Mooring equipment guidelines (MEG4) 4ED 2018 Thuyền Viên Hàng Hải

Mooring equipment guidelines (MEG4) 4ED 2018 dành cho các thủy thủ sinh viên thuyền viên hàng hải tham khảo về các tài liệu cũng như trong học tập đi tàu biển Mooring equipment guidelines (MEG4) 4ED 2018 dành cho các thủy thủ sinh viên thuyền viên hàng hải tham khảo về các tài liệu cũng như trong học tập đi tàu biển

Mooring Equipment Guidelines (MEG4)

Fourth Edition 2018

OCIMF

OCIMF

Mooring Equipment Guidelines (MEG4)

Fourth Edition 2018

The OCIMF mission is to be the foremost

authority on the safe and environmentally

responsible operation of oil tankers, terminals

and offshore support vessels, promoting

continuous improvement in standards of

design and operation

© Copyright OCIMF 2018

Issued by the

Oil Companies International Marine Forum

29 Queen Anne's Gate

London

SWlH 9BU

United Kingdom

First Edition Published 1992

Second Edition Published 1997

Third Edition Published 2008

Fourth Edition Published 2018

Book ISBN: 978-1-85609-771-0

© Oil Companies International Marine Forum, Bermuda

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

The Oil Companies International Marine Forum (OCIMF)

is a voluntary association of oil companies with an interest in the shipment and terminalling of crude oil, oil products, petrochemicals and gas Our mission is to be the foremost authority on the safe and environmentally responsible operation of oil tankers, terminals and offshore support vessels, promoting continuous improvement in standards of design and operation

Terms of Use

The advice and information given in 'Mooring Equipment Guidelines (MEG4)' (the Publication) is intended to be used at the user's own risk Acceptance or otherwise of recommendations and/or guidance in this Publication is entirely voluntary The use of the terms 'will', 'shall', 'must' and other similar such words is for convenience only, and nothing in this Publication is intended or should be construed as establishing standards

or requirements No warranties or representations are given nor is any duty of care or responsibility accepted by the Oil Companies International Marine Forum (OCIMF), the membership or employees of OCIMF or by any person, firm, corporation or organisation (who or which has been in any way concerned with the furnishing of information or data, the compilation or any translation, publishing, supply or sale of the Publication) for the accuracy of any information or advice given in the Publication or any omission from the Publication or for any consequence whatsoever resulting directly or indirectly from compliance with, adoption of or reliance on guidance contained in the Publication even if caused by a failure to exercise reasonable care on the part of any of the aforementioned parties

Foreword

Foreword

Each year too many seafarers and terminal operators are injured, or worse, when mooring lines fail under tension In the ten years between 2007 and 2016 the Marine Accident

Investigation Branch (MAIB) received 37 such reports In the five years between 2009 and

2014, another major maritime nation recorded more than 90 accidents in its ports involving broken mooring lines, with two lives lost That these statistics are reported by just two of the many maritime authorities around the world suggests a much larger problem, which has been reflected by recent extensive discussions within the industry and at the International Maritime Organization (IMO)

The MAIB recently investigated an accident involving the failure of an HMSF mooring line on board a large LNG carrier Our investigation revealed widespread misunderstanding over the properties, use and maintenance of this type of line I was therefore delighted to have been asked by the Oil Companies International Marine Forum (OCIMF) to write the foreword for this, the fourth edition of their Mooring Equipment Guidelines (MEG4}

This publication represents best known mooring technology and practice Importantly, it also reflects the move by industry and regulators towards Human-Centred Design principles, a systems approach to mooring equipment in general as well as a more holistic application to the selection, inspection and maintenance of mooring lines The overarching result of such measures will be to ensure that mooring equipment is properly selected for the type, size and expected trading pattern of the ship and its mooring lines are retired from use before they fail This will undoubtedly reduce the number of accidents to seafarers and terminal staff during mooring and unmooring operations

On behalf of all mariners, I would like to take this opportunity to thank OCIMF for its excellent work and ongoing commitment to updating and improving what is universally held to be the most important reference book on mooring equipment and best mooring practice I recommend MEG4 as an essential read, not only to the hydrocarbon and chemical industry sectors but to all ship and terminal operators, regulators, ship designers and Classification Societies throughout our maritime industry

