• Published: 21 May 2012
  • Incident ID: 3428

Retrieval of Corrosion Coupons from Pressurised Lines

Cause & Consequence

  • Failure of vessels or pipework
Incident Consequence

Incident Location

Any Location Type

Incident Activity

Umbilical / pipe laying

Lessons Identified

The investigation of this incident is not yet complete. Insight gained to date: It is understood that for bottom-of-line applications ("6 o'clock"), the assembly can be vulnerable to fouling due to corrosion product settling in low points / the bottom-of-line and can drop down into the corrosion coupon balancing path. This can lead to pressure imbalance within the retrieval tool resulting in an uncontrolled outward movement of the outer barrel (piston) upon disengagement of the coupon threads.

Incident Recommendations

While the incident investigation is ongoing, it is recommended that the following action be considered as precautionary measures -

1. Stop all corrosion coupon retrieval operations on pressurised lines. When the investigation of this incident is complete, a subsequent LFI Alert (expected end May) will communicate the learnings and advise if this type of work can recommence.

2. Prior to the start of work Contract Holders, with the support of Shell maintenance and inspection personnel, are to assess whether contractors who perform corrosion coupon retrieval operations on pressurised lines have a Competence Assurance process for their personnel and assure they are competent. This type of work is a specialist operation normally contracted out to Original Equipment Manufacturer (OEM) approved contractors with certified personnel. (Refer Shell HSSE & SP Control Framework Contractor HSSE Management Manual (requirement 3.3).

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