高压大口径管件,特别是弯头、三通(含清管三通)是大型输气管道工程不可缺少的重要组成件。弯头、三通在介质内压作用下的受力状态远比压力容器内压筒体复杂,其结构和制造工艺导致弯头、三通各部位的形状和壁厚差别较大,尤其是三通属于变壁厚异形元件。高压大口径管件采用管件标准规定的公式法(即数学分析法)计算壁厚,技术落后保守,浪费资源,且在一定设计参数和环境条件下,有的厚壁三通已超出了中国的管件制造公司装备制造能力和工艺技术水平,三通产品某些重要性能如低温下的冲击韧性达不到设计技术要求,导致只有在工程上采用其他技术措施予以完善,管道长期运行存在潜在的安全风险。美国管件标准 MSS SP75 Highstrength,wrought,buttwelding fittings和ASME B16.9 Factorymade wrought buttwelding fittings对管件设计计算规定了公式法和验证试验法两种方法,中国大型输气管道工程的陕京管道工程、西气东输管道工程和陕京二线管道工程进口管件的外国制造公司均采用验证试验法计算壁厚,较公式法计算的壁厚薄很多,运行至今安全可靠;解决中国大型输气管道工程用高压大口径管件设计计算技术落后和某些厚壁三通性能不合格困境的唯一方法,是采用验证试验法确定壁厚,以及采用验证试验法所进行的工作和技术程序。中国大型输气管道工程用管件钢标准及管件钢的使用尚处于初期发展阶段，标准规定的钢材类型、管件钢系列、夏比V型缺口冲击试验温度及管件钢原材料公司与管件公司的协调机制等内容均有商榷余地，改进三通制造工艺提高低温冲击功值的问题有待迅速解决。

High pressure and large diameter pipe fittings, especially elbows and tees (including pigging tees) are essential and important components of large gas pipeline engineering projects. The stress state of elbow and tee under process medium pressure is far more complicated than that of pressure cylinder in pressure vessel. Tee is an abnormal component with variable wall thickness, whose shape and wall thickness of each part are quite different due to the structure and manufacturing process. The formula method (i. e., mathematical analysis method) stipulated in pipe fitting standards is used to calculate wall thickness for high-pressure large-diameter pipe fittings, which is technically backward and conservative and resource consuming. In addition, under certain design parameters and environmental conditions, some thick-walled tees have exceeded the equipment manufacturing capacity and technological level of Chinese pipe fitting companies. Some important properties of tee products, such as impact toughness at low temperature, cannot meet the requirements of the design, leading to the adoption of other technical measures to improve, leading to potential safety risks for long-term operation of the pipeline. American pipe fitting standard MSS SP-75 High-strength,wrought,butt-welding fittings and ASME B16.9 Factory-made wrought buttwelding fittings prescribe two methods for pipe fitting design and calculation: formula method and verification test method. Imported pipe fittings from overseas manufacturers used verification test method for Shaanxi-Beijing Pipeline, West to-East Pipeline and Shaanxi-Beijing Second Pipeline Projects. The thickness of these pipe fittings is significantly thinner, and they are operating in a safe and reliable manner so far. Therefore, the only way to solve the backwardness of high pressure and large diameter pipe fitting design and the non-conformance of some thick wall tee to the standard is to determine the wall thickness using the verification test method and develop the work and technical procedures associated with the verification test method. Pipe fitting steel standards for China‘’s large gas pipeline engineering and the use of pipe fitting steel are still in the early stages of development. The type of steel, pipe fittings steel series, Charpy V-notch impact test temperature specified by standards and the coordination mechanism between pipe fittings steel raw material companies and pipe fitting company are open to discussion. The tee manufacturing process should be upgraded as soon as possible to improve the low-temperature impact energy value.