Steve Clinch MNM

Chief Inspector of Marine Accidents

UK Marine Accident Investigation Branch

iii

Mooring Equipment Guidelines in this fourth edition, with a focus on the safety of ship and terminal personnel It addresses four significant areas of interest:

• Lessons learned from incidents, most notably from failures of HMSF mooring lines

• Human-centred mooring designs and human factors in mooring operations

• New and in-development regulations and guidance from the IMO on the safety of mooring

• Alternative mooring technologies and how they can be incorporated safely into the design

of mooring systems both for ships and terminals

OCIMF is grateful for the support and contribution made by other shipping industry associations, equipment manufacturers, port and terminal associations and pilot associations OCIMF would also like to extend a special thank you to the following organisations that played a significant role in the sections with the largest changes and new content: Cordage Institute, Eurocord, International Association of Classification Societies (IACS) and Ship Builders Association of Japan

OCIMF would also like to thank the Marine Accident Investigation Bureau (MAIB) for input and feedback during the development of this publication

The main changes from the third edition include:

• Four new sections:

- Section two: Human factors

- Section nine: Berth design and fittings

- Section ten: Ship/shore interface

- Section eleven: Alternative mooring technology

• One new appendix:

- Appendix B: Guidelines for the purchasing and testing of mooring lines and tails

• New tools to help operators manage equipment and lines from design to retirement:

- Line Management Plan (LMP)

- Mooring System Management Plan (MSMP)

• Updated and expanded guidance on mooring lines

• New terminology to describe the strength of mooring lines and equipment (see A note on new terminology)

• Updated wind and current drag coefficients (appendix A), which have been re-validated by

a leading Classification Society from IACS These are now considered the most up-to-date coefficients covering tankers in the size range from 16,000 DWT and above

It is recommended that on board mooring equipment and fittings, including mooring lines, are identified as critical equipment or systems OCIMF defines safety critical equipment as an individual piece of equipment, a control system or an individual protection device which in the event of a single point failure may:

• Result in a hazardous situation which could lead to an accident

Or

• Directly cause an accident that results in harm to people or the environment

OCIMF: enquiries@ocimf.org

Introduction

Alternatives to the recommendations in this publication should only be introduced on the basis of a risk assessment and should be implemented through a proper management of change process Any mitigation measures or contingency plans should take into account the environmental limits for mooring, stopping cargo transfer and departing the berth

This publication establishes recommended minimum requirements that will help ship designers, terminal designers, ship operators and mooring line manufacturers improve the design, performance and safety of mooring systems

To make sure improvements in mooring system design are implemented as soon as possible

in the industry, it is recommended that:

• New ships and terminals are designed and built using the recommendations in this publication

• New ships already under construction and existing ships consider making changes that will use the recommendations in this publication

• If new build ships under construction or existing ships are unable to follow the recommendations in this publication, they should, as a minimum, develop a Mooring System Management Plan (MSMP) and a Line Management Plan (LMP) that will:

- Remain on the ship throughout its life as part of the management of change records

- Identify a timeline and measures needed to follow the recommendations of this publication

- Detail interim measures taken to address the recommendations in this publication, with reasons given for why the changes have not been implemented yet

• Where a terminal is already in service, the terminal management should perform a gap

assessment with the recommendations in this fourth edition of the Mooring Equipment Guidelines and, where there are gaps, perform a documented risk assessment to ensure these gaps are appropriately managed in accordance with the site's risk management guidelines to reduce risk and enhance safety For new build terminals under consideration,

or engineering not yet completed, where applicable, consider and implement the recommendations in the fourth edition of MEG

This publication is primarily aimed at the hydrocarbon and chemical industry sectors, conventional tankers, gas carriers and the terminals they visit Many of the guidelines and recommendations in this publication could also be applied to non-conventional tankers and terminals such as Floating (Production) Storage and Offloading units (F(P)SOs) and Floating Storage and Regasification Units (FSUs), particularly where they interface with conventional tankers In addition, some of the guidance and recommendations can be considered to be equally applicable to other industry sectors and non-tanker ship types

With the publication of this edition, the following documents have been superseded and are removed from distribution:

• Books:

- Mooring Equipment Guidelines, Third Edition (MEG3}

- Effective Mooring, Third Edition

Introduction to the Mooring System Management Plan and

Section one

Section four

vii

Mooring Equipment Guidelines (MEG4)

