Research On Quality Of Polyethylene Gas Pipeline Welding

Polyethylene(PE)gas pipeline has gradually replaced steel pipeline in buried pipeline network due to its excellent performance of corrosion resistance,flexibility,long service life and environmental protection.More than 90% of buried pipelines have adopted PE gas pipelines recently.PE gas pipe connections are divided into hot-melt welding and electro-melt welding usually,the welding parameters is different between companys,these welded joints are buried under streets and roads in cities,and their failure will lead to a huge explosion with mass casualties and injuries.Therefore,it is important to study the quality of urban PE gas pipeline welded joints.This paper analyses the quality of hot-melt welded joints and electro-melt welded joints in PE gas pipeline,and studies the influence of key welding parameters on the quality of welded joints deeply.The main work is as follows:(1)Study the quality of hot-melt welding of PE gas pipeline which is mostly used.Welding temperature and pressure are important factors in hot-melt welding of PE gas pipeline.Investigate the influence of welding temperature and pressure on welding quality,by using tensile test,slow crack growth test,oxidation induction time,izod impact test and microstructure.According to the research,the performance of the welded joints is better when the actual welding temperature is 220 ? to 240 ? and the welding pressure is 8.5 bar to 11.5bar.The optimum hot-melt welding parameters of PE pipeline are 230 ? and 10 bar,then the performance of the welded joints is as follows: the tensile strength is 23.24 MPa,the slow crack growth time is 196.2h,the oxidation induction time is 92.65 min,the izod impact strength is 33.52 k J/m2.(2)Electro-melt welding is easy to cause problems for PE gas pipeline.Welding voltage and time are two main factors affecting the quality of electro-melt welding.Investigate the influence of welding voltage and time on welding quality,by using peel decohesion test,press test,oxidation induction time,and microstructure.According to the research,the quality of the welded joints can meet the engineering requirements when the actual welding voltage is39.0V to 40.0V and the welding time is 450 s to 550 s.The optimum electro-melt welding parameters of PE gas pipeline are 39.5V and 500 s,then the performance of the welded joints isas follows: the peel force is 5.34 k N,the duration time of press test is 212.5h,the oxidation induction time is 93.23 min.