Adaptive Passive Heave Compensation
A passive core. Different settings for different demands.
Change the settings as the lift changes.
The gas spring remains the passive core. Adaptive functions change its operating point and damping to suit the assessed lift phase.
How strongly force changes with stroke.
Changing the connected gas volume changes the spring response. The required setting comes from the lift model.
How motion energy is dissipated.
Changing hydraulic restriction changes the response during extension and retraction.
Where the rod sits in its travel.
Pressure adjustment manages the operating point as payload, temperature and external pressure change.
The modes below describe the ANTARES approach on this page. Available functions, limits and operating sequences belong to the specified equipment and lift plan.
Match the operating mode to the demand.
These sketches place the first four modes in context. The lift plan defines which settings and transitions are appropriate.
Locked
Hold the rod position while handling the load above deck.
Read mode detail
Rod held for deck handling
The piston rod is locked so it cannot extend when the payload is picked up, which keeps the required lifting height down while the load is still over the deck.
Splash zone
Adjust stiffness, damping and equilibrium for the assessed crossing.
Read mode detail
Stiffer and better damped through the surface
Higher stiffness and higher damping in both directions, with the equilibrium position offset to allow for the buoyancy the load picks up as it enters the water.
Subsea and depth
Manage the operating point as cooling and depth change.
Read mode detail
Cooling and depth corrected on the way down
Seawater cools the unit and its gas pressure falls, so onboard high-pressure gas is injected to hold the pressure at the right level. As depth builds, external pressure pushes the rod inwards and gas pressure is adjusted down to match. Extremely deep water with light payloads needs a different technique again: contact us for that case.
Low stiffness
Use a lower spring rate where the landing case calls for it.
Read mode detail
Soft for landing and resonance avoidance
A larger gas volume is connected to the cylinder, lowering the spring rate. That cuts load variation over stroke at set-down — whether it also moves the system clear of a resonance concern is checked in the lift model, not assumed.
Illustrative contexts, not a prescribed operating sequence or equipment drawing. Read the mode detail for the mechanism and its limits.
Two further capabilities for specific events.
Controlled lift-off, repeatable
Tension is first held below the weight of the payload, then raised quickly so the rod retracts in a controlled way. The sequence can be run more than once, which matters when a lift-off has to clear on the first attempt.
Asymmetric damping for snap and overload
Extension damping is limited while retraction damping is raised, so the unit yields through its stroke on the event and controls the return. How much of the peak that removes is read off the event’s force–stroke response in the model.
Three capabilities run underneath all six rather than being modes themselves. Filling and preparation are software controlled, checked against the parameters of the lift being prepared. The unit weighs the payload once it is attached and corrects its gas pressures on the fly if the figure differs from plan, with no trip back to deck. And every lift is logged, so stroke usage, DAF and landing speeds can be read back afterwards.
Which adjustments does this lift need?
A fixed-setting baseline and the ANTARES capabilities described here are different configurations. Check the actual supply scope before comparing features or cost.
| Capability | Fixed-setting passive baseline | ANTARES adaptive approach |
|---|---|---|
| Gas volume, stiffness and damping | Settings and gas volume are chosen for the planned duty. Check the adjustment provisions of the specified unit. | Gas reserve and in-service adjustment support different operating points; stiffness and damping can be changed during use. |
| Stroke equilibrium; temperature, weight and depth | Assess the resulting equilibrium drift and available travel across the operation. | Pressure adjustment manages the operating point as these conditions change, within the configured limits. |
| Quick lift and rod locking | Check whether these functions are included; a fixed-setting baseline does not establish their availability. | The quick-lift and locked modes described above support the relevant lift tasks. |
| Battery operation and data logging | Monitoring, logging and power arrangements depend on the equipment configuration. | Onboard battery and control systems support adjustment and logging without an umbilical. |
| Performance and selection | Demonstrate that the passive response meets the governing criteria through the required duty. | Demonstrate the benefit of changing settings, including transitions, control limits and failure behaviour. |
Compare like-for-like cost. Use the same SWL, stroke, depth rating, instrumentation, operating functions and certification scope. There is no universal 2–3× price ratio.
Adaptive passive heave compensation is an advanced form of passive heave compensation that can adjust its performance characteristics to suit different phases of an offshore lifting operation. Unlike basic PHC systems with fixed settings, adaptive compensators can switch between operating modes (such as locked, splash zone, and subsea) to optimize performance for each stage of the lift.
Adaptive adjustment can be useful where the required response changes between lift phases. Its benefit and operating limits are established for the project case.
All six modes are the same gas-spring hardware under different settings, applied on the fly and logged for review afterwards. The primary load path stays passive alongside the added capability; the adaptive functions add valves, sensors, controls and a battery, each with a defined safe state on loss. That operating envelope is what ANTARES was built around.
When should an adaptive PHC be used instead of a basic PHC?
- ResponseA fixed-setting passive option cannot meet the required response through the assessed duty, including landing.
- Available travelBuoyancy, temperature or depth changes would move equilibrium too far within the available stroke. Compare adjustment with the other design options.
- Changing demandsDifferent lift phases need different settings to meet the target dynamics. Assess the transitions and failed-adjustment behaviour as well.
Adaptive passive HC — frequently asked
What is adaptive passive heave compensation?
What is the difference between an adaptive and a basic PHC?
Does an adaptive PHC need external power?
What happens when the compensator cools down in seawater?
When is an adaptive PHC worth it over a basic one?
Need one unit to cover several lift modes?
ANTARES is our adaptive passive compensator — same hardware, multiple operating points. Tell us the lift data and we'll come back with sizing.
See it in action
ANTARES adaptive passive heave compensation — deck to seabed, simulated in CONSTELLATION
