Subsea Spool Tie-In Incident

Study Notes

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

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

Diver 2 promptly assisted Diver 1, and both divers immediately returned to the bell safely
Both divers and the crane block had locating beacons fixed to them, enabling accurate tracking
All procedures, lifting plans and Job Hazard Analysis (JHA's) were followed throughout the operation
Protective equipment worked, and 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
This resulted in a 'no weight' reading, leading the crane operator to assume the hook had reached the seabed
As the diver approached the disconnection point, the hook slipped off the beam and struck the side of the diver's helmet

Inadequate length of crane pennant/stinger 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
Alternative methods in environments with poor visibility, such as additional locating beacons, underwater cameras, or sonar, should 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
Clear communication and confirmation procedures between the dive supervisor, crane operator, and divers should be reinforced to ensure all parties are fully aware of the equipment's location at all times
Updated project procedures to specify minimum pennant lengths for different operations
Conduct pre-operation inspections of all rigging and lifting equipment, including crane hooks and pennants, to ensure they meet safety standards and are appropriate for the operation
Updated the Job Hazard Analysis (JHA) to incorporate lessons learned from this incident, particularly regarding safe distances, visibility, and communication requirements for subsea lifting operations