Loading …
Flame cutting plasma and handling pressure cylinders
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.
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 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.
Thermal cutting in metal is subject to the same training requirement as welding (BEK 1978/2021 § 14 and BEK 582/2026 § 16). Flame cutting has its own process-related limit value for the total fumes: 1.7 mg/m³ (BEK 613/2026, Annex 2). Flame cutting and plasma cutting also produce large amounts of nitrous gases, and there are no gas filters for respirators that protect against them. In ISO 4063, cutting belongs to main group 8.
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.
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.
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.
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.