Thermal cutting and safe gas handling

A welder cuts just as often as he welds — workpieces need to be cut short, joints prepared and old material removed. Thermal cutting and work with gas cylinders are therefore fundamental skills in the trade, and both involve hazards that require respect and routine.

§Flame cutting

With flame cutting (autogenous cutting), the steel is heated with a flame of fuel gas and oxygen to a temperature where a jet of pure oxygen makes the metal burn and is blown away. The method works on unalloyed and low-alloy steel and is widely used for shortening and rough cutting. It does not work on stainless steel and aluminium without further work.

§Plasma cutting

Plasma cutting uses a powerful ionized gas jet to melt and blow the material away. It cuts both unalloyed steel, stainless and aluminium, is fast and gives a nice cut edge. Plasma is therefore a versatile choice where flame cutting falls short.

§Pressure cylinders — the daily danger

Gas bottles contain gas under high pressure and are heavy. A fallen bottle with a damaged valve can become a dangerous projectile, and the contents can be flammable, oxygen-enriching or asphyxiating. Therefore, there are fixed rules for how bottles are stored, transported and used.

• 01Always secure bottles so they cannot tip over — also during transport
• 02Place the protective cap on when the bottle is not in use
• 03Keep oil and grease away from oxygen bottles and oxygen fittings — oxygen and grease are a dangerous combination
• 04Store bottles upright, ventilated and separated by gas type
• 05Close the bottle after use and check hoses and connections for leaks

§Kickback and safety equipment

With gas cutting and gas welding the flame can in unfortunate cases bounce back into the hoses — a backflash that in the worst case can reach the bottle. Therefore flashback arrestors are used on the fitting and torch. Knowing the risk and checking that the safeguards are in place is part of the daily routine check.

§Oxygen-enriched and oxygen-poor air

A leaking oxygen bottle can enrich the air with oxygen so materials burn unusually easily and powerfully — including clothing. Conversely cover gases and inert gases can displace oxygen in enclosed spaces and create suffocation hazard without warning. Work in tanks and confined spaces therefore requires special attention to air composition.

§The routine that saves

Most accidents with gas and cutting are caused by broken routine: a bottle that was not secured a leak that was not detected or hot work without sufficient preparation. The skilled welder has made safety a habit that runs on its own — even when busy.