Anchor Chain Selection Guide: Grades, Sizes, and Certification for Marine Vessels

Anchor chain is one of the most critical components of any marine vessel – from small fishing boats to ultra‑large container ships and offshore platforms. It is the only link between the anchor and the ship, and its failure can lead to dragging, collision, grounding, or total loss of the vessel.

Choosing the right anchor chain is not a matter of guesswork. You must consider the chain grade (strength), diameter (size), and the required marine classification society approval.

This guide provides a clear, practical framework for selecting the correct anchor chain for your vessel, whether for newbuilding, replacement, or retrofit.

Step 1: Understand Anchor Chain Grades – Strength and Material

Anchor chains are manufactured according to international standards, primarily ISO 1704 and the rules of classification societies. The most common grades are:

Key points:

• Higher grade allows a smaller diameter for the same breaking load – important for weight‑sensitive vessels.

• Grade 3 is the most widely used anchor chain grade for ocean‑going vessels.

• For permanent mooring systems (e.g., floating production units), grades R3, R4, R5 are used, which include special requirements for fatigue and corrosion resistance.

Always check your vessel’s classification society rules or the anchor windlass manufacturer’s recommendation – using a lower grade than specified is not permitted.

Step 2: Choose the Correct Chain Size (Diameter)

Anchor chain size is expressed by the nominal diameter of the wire (in millimetres), measured across the cross‑section of the link.

Common anchor chain diameters:

• Small craft: 6 mm – 12 mm

• Fishing vessels / tugs: 14 mm – 22 mm

• General cargo / bulk carriers: 24 mm – 48 mm

• Large container ships / VLCCs: 54 mm – 84 mm or even larger

How to determine the required diameter:

1. Based on the vessel’s equipment number (EN) or anchor chain length and holding power required by your classification society.

2. Refer to the anchor windlass (chain lifter) specifications – the chain must fit the pocket wheel precisely.

3. For replacement, measure the existing chain or consult the original ship design drawings.

Practical rule: Do not arbitrarily increase or decrease diameter. A larger chain may not fit the windlass; a smaller chain will jump or jam on the lifter wheel.

Step 3: Know the Two Main Chain Types – Stud Link vs. Studless

Anchor chains come in two basic configurations:

When to use each:

• Most ocean‑going vessels use stud link chain for the first one or two shots (each shot = 27.5 metres) near the anchor, because it handles better in the hawsepipe and resists fouling.

• Some smaller vessels or buoy moorings use studless chain for economy.

• For very deep water or permanent mooring, studless chains are sometimes preferred due to weight savings.

Step 4: Certification – What You Must Demand

For commercial vessels, anchor chain without valid classification society certification is not acceptable. The certification proves that the chain has been manufactured, tested, and inspected according to internationally recognised rules.

Required documentation for each chain length (shot):

1. Mill certificate – showing chemical composition, mechanical properties (tensile, yield, elongation), and heat treatment details.

2. Proof load test certificate – each link must be proof‑loaded to a specified percentage of its breaking load (typically 1.5× to 2.5× WLL, depending on grade).

3. Classification society stamp – the chain is stamped with the society’s mark (e.g., ABS, DNV, LR, BV, CCS, NK, RINA) at intervals.

Major classification societies accepted worldwide:

• ABS (American Bureau of Shipping)

• DNV (Det Norske Veritas) – often combined with GL

• LR (Lloyd’s Register)

• BV (Bureau Veritas)

• CCS (China Classification Society)

• NK (Nippon Kaiji Kyokai / ClassNK)

• RINA (Registro Italiano Navale)

For new anchor chain, always request a full certification package before delivery. For used or second‑hand chain, you must verify that the original stamps are intact and the chain has not been over‑stretched or corroded beyond limits.

Step 5: Inspect and Maintain Your Anchor Chain

Even a correctly selected, certified chain will degrade over time due to corrosion, wear, and fatigue. Regular inspection is mandatory:

What to check:

• Corrosion – pitting, wastage, or reduction in link cross‑section. If the diameter is reduced by more than 10% of nominal, replace the chain.

• Cracks – especially on the inside of links and at the welds (stud‑to‑link welds in stud link chain). Use dye penetrant or MPI (magnetic particle inspection) where possible.

• Elongation – measure the length of a shot (27.5 m). If it has stretched more than 5% over original length, the chain has lost ductility and should be retired.

• Stud condition – loose or missing studs reduce the chain’s resistance to kinking and may get stuck in the windlass.

Maintenance tips:

• Rinse anchor chain with fresh water after operations in salt water, especially for chains not continuously submerged.

• Turn end‑for‑end after several years of service to distribute wear evenly.

• Store spare chain in a dry, ventilated locker.

Your next step:
Contact our marine chain team with your vessel type, classification society, and required diameter. We will provide a certified anchor chain quotation, complete with mill certificates and class approval documents.