管件防脆断控制技术现状与思考

Technical status and considerations of brittle fracture control of pipe fittings

中俄东线天然气管道工程站场设计温度低至-45℃,对管道设施防脆断能力提出了新挑战,为了防止低温环境下服役构件发生脆性断裂,需要制定科学、合理的韧性指标要求。系统阐述了防脆断控制技术的发展历程:经验方法→断裂分析图法→断裂力学方法。以中俄东线天然气管道工程为例,分析了油气管道管件基于经验方法的防脆断技术现状,并对比分析了ASME BPVC(Boiling and Pressure Vessel Code)的防脆断控制要求,指出油气管道管件防脆断控制措施存在的不足。基于经验的夏比冲击韧性指标应用于高韧性管线钢时,可能存在不足以防止脆性断裂的风险,因此提出:①建立完善的基于断裂力学的高钢级高韧性管件防脆断控制指标体系;②在现有防脆断控制指标的基础上增加NDT(Nil-Ductility Transition)测试要求;③建立基于断裂力学评估的防脆断控制要求。

The station temperature of China-Russia Eastern Gas Pipeline Project is designed low to-45 ℃,which poses new challenges to the brittle fracture prevention capability of pipeline facilities,so it is necessary to set up scientific and reasonable toughness index requirements to prevent brittle fracture of in-service components under low temperature conditions.The development process of brittle fracture control technology,from empirical method to fracture analysis diagram method and then to fracture mechanics method,was systematically described.The empirial method based technical status on brittle fracture control of oil and gas pipelines was analyzed with China-Russia Eastern Gas Pipeline as the example.Meanwhile,through the comparison and analysis with the brittle fracture control requirements in ASME Boiling and Pressure Vessel Code(BPVC),the deficiencies of brittle fracture control measures for oil and gas pipeline fittings were pointed out.Analysis shows that the experience-based Charpy impact toughness index may be insufficient to prevent brittle fracture when applied to high toughness pipeline steel.Therefore,it is suggested to ① build a perfect fracture mechanicsbased brittle fracture control index system for high-grade high-toughness pipeline steel,② add Nil-Ductility Transition(NDT) test requirements based on the existing brittle fracture control indexes,③ and establish brittle fracture control requirements based on fracture mechanics evaluation.