Thomas Industrial Library

What is the best way to weld on a sealed cylinder, tank or container?

Never weld on a sealed container regardless of its size. Even if the vessel is clean and empty, penetration of the shell could release hot gases from the interior. They could also drive the torch flame back towards the weldor. If the cylinder is empty and contains no residual vapors, vent it to atmosphere by opening a valve, hatch, bung, or by drilling a hole. This hole may be welded shut later when all other welding is complete. An even more dangerous situation results when the cylinder contains residual flammable vapors whether it is vented to atmosphere or not. This will almost certainly result in an explosion. Clean or purge the cylinder with an inert gas, then have it checked for lack of explosive vapors by a qualified person. Vent it to atmosphere and begin welding. In some cases filling the vessel with water, or other liquid and welding below the liquid is acceptable, but this is an area for experienced, knowledgeable weldors.

Why use a striker to light an oxyfuel torch and not a match?

The striker keeps your fingers away from the flame that can ignite into a large flame. The use of a butane cigarette lighter for torch ignition can cause a large fire or explosion with the potential power of a half-stick of dynamite.

Why should the welding area be well ventilated to draw the weld fumes away from the weldor?

Many fumes from the welding process are poisonous and must be avoided. Welding fumes from cadmium plating, galvanized sheet metal, lead, brass (which contains zinc), and many fluxes (especially those containing fluorine) are poisonous. They can have both immediate and long-term adverse health effects. Welding supply companies, welding equipment manufacturers, and materials suppliers will provide MSDSs (Material Safety Data Sheets) on request. Often they are available for downloading via the Internet from the manufacturer. They detail the hazards of materials and equipment and show how to deal with them safely. They are particularly helpful in understanding the fume hazards of fluxes, solders, and brazing materials.