The flexible tubing used to supply gases to the welding or cutting torch. This hose must be sturdy enough to resist the pressure: of the gases and stand up under the constant flexing and twisting of welding operations. Hose specifically manufactured for weld-
ing in accordance with Specification 1-P-7for Rubber Welding Hose, published by the Compressed Gas Association and the Rubber Manufacturers Association, should be used. Lesser grades may disintegrate inside, and the resulting particles can clog the torch valves and contaminate the weld.
To prevent error in connecting apparatus for oxyfuel gas welding, two colors of hose are used: red for fuel gas and green for oxygen. Hose connections must be checked for tightness to avoid gas leakage. When parallel lengths are strapped together for convenience, no more than 100 rnm (4 in.) of any 400 rnm (12 in.) section of hose should be covered by the strapping. Ferrules and clamps made specifically for welding hoses should be used to secure hose to fittings.
Long runs of hose should be avoided. Excess hose should be coiled to prevent kinks and tangles, but should not be wrapped around cylinders or cylinder carts while in use. Twin hose lines, with two hose lines molded into a single casing of rubber, are convenient and prevent twisting and kinking. Welding hose will be much safer and have longer service life if it is kept away from flames, sparks or molten metal. Before
starting to weld, the operator should also see that hose is not left where it can be walked on or run over by vehicles while the operator is concentrating on the weld. This is likely to happen if very long lengths of hose are used.
A backfire which reaches back into the hose ruins it completely, and if it is used for any length of time after such an accident the gas passages in the torch will become clogged with fine particles of the burned lining. Contact with grease or oil is unsafe with oxygen use. Leaky hose is dangerous (and wasteful); hose should be tested at regular intervals by immersing it in water while under pressure. When leaks are found, they should not be repaired with tape. The section with the leak should be cut out and a union inserted, fastened securely with clamps.