OCIMF MEG4 & SOLAS II-1/3-8 · Mooring & Deck

MEG4 Mooring & Line Management Plan Guide: MBLSD, LDBF, Winch Brakes & SOLAS II-1/3-8

Q: Why does MEG4 require Line Design Break Force (LDBF) to be between 100% and 105% of Ship Design MBL?

If a mooring line’s LDBF is below 100% of the Ship Design MBL (MBLSD), the line is under-strength for the vessel’s design environmental forces. Conversely, if a crew orders an oversized line with LDBF well above 105% of MBLSD, the line can become stronger than the winch brake or deck bollards/fairleads, shifting the point of failure from the winch brake rendering mechanism to a catastrophic structural failure of deck fittings.

Q: Why did OCIMF MEG4 stop recommending painted yellow/black "snap-back zones" on the mooring deck?

MEG4 found that painting fixed geometric triangles or boxes on deck gave crew a false sense of security just outside the painted line. Because mooring lines often run around multiple pedestal rollers and fairleads, the entire mooring deck is a potential snap-back area whenever lines are under tension. Instead of painted deck boxes, the whole mooring workspace must be managed as a danger zone, with clear line-of-sight supervision and crew standing well clear of tensioned leads.

Q: What is the difference between the Mooring System Management Plan (MSMP) and the Line Management Plan (LMP)?

The Mooring System Management Plan (MSMP) is the vessel-specific master document (structured in a standard register from Part A ship details through Part G audit/review) that stays with the ship for its entire life and covers design philosophy, MBLSD, deck equipment, winch brake testing and human factors. The Line Management Plan (LMP) is the specific section/plan inside the MSMP that governs the lifecycle of mooring lines, wires and tails — from base specification and Appendix B certificates to pre-use checks, periodic inspection intervals, end-for-ending, residual strength testing and retirement criteria.

Q: What do SIRE 2.0 Chapter 9, RightShip RISQ Section 10 and PSC inspectors check in the mooring log?

Inspectors cross-check: (1) that every mooring line and tail on winches and in storage has a matching manufacturer’s test certificate with a unique serial/ID tag; (2) that every line’s LDBF is 100%–105% of MBLSD (and tails are 125%–130% of MBLSD); (3) that all lines in the same service group (e.g. breast lines or spring lines) are of the same material and elasticity (never mixing wire/HMSF and high-stretch synthetic lines on the same duty); (4) documented winch brake rendering test records (60% of MBLSD on the first layer); and (5) that no line or tail has exceeded the company LMP retirement age or operation count.

Mooring operations remain one of the highest-risk activities on board any ship, and Chapter 9 (Mooring and Anchoring) of SIRE 2.0, Section 10 of RightShip RISQ 3.2, CDI and Port State Control all treat mooring line certificates, winch brake test records and deck fitting markings as high-priority inspection items. Since 1 January 2024, SOLAS Regulation II-1/3-8 and IMO Circular MSC.1/Circ.1620 have made documented mooring line inspection, maintenance and retirement mandatory on every SOLAS ship, not only tankers.

This guide explains OCIMF Mooring Equipment Guidelines (MEG4) terminology (MBLSD, LDBF, WLL and tail sizing), the Mooring System Management Plan (MSMP) and Line Management Plan (LMP), winch brake rendering tests, and how to maintain a compliant mooring line log.

Updated 22 October 2026 · Written by SeaReady in our own words. Not affiliated with OCIMF, RightShip, CDI, any MoU or any administration — always check the current official documents.

1. MEG4 Core Parameters: MBLSD, LDBF, WLL & Mooring Tails

OCIMF MEG4 replaced ambiguous legacy terms (“nominal breaking strength” or “safe working load of ropes”) with a strict engineering hierarchy tied to the vessel’s Ship Design Minimum Breaking Load (MBLSD / SDMBL):

