The control chain is not directly connected to the SDV and only rests within the chain tower, therefore the surface vessel and SDV can move independently.

Rapid vertical movement of the surface vessel only raises and lowers the control chain and not the SDV. Consequently there will be minimal variation in the down-line tension.

The mass of the SDV and structure is large compared to the weight of control chain and consequently the motion of the chains due to surface vessel motions causes minimal dynamic response of the SDV.


Motion Relationship between SDV and Surface Vessel