| 摘要 |
In a device for shutting off one (25) of two pipes (25, 26) to be joined by welding (at 27) and supplying purge gas, the main novel features are that the purge gas is distributed through evenly distributed radial nozzles (14) into a gap (28) of limited radial depth, so that the purge gas flows laminarly or quasi-laminarly past the welding line (27), and that the composition of the purge gas (especially its oxygen content) is sensed at the free end of the gas sampler or sensor (6), i.e. well downstream of the welding site (27).
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