Acceptability of Pipeline Carbon Steel Flanges with Yield Strength lower than ASTM A694 Tensile Strength Requirement for Service.
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Kean Leong Chee
Kean Leong Chee, Andrew Tuong Thai Ling, Sean Lok Ng, Wan Mohd Hariri bin Mohd Nasihuddin, Brian Lim
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This paper presents a case study on the journey starting from the finding of low yield strength mechanical property impacting carbon steel flanges of a gas pipeline, to the investigation and recovery measures that followed, and how the learnings are incorporated into the supply chain strategy and quality assurance for future projects.

A total of 21 pieces of flanges were procured by the local EPC contractor from an oversea-based flange supplier via a local vendor. Type 3.2 inspections were performed, and material test certificate issued. However, further tests upon receipt of materials proved otherwise. 16 pieces of flanges were immediately quarantined, but three already installed offshore and remaining two in the midst of installation offshore. Root Cause Analysis-based investigation was conducted and recovery plan initiated. Risk assessment was carried out to evaluate the decision to proceed with the installation of flanges offshore and interim measures implemented, while the remaining 16 replaced with new flanges from a new supplier. 

Engineering consultant was contracted to assess the integrity of the five already-installed flanges and a decision was also made to engage an established independent consultant to verify the assessment. Credible worst-case scenarios were assessed based on a range of possible outcomes of engineering assessment. More robust inspection controls were implemented for the procurement of new flanges from the new supplier to prevent recurrence of similar quality issue. Initiatives to optimise the production and delivery lead time of flanges were carried out in order to meet the offshore installation timeline while maintaining safety and quality. The regulator who is responsible to issue the permit to install and operate was engaged and informed of this issue.

The main learning stems from the extent of third-party inspection/ control points required and how supply chain strategy and quality assurance can be further enhanced in future projects.

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