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16. WELDING AND FLAME CUTTING Use of flame-cutters Gas flame welding and allied processes produce fumes and gases, which may be harm- ful to your health. Nitrogen oxides produced in heat may cause serious respiratory symptoms if there is not enough ventilation. Local spot exhaust ventilation is a good way to arrange ventilation. Before lighting your torch Make sure you have taken care of local exhaust ventilation, sufficient general ventilation and any other means, if needed. When the hoses are released from the valves or the torch from the hoses, there is a risk of an explosive gas mixture of acetylene and air or oxygen. Flush the hoses by letting acetylene or propane flow from the torch (for 10 - 30 seconds, with smaller torches the time is longer) to the open air before you light the torch always in the following cases: 1. When the pressure regulator (with its hoses) is fitted to the cylinders or distribution network. 2. When the valves of the cylinders or distribution manifold have been close during a break and you have re-opened them to continue the work. Lighting the torch 1. Open the acetylene valve of the torch. 2. Ignite the gas. 3. Open the oxygen valve to adjust the flame. 4. Test the accuracy of the flame by opening the cutting oxygen jet just for a moment (cutting torch). Turning off the torch 1. Close the acetylene valve. 2. Close the oxygen valve. 3. Close the valves in the distribution network or cylinders (for breaks and after your working day). 77


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