Casing and Inserted Pipe Inspection Program on the San Francisco Peninsula Using Robotic ILI

Pacific Gas & Electric Company (PG&E) operates multiple gas transmission pipelines on the San Francisco Peninsula, a significant portion of which operate at low Maximum Allowable Operating Pressure (MAOP), typically below 300 psig and are challenging to inspect using traditional ILI technology. This paper describes PG&E’s use of Non-Traditional robotic ILI technology to inspect numerous cased pipelines located in High Consequence Areas in the highly populated and dense urban area between the San Francisco International Airport (SFO) and central San Francisco. Examples will be provided for pipeline segments installed in various casing types, including sections inserted through utility infrastructure that was made available for use as a gas pipeline casing. Examples include pipe that was installed in the 1940’s and cased pipe installed without corrosion test stations. In some instances, the length of cased pipe sections were several hundred feet long and traversed locations difficult to access, such as major highway crossings and cased spans above water crossings. These inspections were executed in 2015 on 24 separate pipeline segments totaling more than 12,000 feet of pipeline. This paper explains how the inspection team utilized current technology and identified Non-Traditional ILI (NT ILI) as the preferred method. It also explains how the locations were scoped, project parameters and program strategy were developed, NT ILI tool selection, project outcomes, and lessons learned. An overview of the advantages of NT ILI methods to perform these cased pipeline inspections in-lieu of External Corrosion Direct Assessment (ECDA) and Traditional ILI will be discussed. This paper is applicable to Track 3 (Pipelines & Facilities Integrity) and also to Track 2 (Project Management, Design, Construction & Environmental Issues), and will be of interest to Pipeline Operators, Integrity Management Engineers, and Project Managers. The intent is to share PG&E’s experience utilizing Non-Traditional robotic ILI tools to perform difficult pipeline inspections in casings, as well as practical advice on scoping, planning, and execution of non-traditional ILI projects.