Fire and Explosion Prevention
Molten metal, sparks, spatter, and slag are developed by welding, cutting, and allied processes. If preventative measures are not followed, these combustible materials can create a fire or explosion.
Sparks, spatter, and molten metal are the main reasons for fires and explosions in welding and cutting applications.
They can travel up to 35 feet from the work area or travel greater distances when falling or during plasma arc cutting and air carbon arc cutting or gouging.
In certain welding processes, combustible materials can pass through or become lodged in cracks, clothing, pipe holes, and other openings in walls, floors, or partitions. Heat can be transferred through walls and surfaces.
Typical combustible materials inside of building include
Parts of buildings such as floors, partitions, and roofs may also be combustible. Typical combustible materials outside of buildings include
Welding and cutting can cause explosions in spaces containing flammable gases, vapors, liquids, or dust.
Remove combustible materials and prevent flammable gases, vapors, and dust from accumulating in the work environment to prevent the chances of a fire or explosion. Always have appropriate fire extinguishing equipment nearby.
How to Avoid the Hazard
Develop adequate procedures, and use proper equipment to do the job safely
Ensure that appropriate fire extinguishing equipment is nearby and know how to use it
Remove combustible materials from a sphere securing a minimum radius of 35 feet (10.7 meters) around the work area or move the work to an area far away from combustible materials.
Make sure all electrical equipment and wiring are installed properly and have recommended circuit protection
If relocation is not possible, protect combustibles with fire-resistant covers
Do not overload or improperly size input conductors and/or weld output conductors to prevent fire hazards
If possible, enclose the work area with portable, fire-resistant screens.
Connect the work cable to the work as close to the welding zone as practical to avoid stray current paths
Cover or block all openings within the 35-foot radius, such as doorways, windows, cracks, or other openings with fire-resistant material.
Do not weld or cut in atmospheres containing reactive, toxic, or flammable gases, vapors, liquids, or dust
Do not weld on or cut material with a combustible coating or internal structure such as walls or ceilings without an appropriate method to eliminate hazards.
Do not create dust clouds. Some dust clouds can explode
When needed, have a qualified firewatcher in the work area during and for at least 30 minutes after the job is finished
Do not apply heat to a workpiece covered by an unknown substance or coating that can produce flammable, toxic, or reactive vapors when heated.
When finished welding or cutting, audit the area for evidence of a fire.
Easily visible smoke or flame may not be present for some time after a fire has started. Combustibles like wood dust can smolder for extended periods of time (days).
Do not apply heat to a container that has held an unknown substance or a combustible material unless container
is made or declared safe.
Do not put hot slag in containers holding combustible material
Provide adequate ventilation in work areas to prevent accumulation of flammable gases, vapors, or dust.
Resource: AWS Health and Fact Sheet No. 6 - Fire and Explosion Prevention