Why are transfer lifts riskier than ordinary deck lifts?

Because at pickup and set-down the relative heave between the two bodies changes the gap faster than any operator can follow: the slings can go from slack to taut in an instant (a snap load), or a rising deck can strike the load that just left it (re-contact).

What causes a snap load at pickup?

The two hulls heaving out of phase. If the receiving deck drops while the crane rises, the wire snatches taut and the tension spikes well above static weight — the classic transfer-lift failure mode a compensator exists to absorb.

How does heave compensation manage a transfer lift?

A passive compensator absorbs the relative motion at the hook so the load follows one body's motion rather than being driven by both. An adaptive unit is preset to the load and expected motion — softening the moment the weight comes on or off, and matching the load to the receiving deck through touchdown. A shock absorber caps a single discrete snap peak.

Which compensator fits a transfer lift?

RIGEL for absorbing relative heave on routine transfers; ANTARES when the pickup and set-down need preset tension and a controlled touchdown window — including the quick-lift snatch off a heaving barge; POLARIS where one discrete snap must be capped. Where the two bodies' motions diverge beyond passive reach, active stroke control (VEGA, in development) holds position through the transfer.

Knowledge Hub · Transfer lifts

Transfer Lifts: Heave Compensation Between Two Moving Bodies

Q: What is a transfer lift?

A lift that moves a load between two bodies that move independently — vessel to platform, vessel to vessel, or deck to deck. Each body rises and falls on its own response to the sea, so the lift must manage the relative motion between them, not just the crane vessel's heave.

Vessel to platform, vessel to vessel, deck to deck — two hulls that never move together, and a load that must change hands between them cleanly.

A transfer lift moves a load between two bodies that rarely move together. Each rises and falls on its own response to the sea, so at the moment of pickup or set-down the relative heave between them can slacken the wire and then snap it taut — or drop the load back onto a deck moving the other way. Heave compensation absorbs that relative motion at the hook, keeping line tension and contact loads inside the rigging limits: a wider workable sea state, and a de-risked handover.

The classic case: lifting a load off the deck of one vessel with a crane on another. The two hulls heave in opposite directions, so the slings swing from slack to taut in an instant. That snap at lift-off is the load case a heave compensator absorbs — a controlled pickup instead of a shock-loaded one.

Relative heaveTwo bodies out of phase — the gap changes faster than any operator can follow

Snap at pickupSlack slings going suddenly taut spike tension well above static weight

Re-contact at set-downA rising deck strikes the load that just left it — or the load bounces on release

The handover, load case by load case

Phase	What the sea does	Compensator’s job
Pickup	Decks heave out of phase; slings flick slack–taut	Absorb the relative motion — take the weight smoothly, no snap
Suspended	The load inherits the crane vessel’s motion	Isolate the load so it follows one body, not both
Set-down	The receiving deck keeps moving under the descending load	Match the load to the deck through touchdown — inside the speed window, no bounce, no re-contact

Sketch of a vessel-to-vessel cargo transfer with the compensator absorbing relative heave between the two hulls — Vessel-to-vessel transfer: two independent motions, one load path — the compensator absorbs the difference.

How compensation carries the handover

Need	Answer
Absorb relative heave at the hook	A RIGEL passive compensator takes the relative motion so the load follows one body’s motion rather than being driven by both
Soften pickup and set-down	ANTARES is preset to the load and expected motion — tension comes on and off gently, and the touchdown speed stays inside the window
Clear a heaving deck fast	The ANTARES quick-lift snatches the payload vertically clear before the next wave can bring the deck back up
Cap one discrete snap	Where a single pickup can still drive a snap event, POLARIS caps that one peak — and resets between lifts
When passive is not enough	Where the two bodies’ motions diverge too far for a passive or adaptive device, active stroke control (VEGA, in development) holds position against the relative heave through the transfer

See it in action

ANTARES quick lift — “clear first time” off a heaving feeder barge, simulated in CONSTELLATION. The modelled barge lift-off — re-contact probabilities across crane hoist speeds — is on the quick lifting page.

Transfer lifts — frequently asked

What is a transfer lift?

A lift between two independently moving bodies — vessel to platform, vessel to vessel, deck to deck. The problem is the relative motion between them, not just the crane vessel’s heave.

Why is it riskier than an ordinary deck lift?

At pickup and set-down the relative heave changes the gap faster than an operator can follow: slings snap from slack to taut, or a rising deck strikes the load that just left it.

What causes the snap at pickup?

The hulls heaving out of phase — if the receiving deck drops while the crane rises, the wire snatches taut and tension spikes well above static weight.

How does compensation manage the handover?

It absorbs the relative motion at the hook: the load follows one body’s motion, tension comes on and off gently at either end, and touchdown stays inside the speed window — see subsea lifts for the set-down half.

Which compensator fits?

RIGEL for routine transfers, ANTARES for preset pickup/set-down and the quick-lift snatch, POLARIS for capping one discrete snap; active control (VEGA, in development) where the divergence exceeds passive reach. The selection guide walks the choice.

Have a transfer lift to plan?

Send SWL, stroke, sea state, payload and the operation sequence — we’ll come back with a recommended compensator, an operating-window view and the next engineering step.

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