Use of a custom Box-Fit to envelope and re-enforce a leaking flange

The Damage

Leakage of a Taper-Lok Zero Leak flange misalignment gap become an emergency issue for the POGC team when the effects of the leak’s high pressure (122 bar) on the structural integrity of the pipeline joint seriously threatened the safety of the staff aboard the nearby (50m) manned extraction platform.

At each shutdown/ start-up cycle, the flange would experience axial movement due to the whiplash of the pipeline, further increasing the probability of a total rupture at the flange site. Being so close to the platform also meant there stood a 4” 220 Barg MEG piggyback line within 1 meter distance of the leak. At the depth of 75m and under volatile weather that season, the repair project - with its technical sensitivities - was deemed too risky to attempt by many industry participants.

In addition to these technical sensitivities, the damage also carried economic ramifications. The pressure drop caused by the leak decreased the efficiency of gas supply efforts to refineries 120 kms away on the shoreline which would cause possible shortages in the colder months.

The Solution

Our task was to rapidly design and manufacture a custom iteration of our Box-Fit product, completed with a custom skid, a new saddle design, and subsea sealant injection capabilities. We first analyzed the effect of the clamp weight on spool and flange and continued modeling and testing the flange assembly for FAT and SIT factory tests. We then designed an installation mechanism that would leave the nearby MEG piggyback line completely undisturbed. Further analysis on site metrology, excavation, coating removal, bolt tensioning, skid removal, and post commissioning surveys was conducted and a custom-designed sealant injection machinery was designed and fabricated to accommodate the intricacies of the project.

The resulting product successfully reinforced the flange both in axial and lateral directions without ever requiring the shutdown of the MEG piggyback line nearby. With its double sealing mechanism, Box-Fit not only stops the leak from the gap, but also envelopes the whole flange assembly for a longer term guarantee.
The Fixpipeline repair package included custom high pressure Box-Fit design, skid and saddle design and fabrication, sealant injection mechanism design and fabrication, marine crew, DP2 IMR vessel, saturation diving system, HSE planning.



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