How to select the optimal mooring system

As a first general rule of thumb, only ropes holding the appropriate certificates of makers and never of intermediary suppliers should be considered for deployment in mooring line systems. Obtaining the appropriate mooring system for the job means that the system’s service life can potentially be dramatically enhanced and also ensures a maximum level of safety, which ultimately boosts cost efficiency.
It is strongly advised that “mixed mooring” set-ups should not be used. This is largely due to the generally significant differences that can exist in the levels of Elongation/Elasticity and Strength of two or more different types of lines. Mixed mooring causes potentially serious safety hazard!
With the help of the ship design MBL and equipment number, the breaking loads of the mooring lines can be calculated. But many other factors also influence the selection of the optimal mooring line system. This is why it is crucial to take the time to identify and make a careful assessment of these variables, which include but are not limited to:
• In what waters/ports will the vessel be primarily active (what are the local facilities like, and what conditions are anticipated to be regularly encountered)?
• How often will the vessel berth and be moored?
• What type of equipment and components are found on board of the vessel (e. g. fairleads, bollards, winches, etc.)?
Also needing consideration are the special conditions that exist on board, which can have a potential effect on the rope service life and therefore will influence the selection of which lines to choose for the mooring systems. These special conditions may include factors such as any tight angles that the lines will be exposed to during use, or the effects that multi-purpose hawsers may have on the ropes.
When converting from a wire-based to a synthetic fiber based in mooring system, then special attention is required to ensure that all points that come into contact with the rope on the vessel must be smooth in order to prevent the rope from snagging and being damaged.

Black Rope will be glad to help at any point in the selection process – and can even advise operators from the very beginning in the process of choosing the right mooring line system set-up, offering possible alternatives for their individual needs.

info@blackrope.com , (+30) 69522 90682-3-4

MEG4: The new standards of mooring ropes and the solution of 3 steps

The updated MEG4 represents the output of a multi-discipline working group representing members of various shipping trade organizations, mooring line manufacturers, shipyards, and OCIMF members. In previous guidelines of MEG requirements there was no specific jurisdiction of industry guidance on condition-based monitoring of mooring lines and tails. The new MEG requirements have strived to provide guidance and clarity on the condition-monitoring of mooring lines. Below is a list of some new terms that will be introduced in MEG4.

New terminology during the revision of MEG4

Ship Design Minimum Breaking Load – SDMBL. 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 SDMBL is the main parameter against which all the other components of a ship’s mooring system are sized and designed with defined tolerances.
Line Design Break Force – LDBF. LDBF is the minimum force that a new, dry, spliced mooring line will break at when tested according to appendix B. This is for all mooring line and tail materials except those manufactured from 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 it 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 SDMBL.

Line Design Break Force – LDBF.

LDBF is the minimum force that a new, dry, spliced mooring line will break at when tested according to appendix B. This is for all mooring line and tail materials except those manufactured from 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 it 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 SDMBL.

Tail Design Break Force – TDBF.

TDBF is the minimum force that a new, dry, spliced mooring tail will break at when tested according to appendix B. This is for all mooring line and tail materials except those manufactured from 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 it is stated on a manufacturer’s line data sheet. As outlined in appendix B, when selecting lines, the TDBF of a line shall be 125%–130% of the SDMBL. The TDBF for nylon mooring lines should be specified as break tested wet because nylon tails change strength characteristics once exposed to water.

Working Load Limit – WLL (instead SWL).

The maximum load that a mooring line should be subjected to in an operational service, calculated from the standard environmental criteria. The WLL is expressed as a percentage of ship design MBL and should be used as a limiting value in both ship design and operational mooring analysis. During operation, the WLL should not be exceeded.

• Steel wire ropes have a WLL of 55% of the SDMBL
• Cordage (synthetic) ropes have a WLL of 50% of the SDMBL

Line Management Plan – LMP.

LMP is used to manage the operation and retirement of mooring lines and tails. The LMP also documents the requirements, assumptions and evaluation methods which used in determining the line retirement criteria. The LMP is specific to an operator, ship type, mooring line type and trade route.

Mooring System Management Plan – MSMP.

The MSMP which will complement the ship’s SMS. Through a ‘goal-based’ approach core elements of the mooring system are identified, against which high level ‘goals’ are established supported by more detailed ‘functional requirements’.

