Welding gas is a mixture of various hydrocarbons, principally, methylacetylene , propadiene and propane(mapp). It produces a relatively hot flame (2, 976c) with a high heat release in the primary flame (inner cone) (15, 445kj/m 3 ), less than for acetylene (18, 890kjm 3 ) but much higher than for propane (10, 433kjm 3 ). The secondary flame (outer cone) also gives off a high heat release, similar to propane and natural gas. The combination of a lower flame temperature, more distributed heat source and larger gas flows compared with acetylene results in a substantially slower pierce time. Disposable steel cylinder (size: ª)75x280mm; net:16 oz; 12 pcs/ctn, 17004 cyls per 20ft container)