On 4 and 15 September 2009, there were two fatal workplace accidents involving the explosion of flammable vapours during the cutting of metal tanks. These tragic accidents highlight the dangers of working on tanks and containers that contain, or used to contain, flammable liquids.
The first fatality occurred while a person was working on top of a tank that contained heated bitumen. It is believed that flammable vapours from the tank vent were ignited by electrical equipment.
The second occurred when a worker was dismantling a tank that had contained petrol. It is believed that a gas cutter ignited flammable vapours within the empty tank.
The risks of doing 'hot work' – involving torches or flame cutting equipment – on containers that previously contained flammable substances, are well known.
Examples of flammable substances are petrol, aviation fuel, diesel, and bitumen.
The Department of Labour recommends the following steps are taken before work begins on or near tanks that previously contained flammable substances.
- realise that doing 'hot work' around flammable substances creates an extreme danger of explosion or fire
- identify the hazards that can be created when you work on or near tanks and containers that hold, or have held flammable substances
- assess the hazards and ensure the correct controls are in place.
- plan the work so you eliminate all sources of ignition from the area
- provide employees with appropriate information, training and supervision so they can work safely around flammable substances.
- Hot Work on Drums and Tanks, Department of Labour (1988) (http://www.osh.dol.govt.nz/order/catalogue/229.shtml)
- Health and Safety in Welding, Department of Labour (2006) (http://www.osh.dol.govt.nz/order/catalogue/welding.shtml)
- Relevant Standards
- Standards applying to welding processes include:
- NZS 4711:1984 Qualification tests for metal-arc welders.
- AS/NZS 1338.1:1992 Filters for eye protectors – Filters for protection against radiation generated in welding and allied operations.
- The AS/NZS 1554 Series Covers: Welding of steel structures; welding of high strength quenched and tempered steels; welding of steel structures to high levels of fatigue loading; welding stainless steel for structural purposes.
- AS 1796:2001 Certification of welders and welding supervisors.
- AS 2214:2004 Certification of welding supervisors – structural steel welding.
- AS/NZS 3100:2002 Approval and test specification – General requirements for electrical equipment.
- AS/NZS 3195:2002 Approval and test specification – Portable machines for electric arc welding and allied processes.
- AS/NZS 1995:2003 Welding cables.
- AS/NZS 3957:2006 Light-transmitting screens and curtains for welding operations.
- AS/NZS 1715:2009 Selection, use and maintenance of respiratory protective equipment.
- AS/NZS 2161 Series Occupational protective gloves.
- AS/NZS 2210 Series Occupational protective footwear.
- NZS 4781:1973 Code of practice for safety in welding and cutting.
- Code of Practice for the Transportation and Disposal of Underground Petroleum Storage Tanks and Related Wastes, Department of Labour (1995) (http://www.osh.dol.govt.nz/order/catalogue/193.shtml)
- Code of Practice for Disused Below-Ground Stationary Tanks on Farms Environmental Risk Management Authority New Zealand (2007)(http://www.ermanz.govt.nz/resources/publications/pdfs/COP19-1.pdf)
Note: This material has been prepared using the best information available to the Department of Labour at the time of publication. Information may change over time and it may be necessary for you to obtain an update. This material is also only intended to provide general advice and does not constitute legal advice. You should make your own judgement about action you may need to take to ensure you have complied with your workplace health and safety obligations under the law.
Which industries/sectors or matters will this information be relevant to?
- Manufacturing, recycling, repairs, and maintenance.
Reproduced and adapted from a Hazard Alert from the Department of Labour 18 September 2009.Standards are available from Standards New Zealand website(http://www.standards.co.nz/), email email@example.com or call 0800 782 632.