Anchor chains are the "lifeline" of ships. When they rust or exceed wear limits, it can lead to loss of control, damage to submarine facilities, and even casualties. In April 2025, a Chinese cargo ship (1,422 gross tons) was urgently grounded due to anchor chain diameter wear exceeding 28%, sounding a safety alarm for the industry. This article combines regulations and engineering data to offer a guide on anchor chain replacement.

The Fatal Risk of Excessive Anchor Chain Wear

For every 1 mm reduction in anchor chain diameter, the load-bearing capacity decreases by approximately 8%-10%. When wear exceeds the regulatory limit, the risk of breakage soars. A 15% diameter reduction results in a 30% decrease in load-bearing capacity. In 2025, the anchor chain of the Chinese cargo ship "L" wore from 28mm to 20mm (28.6% reduction), causing it to break while anchoring. The ship drifted into shallow waters, nearly causing a major accident, and this case was included in the China Maritime Safety Administration's "Collection of Ship Safety Warning Cases (2025)."

China's "Technical Regulations for the Legal Operation Inspection of Seagoing Vessels" stipulates that if the average diameter of the most worn part of the anchor chain decreases by more than 15% compared to the original, it must be replaced. Failure to comply can lead to detention, fines, or revocation of the ship's seaworthiness certificate.

High-quality anchor chains must pass three levels of inspection:

· Material Certification: Use DNV GL-certified 690MPa high-strength alloy steel (common steel has a tensile strength of about 490MPa).

· Manufacturing Precision: Diameter tolerance is controlled within ±0.5mm (industry standard is ±0.8mm).

· Anti-Corrosion Treatment: A hot-dip galvanizing + double-layer epoxy coating system, certified for 3000 hours of salt spray testing (conventional hot-dip galvanizing lasts about 1000 hours).

Regulatory Requirements and Technical Standards for Replacement

When is replacement required?

· Single Chain Link: Measure the smaller of the chain link's minimum diameter (D₁) and the perpendicular diameter (D₂). If the reduction exceeds 15% from the original diameter, the chain link must be replaced. For example, a 28mm diameter anchor chain must be replaced if the diameter after wear is ≤ 23.8mm.

· Entire Anchor Chain Sections: If more than one-third of the links in a section show significant elongation, deformation, or excessive wear, the entire section must be replaced. IMO SOLAS Convention Chapter III, Regulation 20 requires the overall strength of the anchor chain to meet the design load.

· Special Component Restrictions: A studless link or shackle must be scrapped if wear exceeds 8% of its original diameter. For example, a 20mm original diameter studless link must be replaced if its diameter after wear is ≤18.4mm.

How to Properly Replace It?

· Interim Measures: If the excessive link cannot be replaced immediately, a Kent shackle can be used to temporarily connect adjacent links. However, Kent shackles are for temporary use only. High-strength temporary connectors are recommended, as they extend the lifespan by 50% compared to traditional products.

· Permanent Repair: Prioritize replacing the entire anchor chain. High-quality anchor chain is made of 690MPa alloy steel, with a tensile strength 1.4 times that of ordinary anchor chain. After replacement, request a temporary inspection from the ship's inspection agency. Select suppliers certified by LR, DNV, CCS, and ABS.

Quality Selection Criteria for Global Purchasing Decision-Makers

The 2025 report of the International Chamber of Shipping (ICS) indicates that high-quality anchor chain suppliers must have:

· Certification System: Certifications from LR, DNV, ABS, and CCS.

· Traceability: Each anchor chain is stamped with a classification society certification code, traceable to the raw material batch, production station, inspection records, and manufacturer.

· Data Support: Provide an AI-based wear prediction model and full lifecycle cost analysis.

The health of the anchor chain is directly related to the ship's survival. If a single link wears over 15%, it must be replaced. When more than one-third of the links in a section exceed the standard, replacing the entire section is the only compliant solution. As a leading global anchor chain supplier, SMEOCEAN builds products to military-grade standards, offering certifications from ten classification societies.

For inquiries, contact us at sme@smeocean.com | +86-13792888865.

More Links：

What are Anchor Chains Used for ?

How to Extend the Life of Anchor Chain?

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