Anchor Chain Wear Limit: SMEOCEAN Safety Guide for Ship Lifeline
Anchor Chain Safety Alert: How to Protect Ship Safety When the "Lifeline" Exceeds Limit Wear?
—Analysis of the Critical Lines of Defense for Global Ship Safety
Anchor chains are the "lifeline" of a ship, but when they rust or exceed limits due to wear, they can cause loss of control, damage to submarine facilities, and even casualties. In April 2025, a Chinese cargo ship (1,422 gross tons) was urgently grounded by the China Maritime Safety Administration due to anchor chain diameter wear exceeding 28%. This case sounded a safety alarm for the industry. This article combines the "Technical Code for Mandatory Surveys of International Seagoing Vessels" with actual engineering data to provide global procurement decision-makers with an authoritative guide to anchor chain replacement.
I. The Fatal Risk of Excessive Anchor Chain Wear: A 1% Loss Can Lead to a 100% Disaster
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 increases dramatically: A 15% reduction in diameter results in a 30% decrease in anchor chain load-bearing capacity. If broken in strong winds and rapids, the ship could drift and collide with submarine cables, resulting in repair costs reaching millions of yuan.
Case Study: In 2025, the anchor chain of the Chinese cargo ship "L" wore from 28mm to 20mm (a 28.6% reduction), causing it to break while anchoring. The ship lost control and drifted into shallow waters near the shore, nearly causing a major accident. This case has been included in the China Maritime Safety Administration's "Collection of Ship Safety Warning Cases (2025)."
Regulatory Bottom Line: China's "Technical Regulations for the Legal Operation Inspection of Seagoing Vessels" clearly stipulates that if the average diameter of the most worn portion of the anchor chain decreases by more than 15% compared to the original diameter, it must be replaced. Failure to do so will result in detention, fines, or even revocation of the ship's seaworthiness certificate (in accordance with Article 92 of the "Maritime Traffic Safety Law of the People's Republic of China").
Core Quality Control:
High-quality anchor chains must pass three levels of inspection:
Material Certification: Uses DNV GL-certified 690MPa high-strength alloy steel (common steel has a tensile strength of approximately 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 approximately 1000 hours). Commonly used in FPSO/wind power/high-end offshore engineering projects.
II. Four Major Causes of Anchor Chain Wear and Scientific Prevention Solutions
Anchor chain wear is not accidental; it is the result of multiple factors. The following is a prevention system recognized by the International Maritime Organization (IMO):
III. Regulatory Requirements and Technical Standards for Anchor Chain Replacement
(I) When is replacement required?
Exceeding the standard for a single chain link:
Measurement method: Take 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.
Risks for Entire Anchor Chain Sections:
If more than one-third of the links in a given anchor chain section show significant elongation, deformation, or excessive wear, the entire section (not just individual links) must be replaced.
Regulatory Basis: Chapter III, Regulation 20 of the IMO SOLAS Convention explicitly requires that the overall strength of the anchor chain meet the design load. Exceeding the specified load in a particular location may lead to systemic failure.
Special Component Restrictions:
A studless link or shackle must be scrapped if wear exceeds 8% of its original diameter. For example, a studless link with an original diameter of 20mm must be replaced if its diameter after wear is ≤18.4mm.
(II) How to Properly Replace It?
Interim Measures:
If the excessive link cannot be replaced immediately, a Kent shackle (consisting of two halves, a crosspiece, and a tapered pin) can be used to temporarily connect adjacent links.
Technical Notice: Kent shackles are for temporary use only. Long-term use may weaken the joint. 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 (not individual links). High-quality anchor chain is made of 690MPa alloy steel, with a tensile strength 1.4 times that of ordinary anchor chain.
After replacement, a temporary inspection must be requested from the ship's inspection agency. It is recommended to select suppliers certified by the four major organizations: LR, DNV, CCS, and ABS (no more than 10 suppliers worldwide).
IV. 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 possess the following characteristics:
Certification System: Certifications from the four major organizations: LR, DNV, ABS, and CCS.
Traceability: Each anchor chain is stamped with a classification society certification code, which can be traced back to the raw material batch, production station, classification society inspection records, and manufacturer.
Data Support: Provides an AI-based wear prediction model and full lifecycle cost analysis.
Conclusion: Safeguarding Safety at Every Journey with Quality
The health of the anchor chain is directly related to the survival of the ship. From the thrilling incident of the "L" vessel to the clear regulatory requirements, we all need to remember:
If a single link wears over 15%, it must be replaced; don't take chances.
Risk of an entire anchor chain section: When more than one-third of the links exceed the standard, replacing the entire section is the only compliant solution.
Temporary measures are limited: Kent shackles are only for emergency use; long-term reliance on them can lead to endless problems.
As a leading global anchor chain supplier, SMEOCEAN consistently builds products to military-grade standards. We offer certifications from ten classification societies, including LR, ABS, DNV, and CCS, ensuring high-quality anchor chain products.
If you have any inquiries, please contact us immediately: sme@smeocean.com | +86-13792888865
More Links：
What are Anchor Chains Used for ?
How to Extend the Life of Anchor Chain?
How is the Surface of the Anchor Chain Treated?