| 摘要 |
A safety device for gas welding has a cylindrical main body having a flow path for an inflammable gas. A cylindrical cover is mounted on the outer periphery of the main body in such a manner that it can reciprocate on the outer periphery. The main body is provided with a normal-flow indicating mark and a counter-flow indicating mark which are positioned in space-apart relation on the outer periphery of the main body. One of the counter-flow and normal-flow indicating marks is exposed and the remaining one is covered alternately, depending on whether the flow condition is counter-flow or normal-flow.
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