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Explosive Conditions: Pre-Heating On Confined Space Prior to Welding

Pre-Heating On Confined Space Prior to Welding

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A number of incidents involving cutting or pre-heating prior to welding on a confined space (eg. structrual box sections) have resulted in violent explosions.


When a propane torch is used to pre-heat a welding job on an enclosed, but not totally sealed place, and where the flame is played on the work, partial combustion products are projected inside the enclosed space. When the torch is first applied the mixture quickly becomes inert (too little oxygen and too little fuel), then shortly afterwards becomes rich (too little oxygen but substantial fuel)...


Conduct a risk assessment to determine controls to be implemented to prevent explosions of gas in relation to welding repair work where accumulation of explosive mixtures of gas may occur. Controls may include: Continously purging the space with an inert gas; Cleaning the area and surrounds; Considering mechanical restraints across items such as inspection plates; Establishing a safety zone around the work; Ensuring only the person carrying out the repair work is within this zone; Establish safe work procedures for the person within this zone.


Mineral Resources- New South Wales

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Relates to New South Wales (NSW)

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NSW - New South Wales




NSW Government


23 Nov 2003

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