Recertification accumulator bottles
Accumulator bottles contain nitrogen stored under high pressure. They are used on rigs as a backup in case a borehole needs emergency sealing and the blowout preventer (BOP) operating system fails. Depending on the rig, they are attached to each other in a series of twenty to over a hundred. They should never fail in an emergency.
Testing of accumulator bottles
For this reason, accumulator bottles are regularly subjected to rigorous testing, says Jochen Bruil, certified inspector at Allrig. “We disassemble the bottles and remove the valve and the rubber nitrogen bag inside. We then conduct a MPI for cracks and take wall thickness measurements. If we find cracks, then a bottle is immediately rejected. If the wall is intact, then we subject the bottle to pressures of 315 bars (4500 psi, ed.) for fifteen minutes. If the pressure remains stable, then we perform another MPI.
Then we fit a new nitrogen bag and refit the valve. Finally, on the basis of the inspection report, the witness report and the recorder card, DNV puts the final stamp on the report.” Here you can find a picture report of one of our recertifications.
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