New standards for purchasing mooring line during of OCIMF

AIM: For the selecting right mooring line

During MEG3, only
• Length
• Diameter
• MBL

During MEG4, furthermore
• Load bearing linear tenacity
• Type of Vessel, frequency and type of mooring.
• Line tenacity
• Axial compression resistance
• Temperature conditions
• Specifications of vessel’s mooring equipment
• Material (no brand’s name)
• The replacement reason of mooring line

and more

New philosophy of inspection and monitoring of mooring lines during the revision of MEG4

AIM: To minimize the risk of failure of mooring lines and increase crew safety

New standards of inspection-monitoring
i)Environmental criteria
• Direction & force of wind and current
• Temperature
• Swell of sea
• Humidity
ii) Other criteria
• Type of work of line (ex. spring, head, breast, stern etc.)
• Hours of working operations
• Type of mooring operation (ex. STS, Open sea port etc.)
• Type of mooring equipment (ex. chock, fairlead, rollers and other deck fittings.)
• Protection of mooring lines (ex. chafe sleeves, protectors etc.)
• Construction & specification of mooring line or tail from the manufacturer
and more

The solution of 3 steps

First step: Planning

Support for optimal mooring line selection and LMP according to MEG4. Expert rope makers will be assigned to your project and will work closely with your managers. The support offered includes conference calls, on-site visits from the assigned sales account manager as well as from an expert Engineer. Furthermore, we will follow up whenever changes in specifications or production schedules are applied, in order to fully serve your project’s specific requirements.

Second step: Training

Training courses from expert rope makers can train your crew and executives in safety, maintenance, inspection and management of your mooring lines according to OCIMF MEG4, IMO & ISO/CI standards. The training courses are designed to provide you with increased crew safety and improved management of your mooring ropes. The training courses include instructional videos and presentations, easy-to-fill checklists for on board procedures and online technical support.

Third step: Monitoring

Makers of ropes must help you assess the condition of your mooring lines worldwide, at any time. Technicians of ropes can perform on board visual quality inspections and audit your mooring operation. After the inspection, you will receive a comprehensive official inspection report about the condition of your mooring lines and recommendations for your mooring operation. Also monitoring software from makers of ropes can be used to track line usage & condition in order to reliably prevision the replacement of your mooring lines & tails according to MEG4. Last but not least makers of ropes must evaluate precisely the remaining operational life of your mooring lines. All testing will be done according to the latest OCIMF & ISO/CI standards. Your mooring lines & mooring tails must be replaced with strength not less than 75% of SDMBL strength.

Results

• Reduce your operational costs by improving the working life of mooring lines
• Reduce mooring operation risks by preventing incidents
• Improve your safety by trusting the monitoring of your lines to the experts

Capt. Vasilis Giannopoulos
Marine Mooring Consultant
COO at Black Rope

New terminology according MEG4

Creep
Creep indicates the time and temperature dependent deformation or lengthening under load. As synthetic materials are made of large, in the case of thermoplastics and elastomers, entangled molecule chains, these glide or disentangle under external load by which irreversible elongation occurs. This means that such ropes increase in length and will not return to the original length even when the load is removed (such as with HMPE ropes).

D/d ratio
The diameter of the bend (e.g. the roller or sheave) divided by the diameter of the mooring line. As the D/d ratio decreases, the greater is the negative effect that the bending has on the rope’s strength. A D/d ratio of at least 15 should be applied for HM mooring lines.Design basis load (DBL) Refers to the design load on a fitting. Calculated by multiplying the ship design minimum breaking load (MBL) by the geometric factor (GF).

dtex
dtex is the expression of weight in grams for filaments, yarns or twines of 10,000m length (g/10,000m). The higher the dtex number, the thicker the filament, yarn or twine. Elastic modulus The relationship between tenacity and elongation. The lower the elongation under load, the higher the elastic modulus. Elongation indicates by how much the rope will stretch under load. Unit of elongation is indicated in %.

Equipment Number
Ships will generally be assigned with an Equipment Number. It is derived through a complex calculation based on the vessel’s dimensions and specifications. The calculated Equipment Number then defines, for example, the required dimensions and strengths of the bollards, hawsers, anchoring equipment, towing lines and mooring lines that are to be used with the vessel.

Fatigue
The weakening or failure of a rope or other material during alternate tension-tension or tension-compression cycles. May be caused by internal abrasion or damage to fibres due to compression. Geometric factor (GF) The factor by which the line tension is multiplied to take the angle through which a line is deflected around a fitting into account. The wrap angle is defined as Θ, then the theoretical GF is GF = 2 sin(Θ/2)

High Modulus (HM) synthetic fibres
The generic term given to a range of fibre materials that include Aramid, LCP and HMPE fibres.

