Why Add Swivel Groups Between Anchor Chains and Anchors - Part 1

Adding a swivel group (also known as a "swivel shackle" or "rotating connection ring") between the anchor chain and the anchor is a very important and professional design. Its main functions can be summarized as follows:

Core function: Prevent the anchor chain and anchor from twisting

This is the most fundamental and important purpose. After a ship is anchored, it will be subject to the combined effects of external forces such as wind, water flow and surges, which will cause the hull to rotate around the anchor point.

1. Eliminating rotational stress: Without a swivel, the rotation of the hull would be directly transmitted to the anchor itself through the anchor chain. The anchor is deeply rooted in the seabed, and its posture is fixed, making it very difficult to rotate along with it. This will lead to the accumulation of huge torque (torsional stress) on the anchor chain and anchor rods.

2. Avoid anchor chain twisting : Continuous torsion can cause the anchor chain itself to twist into a "twisted" shape, resulting in severe twisting. The structural strength of the twisted anchor chain will be greatly reduced, making it prone to fatigue and damage. In severe cases, it may even jam the anchor chain compartment during lifting, causing serious accidents.

3. Maintain the anchor's bottom-grasping posture: For a well-grasping anchor, its anchor claws must stably penetrate into the seabed. If the anchor is forcibly dragged and rotated, it will disrupt its optimal bottom-grasping posture, which may cause the anchor to be pulled out of the seabed, resulting in a "drifting anchor" phenomenon, causing the vessel to drift and endangering safety.

The ring assembly acts like a "bearing", allowing the upper anchor chain to rotate freely while isolating the lower anchor and part of the anchor chain, keeping them stable and thus eliminating these harmful torsional forces.