WORKCOVER NSW has published a safety alert after two plumbing apprentices were seriously injured in March 2009 while purging a natural gas supply line.
The apprentices were undertaking the work at a residential tower block when flammable gases from the supply line escaped into a plant room and ignited.
According to WorkCover NSW, the incident is still being investigated, but it serves as an important reminder of the potentially catastrophic results of the uncontrolled release of a flammable gas within a building.
WorkCover NSW says there needs to be adequate systems in place to purge large volume gas installations and any associated appliances to a safe location on the outside of the building, away from potential ignition sources.
Other important factors in preventing such explosions include the volume of the pipe work, and the fact that natural gas is lighter while liquid petroleum gas is heavier than air.
Purging is carried out to avoid the possibility of an explosive air/gas mixture existing or forming in consumer piping, appliances or confined spaces. The process involves displacing air or an inert gas by a fuel gas, or displacing fuel gas by air or an inert gas.
WorkCover NSW says workers and employers can employ several control measures when purging large volume installations of fuel gas.
The purging operation should not start until a purge area has been defined, made safe, and cleared of all ignition sources.
The purge outlet should be at least six metres away from any ignition source and well clear of any opening into a building.
The purge area should be clearly defined by warning signs and/or barriers, and no smoking should be allowed in or near the purge area.
Where the network operator permits other persons to purge a service pipe, the purge is to be carried out in accordance with the network operator’s procedures.
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