High Tenacity (HT)
Ropes made from High Tenacity fibres are made from Polyester, Polyamide, Polyester/Polyolefine mix. The tenacity of these fibres is less than 9 cN/dtex. The elongation at break is between 10 and 28%.

Line design break force (LDBF)
The minimum force at which a new, dry and spliced mooring line will break at, when tested according to Appendix B of MEG4

Line management plan (LMP)
The LMP outlines the ship operator’s requirements regarding the maintenance, inspection and retirement of mooring lines throughout the operational phase of the mooring lifecycle.

Minimum break load (MBL)
Describes the maximum force a length of new rope can be exposed to, under a straight pull, until it breaks. Safe working load (SWL) The usual working load of a rope in use. The working load is determined depending on the type of application. In most applications, 1/5th the break load is customary.

Ship design MBL
Refers to the minimum break load of new, dry mooring lines for which a ship’s mooring system is designed, to meet OCIMF standard environmental criteria restraint requirements. It is the central parameter against which all other mooring system components of the ship are dimensioned and designed with tolerances.

Specific tensile load
Refers to the maximum tensile force that can be subjected to a filament, yarn or twine before it comes to a break. It enables a direct comparison to be made between filaments, yarns and twines of varying fineness. The unit of measurement is cN/dtex.

Working load limit (WLL)
The maximum weight/strength a fibre rope can be subjected to in general use.

Safe working load (SWL)
The usual working load of a rope in use. The working load is determined depending on the type of application. In most applications, 1/5th the break load is customary.
Ship design MBL
Refers to the minimum break load of new, dry mooring lines for which a ship’s mooring system is designed, to meet OCIMF standard environmental criteria restraint requirements. It is the central parameter against which all other mooring system components of the ship are dimensioned and designed with tolerances.

Specific tensile load
Refers to the maximum tensile force that can be subjected to a filament, yarn or twine before it comes to a break. It enables a direct comparison to be made between filaments, yarns and twines of varying fineness. The unit of measurement is cN/dtex.

Working load limit (WLL)
The maximum weight/strength a fibre rope can be subjected to in general use.

info@blackrope.com , (+30) 69522 90682-3-4

Preparation and installation of mooring line

Preparing the environment where the mooring system is to be deployed is the first step in maximizing the service life of the mooring line system. All surfaces and equipment that the mooring line may come into contact with on the vessel’s deck must be carefully inspected and prepared. Before installation commences, all surfaces must be smooth and free of:
• Rust
• Snags
• Burrs
• Scoring
• Any other types of sharp edges or irregularities
All rollers/sheaves used, such as on fairleads, should also be checked to ensure they roll freely, and all further deck equipment is to be inspected.
When installing the mooring system, it is vital to ensure that all installation instructions provided by the manufacturer are followed in detail.

Installation instructions

Short lengths of ropes may be rolled off from the ground. Never uncoil braided rope from the inside!

Ropes can be unwound from a drum. A temporary brake ensures the line will remain taut.

Ropes can be uncoiled by using a turning base. Never uncoil braided rope from a lying position!

info@blackrope.com , (+30) 69522 90682-3-4

The lifecycle of your mooring line according to MEG4 is:

Black Rope will be glad to help at any point in the selection process – and can even advise operators from the very beginning in the process of choosing the right mooring line system set-up, offering possible alternatives for their individual needs.

info@blackrope.com , (+30) 69522 90682-3-4

Mooring ropes maintenance

External abrasion
In principle, all type of contact with the rope will lead to some form of abrasion. The severity will depend on the type of rope in question and what the rope comes in contact with.
The following outlines some examples of what may cause abrasion:
• The type and design of fairleads affects the amount of abrasion mooring lines are exposed to.
• Closed fairleads should have a D/d of at least 15.
• Roller fairleads will usually have lower D/d ratios, but roller performance must be considered.
• Rollers that do not rotate result in significantly increased rope abrasion.
• As superyachts often exhibit very small D/d ratios in line with the equipment number, special attention needs to be paid in this respect.
• Slippage and other movement when on bollards.
• Avoid all type of movement on bollards as much as possible.
• Owing to the low friction coefficient of HMPE ropes, they should always be deployed with a cover in the bollard area.
• The potential for severe abrasion exists directly behind the eyes of mooring lines, as the rope is pulled over the edge of the quay when mooring and unmooring.

