Heave Compensation for Offshore Wind

Three places an in-line heave compensator or shock absorber helps an offshore wind campaign: subsea lifts for floating wind and foundations, setting loads down from a floating vessel, and pile runs during driving. And where grippers, guides and tugger lines do the job instead.

By Tord Martinsen & Peter Wang · April 2026 · Updated September 2026 · 10 min read

Three-blade offshore wind turbines and yellow transition pieces under changing coastal light.

In brief

From an elevated jack-up, which stands on its legs on the seabed, the waves do not heave the hook. From a floating vessel they do: the crane tip moves with the vessel’s heave, roll and pitch.
An in-line unit helps in three places: subsea lifts through the splash zone to the seabed, such as suction anchors, templates and protection covers; setting a load down from a floating vessel, where its stroke takes up the crane-tip motion after contact, so the line force changes gradually instead of snatching the load off again; and pile runs during driving, where a shock absorber limits the peak load on the crane.
It works on the vertical load path only. Horizontal position and orientation need guides, grippers or tugger lines.
Our in-line units cover 12.5 to 10,000 t (RIGEL, CYGNUS and ANTARES), and POLARIS shock absorbers range from 75 to 4,000 t. Each is sized from a lift model of the vessel, crane, rigging, payload and sea states.

Most offshore wind lifts are made either from a jack-up standing on its legs or from a floating heavy-lift or construction vessel. Which one the crane stands on decides whether heave reaches the hook, and so most of what an in-line heave compensator has to do.

Jack-up or floating vessel

An elevated jack-up stands on the seabed, so the waves do not heave its hull or its crane. Its lifts are governed by the wind on the component, the flexibility of the crane and structure, and the motion of anything the load is taken from or set onto, such as a feeder vessel alongside. Two jack-up cases still give an in-line unit a job: a load picked from a floating feeder moves with the feeder until it clears the deck, and a subsea lift through the splash zone meets the waves whatever the crane stands on. Our quick lifting article shows how an adaptive unit lifts a load clear of a moving deck.

A floating vessel keeps moving with the waves. The crane tip’s vertical motion combines the vessel’s heave with its roll and pitch, the roll part scaled by the tip’s distance from the centreline and the pitch part by its distance from midships, so a crane tip far out to the side or towards the bow or stern can move more than the vessel heaves. Through a rigid wire and slings, that motion reaches the load. Our vessel motions article shows how it is calculated.

Where an in-line unit helps

Subsea lifts for floating wind and foundations

Suction anchors and mooring hardware for floating wind, pre-piling templates, subsea structures and protection covers are lowered from a floating vessel through the splash zone to the seabed. They meet the same loads as any subsea lift: slamming, drag, buoyancy and added mass in the splash zone, then the landing speed at the seabed. A passive compensator in line makes the hoisting system soft, which cuts the snap loads, and reduces the crane-tip motion that reaches the load at landing. In our splash-zone study of a 35 t GRP cover at Hs 1.8 m, a RIGEL 75 t / 4.5 m cut the peak line load from 1,846 kN to 655 kN and removed every slack-sling event; the stroke margin was the limit. Splash zone crossing and subsea lifts explain the loads.

Setting a load down from a floating vessel

When a floating vessel lands a load on something fixed, such as a jacket onto pre-installed piles, a transition piece onto a monopile or a template onto the seabed, the crane tip keeps moving after first contact. With rigid rigging, each upward motion of the crane tip can lift the load off again, and it lands hard on the way down, cycle after cycle, until enough wire is paid out (Figure 1).

Figure 1. Setting a load down on a fixed foundation from a floating vessel, here a transition piece on a monopile. (A) With rigid rigging, the crane tip’s upward motion lifts the load off again and it lands hard, cycle after cycle, until enough wire is paid out. (B) With a passive compensator in line, the crane-tip motion after contact goes into stroke, so the line force changes gradually instead of snatching the load off; the load settles and its weight passes to the foundation as the wire is paid out. The payout and the unit’s tuning are checked in the lift model. Alignment is a separate job for guides. Schematic, not to scale.

With a passive compensator in line, the crane-tip motion after contact goes into stroke, so the line force changes gradually instead of snatching the load off the flange. As the wire is paid out, the unit retracts, its force falls and the weight passes to the foundation. Until then the load is almost weightless on its seat, so the payout still has to keep ahead of the crane tip, and the unit’s natural period with the load has to stay clear of the wave periods. The lift model checks the touchdown speed, the stroke and the tuning for the sea states of the campaign. ANTARES adds a landing mode that opens its valves and releases its EQ function for a soft set-down.

Pile runs during driving

Monopiles and pin piles are usually driven with a hydraulic hammer. If the pile tip reaches a weak soil layer, the pile can run, and the crane line has to stop whatever it still holds. A POLARIS shock absorber in the crane fall caps the force at its valve setting while it strokes, instead of passing the full arrest to the crane. Pile run protection explains the load case and the sizing.