Section five

Section six

Section seven

Section nine

viii

Ship/shore interface Introduction

Ship operator responsibility Terminal operator responsibility Ship responsibility

Berth operator responsibility Ship mooring personnel responsibility Joint ship/shore meeting and inspection Tug and line boat operations

Records of mooring operations

Introduction Symbols and notations Wind and current drag coefficients for large tankers Wind and current drag coefficients for gas carriers Example force calculations for VLCC

Introduction

How to use these guidelines Stakeholders

Documentation Base design process Purchasing process Base design manufacture Base design testing Product supply manufacture Product supply quality assurance testing Nonstandard testing

Abrasion resistance The ability of a fibre or rope to withstand surface wear and rubbing due

to motion against other fibres of rope components (internal abrasion) or a contact surface such as a fairlead (external abrasion)

Angled break force The break force of a mooring line when bent at 180 degrees around a pin (see also table B12: Guidance on performance indicator interpretation for mooring lines) Angled endurance The residual break force (or cycles to failure) of a mooring line when bent

at 180 degrees around a pin and then pulled to destruction (see also table B12: Guidance on performance indicator interpretation for mooring lines)

Aramid A manufactured fibre consisting of very long molecular chains formed by rearranging the structure of aromatic polyamides

As Low As Reasonably Practicable (ALARP) Each company should develop their own definition of ALARP OCIMF uses the UK Health and Safety Executive (UK HSE) definition in this publication:

Making sure a risk has been reduced to ALARP is about weighing the risk against the sacrifice needed to further reduce it The decision is weighted in favour of health and safety and against commercial interest because the presumption is that the duty-holder (e.g the ship operator) should implement the risk reduction measure To avoid having to make this sacrifice, the duty-holder must be able to show that it would be grossly disproportionate to the benefits

of risk reduction that would be achieved Thus, the process is not one of balancing the costs and benefits of measures but, rather, of adopting measures except where they can be ignored because they involve grossly disproportionate sacrifices

Axial compression fatigue The tendency of a fibre to fail when it is subjected to cyclic loading which exerts compression along its axis

Base design The manufacturer demonstrates the typical performance of their designs by making and testing base design mooring lines or tails Base design samples are identical in every respect, including material, structure, manufacturing methods and splicing technique

to the lines or tails offered for sale

Base design certificate Completed by the manufacturer and verified by an independent inspector at the end of the base design process for mooring lines or tails Demonstrates that the product has been manufactured, tested and documented following the guidelines in appendix B The base design certificate includes guidance on the interpretation of mooring line performance indicators to help make sure that users and manufacturers are using the same definitions

Batch The shortest of the following:

• The length required to manufacture a total order of line or tail

• The maximum continuous length without strand interchanges that can be produced on rope making machinery This is normally dictated by strand length

Best practice OCIMF views this as a method of working or procedure to aspire to as part of continuous improvement

Bitts Vertical steel posts or bollards, mounted in pairs, around which a line can be secured Bollard A vertical post ashore to which the eye of a mooring line can be attached

Bow chain stopper A mechanical device for securing chafe chains on board a tanker

Braided rope A rope produced by intertwining a number of strands

Breaking strength For cordage, the nominal force (or load) that would be expected to break or rupture a single specimen in a tensile test conducted under a specified procedure

On a group of like specimens, it may be expressed as an average or as a minimum based on statistical analysis

Coating Also known as finish An oil, emulsion, lubricant or the like, applied to fibres (and/or

rope), to prevent damage during textile processing and/or to improve performance during use

of the product Coatings are used by line and tail manufacturers to help improve performance Coating materials and processes are varied and the impact of coatings on performance should

be assessed at the rope level through the testing outlined in appendix B

Coefficient of friction The limiting value of the coefficient given by dividing the force

tending to cause one body to slide over another by the normal force between the two bodies Generally, the higher the value, the lower the tendency of one object to slide over another

Conventional Buoy Mooring (CBM) See Multi Buoy Mooring

Conventional fibre Manmade, continuous filament synthetic fibres or split films with

modulus below S0GPa

D/d ratio The diameter of the bend divided by the diameter of the mooring line

Deadweight (DWT) The carrying capacity of a ship, including cargo, bunkers and stores,

in metric tonnes It can be given for any draught, but here it is used to indicate summer deadweight at summer draught

