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It is not uncommon for in-line inspection (ILI) to reveal numerous dents within a relatively short section of an examined pipeline. Fatigue is the most common failure mechanism of dented pipelines and API RP-1183, Assessment and Management of Dents, was published in November 2020 to provide guidance for the fatigue assessment of pipeline dents. This recommended practice broadly provides three levels of fatigue assessment with varying levels of complexity and conservatism.
SESC has developed an automated, finite element based, Level 1 fatigue screening tool. The tool reads measured ILI caliper data, builds finite element models based on this data, and estimates the stress concentration factor of the dent. This fully automated procedure enables processing dozens of dents in the matter of minutes with a high level of accuracy. As an example, the radial coordinates and principal stress obtained from the Level 1 fatigue screening tool is shown below. This screening tool can assist in quickly reducing the number of identified dents that need further detailed assessment.
API RP-1183 provides Level 2 fatigue life assessment methodology that is much more detailed. This methodology takes into consideration dent restraint condition and shape to calculate fatigue life. SESC has developed an automated tool that uses ILI measurement and calculates fatigue life using the tables provided in API RP-1183.
Level 3 assessment of dents is finite element based and includes the dent formation process. Typically, this is an iterative process where the indenter shape is modified until the desired dent shape is obtained. SESC has significant experience in this type of assessment and has developed a proprietary method that efficiently determines the proper indenter shape. An example of a dent radius comparison between the finite element model and ILI measurements is shown below.
Stress Engineering Services Canada knows pipelines, and we know that you need accurate, effective, and efficient dent fatigue assessments to quickly inform your run (as-is), repair, rerate, or replace decisions. Through optimization of the fatigue assessment procedures recommended within API 1183, SESC is saving time and money for our clients by providing results in an expedient and cost-effective manner.
For more information contact: [email protected] or [email protected]
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