Internal abrasion
Internal abrasion is caused by the scissor motion of yarns or other material rubbing within the rope structure. This predominantly occurs when the rope is bent, particularly when under load. Dirt or other abrasive particles that enter the rope can also cause internal abrasion. Care should therefore be taken to avoid the rope coming into contact with such particles.

Excessive/ shock/dynamic/ continuous loads

Excessive loads can cause a rope to break. Mooring lines are exposed to dynamic loads and shock loads.
Dynamic loads:
The changing load conditions in the mooring line that can lead to excessive loads or shock loads

Shock loads:
When the load on the mooring lines increases very swiftly. If the working load of the rope increases by more than 10% within a very short timeframe, this is referred to as a shock load.
To protect the mooring line against potential damage, care should be taken to ensure that the dynamic load does not exceed 50% of the LDBF (Line Design Break Force).
Excessive shock loads can have serious consequences leading to a reduced breaking load and the risk of tearing in subsequent applications. Shock loads can cause:
• Fusing of rope fibres
• Rope becoming stiffer/less flexible

Play it safe!
Any rope that exhibits recognizable effects of being subjected to excessive shock loads should be retired immediately!

What happens when ropes break under load?
HMPE rope: Elongation at the point of break is low. The energy released during the break is high. High tenacity (HT) rope: High elongation at the point of break. A large amount of kinetic energy is released. High snapback! Danger!

Sharp deflections
If a mooring line is bent, such as on a roller/sheave, the bending action means there is a loss in strength. HMPE ropes are affected more in this respect by the effect of bending than HT ropes.
The effect is measured by the D/d ratio:
D = the diameter of the roller/sheave
d = the rope’s diameter (d).
As the D/d ratio decreases, the greater is the negative effect that the bending has on the rope’s strength.
Be aware that sharp deflections also lead to greater pressures being subjected to bollard, fairleads, etc.
For HM mooring lines, a D/d ratio of at least 15 should be applied, in accordance with OCIMF MEG4.

Exposure to UV light and chemicals
The exposure of mooring lines to ultraviolet (UV) light and chemicals should be avoided as much as possible.
• UV light and chemicals cause degradation of the ropes
• Degree of rope degradation depends on the raw materials used in their manufacture
• Exposure to UV light and chemicals can lead to a reduction in break loads and premature rope ageing
Please refer to the section on rope construction types and raw materials used (p. 15), for an overview on the UV light and chemical resistant attributes of the various mooring lines.
In instances where the lines have come in contact with chemicals:
• Rinse thoroughly with lukewarm running water only
• Inspect carefully to ensure the line’s suitability for further use
• Retire the line immediately, if necessary

Heat
Heat is a natural enemy of synthetic fibre ropes. Among the main causes of heat is friction, such as when ropes are used in closed hawses. This can lead to:
• Internal rope fusing
• Rapid wear
• Degradation
Exposure to high temperatures over extended periods can also lead to a reduction in the break load – without any visible sign.
To avoid damage, mooring lines should not be exposed to any external sources of heat or hot surfaces, such as:
• Exhaust funnels/pipes/systems
• Naked lights
• Anything causing friction
As different materials used in the construction of mooring lines will have varying levels of susceptibility to heat-induced damaged, please refer to the technical specifications for the fibres used in the rope types in question.
Please also refer to the appendix for examples of the effects of heat on synthetic rope and criteria for discarding damaged mooring lines.

Twisting / torsion
Prevent the twisting of mooring lines. Any twists should be eliminated prior to use. Longitudinal markings on the rope allow any twist to be identified quickly and easily. Moreover, twisting reduces the break load!
As a rule of thumb: Only four turns per meter cuts the break load by 10–30%.

Knots
Always bear in mind that knots reduce the strength of ropes. If the application does not explicitly require a knot, none should be used. If unavoidable, the working load must be reduced accordingly, to ensure safety.
Depending on the type of rope and knot used, a single knot can reduce the rope’s breaking load by approx. 40–80%!