Design Basis Load (DBL) The design load on a fitting given by multiplying the mooring ship

design Minimum Breaking Load (ship design MBL) by the Geometric Factor {GF)

Design parameters Choices made by the manufacturer in the material, construction and assembly of the line or tail

Design range The range of line/tail sizes (described by nominal diameter) to which the

manufacturer has applied the procedure in appendix B

Directional environment A location where a single direction for environmental forces dominates

Displacement The mass of water in tonnes displaced by a ship at a given draught

Dolphin An independent platform incorporating mooring hooks or bollards for securing ship's mooring lines It may also incorporate mooring fenders such as breasting dolphins

Elasticity The elastic (non-permanent) elongation of a unit length of an element caused by a unit load May refer to a material or a composite structure such as a mooring line

Elongation The total extension (elastic and plastic) of a line

Emergency towing arrangement Equipment and fittings provided at both ends of the tanker to facilitate towing in an emergency in accordance with the provisions of SOLAS

Emergency tow-off pennant A line rigged to the waterline over the off-berth side of a ship to facilitate towing off in an emergency (Previously known as a fire wire)

Fairlead A guide for a mooring line that enables the line to be passed through a ship's

bulwark or other barrier, or to change direction through a congested area without snagging or fouling Also known as a chock

Fatigue The tendency of a material to weaken or fail during alternate tension-tension

or tension-compression cycles In cordage, particularly at loads well below the breaking strength, this degradation is often caused by internal abrasion of the fibres and yarns but may also be caused by fibre damage due to compression Some fibres develop cracks or splits that cause failure, especially at relatively high loads

Fibre A long, fine, very flexible structure that may be woven, braided, stranded or twisted into

a variety of fabrics, twine, cordage or rope

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Mooring Equipment Guidelines (MEG4)

First line ashore A line put ashore first to help in hauling the ship into berth

Fleet angle The maximum angle subtended by a rope to a line drawn at right angles to the winch drum or warping end, through the point at which the rope leaves the drum of warping end

Geometric Factor (GF) The factor by which the line tension is multiplied to take account of the angle through which a line is deflected around a fitting

Guidance P rovision of advice or information by OCIMF

Hawser Synthetic or natural fibre rope or wire rope used for mooring, warping and towing

Head lines Mooring lines leading ashore from the fore end of a ship, often at an angle of about 45 degrees to the fore and aft line

Heaving line A very light line that is thrown between the ship and the berth and used to draw

a messenger line ashore

High Modulus Polyethylene (HMPE) A manufactured fibre based on Ultra High Molecular Weight Polyethylene (UHMWP E)

High Modulus Synthetic Fibre (HMSF) Manmade, continuous filament synthetic fibre with modulus in the range of 50 - lS0GPa

Independent inspector An individual experienced with mooring line inspection and testing, meeting the qualification given in appendix B, independent of the manufacturer, and contracted by the line manufacturer to observe, inspect and certify the manufacturing and testing of lines made for either prototype or project purposes The independent inspection agency is normally a member of the International Association of Classification Societies and the independent inspector is the representative of the independent inspection agency Independent Wire Rope Core (IWRC) A type of construction of steel wire rope that has an independent wire rope core, as opposed to steel wire rope having a fibre rope core

lnfragravity wave remnants Low frequency waveforms approaching ports/harbours from the ocean (infragravity waves) often have reflections from land/structures or suffer focussing into a small area (the remnants) that shorten the period and can add confusion to multi-modal waveforms experienced with the port/harbour

Inspection and Test Plan (ITP) A document describing the identifying steps in product manufacture and testing, relative to both internal and external quality assurance For each step identified in the ITP, control and verifying documents are described along with Hold (H), Witness (W) and Monitor (M) points for both internal and external agencies

Joining shackle A shackle used to connect a mooring line to a synthetic tail

Lead The direction a mooring line takes up while being handled or when made fast

Length Between Perpendiculars (LBP) The length of a ship, generally between the aftermost surface of the rudderpost and forward of the main bow perpendicular

Length Overall (LOA) The extreme length of a ship

Light line speed The speed that can be achieved by the winch with negligible load on the line High speed is essential to pass a line quickly to a shore mooring point or to bring the line quickly back on board Also known as no-load speed or slack-line speed

Line Design Break Force (LDBF) The minimum force that a new, dry, spliced mooring line will break at when tested according to appendix B