What it does not do

An in-line heave compensator works on the vertical load path. It does not position a load in the horizontal plane or turn it: guides and bumpers, motion-compensated pile grippers and tugger lines do that, and a lift plan usually needs one of them as well. Nor does it help a lift in which neither the hook nor the load’s support moves: a nacelle or blade lift from an elevated jack-up’s own deck is governed by the wind on the component and the crane’s own dynamics.

Wind lifts at a glance

Lift	Usually from	What governs it	In-line unit
Monopile: upending, lowering and driving	A floating vessel with a pile gripper, or a jack-up	The gripper’s position control; the risk of a pile run while driving	POLARIS for a pile run; the gripper holds the position
Transition piece onto a monopile	A jack-up or a floating vessel	Alignment, and the set-down on the flange or the grout supports	From a floating vessel, a compensator can soften the set-down; sized per lift
Jacket onto pre-installed piles	A floating heavy-lift vessel, sometimes a jack-up	The splash-zone crossing, then the set-down on the piles at the seabed, with stab-in guides for alignment	A compensator can soften the crossing and the set-down; sized per lift
Substation topside onto its jacket	A floating heavy-lift vessel	The set-down on the jacket, with bumpers and guides	A compensator can soften the set-down; sized per lift
Templates, anchors, subsea structures and covers	A floating construction vessel	Splash-zone loads and the landing on the seabed	RIGEL, CYGNUS or ANTARES
Tower, nacelle and blades	A jack-up	Wind on the component, and alignment at height	None from the jack-up’s own deck; for a pick from a floating feeder, an ANTARES quick lift

Sizing a unit for a wind lift

The unit is sized from a lift model: the vessel’s motion at the crane tip in the sea states of the campaign, the crane and rigging, the payload’s mass, geometry and hydrodynamics, and the landing or set-down criteria. On a heavy lift, the unit’s own length and weight also count against the crane’s hook height and load chart. CONSTELLATION runs the lift with and without the compensator and reports the loads, the stroke used and the margins.

RIGEL (55 to 1,000 t), CYGNUS (12.5 to 10,000 t) and ANTARES (30 to 4,000 t) cover in-line lifts, all rated to 3,000 m. ANTARES can change its setting during the lift: stiffer and better damped through the splash zone, softer below it, and a landing mode that opens its valves and releases its EQ function for a soft set-down. It can also quick-lift a load clear of a moving deck. POLARIS shock absorbers range from 75 to 4,000 t.

Sources and assumptions

The loads named for subsea lifts follow DNV-RP-N103. The case figures are from our CONSTELLATION study CS-2026-004 (35 t GRP cover, RIGEL 75 t / 4.5 m, Hs 1.8 m, Tp 7.5 s, worst of eight realisations), a screening study of the splash-zone crossing only, with no landing or set-down phase, not a certified analysis. Figure 1 is schematic.
The descriptions of installation methods are general. A campaign’s method, vessel and equipment come from its own engineering.
Product ranges are from our product data, September 2026.

Frequently asked questions

Does offshore wind installation need heave compensation?

Not for most lifts from an elevated jack-up, which stands on the seabed, so the waves do not move its crane; the exceptions are loads picked from a floating feeder and subsea lifts through the splash zone. From a floating vessel the crane tip moves with the waves, and an in-line compensator helps where that motion matters most: subsea lifts through the splash zone, and setting loads down on a fixed foundation or the seabed.

Can a heave compensator help lift components off a feeder barge?

It can help. A jack-up’s hook stands still, but a component on a floating feeder moves with the feeder until it clears the deck, and a slow hoist can let the deck hit it again. An adaptive unit such as ANTARES can quick-lift the load clear of the deck; whether that suits the crane, its hook height and the component is checked in the lift model.

What is the difference between a heave compensator and a pile gripper?

A heave compensator works in line on the vertical load path: it takes up crane-tip motion as stroke. A motion-compensated pile gripper holds a monopile in position in the horizontal plane while it is lowered and driven from a floating vessel. They do different jobs.

How does a shock absorber protect the crane in a pile run?

If a pile runs while it is being driven, the crane line has to stop whatever it still holds. A shock absorber such as POLARIS in the crane fall caps the force at its valve setting while it strokes, so the crane sees a capped force instead of the full arrest peak.

Which Norwegian Dynamics units suit offshore wind?

RIGEL, CYGNUS and ANTARES for in-line lifts, covering 12.5 to 10,000 t and rated to 3,000 m, and POLARIS for pile runs; POLARIS shock absorbers range from 75 to 4,000 t. The choice follows from a lift model of the payload, vessel and sea states.