The “A” manifold header replacement is presented within this paper as a case study to demonstrate how laser scanning (both of the existing piping and the newly fabricated spools) as well as off-site spool fabrication and testing, when combined with detailed pre-planning of activities and mapping of facility impacts to optimize the execution of a complex in-situ piping modification with an extremely tight facility outage window.
This paper explores the design and execution strategies used for the complete replacement of the southern portion of the NPS 24 piping header in “A” manifold at Enbridge’s Sarnia Terminal as contained within the Project Leave-to-Open packages. The piping header was fully replaced and upsized to NPS 30 as part of the Line 9B Reversal & Line 9 Capacity Expansion Project during a four-day facility outage in the summer of 2014. The work was managed by Enbridge Pipelines Inc. and executed by a regional industrial construction company (“contractor”). The header is a straight run of approximately 55m and includes 14 process tie-points. Certain stages of the replacement required a total shutdown of Sarnia Terminal, which mandated a very tight execution window. To enable completion of the work within the allotted outage, the new piping header was fabricated and hydrostatically tested in three sections at the contractor’s fabrication shop. All on-site tie-ins were designed to be bolted connections.
The factors which influenced the design and the staged execution strategy used during the outage are discussed in detail within the paper. Three key operability and technical factors influenced the design and execution strategies employed. Firstly, the Sarnia Terminal is fully interconnected to allow delivery to and from all 17 storage tanks on all 5 connected pipelines which enables a high level of operational flexibility. The result of this facility arrangement is a very complex isolation plan and requires large product drain-up volumes. Secondly, it was a requirement that the replacement piping, which is both larger diameter and heavier walled than the pre-existing piping header, did not increase the stress on any components of the existing piping system during or after installation. Finally, the length and number of connections on the manifold provided fit-up challenges and mandated an extremely high level of accuracy in the fabrication process to remove the requirement for on-site “field-fit” welds which could not be accommodated with the execution schedule. These factors posed numerous structural, mechanical and process challenges for which a detailed discussion is presented to provide insight into, and justification of the design and execution methodologies utilized.