Oxy-Fuel Cutting: Flames, Tips, and Steel Up to Four Inches Thick

What the work looks like

Oxy-fuel cutting is the original industrial process for cutting steel. A torch mixes fuel gas (acetylene is most common, propane or propylene for thicker or specialty work) with oxygen, burns at around 5600 F, and cuts carbon steel up to 12 inches thick. It is still the dominant process in scrap yards, shipyards, demolition, pipeline work, structural steel, and emergency repair where a laser or plasma cutter is not available. The torch is hand-held or rides on a track-burner (portable automated cutter) or CNC cutting table.

The cut itself is not "melting"; it is a rapid oxidation reaction. The flame preheats the steel to ignition temperature (about 1700 F), then a jet of pure oxygen through the torch's cutting lever burns the steel away. This only works on carbon steel. Stainless steel and aluminum do not oxidize readily and cannot be cut with oxy-fuel.

Job titles: Steel Cutter, Fabricator, Shipyard Worker, Pipeline Worker, Demolition Worker, Structural Iron Worker. Pay $18 to $35 per hour at entry; more in specialty sectors (shipyards, pipeline).

Safety and tools

Oxy-fuel kills more workers per year than most industrial processes. The hazards are fire, burns, explosion from fuel-gas leaks, and asphyxiation in confined spaces. Rules:

• Never use grease or oil on oxygen fittings. Oil plus pure oxygen equals spontaneous fire.
• Check for leaks with soap solution, never a flame.
• Acetylene cylinders must stay upright (if tipped, the acetone solvent inside can enter the line and cause instability). Never use acetylene at over 15 psi (above that it can decompose explosively).
• Flashback arrestors on both torch and regulator ends of the hoses (required by NFPA 51B).
• Keep oxygen and fuel gas cylinders separated by 20 feet or a 5-foot fire-rated barrier when in storage (NFPA 55).
• Fire watch: a dedicated person with an extinguisher for 30 minutes after cutting stops. NFPA 51B hot-work permit required in most industrial settings.
• Ventilation: cutting in a confined space requires atmospheric testing and forced-air ventilation. Oxygen enrichment is a fire hazard.

PPE: flame-resistant shirt and pants (no synthetic), leather apron for torch work, leather gauntlet gloves, cutting goggles or shaded face shield (Shade 4 to 6 for oxy-fuel cutting, not the darker Shade 10 to 14 used for welding), hearing protection.

Tip sizes: each tip is sized for a thickness range. A #0 tip cuts 1/8 to 1/4 inch. A #2 cuts 1/2 to 1 inch. A #5 cuts 2 to 4 inches. Using the wrong tip wastes gas, cuts poorly, and can damage the torch. Consult the manufacturer's tip chart (Victor, Harris, and Smith all publish one).

Tools: torch (Victor or Harris, handheld), tip cleaner set, striker (never a lighter or match), hose (double hose, red for fuel, green for oxygen, B-B fittings), regulators (green for oxygen, red for acetylene), cylinder wrenches (two wrenches, one for the cylinder valve, one for the regulator), cart.

Your first exercise

Find an oxy-fuel setup in a shop you have access to. With supervision, identify: the oxygen cylinder (green, right-hand thread), the acetylene cylinder (red, left-hand thread, notched flats on the valve nut), the regulators (high-pressure and low-pressure gauges each), the hoses (red for fuel, green for oxygen), the torch body, the cutting attachment, the tip. Practice the lighting sequence on paper: open fuel valve 1/4 turn, light with striker, open oxygen valve, adjust flame to neutral (no feather on the inner cone), pull cutting lever to test.

Do not actually light until a competent trainer is standing with you.

Where to go next

Build on Oxy-Fuel Cutting with Plasma Cutting, Laser Cutting (Introduction to Laser Cutting), Waterjet Cutting (Introduction to Waterjet Cutting), Welding Fundamentals, Structural Welding (Introduction to Structural Welding), and Stick Welding (Introduction to Stick Welding). Safety: NFPA 51B Hot Work, Fire Safety & Prevention, Confined Space Entry, Hazardous Materials Handling.