Strain-Based Design of Pipelines

摘要

In recognition of the increasing trend toward strain-based design of pipelines and the need for basic guidance on strain-based design, the Minerals Management Service (MMS) and the Office of Pipeline Safety (OPS) co-funded EWI to provide a general guidance on strain-based design for pipelines both for the on-shore and off-shore environment. The resulting guidance can be found in this report. Special consideration has been given to the choice and qualification of pipe material, the choice and qualification of girth welding procedures and the demonstration that both pipe and weld areas have sufficient strain capacity to meet the requirements of the design. The current use of strain-based design has many project-specific components. This limits the ability of a cookbook approach where each step can be laid out as part of common design sequence to apply to all areas of pipe strain-based design. This situation would indicate that taking the current state-of-the-art methods and creating a code or standard would be ineffective at covering the range of needs for future pipeline designs. Yet, because there are many choices that are part of a particular pipeline strain-based design, the availability of guidance and recommended practices can help simplify the design and qualification process for many pipelines. Going forward with this approach, the guidance provided in this report could profitably be taken forward by the industry into, for instance, an API-recommended practice. The primary areas where strain-based design will be used are in design of reeled laying of offshore pipelines, in thermal design of arctic pipelines, in design of types of offshore pipelay systems, in design and assessment of pipelines in areas with significant expected ground movement, and in high-temperature and high-pressure HT/HP pipeline designs. Pipeline may also have some applications of strain-based design where cyclic loadings cause occasional peak stresses above the pipe yield strength. Here, the cyclic lifetime assessment is improved by using strain ranges for the cycles, instead of stress ranges.