Continuing data assessment of 16' williams pipeline inspected with the recently developed ultrasonic crack detection tool

摘要

The in-line-Inspection of Williams' Gas West Pipeline in September 2001 was successfully completed using the newly developed 16" UltraScan~R CD tool of GE PII Pipeline Solutions. The particular pipeline section inspected was known to be affected by Stress Corrosion Cracking (SCC). The inspection was carried out using the liquid batching technique developed by PII Pipeline Solutions. A special launcher and receiver barrel was designed to enable the handling of a series of three batching pigs in front of and two behind the inspection tool. A manifold of "kicker lines" was mounted to the barrel to launch the batching pigs and the inspection tool. The main benefits of this new design were minimizing operational downtime, ensuring complete air/natural gas displacement from the launcher, and providing for a smoother launch procedure. Due to the large elevation changes within the pipeline section, a key concern was maintaining pig velocity within lm/s for adequate data resolution. Rather than rely on a general "rule of thumb", a transient analysis was performed to define a range of possible batch sizes and better understand the expected pressure gradients while pumping the water slug. Based on actual data collected during this successful run, the transient model will be refined to better handle friction effects between the sealing cups and disks in future batch inspection runs. The pig data was successfully acquired, processed, verified, and excavations performed in 2002. Results from the twenty digs will be presented, as well as a discussion of the on-going fracture mechanics assessments which are being used to develop an overall integrity management plan for the continued, safe operation of the pipeline. To better understand the mechanism for SCC and enhance the integrity management plan, key metallurgical and environment elements are being investigated with advanced analytical tools, including high resolution SEM and EDS. In-situ crack growth monitoring system is also being developed. Preliminary results from these studies will be presented.