Views: 0 Author: Site Editor Publish Time: 2026-05-21 Origin: Site
"If the mooring tail is slightly weaker than the main line, it will wear out and fail first, protecting the more expensive main rope while making maintenance and replacement easier."
This line of thinking is not uncommon in some mooring arrangements. However, from both a mooring mechanics perspective and an industry standards standpoint, it is a common misconception.
Strength Relationship Between Mooring Tails and Main Lines
According to the OCIMF Mooring Equipment Guidelines (MEG4), the Minimum Breaking Load (MBL) of a mooring tail should typically be 25%–30% higher than that of its corresponding main line. This is because mooring tails are often subjected to the highest concentration of wear and degradation within the mooring system.
During operation, mooring tails continuously absorb dynamic loads generated by vessel movements while frequently passing through high-friction areas such as fairleads and bollards. As a result, they generally experience fatigue and abrasion at a faster rate than the main lines.
If a mooring tail starts with a lower strength than the main line, its residual strength will reach a critical level much sooner. At the same time, the main line may be exposed to additional and uneven loading, accelerating fatigue damage and reducing the service life of the entire mooring arrangement.
In other words, the higher initial strength of a mooring tail is not a form of overdesign—it is compensation for the accelerated wear and strength loss that occurs during service.
The Real Principle of Safe Load Release
Another important point is that allowing the tail to fail first should never be considered a reliable risk-control strategy.
When a rope breaks, the stored energy can be released violently, generating dangerous snapback forces. Rope failure has long been recognized as one of the most significant causes of injury during mooring operations.
In a properly designed mooring system, abnormal loads are not intended to be relieved by the failure of a rope component. Instead, load release is typically managed by the mooring winch brake system, which is designed to slip or render in a controlled manner at predetermined load levels, thereby dissipating excess force safely.
The Goal Is System Stability, Not Controlled Failure
A well-designed mooring arrangement is not built around deciding which rope should break first. The objective is to ensure that the entire system maintains a stable and predictable load distribution throughout its service life.
The requirement for mooring tails to have higher strength than the corresponding main lines is therefore not a waste of material or cost. Rather, it is an essential part of mooring system design, helping to preserve service life, maintain load balance, and provide the necessary safety margin for reliable operations.