OCIMF MEG4 mooring line, tail, winch brake and deck fitting strength ratios relative to Ship Design MBL (MBLSD).
MEG4 Parameter	Required Value / Ratio to MBLSD	Meaning & Inspector Verification Check
Ship Design Minimum Breaking Load (MBLSD / SDMBL)	100% reference baseline (kN)	The core design parameter for the ship’s mooring restraint system, calculated for standard environmental criteria under OCIMF MEG4 and IMO MSC.1/Circ.1619 and shown on the Mooring Arrangement Plan.
Line Design Break Force (LDBF)	100%–105% of MBLSD (synthetic) · 100% of MBLSD (steel wire)	The minimum break force at which a new, dry, spliced mooring line will part when tested under OCIMF MEG4 Appendix B (or wet-tested for nylon/polyamide). Lines with LDBF < 100% or > 105% of MBLSD trigger an immediate SIRE 2.0 / RightShip observation.
Working Load Limit (WLL)	50% of MBLSD (synthetic lines) · 55% of MBLSD (steel wire)	The maximum load that a mooring line should be subjected to in operational service, used as an operational design limit (never exceeded during normal mooring).
Mooring Tails (Synthetic)	LDBF = 125%–130% of MBLSD	Synthetic mooring tails fitted to wire or HMSF lines must have a higher LDBF (125%–130% of MBLSD) to account for higher cyclic fatigue and UV/abrasion exposure at the shore bollard.
Winch Brake Rendering Capacity	Set at 60% of MBLSD (tested annually on the 1st / operating layer)	Winch brakes are set to hold 60% of the ship’s MBLSD on the first (operating) layer of the split drum so the brake renders before the line or deck fitting reaches its breaking load (design brake holding capacity is 80% of MBLSD).
Deck Fittings (Bollards, Chocks, Fairleads, Rollers)	SWL ≥ 100%–125% of MBLSD (marked permanently on the fitting)	Under SOLAS Regulation II-1/3-8 and MSC.1/Circ.1619 / MSC.1/Circ.1175/Rev.1, every bollard, fairlead, Panama chock and pedestal roller must have its Safe Working Load (SWL) permanently marked by weld bead and painted clearly.

Never mix mooring line materials in the same service group: High-Modulus Synthetic Fibre (HMSF / HMPE) lines and steel wires have very low elongation (2%–3% at break), whereas polyamide (nylon) or polypropylene/polyester lines stretch 15%–30%. If a low-stretch HMSF or wire line is used in parallel with a conventional synthetic line as a breast or spring line, the stiffer line takes almost 100% of the load and parts first.
Synthetic mooring tail service life: Because synthetic tails absorb shock loads and suffer chafe on shore bollards, company Line Management Plans typically mandate retiring tails after 18–24 months in service (or earlier if cut, glazed, fused or chemically contaminated) and require a Mandal shackle /Tonsberg shackle connected in the correct orientation per manufacturer instructions.

2. SOLAS II-1/3-8, MSC.1/Circ.1619 & MSC.1/Circ.1620 (Mandatory on All Ships)

While MEG4 began as tanker/gas industry best practice, IMO Resolution MSC.474(102) amended SOLAS Regulation II-1/3-8 (effective 1 January 2024) to bring MEG4-aligned maintenance and line-management rules to the entire merchant fleet (bulk carriers, containerships, ro-ro vessels, passenger ships and tankers alike):

SOLAS II-1/3-8, IMO MSC.1/Circ.1619, MSC.1/Circ.1620 and OCIMF MEG4 mooring requirements.
Regulation / Circular	Scope & Effective Date	Mandatory Onboard Requirement
SOLAS Reg. II-1/3-8 (paras 7–9)	In force 1 January 2024 (IMO Res. MSC.474(102))	Requires safe design of mooring arrangements for ships constructed on or after 1 Jan 2024 AND requires ALL ships (regardless of build date) to inspect and maintain mooring equipment, lines and tails under documented procedures.
IMO MSC.1/Circ.1619	Guidelines on the Design of Mooring Arrangements and the Selection of Appropriate Mooring Equipment and Fittings for Safe Mooring	Applies to ships constructed on or after 1 January 2024 (≥ 3,000 GT, plus guidance for < 3,000 GT): requires human-centric mooring deck layout, unobstructed winch operator sightlines, minimal deflecting sheaves/pedestal leads, and a Towing and Mooring Arrangement Plan.
IMO MSC.1/Circ.1620	Guidelines for Inspection and Maintenance of Mooring Equipment Including Lines	Applies to ALL existing and new ships from 1 January 2024: requires periodic inspection procedures, documented retirement criteria for mooring lines and tails, record-keeping of line certificates and replacements, and compatibility checks when purchasing replacement lines.
OCIMF MEG4	Mooring Equipment Guidelines, 4th Edition	Establishes the Mooring System Management Plan (MSMP), the Line Management Plan (LMP), the MBLSD / LDBF / WLL nomenclature, Base Design and Line testing standards (Appendix B), and rejection of permanent painted "snap-back zone" deck markings.

