Pipe Joint Management for Risers and Pipelines

Abstract

Minimizing the stress concentration factor (SCF) in pipe joint welding subjected to fatigue is a major concern. Machining the joint ends is one way to achieve this. However, this adds cost, time, risk of potential crack starters, and loss of wall thickness which is detrimental for fatigue, strength, and engineering criticality assessment (ECA) in particular. Pipe joint sorting (certain joints in sequence) and end matching (rotating the pipe joints for best fit) are other ways. However, this adds time, costly logistics, risk of errors, and does not guarantee the minimum possible SCF is achieved. In a typical project, more pipe joints are procured than required in order to mitigate contingencies. For pipelines, this overage is typically a percentage of the required number of joints or pipeline length. For risers, typically double the required number of joints is procured where half of the joints is sent offshore for installation and the remaining half is kept onshore for a spare riser. Then, it becomes very important to send for installation the best pipe joints that produce the best (lowest) SCFs out of the entire batch of pipe joints. This requires calculating the SCF for every potential match of any random joints to be welded together, and then choosing the best joints. Performing such calculations by spreadsheet is not feasible considering the tremendous number of required iterations and calculations. A pipe joint management software development is presented herein which accomplishes this task and examples provided to illustrate the benefits. Note: Selecting pipe joints with the best end measurements, whether ID, OD, OOR, or thickness does not guarantee that the minimum possible SCFs will be achieved since the SCF is a function of all those measurements.