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在役天然气长输管道停输检修或改线碰口动火作业中,为了确保动火施工的安全,需要对动火段管道内天然气放空后用氮气置换,但线路截断阀内漏会造成氮气置换天然气时发生混气,无法做到置换彻底。由此提出采用中间注氮方法,即在管道放空至微正压后,在碰口部位不动火开一注氮口,自管道中间向两端进行氮气置换。在陕西省天然气长输管道碰口作业中的实践应用,表明:与传统注氮置换方法工艺相比,中间注氮方法可以有效避免线路截断阀内漏带来的带气动火风险,做到置换彻底,动火安全。
In-service natural gas long-distance pipeline shutdown maintenance or re-line touch the mouth moving fire job, in order to ensure the safety of fire construction, the need to move the gas pipeline after the natural gas venting with nitrogen replacement, but the line cut-off valve leakage will cause nitrogen replacement Gaseous gas occurs, can not be completely replaced. It is proposed to use the middle of nitrogen injection method, that is, after the pipeline vent to a slight positive pressure, the mouth part of the immovable fire opened a nitrogen inlet, from the middle of the pipe to the ends of the nitrogen replacement. The practical application of natural gas long-distance pipeline in Shaanxi Province shows that the middle nitrogen injection method can effectively avoid the risk of pneumatic fire caused by the internal leakage of the line cut-off valve compared with the traditional nitrogen injection replacement process, Thoroughly fire safety.