Transfer lifts are lifts between two topside locations, typically from a supply vessel to a platform or a floating vessel. Wave motion reduces the lifting capacity of offshore cranes. Our solutions remove or partially remove this capacity reduction by significantly increasing the crane’s ability to absorb energy.

OPERATIONAL CHALLENGES

• Reduced lifting capacity due to wave motion
• Slack wire when offloading
• Re-entry at lift off

SAFELINK SOLUTIONS

• Increased lifting capacity
• Smooth offloading
• Quick lift off function

Lifting through the water column, also known as the splash zone, can often be troublesome. Rapid changes in buoyancy, added mass and slam forces caused by the interaction between payload and waves, can often lead to high dynamic forces and slack wire/rigging.

Principle:

• If there is tension in the wire rope, a slack sling situation will not occur. A compensator can ensure this if enough stroke is available and the damping is set correctly.
• Vessel heave, pitch and roll can cause significant crane tip motion. This motion can lead to huge dynamic loads. A compensator will simply stroke in and out, with small changes in tension, and eliminate the problem.

OPERATIONAL CHALLENGES

• Slack wire followed by snap load
• Pendle motions
• Slam forces caused by waves hitting the payload
• Varying buoyancy and added mass

SAFELINK SOLUTIONS

• Shock absorption
• Constant tension
• Record actual dynamics (our more advanced units)
• Control system (our more advanced units)

Lifting operations in deep waters have a significant risk of entering resonance. This happens when the natural period of the crane wire and payload matches (or is close to) the wave period. The natural period increases when the length of the wire rope increases (the wire rope acts like a spring).

OPERATIONAL CHALLENGES

• Natural period of lifting system and wave period converges
• Calculating the exact water depth for when resonance occurs

SAFELINK SOLUTIONS

• Change the natural period of the lifting system beyond the maximum wave period, completely avoiding resonance
• Always have full coverage against resonance at any water depth (our more advanced units)

Landing speed is often an issue for cranes and winches that do not have active heave compensation. Safelink solutions significantly reduce the landing speed for almost all structures for wave periods up to 20 seconds. Safelink Kraken has the ability to achieve reduced landing speed even for very long wave periods (up to 40s). The performance depends on payload, wave period and water depth.

OPERATIONAL CHALLENGES

• Landing speed requirement to protect payload
• Insufficient active heave compensation
• Limited weather window
• Vessel with no active heave compensation
• Ultra-deep-water installation

• Significantly reduce payload heave velocity
• Replacement or backup to active heave compensator
• Extend the weather window
• Heave compensation for short, medium and long wave periods

Retrieval of items such as suction anchors can be problematic. The suction forces have to be overcome, and it takes time to remove vacuum. During this phase, the crane or winch will be exposed to large dynamic loads due to wave motion. This problem can be completely avoided by using a compensator.

OPERATIONAL CHALLENGES

• Unexpected high pull-out forces
• Overload on crane or payload lifting points

SAFELINK SOLUTIONS

• Overload protector
• Constant tension

Safelink delivers passive heave compensation solutions to a wide range of clients and application areas. We target all dynamic challenges, both topside and subsea –  our team of engineers enjoy new challenges.

Some of our custom applications:

• Shock absorbers for MOB boats
• Deck installation of shock absorbers for deployment and retrieval of mini-submarines
• Solutions to reduce dynamic load variations on coil tubing (see image to the right)

Tell us about your challenge! Our highly skilled team of engineers are ready to solve your challenges.