a workplace. Clause 355 requires steps to be taken to prevent the introduction of an ignition source, (including those caused by static electricity), into a hazardous area. If it is not reasonably practicable to eliminate the risks, they must be controlled as far as is reasonably practicable.
The controls identified in this safety alert are not exhaustive and a number of measures could be integrated into a system of work to ensure risks associated with the transfer of dangerous goods are effectively controlled.
The following are some of the control measures that should be considered to reduce the risks from the discharge of static electricity:
- all tanks, pipework, transfer systems (including decanting) and process plant associated with dangerous goods should be electrically bonded to each other and earthed, or otherwise protected (see AS/NZS1020 and AS4979 for advice)
- completely drain previously loaded liquid with the lower flashpoint
- ‘gas free’ the compartment where appropriate
- reduce loading rates to less than one m/s until the fill pipe is submerged
- use anti-static additives in non-conductive liquids
- ensure that hose and hose assemblies are appropriate for use with petroleum products (see AS2683 for advice)
- AS1940: 2004 Storage and handling of flammable and combustible liquids
- AS4979: 2008 Flammable and combustible liquids – Precautions against electrostatic ignition during tank vehicle loading
- AS/NZS1020: 1995 The control of undesirable static electricity
- AS2683: 2000 Hose and hose assemblies for distribution of petroleum and petroleum products (excepting LPG)
- AS/NZS60079.10.1: 2009 Explosive atmospheres part 10.1: Classification of areas – explosive gas atmospheres
- Storage and handling of dangerous goods
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