Wilhelmsen

The Line design break force/tail design break force is the minimum force that a new, dry, spliced mooring line or tail will break at when tested according to appendix B of MEG4. This counts for all mooring lines and tails except polyamide (nylon) which is tested wet and spliced. This value is declared by the manufacturer on each line’s mooring line certificate (see appendix B) and is stated on a manufacturer’s line data sheet. As outlined in appendix B, when selecting lines, the LDBF of a line shall be 100%–105% of the ship design MBL.TDBF shall be 125-130% of the ship design MBLstated on a manufacturer’s line data sheet. As outlined in appendix B, when selecting lines, the LDBF of a line shall be 100%–105% of the ship design MBL.TDBF 125-130% of the ship design MBL 
 
The LDBF for polyamide (nylon) mooring lines should be specified as break tested wet and spliced because the strength characteristics changes when exposed to water and generally do not fully dry to their original construction state.  

• The Ship Design Minimum Breaking Load (sdMBL) is the minimum breaking load of new, dry mooring lines for which a ship’s mooring system is designed, to meet OCIMF standard environmental criteria restraint requirements. The ship design MBL is the core parameter against which all the other components of a ship’s mooring system are sized and designed with defined tolerances.
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• Ships built to MEG4 will already have a ship design MBL to satisfy OCIMF Standard Environmental Criteria restraint requirements and each mooring line will have a LDBF. Mooring fittings and mooring winch brake rendering values are based on the ship design MBL. 
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  • Ships built prior to MEG4 that do not have an established sdMBL shall undertake the necessary due diligence by contacting a class society and collate required information, such as safe working load and brake capacity of the winch, and safe working load of the deck equipment.

The vessels equipment number, often referred to as EN, is used to determine the size and number of anchors, cables, towing, and mooring ropes on board the ship.

Whenever possible, it is recommended to use the sdMBL for selecting the right ropes, rather than the EN, as this will lead to a more accurate selection of the mooring lines.

Section 5 of IMO SOLAS circ. 1619 states:
“To facilitate safe mooring operations, it is necessary for mooring equipment, fittings and mooring lines to be considered as a complete system within which all components are compatible”.

According to OCIMF MEG4, the SWL of mooring equipment on deck should be equal to 100% of the SDMBL. This means that, as long as the mooring lines are selected with the correct strength, the mooring deck will be able to withstand the maximum load possible from the mooring lines.

Additionally, it is important to consider the effect of the bending radius on the performance of mooring ropes, which is often referred to as the D/d - ratio between the diameter of the hardware and the diameter of the rope.

Smaller D/d ratio will lead to strength loss and shorter lifetime of the rope. OCIMF MEG4 recommend a D/d ratio of 15 or above.

If the mooring setup follows the recommendation from MEG4 and RightShip RISQ, the load factors in the arrangement will be (all the loads are in % of sdMBL): 

• SWL of mooring winch: 100%  

• Brake rendering point: 60% 
• Strength of the line mooring line: from 105% (brand new line) to 75% (line to be retired) 
• Strength of the tails : from 130% (brand new tail) to 75% (tail to be retired). 

Therefore, the weakest link of the mooring arrangement is the operational brake rendering point of the winch, which should be set at 60% of the sdMBL. 

 You can find more information in the video in the link below: 

LINK to VIDEO 

Accommodating all port regulations is difficult and local requirements might conflict with the regulations and guidelines from the global regulatory bodies. 

As mentioned in our use and care guidelines, ropes from different manufacturers may have slightly different elongations. Ropes working in parallel must be of the same construction, material, running time and condition (used/new), to prevent one of the two ropes from bearing the whole load which will result in increased wear and an unsafe setup. There is no need to change the full ship set. In addition, we recommend using the same model of rope or tail.

Yes, this will be generated automatically when a vessel establishes a sdMBL and it is registered in our system.

• In our Knowledge Base, you can find all relevant documentation, in addition to other relevant information and insights. 

We recommend a minimum of 5-6 full turns for conventional mooring ropes and 10 full turns for HMPE on the tension drum, in one layer only. If number of full turns are not possible, we recommend making as many wraps as possible in one single layer. The main intention is to avoid slippage of the rope on the tension drum and avoid transfer of tension to the storage drum of the winch.

Yes, certain regulations/guidelines such as RightShip RISQ 2.0, SOLAS 2024, and OCIMF SIRE 2.0 are conducting regular inspections on ropes. To ensure compliance and be prepared, we recommend that you follow your internal inspection criterias. Rope inspections can help reveal stress, damage, or wear on mooring ropes, and help prevent accidents before they occur. Expert advice from third parties can provide the crew with useful knowledge on how to optimize the working conditions for the ropes. Conduct regular inspections using Timm inspection and retirement guidelines in line with the operators retirement and inspection plan.

Incorrectly installed ropes have a high risk of becoming twisted. Twisting can cause a mooring rope to weaken by as much as 6% per turn per meter and this may become a safety hazard for the crew and port workers. Using a turn table or manually remove the twist before installation on the winch will avoid twist when installing the rope. Apply a certain back tension (approximately 40KG) either by man handling or using the rope bitts as mean of tension. For best practice, you should always follow manufacturers guideline.