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Jacket levelling tool assembly link plate and pin failure

Country: QATAR - Middle East

Location: OFFSHORE

Incident Date: 14 December 2021   Time: ---

Type of Activity: Construction, commissioning, decommissioning

Cause: Dropped objects

Function: Construction


What happened?:

A jacket level survey was ongoing, using a levelling tool installed on the top of the jacket pile and connected with grommets and shackles to the jacket legs on both sides.

Pins of the right assembly slipped out from their position causing the grommet, right side link plate and lower pin to fall down.

As a result of the event, the grommet remained on the scaffold being connected to the jacket leg, and the link plate with the pin (weight approximately 600kg) fell into the sea and landed on the jacket mud mat. The area around the levelling tool was restricted, with access to workers as per JSA control measures, in order to not have any personnel in the line of fire (LOF) during this activity and further level survey.

What Went Wrong?:

  • The levelling system design (configuration with link plate, grommet, and shackles) did not allow the perfect alignment of the link plate with the shackle (presence of lateral forces).
  • The engineering design of the system did not consider the possibility of a system misalignment with the proposed configuration that could determine lateral force on the safety pin.

Corrective Actions and Recommendations:

  • Identified a proper engineering solution (replace the link plate and pin with an 800t shackle) in order to rectify the inadequate design, allowing the safe completion of the jacket operations.
  • Reviewed the installation procedure, inserting a dedicated section concerning the alignment check before commencing operation and revised the drawing according to the modified configuration for performing the jacket levelling completion.
  • Share the lesson learned to all project and areas, in particular to consider the system misalignments and the presence of lateral forces.
  • Consider the line of fire and the positions of personnel during the whole process.
  • Use the levelling system with link plates when directly connected to the pad eyes. If not possible, the revised solution with the shackle instead of the link plates should be preferred, as the shackle would have sustained a portion of the horizontal load.
  • Revise the safety pin design of the levelling tool equipment in order to take into account any potential lateral forces. Welding of washers/bolts on the pin shall not be considered a possible solution due to the risk of cold cracks.

Figure 1: Jacket top view with levelling tool position indication

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Figure 2: Side view of levelling tool position

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Figure 3: Levelling tool and affected pin assembly

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Figure 4: Levelling tool after the event

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Safety Alert number: 342
IOGP Safety Alerts http://safetyzone.iogp.org/

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