In-Line Inspection has become the first choice for integrity assessment for most pipeline operators. The data generated from modern ILI tools allows operators a comprehensive assessment of the condition of their pipelines so they can plan out integrity actions based on the condition of the line. In-line inspection vendors continue to upgrade their tools and provide new services to pipeline operators to enhance integrity management programs. The data provided by these tools is relied upon by operators, regulators, and the public to be correct and complete and in most instances it is, but when near critical features are missed or data is used improperly, the results can be catastrophic.
Hydrostatic testing has fallen out of favor with many pipeline operators due to the operational headaches, costs, difficult logistics, and lack of data generated during a hydrotest to conduct future integrity work. However, in light of a number of high profile accidents on pipelines that failed after an ILI run was performed, it may be time to reassess the role that hydrostatic testing plays in modern pipeline integrity management programs.
This paper will explore failures and other case histories that have occurred on lines regulated by PHMSA where ILI results alone have failed to provide all of the necessary information to maintain pipeline integrity and how hydrostatic testing may provide value to integrity management programs. Limitations and misconceptions of ILI and hydrostatic testing will be discussed, particularly for seam defects and similar types of defects. Based on these analyses and observations, the roles of hydrostatic testing and ILI tools in a successful integrity management plan will be discussed along with flaw growth rates, predicted failure pressure calculations, re-inspection intervals, and other elements of successful integrity management programs.