Oxy-Fuel Cutting: First Days on the Torch

Torch cutting, also called burning, uses a flame and a jet of oxygen to slice through steel. Scrap yards, demolition crews, shipyards, steel erectors and repair shops all use it, because a torch needs no electricity and can go almost anywhere. A beginner can make a rough cut after a short lesson, but the gases can kill you if you treat them casually. Your first days are about learning respect for the rig as much as learning to cut.

What You Will Be Able to Do

• Say what oxy-fuel cutting does and where it is used.
• Name the main parts of a torch rig.
• Name the hazards that can hurt you on day one.
• Dress for torch work.
• Make your first practice cut with a trainer.

What the Work Looks Like

The flame heats a spot on the steel to a bright cherry red. You press a lever, and a stream of pure oxygen burns through the hot metal and blows it out the bottom. The torch then moves along a line, with the cut following.

The work varies a lot by job:

Oxy-fuel works on carbon steel. It will not cut stainless steel or aluminum, because they do not burn the same way. A fabrication shop may have a track burner or CNC table that moves the torch for you, but hand cutting is where most people start.

The Rig

• Oxygen cylinder and fuel cylinder, usually acetylene or propane
• Regulators that lower cylinder pressure
• Hoses, green for oxygen and red for fuel
• Flashback arrestors that stop a flame from going back up the hose
• Torch and tip that mix the gases and shape the flame
• Flint striker for lighting the torch

What Will Hurt You on Day One

Fire

Sparks and molten slag can travel a long way, and they roll and fall through gaps. They can start a fire on the other side of a wall or under a floor, sometimes long after you leave. Clear combustibles, check your hot work permit, and know who is on fire watch.

Oxygen and Grease

Pure oxygen makes things burn much faster, and oil or grease can catch fire on their own in it. Keep oily gloves and rags away from oxygen fittings. Never blow off your clothes with oxygen, because a spark could then set you alight.

Fuel Gas

Acetylene is never used above 15 psi, because it can become unstable and explosive. Propane is heavier than air, so it collects in low spots. Leaks can fill a room or tank without you noticing. Check for leaks with leak-test solution, never with a flame.

Cylinders

A cylinder that falls can snap its valve and become a missile. Keep cylinders upright and chained, and move them only with caps on.

Hot, Heavy Steel

The piece you cut will fall. Plan where it goes, and keep your feet and hoses out of the way. Fresh cuts stay hot for a long time, so use pliers, and mark hot steel for others.

Fume

Cutting painted or galvanized steel can release lead, zinc and other metals. Find out what is on the steel before you start. Old paint often contains lead. If you get flu-like symptoms after burning galvanized steel, tell your supervisor. Use the ventilation and respirator your employer requires.

Tight Spaces

Never take a torch into a tank or a closed space without a permit and air testing. Leaked oxygen and fuel can build up, and oxygen soaks into your clothing.

Dressing for the Torch

• Shaded cutting goggles or a face shield with a lens. Shade 5 is a common choice. OSHA sets minimums by thickness.
• Leather gloves and flame-resistant clothing, buttoned up
• No synthetic clothes, which melt onto skin
• No cuffs or open pockets, which catch sparks
• Boots with laces covered, or leather spats on heavy work
• A cap under your hood

Your First Week

Your trainer should walk you through the rig before you light anything. Expect to:

1. Secure and inspect cylinders.
2. Attach regulators and hoses.
3. Leak-check every connection.
4. Set pressures from the tip chart.
5. Light the torch with a striker, and adjust to a neutral flame, with a sharp inner cone.
6. Shut down and bleed the lines.

Do that sequence until it becomes a habit. Then you can start cutting.

Your First Exercise

Clamp a piece of 1/4 or 3/8 inch scrap steel so that the cut will fall clear. Draw a line with soapstone, and practice moving along it with the flame unlit, keeping your hands braced. Then, with your trainer next to you, heat the edge to bright cherry red, press the lever and cut along the line. Do not worry about looks yet. Watch where the sparks go. When they stream out the bottom, you are cutting through. If they spray back up at you, slow down.

Cut 10 strips, and compare the first to the last.

What a Bad Day Sounds Like

Learn these sounds before you need them.

• A sharp pop that puts out the flame is usually a backfire. Find the cause before you relight.
• A squeal or hiss from the torch may be a flashback. Shut the oxygen valve first, then the fuel, then the cylinders, and get help.

Common Mistakes

• Lighting with a lighter. Use a flint striker.
• Standing in front of the valve. Stand to the side when you open a cylinder.
• Dragging a hose through hot slag. Melted hose means a leak and a fire.
• Cutting over your feet or a lead. Plan for the piece and slag.

Check Your Understanding

Your gloves are oily from working on a machine, and you are asked to change a regulator. What do you do?

Change into clean gloves. Oil near an oxygen fitting can ignite.

You finish a cut near a wooden wall and pack up right away. What did you miss?

Fire watch. Sparks can smolder for a long time, so someone has to stay and watch as your permit requires.

A coworker asks you to cut a stainless steel bracket with the torch. What do you say?

Oxy-fuel will not cut stainless. Use another process, such as plasma.

You start cutting a beam with old flaky paint. What should you find out first?

Whether the paint contains lead. Ask for it to be tested or treat it as lead, and use the controls your employer requires.

Key Takeaways

• Oxy-fuel burns through carbon steel with a jet of oxygen.
• Clear combustibles, and keep a fire watch.
• Keep oil and grease away from oxygen.
• Never use acetylene above 15 psi, and check for leaks with solution.
• Dress in leather and natural fibers, and use shaded eye protection.
• Practice setup and shutdown until they are automatic.