• Published: 20 Jun 2011
  • Incident ID: 3347

Instrument Tubing Failure

Cause & Consequence

  • Failure of vessels or pipework
Incident Consequence

Incident Location

Drilling unit

Incident Activity

Drilling, workover

Incident Info Source

Step change in safety

Lessons Identified

  • The tubing was 3/8” .049 wall thickness stainless steel. The fitting is a double ferrule style. All met manufacturer’s specs.
  • The tubing had been installed into the fitting nut to the correct depth and the ferrules were installed in the correct order
  • The fitting nut had not been tightened as per manufacturer’s recommendations (finger tight plus 1 ¼ turns) therefore the ferrules were not “set” into the tubing. When examined post event, the nut was found to be finger tight (3 full turns).
  • The installer had ‘batch marked’ the fittings in his post installation check vs. checking then marking one at a time.
  • The well commissioning process had not caught the leaks.
  • Fittings under pressure need

Incident Recommendations

  • Leaking tubing fittings under pressure can be extremely dangerous and must be depressurized before being touched.
  • Field correcting of tubing installation deficiencies without follow up with the contractor prevents the sharing of findings and the opportunity for the contractor to correct the deficiencies and implement the necessary corrective actions into their procedures.
  • Field installed tubing should be hydrostatically or pneumatically tested per ASME B31.3 methods in conjunction with the contractor’s QA/QC program.
  • Review well commissioning processes to identify tubing installation testing and verification.
  • Verify training for the correct installation and operation of fittings.

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