Enbridge operates the world’s longest hydrocarbon transmission system. The pipeline infrastructure has experienced additions over its 50 years of operation. The expansions were implemented as successively larger pipe sections upstream from pumping stations. After completing three lines (20″, 24″ and 34″) in parallel configuration, 48″ sections were installed upstream from pumping stations in 1972 and 1973. In order to accommodate future throughput requirements, part of the Enbridge’s 1998 Terrace Expansion Project was designed to connect the 48″ pipe sections into a continuous line with 36″ pipe sections.
The first Terrace Expansion design included sending and receiving traps for both the 36″ and the 48″ sections. An intricate network of crossover piping and mainline valves would allow in-line tools to be both launched and received at the diameter transition point without impacting flow. Since the transition points occur anywhere from 10 to 40 kilometers upstream from pumping stations, more aboveground facility locations would be added.
Enbridge approached vendors of the different in-line inspection technologies to conduct feasibility studies for building 36″ by 48″ dual diameter tools for pipeline cleaning, geometry and metal loss inspection applications in January 1998. Enduro Pipeline Services, Williamson Industries (TD Williamson) and Pipeline Integrity International (PII) were selected to assemble the working tools based on the viability of their technical presentations and cost estimates. The development of 36″ by 48″ dual diameter cleaning and inspection tools would save Enbridge time and money by eliminating the need to install traps and associated valving at the transition areas. As a result, the accelerated schedule and targeted project completion for inspection in Enbridge’s Terrace Expansion line within a twelve-month time frame was accepted by all parties.
This paper discusses the phases of the project from the technical feasibility studies, original and progression of design concepts, test loop execution and actual field use and validation of the tool performance and information.