Subsea Spool Tie-in Incident

Study Notes

During subsea spool tie-in operations, a crane hook unexpectedly struck a diver's helmet.

Divers were working on the seabed in poor visibility during subsea spool tie-in operations.
After landing the pipe handling frame (PHF) on the seabed, the Diving Supervisor told the crane operator to lower the crane hook to the seabed to disconnect rigging from crane.
The crane operator reported there was 'no weight' on the crane wire, and the Diving Supervisor assumed the hook had reached the seabed.
The diver was told to disconnect the PHF from the crane.
A crane hook unexpectedly struck the diver's helmet while positioned beneath the PHF and moving to disconnect the rigging.
The diver was unharmed and returned to the dive bell, and the dive was aborted.
The diver's reclaim helmet was damaged beyond repair, including the side block, but the integrity of the helmet was maintained.

Diver 2 promptly assisted Diver 1, ensuring that no injuries were sustained, and both divers returned to the bell safely.
Both divers and the crane block had locating beacons to enable accurate tracking.
All procedures, lifting plans, and Job Hazard Analysis (JHAs) were followed.
The diver was uninjured because the impact was absorbed by the helmet.

When the crane hook was lowered for PHF rigging disconnection, it came to rest on the top beam of the PHF.
The crane operator assumed the hook had reached the seabed because of the 'no weight' reading.
The hook slipped off the beam and struck the side of the diver's helmet as the diver approached the disconnection point.

There was an inadequate length of crane pennant / stinger, which did not provide sufficient distance between the divers and the crane hook.
Poor visibility hindered the ability to accurately observe the position of the crane hook.

Ensure adequate distance between divers and crane hook.
The length of the crane pennant/stinger should maintain a safe distance between the divers and the crane hook during subsea operations to reduce the risk of accidental contact.
Use enhanced visibility aids and monitoring.
In environments with poor visibility, alternative methods such as additional locating beacons, underwater cameras, or sonar should be considered to better track the position of critical equipment like the crane hook.
Improved monitoring can help prevent misjudgements about the location of the crane hook.
Reinforce communications, challenge assumptions; assumptions regarding equipment position should be minimised.
Reinforce clear communication and confirmation procedures between the dive supervisor, crane operator, and divers, to ensure all parties are fully aware of equipment location.
Updated project procedures now specify minimum pennant lengths for different operations.
Pre-operation inspections of all rigging and lifting equipment, including crane hooks and pennants are performed to ensure they meet safety standards.
The Job Hazard Analysis (JHA) was updated to incorporate lessons learned from this incident, particularly regarding safe distances, visibility, and communication requirements for subsea lifting operations.