Internal and External Lifting Tools Used to Prevent Dropped Object Threat From Damaged Caissons

Due to their harsh environment, caissons can experience severe external corrosion at the waterline and galvanic corrosion / erosion at the pump string location. This can result in loss of structural integrity due to fatigue cracking resulting in all, or part, of the caisson becoming detached. Falling caissons have the potential to impact vulnerable asset on the way down or on the seabed.

Should a caisson become detached this would pose a serious safety concern for a platform and risk damage to subsea pipelines and equipment, impacting on production and reputation.

STATS provide a range of caisson handling tools for safely securing and recovering damaged or redundant caissons. Internal and External Lifting Tools (ILT / ELT) cover a range of sizes and safe working loads to allow for safe and controlled caisson removal.

Internal and External Lifting Tools are used to safely secure damaged or corroded caissons in position, until a planned retrieval back to the platform can be performed using the same tool. The compact size of the ELT and modular design of the ILT allows caissons to be recovered where space is limited. Caissons can then be securely lifted and cut into manageable sections to allow safe removal from the platform.

Check out this animation:

STATS mechanical lifting tools ensure safe handling and operation during caisson removal without the need to shutdown production. ILT and ELT taper-locks are hydraulically actuated applying vertical load to the locks set against the caisson. ELT’s feature an array of hydraulic cylinders that are piped with two independently actuated hydraulic circuits. This arrangement has been engineered to allow four of the locks to be actuated via one hydraulic circuit and the remaining four locks to be actuated via the second hydraulic circuit. If the integrity of a hydraulic circuit was lost this contingency system would ensure 50% of the locks remained in their fully set condition with full communication. The tools are designed and tested to prove 50% lock engagement is sufficient for the tool to take its design load of 55 Tonne. The taper-lock design provides a fail-safe locking system independent of hydraulic pressure, once pre-tension is applied to the lifting tool the hydraulic actuation circuit becomes redundant. The lock engagement range allows lifting tools to be simply modified for use with a range of caisson sizes.

For more information on Caissons, register for the ‘Safely Securing and Recovering Caissons‘ free webinar presented by STATS Group on 21st March at 3PM London/11AM New York.

Register Here!

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