Line Management Plan (LMP) Contains the ship operator's requirements for the management of mooring line maintenance, inspection and retirement during the operational phase of the mooring line lifecycle

Line tenacity The ratio between the LDBF and the line linear density or load bearing linear density, depending on the line design

Marine loading arms Transfer units between ship and shore for discharge and loading May

be articulated all-metal arms (hard arms) or a combination of metal arms and hoses

Maximum tenacity The tenacity of the smallest line/tail in the design range

Members Individual components of a more complex structure, e.g beams, girders,

brackets, etc

Messenger line A light line attached to the end of a main mooring line and used to assist in heaving the mooring to the shore or to another ship

Minimum Breaking Load (MBL) See Ship Design Minimum Breaking Load

Mooring restraint The capability of a mooring system to resist external forces on the ship

Multi Buoy Mooring (MBM) A facility where a tanker is usually moored by a combination of the ship's anchors forward and mooring buoys aft and held on a fixed heading Also called Conventional Buoy Mooring (CBM)

Multi-directional environment A location where no single direction for environmental forces dominates or where none of the forces becomes a dominant factor

New Straight Break Force (NSBF) The maximum force sustained by a line or tail in a specific test conducted under the conditions described in this publication

Newton (N) A unit of force A Newton is the amount of force required to accelerate a body with a mass of one kilogram from rest at a rate of one metre per second squared One Newton

is equal to 0.10197 kilogram-force (kgf) lkN = 1,000N

Nominal mooring speed The speed that can be maintained with the rated load applied to the mooring line The nominal mooring speed combined with the drum load determines the power requirement for the winch drive Also known as rated speed or design speed

Panama fairlead A non-roller type fairlead mounted at the ship's side and enclosed so that mooring lines may be led to shore with equal facility either above or below the horizontal Strictly applies only to fairleads complying with Panama Canal Regulations, but often applied

to any closed fairlead

Pedestal roller fairlead A roller fairlead usually carrying a mooring in a horizontal plane Its purpose is to change the direction of lead of a mooring or other line on a ship's deck

Polyamide The common chemical name for nylon fibre

Pre-tension Additional load applied to a mooring line by a powered winch over and above that required to remove sag from the main run of the line

Recommendations OCIMF supports and endorses a particular method of working

or proced ure

Retirement To permanently remove from service

Risk assessment A process of reviewing the risks attached to operations and most often

carried out along quantitative lines

Safe Working Load (SWL) Generally, a load less than the yield or failure load by a safety factor defined by a code, standard or good engineering practice SWL is not in relation to cordage or steel wire mooring lines In this publication, the SWL of a fitting is greater than or equal to the ship design MBL that contacts the fitting

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Mooring Equipment Guidelines (MEG4)

Safety Critical Equipment (SCE) An individual piece of equipment, a control system or an individual protection device, which in the event of a single point failure may:

• Result in a hazardous situation that could lead to an accident

Or

• Directly cause an accident that results in harm to people or the environment

Safety factor A margin over ship design MBL to allow for uncertainties

Safety of Life at Sea (SOLAS) The International Convention for the Safety of Life at Sea, 1974

and 1988 Protocol, as amended

Sea island A pier structure with no direct connection to the shore at which tankers can berth

Seiche A temporary disturbance or oscillation of the water in a harbour, lake, bay, estuary, etc., producing fluctuations over a period of a minute to hours in the water level caused by wind, earthquakes, changes in barometric pressure, etc The effect on the ship is a flow of water past the ship that creates a force on the ship This is dynamic in nature and should not

be modelled by static analysis There is also generally a small change in height but this does not significantly affect the mooring system

Ship design MBL 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 (defined in section three) 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 to I era nces

Ship to Ship (STS) transfer operation Transfer of liquid cargo between two ocean-going ships made fast alongside at anchor or underway The transfer of petroleum to barges and estuarial craft, including bunkering operations, is specifically excluded

Single Point Mooring (SPM) An integrated mooring arrangement for bow mooring a

conventional tanker For example, conventional tanker bow mooring arrangements to a Catenary Anchor Leg Mooring (CALM) system, Single Anchor Leg Mooring (SALM) system, Floating (Production) Storage and Offloading unit (F(P)SO) or Floating Storage and Offloading unit (FSO)

