Hycom delivers, for a company in offshore personnel transfer, several versions of their active heave compensated gangways:

Hydraulic piston accumulator
A Hydac piston accumulator with a maximum content of 540 litres;

Nitrogen set
The nitrogen set consists of up tot to 42 pieces of  75 litre N2 bottles which are mounted on a carbon steel frame/skid. The bottles are mounted horizontally.
The skid includes two pressure gauge  with shut-off valve, two pressure sensors, two fill/test valve blocks including a gas safety valve.