Study On Welding Technology And Reliability Of X80 Pipeline Steel

The long distance oil and gas transportation pipeline has been more and morepained attention by the world since it is an economical, safe and efficient way to oiland gas transmitting. As a result, the development and utilization of pipelineengineering technology have been greatly developted. With the construction andoperation of the West-East Gas Transportation Pipeline Project and Shangxi-BeijingGas Transportation Pipeline Project in China, our national oil and gas pipelineconstruction have been rapidly developed. Since petroleum and gas are dangerouschemicals, their safe transportation has been given top priority by the researchdepartments of many countries as a important topic. The cost and difficulty ofpipeline construction have efficiently been reduced by the development andutilization of high grade pipe steels. X80 pipe steel is one of the new varieties ofadvanced high grade pipe steels which hve been successfully developed and used inrecent years. However, a precise evaluation of its property and the safety coefficientunder service environment should be made before it is practically applied.This research topic is an integral part of the "Research on the Heat-stewed BendTechnology of X80 Pipe Steel" by CNPC. On the basis of the analysis and research ofthe foreign development and application of X80 pipe steel as well as its determinedmechanical properties and malleability standards, in combination with the experimentresults of the mechanical properties and malleability of X80 pipe steel hot-rollingplate as well as the spiral-seam submerged-arc and vertical-seam submerged-arcwelding pipes developed in China, the reference index of the mechanical propertiesand malleability of X80 pipe steel hot-rolling plate developed in China as well as thespiral-seam submerged-arc and vertical-seam submerged-arc welding pipes have beenadvanced.The technical advice for the loop welding technology of X80 pipe steel has beenfor the first time proposed in this dissertation. Through the analysis of mechanicalproperties, this welding method complies with relevant API regulations. The weldingquality is satisfactory and could be the foundation of practical application. Thewelding procedure scheme of X80 pipeline steel (the pipe diameter is Ф1016mm,the wall thickness is 7.9mm) made in our country has been firstly established:E7010-P1 rods for root welding and hot welding, E9018-G rods for fill welding andcap welding. The qualified welding joints can be made. The qualified weldingprocedure scheme for X80 pipeline steel made in Japan is: STT semi-automatic rootwelding with JM-58 welding wires and E10018-G welding rods for the fill weldingand cap welding.Fuzzy random synthetic evaluation method is firstly adopted for conductingfuzzy assessment on the X80 pipe steel welding technology with level II syntheticevaluation module in this dissertation. , and a relevant program FSAP1 has been made.The fuzzy reliability which influences the quality of welding has been determined byexperts' evaluation in combination with fuzzy evaluation.The reliability calculation program X80RW has been established by the methodof "double coefficient" and on the possible deficiency and invalidity anticipation ofX80 pipe steel has been carried out. A number of examples has been calculated inthis dissertation. It turns out to be that the pipeline is in normal operation.