info@blackrope.com , (+30) 69522 90682-3-4

Tips of mooring lines inspections

acc. to MEG4
Conducting ongoing inspections of the mooring line system is a vital task to ensure the maximum service life and safety in every setup. It is important to be aware of and to define when inspections are to be undertaken and by whom.
1. Regular inspections by mooring crew members – upon each use
A visual inspection should be carried out by crew members prior to and during every mooring cycle in order to check for any damage. The inspection should follow the procedure of the checklist provided on page 25 of this manual. A logbook is to be maintained for each inspection and, if necessary, entries should be made to record any incidents, irregularities or observations. The defined rope retirement criteria are to be strictly observed.
2. Routine inspections by a qualified person – after the completion of mooring operation
The OCIMF MEG4 guideline prescribes that a routine inspection must be undertaken after the completion of mooring operation. Only qualified persons may conduct such inspections, who are in possession of a recognized degree or certificate of professional standing in an applicable field, or, who by extensive knowledge, training and experience have successfully demonstrated the ability to solve problems relating to the subject matter and work. During routine inspections, the qualified inspectors should walk the entire length of the line as well as the tail, to examine and document the current condition – and take any further necessary action.
3. Detailed inspections by a qualified person – after the 1000 mooring hours or after 30 mooring operations
The OCIMF MEG4 guideline prescribes that a detailed inspection must be undertaken after the 1000 mooring hours or after 30 mooring operations. Only qualified persons may conduct such inspections, who are in possession of a recognized degree or certificate of professional standing in an applicable field, or, who by extensive knowledge, training and experience have successfully demonstrated the ability to solve problems relating to the subject matter and work. During routine inspections, the qualified inspectors should walk the entire length of the line as well as the tail, to examine and document the current condition – and take any further necessary action.

Visual inspection
All types of wear and damage to the mooring line are to be identified by the mooring crew or a qualified person.
Walk the entire length of the rope and document its overall condition. Special attention is to be paid to contact points on deck, mainly with fairleads, as well as the cross point of split drums.

1. Abrasion/ cuts
2. Kinks/twisting/deformation
3. Inconsistent diameter
4. Glossy or glazed sections
5. Discoloration
6. Compression
7. Strand/ yarn breakages
8. Deformation caused by heat
9. Damage to splices
10. Other types of mechanical damage such as strong wear or general disaggregation

Refer to the examples of damage section in the appendix of this manual for further information on rope retirement recommendations.

Inspections following special incidents Should one of the following instances occur, the mooring line must be immediately inspected by a qualified person!
• Suspected exposure to an excessive shock load
• Clearly audible “cracking” of the mooring line
• Exposure to chemicals
• Unexpectedly strong twisting
• External mechanical damage

Wear zone management
Maximize safety and mooring system service life by ensuring all operators have a high level of awareness of the factors that cause rope damage and that appropriate precautions are taken to avoid damage.
Wear zone management. Mooring line systems are subjected to potential damage day in, day out, due to regular mooring activities. Also having an effect on this are the individual trading patterns of the ship including the design of the terminals being berthed at, the specific type of mooring system setup, the environmental conditions and ship movements while in port as well as the degree to which the ship is loaded. As the wear zone management techniques will vary with each vessel, it is important that these are assessed for each application and documented within the LMP in order to reduce the risk of rope damage most effectively.
Some effective techniques that can be included in an LMP to manage the wear zone include ensuring that:
1. Deck fittings are smooth to ensure mechanical damage is avoided
2. All sections of the mooring line system are protected from the elements and other environmental damage when not in use
3. Sharp deflections are avoided and that the D/d ratio is maximized
4. Interaction with deck fittings is controlled as swell, waves and wind will influence rope fatigue
5. Insufficient wraps around drums are avoided to minimize slippage
6. Mooring system lines are turned and interchanged to enable abrasion to occur evenly on rope sections

info@blackrope.com , (+30) 69522 90682-3-4

Storage and care

Storage:
Following a few simple rules will ensure the mooring lines are correctly stored to prolong their service life and ongoing safe deployment:
• Make sure ropes are completely dry before storing
• Store in dry, well ventilated, dark rooms/areas (or at least adequately covered when on drums)
• Do not store near any sources of heat
• Avoid all contact with chemicals of any sorts
• Ensure the mooring line is not twisted when in storage
• Any mooring lines and tails on winches that are not in use should be protected against the elements with a waterproof cover

Care:
If necessary, rinse using running lukewarm water only.
Never store damaged rope! This may otherwise be inadvertently used and result in a serious risk of injury!

info@blackrope.com , (+30) 69522 90682-3-4

When should mooring system lines be replaced according to MEG4?
This is a fact that has to occur at some point and there is no way to avoid it. But the rate at which ropes age can be substantially influenced. Operators should be aware of all factors impacting on the service life of the mooring system in use on their vessel – and conscious that it has a direct effect on the safety of the crew and port staff. As a general guide, mooring system lines should be replaced when they reach a residual break load of 75% SDMBL.
Ropes should retire when they reach a residual break strength of 75% of SDMBL!

info@blackrope.com , (+30) 69522 90682-3-4