Anchor Swivel Forerunner

What is in the assembly

A forerunner is not a single fitting. Working from the anchor end, it is: an open end link, an enlarged link, the swivel body itself — a barrel with a rotating eye — then a further enlarged link and common stud links terminating in an end link that takes the first shot of chain. The enlarged links either side of the swivel are there to make the diameter change gradually rather than at a step.

Because it is supplied made up, it is quoted by one overall length per chain diameter, roughly 20 times the diameter, rather than by a set of component dimensions.

Why it earns its place

An anchor lying on the bottom rotates as the vessel swings, and every rotation puts a turn into the cable. Without a swivel those turns accumulate: the cable comes up twisted, the anchor arrives at the hawse pipe wrong way round, and the twist stays locked in when the cable is stowed. The swivel lets the turns run out as they are made.

Loads and testing

Like every other accessory, the forerunner is proof-tested at the proof load of the chain grade it serves, and one unit per batch of 25 is destructively break-tested. The table below therefore repeats the chain’s own load columns — by requirement, not by coincidence.

Inspection in service

The swivel is a bearing in seawater at the dirtiest part of the ship. It seizes. A seized swivel is not obvious from the deck — the cable simply stops shedding turns — so check that the eye actually rotates when the cable is ranged at drydock, and check the wear at the swivel’s bearing face while it is out. It is the one component in the cable whose failure mode is silent.