WLD/Processes/TBT-WLD-003

Oxy-Fuel Welding and Cutting

Welding & Fabrication › Processes › Oxy-Fuel Welding and Cutting

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Oxy-fuel processes use oxygen and a fuel gas, typically acetylene, to generate a flame for welding, cutting, and heating metals.
The oxy-fuel flame reaches temperatures of approximately 3,200°C, making it effective for cutting thick steel sections.
Acetylene is unstable above 1.5 bar gauge pressure and can decompose explosively — regulator settings must never exceed this.
Flash-back arrestors prevent flame travelling from the torch back through the hoses into the gas cylinders causing explosion.
Hot slag and sparks from oxy-fuel cutting travel considerable distances and ignite combustible materials in the surrounding area.
A hot works permit must be in place before any oxy-fuel welding or cutting operation begins on a construction site.
Hose condition must be checked before every use — perished, kinked, or damaged hoses create gas leaks and fire risk.
The correct nozzle size must be selected for the material thickness being cut or welded to achieve proper flame control.
Oxygen enrichment of clothing, gloves, and surrounding materials makes them highly flammable — never direct oxygen at clothing.
Proper lighting and shutdown sequences must be followed to prevent flashback and damage to the equipment.

Acetylene instability	Acetylene decomposes explosively above 1.5 bar — exceeding this pressure on the regulator creates a bomb in the hose and cylinder.
Flashback explosion	Flame travelling back through the hoses into a full cylinder causes a devastating explosion — flash-back arrestors prevent this.
Oxygen enrichment	Clothing saturated with oxygen ignites explosively from the smallest spark — never use oxygen to blow dust off clothing.

Don't

Fit flash-back arrestors to both oxygen and fuel gas regulators before any use.
Set acetylene regulator pressure below 1.5 bar gauge at all times.
Obtain a hot works permit before starting any oxy-fuel cutting or welding.
Check all hoses, connections, and regulators for damage and leaks before use.
Select the correct nozzle size for the material thickness being processed.
Clear combustible materials from the work area before starting oxy-fuel operations.
Follow the correct lighting sequence: fuel gas first, then add oxygen gradually.
Follow the correct shutdown sequence: close oxygen at the torch first, then fuel gas.
Close cylinder valves and relieve hose pressure during all breaks and at end of shift.
Maintain a fire watch during and for 60 minutes after oxy-fuel operations.

DON'T use oxy-fuel equipment without flash-back arrestors on both gas lines.
DON'T exceed 1.5 bar on the acetylene regulator under any circumstances.
DON'T carry out oxy-fuel work without a valid hot works permit in place.
DON'T use hoses that are perished, kinked, damaged, or showing signs of leaks.
DON'T use the wrong nozzle size — it produces an uncontrollable or inefficient flame.
DON'T carry out oxy-fuel work near uncleared combustible materials.
DON'T reverse the lighting sequence — fuel gas must be opened before oxygen.
DON'T reverse the shutdown — oxygen closes first at the torch to prevent flashback.
DON'T leave cylinders open and hoses pressurised during breaks or overnight.
DON'T direct oxygen at clothing, skin, or the surrounding area — enrichment causes fire.

See also: Oxy-Acetylene Cutting Safety | Hot Works Fire Watch

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