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Failed Double Studded Adapter (Choke Manifold Test – 4th 10,000 psi; equipment failed)
Rig Commissioning – Yard (Jan 28, 2010)
New double studded adapter (DSA) delivered from pressure testers – ‘ready to go’
Made up the equipment and readied for testing ~ failed at +/- 10,000 psi (5 minutes into a 10 minute test)
Root Cause – Failure
Studs not made-up to the DSA properly – had < ½” make-up
No equipment verification ~ both ‘long bolting / short bolting’ evident
Action – Everyone
Trust-n-verify ~ ensure equipment is inspected & ready to go
Question stud length anomalies (upon make-up)
Establish & maintain buffer zones
Ensure CoW
4 1/16” 10K x 2 1/16” 10K DSA
Incident Location: Contractor’s Yard:
Rig commissioning activities ~ lower pressures worked well…almost up to and including 10,000 psi. Equipment was being hydro-tested and there was a buffer zone with very few people present during test activities.
Short bolting and long bolting were evident; but not questioned.
DSA was inspected; but evidently new or near new…didn’t dawn on anyone to question the equipment’s integrity
Important – Conducted 3 previous test with the equipment & it passed (including 10,000 psi). Failed 5 minutes into a 10 minute test at 10,000 psi!
Immediate Actions:
Contractor stopped operations
Had hydrotester rig-down and take equipment back to the shop
Contractor conducted an internal investigation
BP: Cascade awareness & learning for all to be on alert for a possible repetitive event in the future
Lessons To Retain:
Repeated pressure tests were needed to expose a potential weakness ~ resulted in a catastrophic failure!
Thread make-up needs to be questioned…especially when the make-up lengths vary
Barely threaded into DSA
For more information contact:
Don McKelvey