The range and variety of chains and fittings, used in mooring/marine applications, is probably wider than ever before and to compound the selection problem, almost all components are available in various grades. Different strengths for otherwise identical items are achieved through the use of different steels and heat treatments, some more suited to the marine environments than others.
Grades:
Chain and fittings are manufactured in different strength grades for specific applications, and the strongest component is not necessarily the best for the job in hand. It could be unsuitable for galvanizing, or made from a steel which corrodes more rapidly and it may be disproportionately expensive. As will be seen later, weight is as important as strength in moorings and the lowest and cheapest strength grade usually offers the best combination of properties. Internationally, there are standards covering chains and most fittings and these recognize the following grades:
Grade 3 (L)
This is the lowest grade with components made from mild steel without heat treatment.
Grade 4 (M)
Normally manufactured from low carbon steels and heat treated, this is the lowest grade recommended for lifting applications.
Grade 8 (T)
The highest strength in normal use; components are usually made from alloy steels and hardened and tempered.
Chains

Short Link Chain

Internationally, this is accepted as chain with a link of outside dimensions not exceeding 5 times the material diameter in length and 3.5 times in width – e.g. 10mm chain cannot have links larger than 50mm x 35mm outside dimensions. Excluding stud link chain, short link chain, size for size, is the strongest, heaviest and most flexible of chains, and as such is the best choice for mooring and anchoring. Unfortunately the links are too short to accept shackles of reasonable size, necessitating the fitting of large end links. In effect, short link chain needs to be assembled into a ‘bespoke’ mooring assembly. William Hackett have the ability to do this by means of an ‘all-welded’ assembly negating the need for joining components such as shackles.

Mid Link Chain

These chains have a link of outside dimensions not exceeding approximately 6 times the material diameter in length and 3.6 times in width – e.g. 10mm chain, generally would not have links larger than 60mm x 36mm outside dimensions. Mid link chains are a good compromise, as they offer most of the benefits of short link with the advantage that they will accept like sized shackles without the need for special end links.

Long Link Chain

These chains have a link of outside dimensions not exceeding approximately 8 times the material diameter in length and 4 times in width – e.g. 10mm chain, generally would not have links larger than 80mm x 40mm outside dimensions. Long link chains are also a popular choice for mooring applications, as they offer greater internal dimensions to facilitate a wider range of associated fittings without the need for special end links. They also offer a lighter weight to ultimate breaking strength ratio, which can often be an issue when choosing the correct mooring buoy.

Stud Link Anchor Chain

Originally studs were added to chain to stiffen the links, preventing them from severely deforming when overloaded. They have an added advantage in that they prevent chain from knotting up when twisted, thus avoiding problems when the chain is retrieved with a windlass. Most chain of this type is used on larger vessels, off-shore mooring systems or used as a ‘ground chain’ for a mooring system.