• Published: 12 May 2011
  • Incident ID: 3112

Breaking of Flanged Joints & Migration Of System Contents

Cause & Consequence

  • Not Assigned
Incident Consequence

Incident Location

Any Location Type

Incident Activity

Any Activity Type

Incident Info Source

Austin Hardman Maersk Oil North Sea UK Limited

Specific Incident Equipment

Closed drains system

Lessons Identified

Residual liquids and gases can remain in piping systems in trapped pockets and where there are elevation changes. Vessel movement can cause liquids to migrate from system section to system section.The general rule when breaking into a piping system that has previously contained liquids or gases is “never assume the pipe is empty.”The situation described could have been recovered more easily had all of the bolts not been removed.

Incident Recommendations

The content of this notice is offered as a discussion topic at safety meetings and other suitable forums.

The information provided contains good practice which should be adhered to when breaking flanged joints.

Dismantling Flanged Joints after ensuring that they system has been isolated and depressurised the Work Leader together with the Production Operator responsible for the area shouldl check there is no longer any pressure in the pipe work local to the joint. This is normally done by opening a suitably located drain or vent valve.

Extreme caution must be exercised when venting gas systems as hydrates may form which may result in the blocking of the vent valve.Note that in circumstances where there is no drain or vent valve available and it is suspected there may still be pressure or liquids in the pipe work, the persons carrying out the work when relieving the pressure must take extreme care. The person who is dismantling the joint must not position himself in line with the joint faces. Other persons in attendance should also position themselves well clear of the joint.

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