Compensator Selection

How do the various products perform when used for typical applications?

Application	Example	Shock absorber	Basic PHC	Adaptive PHC	Topside AHC	Subsea AHC
Intermittent shock load	Sudden drop of piling hammer
Frequent shock load	Storm overload protection
Splash zone crossing, low buoyancy	Steel structure lowering
Splash zone crossing, high buoyancy	GRP structure lowering
Resonance avoidance	Lowering to ultra deep waters
Subsea landing, high added mass	Suction anchor
Subsea landing, slender payload	Vertical piping
Subsea landing, long wave period	≥12 s
Subsea retrieval	Pulling anchor out of seabed
Multi-application subsea lift	Splash zone plus subsea landing
Topside motion compensation	Landing of payload in air
Quick lifting	Lift payload from deck quickly

Legend
Best performance
Good performance
Suitable under special conditions
Not suitable

Let’s go into a little bit of details about this table.

Shock absorbers, like Polaris, are unmatched when it comes to shock absorption, but they are useless for other applications as the spring component is effectively missing.
Basic passive heave compensators, like Rigel, has generally a lower gas to oil ratio than an adaptive PHC which gives lower performance.
Adaptive passive heave compensators, like Antares, are the best allrounders, they can do almost everything reasonably well, except for motion compensation in air or subsea motion compensation under unfavorable conditions
Topside active heave compensators, cannot do subsea applications as they not designed to be submerged.
Active heave compensators are not well suited for “fast” applications such as shock absorption and gives generally worse performance than a passive heave compensator when operated in passive mode due to higher weight and friction.

Legend
Lowest cost
Low-medium cost
Medium-high cost
Highest cost

The relative cost is relative to a shock absorber cost (with similar capacity/stroke) and can be considered a rough indicator.

Where shock absorber is the most reliable.