The stresses induced to a pipe during line lowering are the maximum stresses that the pipeline will experience during its lifetime, in regions where there are no excessive environmental loads. During the installation of the TransCanada pipeline at Stittsville, Ontario, it was critical to limit the pipeline stresses that occurred during line lowering. This was required in order to fulfill the requirements of ECA-based flaw acceptance criteria applicable to mainline welding. However, the construction of the pipeline involved numerous challenges with regards to moving equipment during the pipeline installation, regions of deep cover requirements, and spatial restrictions on the right of way. These conditions introduced complicated loading scenarios, which made it difficult to ascertain the resulting stresses that the line lowering would apply to the pipeline. These stresses were evaluated herein using the finite element analysis program PIPLIN, with consideration of the actual in-situ installation conditions. Each loading condition was modeled individually, and the forces in the sidebooms were considered in addition to the pipeline stresses. It was determined that all the stresses in the pipeline during the line lowering were acceptable, so long as the specified boom locations remained within limits.

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