This white paper explains what retiring on residual strength means in practice and how to build a retirement policy for mooring ropes, wires and rope tails that you can defend to an inspector, a terminal or an oil major. Written by Capt. Arjun Singh Kalra and Capt. Sachin Sikka, Master Mariners and the founders behind DigiMoor X7.
Why we wrote it
In 2022 we surveyed 16 ship owners and managers, with fleets from 3 to more than 600 vessels, to learn how they set their rope retirement policies. Most had a similar understanding of the requirements, and that understanding differed from our reading of MEG4. We found a need for one clear, concise document that brings the guidance together.
Whether your ships moor with synthetic ropes, steel wires or wires with rope tails, the same question comes up: when should each line come off, and on what evidence?
What the survey found
68% of the owners and managers we surveyed had set a simple three-point discard rule, applied to whichever comes first:
- Time: for example, a set number of years from the date a line is put into service, and a shorter period for tails.
- Running hours: for example, a fixed number of hours for lines and a lower number for tails.
- Condition: for example, when abrasion exceeds a defined value.
MEG4 does not set a time-based or running-hour-based discard criterion for lines or tails. It is categorical that they should be retired on their residual strength.
What you will learn
- What changed with MEG4, and why the previous edition was revised, including lessons from the 2015 mooring line failure on the LNG carrier Zarga.
- The MEG4 retirement criteria for lines and tails, and the role of manufacturer guidance, operational experience and residual strength.
- Residual strength testing in practice: what the test is, how much rope is usually sent, what cropping does to line length, how many lines to test and how often.
- Whether one line's test result can be applied to other lines on the same ship or on sister ships.
- What to do when testing is costly: how consistent usage records and planned rotation let you estimate residual strength on data.
- How the guidance evolved from MEG2 and MEG3 to MEG4, with references to the relevant sections so you can read the original text from OCIMF.
The Mooring Equipment Guidelines are published by OCIMF. We do not reproduce them: for the full text, see the OCIMF website.
Contents
- White paper contributors
- Synopsis
- Mooring lines were used ever since: what changed now?
- MEG4 recommendations on retirement criteria
- Residual strength testing of lines: a practical outlook
- References to the OCIMF Mooring Equipment Guidelines
Who it is for
Technical superintendents, marine superintendents, HSEQ managers and fleet managers responsible for mooring ropes, wires, tails and fittings on tankers, gas carriers, bulk carriers, container ships and car carriers, and anyone preparing for SIRE 2.0 mooring questions, TMSA 3 Element 6A or a RightShip inspection.
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Optimum retirement policy for mooring lines
Our white paper on retiring mooring ropes, wires and rope tails on residual strength under OCIMF MEG4.
Put your retirement policy on data
A retirement policy is only as good as the records behind it. DigiMoor X7 records each line's usage, inspections, rotations and damage, analyses rope life and manages wear zones at ship and maker level, so lines are retired on data, not estimates. If you need help setting the policy itself, our MEG4 mooring gap analysis and engineering assessment covers residual strength testing and vessel-specific Mooring System and Line Management Plans.
See how one fleet operator did it in our DigiMoor X7 case study.
Frequently asked questions
When should a mooring line be retired under MEG4?
Under MEG4, a mooring line should be retired when its residual strength reaches 75% of the ship design MBL, unless the manufacturer's guidance says otherwise. MEG4 asks operators to decide discard criteria from manufacturer guidance and operational experience, including residual strength testing, rather than from a fixed age alone.
Does MEG4 set a maximum age or running hours for mooring lines?
No. MEG4 does not set a time-based or running-hour-based discard criterion for lines or tails. It expects retirement to be based on residual strength, supported by manufacturer guidance and the operator's own experience. Fixed limits can still be part of a company policy, as long as they are justified by data.
What is residual strength testing of a mooring rope?
It is a test, carried out at a dedicated rope testing facility, that measures how much strength a used rope has left. The test is destructive, so a length is cut from the line, usually from the end with the most abrasion, and broken under controlled conditions. The result shows how close the line is to retirement.
Is the white paper free?
Yes. The white paper is free to download. We ask for your name, work email and company so we know who is reading it and can follow up if you have questions. We do not sell or rent your details to third parties, as our privacy policy explains.