Why is quick lifting needed?

Slow cranes leave the payload hovering near the deck while vessel and barge move with the waves — one unexpected motion and the load recontacts, damaging equipment and costing time. Quick lift shortens that vulnerable phase to a moment chosen by the operator.

How does the quick-lift sequence run?

Tension is held around 50% of the static weight so the rod extends as the crane lifts, to roughly a third to half of stroke. The compensator then rides the heave passively. At a wave top the operator triggers the lift, and the rod retracts fully under control — the load clears immediately.

How is the rapid retraction powered?

Three ways: switching from a low-pressure to a pre-charged high-pressure accumulator, connecting high-pressure gas to the working accumulator through a large connection, or using the AHC power unit to add lifting force. Tension is kept moderate to avoid unnecessary dynamics; end damping protects the unit regardless.

Which compensators offer quick lifting?

Adaptive passive and active units — it is one of the capabilities that separates an adaptive PHC from a basic one. ANTARES performs repeatable quick lifts on battery power.

Crane vessel performing a quick lift off a heaving barge with an ANTARES compensator

Quick lifting

Pick the wave, press the button, clear the deck — first time.

Quick Lifting

Q: What is quick lifting?

A technique for getting the payload clear of the deck first time: the compensator holds reduced tension while extended, then retracts its rod rapidly and in a controlled manner at the operator's command — lifting the load faster than the crane winch alone could.

By Peter Wang, COO · December 2025

Practical application: For practical application of this topic, see POLARIS crane shock absorber and engineering studies and analysis.

What is the benefit of quick lifting?

Offshore lifts present several challenges. When using relatively slow cranes, recontact between the payload and deck can occur, as unexpected wave or vessel motions may induce rapid movements that result in impacts. Such collisions can damage equipment and lead to costly delays. The quick lifting ability provided by adaptive PHC and AHC units helps mitigate this risk by reducing the likelihood of payload-deck contact.

How does it work?

The payload is attached to the adaptive PHC or AHC. Tension is kept at say 50% of static weight causing the rod to extend when the crane is lifting. Extension is then done until about 1/3 to 1/2 of compensator stroke is reached. The compensator is now passively keeping tension in the rigging around 50% as the vessel is heaving up and down. At a top of a wave (recommended) the quick lift is activated by the user by the click of a button. The piston rod is the retracted to the fully retracted position in a controlled manner.

The retraction can be done in several ways:

By switching from a low pressure accumulator to a high pressure accumulator that it pre-charged with oil and gas so that it can fully retract the payload in question.
Connecting high pressure gas (with a large connection) to the current accumulator so that tension is increased.
Using AHC HPU to generate required additional lifting force.

It is important that the tension is not too high, which could cause unnecessary dynamics. Norwegian Dynamics compensators are equipped with end damping that will prevent damage to the compensators, but it is in any case good practice to avoid this.

What happens in a barge lift-off

Lifting a heavy load off a transport barge or supply vessel is one of the most exposed moments offshore. Keeping clear of re-contact — the load lifting clear, then a wave bringing the deck back up into it — is the governing safety criterion for a barge lift-off under DNV-RP-N103 §9.5.

1Take the load. The crane takes the weight off the barge; the slings come tight and the payload is ready to leave the deck. → 2The deck keeps moving. The barge rides the swell, rising and falling under the payload while it hangs close to the deck. → 3Clear, or re-contact. The load must rise clear of the heave envelope before a following crest brings the deck back up. A slow lift can be caught and slammed; the quick-lift snatches clear first.

A barge lift-off, modelled

A CONSTELLATION Monte-Carlo study: the same 250 t payload taken off a transport barge in H_s 2.16 m / T_p 5.5 s, across 120 modelled sea states per point, lifting at the same favourable moment each time. A conventional crane — rigid line, no compensation, hoisting across the realistic heavy-lift range — against the ANTARES quick-lift snatch:

Crane hoist speed	Conventional crane — re-contact	ANTARES quick-lift
1–3 m/min heaviest lifts (≈1,000–2,000 t)	100%	0%
5 m/min	86%	0%
10 m/min ≈ the DNV §9.5 hoist floor	52%	0%
20 m/min fast, lighter loads	15%	0%

The quick-lift re-contacted in none of the 120 modelled seas at any speed (95% confidence 0–3%). In the modelled snatch the payload leaves the deck at a payload DAF of 1.27 and a peak sling load of 3,118 kN — inside the rigging and crane limits, on 64% of the ANTARES stroke. Modelled in CONSTELLATION as one coupled time-domain load path; deck re-contact evaluated as DNV-RP-N103 §9.5 defines it. One sea state, one case — every lift is sized on its own payload, vessel and sea.

Sized to clearGas tank and valve sized so the snatch clears the deck margin within the time the sea allows

Adaptive after the snatchOnce clear, ANTARES holds tuned gas-spring stiffness and damping for the rest of the lift

Checked to DNVDeck clearance and re-contact to RP-N103 §9.5; peaks against the crane’s derated capacity

Matched per caseSpecified across the ANTARES range to your payload, hoist speed, vessel and design sea state

The quick-lift sequence

Hold light. The payload hangs on the compensator at roughly 50% of static weight — the rod extends as the crane starts lifting.
Ride the heave. Extension stops at about ⅓ – ½ of stroke; the unit passively keeps the rigging tensioned while the vessel heaves.
Pick the moment. At a wave top — the recommended trigger point — the operator activates the quick lift with one command.
Clear first time. The rod retracts fully, fast but controlled — the load is off the deck before the next wave arrives.

Retraction method	How it works
Accumulator switch	Low-pressure to pre-charged high-pressure accumulator — sized to retract the payload in question
Gas injection	High-pressure gas connected to the working accumulator through a large connection
AHC power unit	The HPU generates the additional lifting force

Keep the trigger tension moderate — too much invites unnecessary dynamics. End damping protects the unit either way, but not needing it is better practice.

Quick lifting — frequently asked

What is quick lifting?

A compensator-driven technique for clearing the deck first time: hold reduced tension while extended, then retract the rod rapidly and under control at a moment the operator picks.

Why is it needed?

Slow cranes leave the load hovering near a moving deck — one unexpected motion means recontact, damage and delay. Quick lift compresses that vulnerable phase into a chosen instant.

When is the lift triggered?

At a wave top — the recommended point — so the deck is falling away as the rod retracts.

How is the fast retraction powered?

An accumulator switch to a pre-charged high-pressure stage, high-pressure gas injected into the working accumulator, or the AHC HPU adding force — whichever the unit is configured for.

How likely is deck re-contact without a quick-lift?

In the modelled study above: near-certain (100%) at the 1–3 m/min speeds the heaviest lifts are stuck with, 86% at 5 m/min, and still 52% at the ≈10 m/min DNV §9.5 hoist floor — against 0 of 120 modelled seas with the ANTARES quick-lift.

Which units can do it?

Adaptive passive and active compensators — quick lift is one of the abilities that separates an adaptive unit from a basic PHC. ANTARES does it repeatably, on battery. The film below shows a quick lift off a heaving feeder barge.