Uncontrolled ascent of spool and diver during a lifting bag operation

A member has reported the uncontrolled ascent of a spool piece and diver during a lifting bag operation.

In low visibility conditions, whilst preparing a pipe spool for re-positioning on the seabed using air lift bags, the spool became positively buoyant and started ascending to surface in an uncontrolled manner.

The diver working at one end of the spool became entangled with the air lift bag inverter line, resulting in him ascending with the spool from 55msw (seabed) to 36msw.

During this ascent, the diver’s umbilical was damaged, causing restricted gas flow and severing of his communication and video cables. He reverted to his emergency gas supply and managed to cut the line that had fouled on his bail out bottle, enabling him to immediately return to the seabed.

A second diver, also working on the spool (but still on the seabed), followed the umbilical of the ascending diver and subsequently accompanied him back to the bell (at 47msw). The bell was recovered for the immediate examination of the diver and it was confirmed that no injuries were sustained. The spool was later re-positioned without incident.

The member identified that the lift bags had been inflated without appropriate ‘hold back rigging’ in place and that there had been a failure to follow company procedures and guidance detailed in Guidance on open parachute type underwater air lift bags.

The member also noted that the dive plan steps had not been as clear as they should have been and that ‘installing lift bags complete with hold backs’ had been detailed as a single step without a check to confirm that the hold back rigging installation was done prior to inflating the air lift bags.

Members are reminded of guidance document Guidance on open parachute type underwater air lift bags, which addresses the initial and periodic examination, testing, certification and maintenance of underwater type bags (cylindrical totally enclosed, closed and open parachute bags) used to lift submerged objects and also addresses the operational use of open parachute type lift bags and the safety precautions that should be taken during their use.