3. Winch brake rendering tests, split drums & deck walk checks

During a SIRE 2.0, RightShip RISQ 3.2 or Port State Control deck walk on the forecastle and poop deck, inspectors check the physical condition of the winches, lines and fittings against the MSMP/LMP:

Winch brake testing (60% of MBLSD): Verify that every mooring winch brake is tested annually (and after any brake lining renewal or slippage) using the ship’s calibrated hydraulic jack and torque/pressure tables, with the rendering point set at 60% of MBLSD on the first wraps of the tension (working) drum, and the test date plus rendering load stencilled or tagged at the winch.
Split-drum spooling & reeling direction: Check that the working (tension) side of every split drum carries only a single layer of line (typically 4 to 8 turns as specified by the line/winch manufacturer) so the effective drum diameter does not increase and reduce brake holding capacity, and that the rope leads onto the drum in the correct direction relative to the band brake anchor pin.
Bollard, fairlead & roller SWL weld markings: Walk every mooring station and confirm that every bollard, Panama chock, universal fairlead and pedestal roller has its SWL in tonnes (t) or kN permanently marked by weld bead, that rollers turn freely with grease nipples intact, and that pedestal bases show no wastage or grouting cracks.
Anchor windlass, bitter end & chain locker markings: Check that the chain cable lengths are painted on the joining shackles and adjacent links, the bitter-end release outside the chain locker is unobstructed and clearly marked, the spurling pipe covers and canvas/cement sealing prevent water ingress under SOLAS II-1/16-1, and windlass brake bands and declutching gears are in good order.

Questions seafarers ask

Why does MEG4 require Line Design Break Force (LDBF) to be between 100% and 105% of Ship Design MBL?

If a mooring line’s LDBF is below 100% of the Ship Design MBL (MBLSD), the line is under-strength for the vessel’s design environmental forces. Conversely, if a crew orders an oversized line with LDBF well above 105% of MBLSD, the line can become stronger than the winch brake or deck bollards/fairleads, shifting the point of failure from the winch brake rendering mechanism to a catastrophic structural failure of deck fittings.

Why did OCIMF MEG4 stop recommending painted yellow/black "snap-back zones" on the mooring deck?

MEG4 found that painting fixed geometric triangles or boxes on deck gave crew a false sense of security just outside the painted line. Because mooring lines often run around multiple pedestal rollers and fairleads, the entire mooring deck is a potential snap-back area whenever lines are under tension. Instead of painted deck boxes, the whole mooring workspace must be managed as a danger zone, with clear line-of-sight supervision and crew standing well clear of tensioned leads.

What is the difference between the Mooring System Management Plan (MSMP) and the Line Management Plan (LMP)?

The Mooring System Management Plan (MSMP) is the vessel-specific master document (structured in a standard register from Part A ship details through Part G audit/review) that stays with the ship for its entire life and covers design philosophy, MBLSD, deck equipment, winch brake testing and human factors. The Line Management Plan (LMP) is the specific section/plan inside the MSMP that governs the lifecycle of mooring lines, wires and tails — from base specification and Appendix B certificates to pre-use checks, periodic inspection intervals, end-for-ending, residual strength testing and retirement criteria.

What do SIRE 2.0 Chapter 9, RightShip RISQ Section 10 and PSC inspectors check in the mooring log?

Inspectors cross-check: (1) that every mooring line and tail on winches and in storage has a matching manufacturer’s test certificate with a unique serial/ID tag; (2) that every line’s LDBF is 100%–105% of MBLSD (and tails are 125%–130% of MBLSD); (3) that all lines in the same service group (e.g. breast lines or spring lines) are of the same material and elasticity (never mixing wire/HMSF and high-stretch synthetic lines on the same duty); (4) documented winch brake rendering test records (60% of MBLSD on the first layer); and (5) that no line or tail has exceeded the company LMP retirement age or operation count.

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