Near miss: potential dropped objects on a temporary buoys (TBMs)

What happened?

A member has reported two near miss incidents involving potential dropped objects. The objects were left on top of a temporary buoyancy module (TBM) during the installation of a tension leg platform (TLP).

In the first incident, two subsea lamps (each weighing 10kg in the air) were discovered on top of the TBM after it was retrieved back to deck. In the second incident, during an inspection of the top of a TBM, also after it was retrieved back to deck, a rigging crew discovered a wire cable retaining pin (weighing 10kg in the air) lying loose on top of the upper bumper.

Incident 1 – Two temporary subsea lamps found on top of the TBM

What went wrong? What were the causes?

An investigation discovered that the lamps were temporarily fixed to the TBM by the diving team, and should have been removed after they had finished their task in accordance with their post installation dive tasks. All other subsea lamps used during the task had been removed.

• Not all subsea lamps were recovered as per post-installation dive tasks;
• The missing subsea lamps were not identified immediately;
• The company was unaware of the missing subsea lamps; there was no notification given by the subcontractor;
• There was no awareness of the possibility of loose equipment being left behind, causing a dropped object threat to the company lifting crew.

What actions were taken?

• Ensure that subcontractor personnel are properly reminded of the company procedures for subsea material recovery;
• Further emphasize to crew the importance of stop work authority and of speaking up when they see an unsafe condition – which in this case was found to be very effective.

Incident 2 – A wire cable retaining pin was found lying loose on top of the TBM

What went wrong? What were the causes?

Investigation discovered that the object was an ‘ROV friendly’ wire cable-retaining pin. The pin was used to retain a wire in a sheave from which a ball grab was suspended. In order to retrieve the ball grab, an ROV was used to remove the retaining pin. After removal of the pin, the ROV was to let go of the pin, which would then stay suspended under water hanging from a rope. As this pin was not lashed properly, it became loose and landed on top of the upper bumper.

• Inadequate lashing using inappropriate rope made it possible for the pin to drop;
• The importance of proper lashing was not acknowledged by the divers or the dive supervisor.

What actions would be taken?

• This incident would be circulated as a lesson learned.