Smit bracket A fitting for securing the end link of a chafe chain consisting of two parallel

vertical plates mounted on a base with a sliding bolt passing through the plates

Specific gravity The ratio of the mass of a material to the mass of an equal volume of fresh water

Specified Minimum Yield Stress (SMYS) The minimum yield strength prescribed by the specification supplied by the manufacturer

Splice The joining of two ends of yarn, strand or cordage by intertwining or inserting these ends into the body of the product

Spring lines Mooring lines leading in a nearly fore and aft direction to maintain the

longitudinal position of the ship while in a berth Headsprings prevent forward motion and backsprings prevent aft motion

Stern lines Mooring lines leading ashore from the after end or poop of a ship often at an angle of about 45 degrees to the fore and aft line

Stiffness The rigidity of the line and its ability to resist deformation

Stopper A device for securing a mooring line temporarily at the ship while the free end is

made fast to a ship's bitt

Strand The largest individual element used in the final rope-making process and obtained by joining and twisting or braiding together several yarns or groups of yarns

Supporting structure Any members designed to transfer loads on fittings safely into the

ship's structure

Tail A short length of synthetic rope attached to the end of a mooring line to provide

increased elasticity and also ease of handling

Tonne One tonne equals 1,000 kilograms A unit of mass that is often also used for forces (sometimes expressed as 'tf'); ltf = 9.8lkN

Toolbox talk The safety briefing that takes place before an activity commences that informs

all participants of expectations and possible hazards

Ultra Large Crude Carrier (ULCC) Tankers able to transport up to 3 million barrels of oil as cargo, typically above 320,000 DWT

Universal fairlead A fairlead with three or more cylindrical rollers

Very Large Crude Carrier (VLCC) Tankers able to transport up to 2 million barrels of oil as cargo, typically of between 200,000 and 320,000 DWT

Warping The practice of trying to move a ship along a jetty with the use of mooring winches and lines and no assistance from tugs or engine power

Yarn A generic term for a continuous strand of textile fibres, filaments or material in a

form suitable for intertwining to form a textile structure via any one of a number of textile processes

Yield stress The limiting stress that, in a uniaxial tensile test on mild steel, is associated with

a sudden departure from linear elastic behaviour and a plastic growth in extension without further increase in stress

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Mooring Equipment Guidelines (MEG4) Abbreviations

ABB ALARP BSI CBM CCTV CDI CSR DBL D/d DWT

EN ETA FLNG F(P)SO FSO FSRU

GF HCD HFE HMPE HMSF HSE HTS IACS ILO IMO ISGOTT ISO ITP IWRC LBP LCP LDBF LMP LNG LOA MBL MBM

All Buoy Berth

As Low as Reasonably Practicable British Standards Institution Conventional Buoy Mooring Closed Circuit Television Chemical Distribution Institute Common Structural Rules Design Basis Load Diameter of bend divided by diameter of line Deadweight Tonnage

Equipment Nu mber Estimated Time of Arrival Floating Liquefied Natural Gas Floating (Production) Storage and Offloading unit Floating Storage and Offloading unit

Floating Storage and Regasification Units Geometric Factor

Human-Centred Design Human Factors Engineering High Modulus Polyethylene High Modulus Synthetic Fibre

Health, Safety and Environment

High Tensile Steel

International Association of Classification Societies International Labour Organization

International Maritime Organization International Safety Guide for Oil Tankers and Terminals International Organization for Standardization

Inspection and Test Plan

Independent Wire Rope Core

Length Between Perpendiculars Liquid Crystal Polymer

Line Design Break Force Line Management Plan Liquefied Natural Gas

Length Overall Minimum Breaking Load Multi Buoy Mooring

Marine Oil Terminal Engineering and Standards

Mooring System Management Plan

Mooring System Management Plan Register

Marine Terminal Information System

Non-Destructive Testing

New Straight Break Force

Oil Companies International Marine Forum

Original Equipment Manufacturer

Permanent International Association of Navigation Congresses

Planned Maintenance System

Quantitative Risk Analysis

Safety Critical Equipment

Specified Minimum Yield Stress

Single Point Mooring

Ship to Ship

Safe Working Load

Tail Design Break Force

Training Needs Analysis

Ultra Large Crude Carrier

Ultimate Tensile Strength

Ultra Violet

Very Large Crude Carrier

Vessel Particulars Questionnaire

Water depth to draught ratios

Working Load Limit

xvii

A3Anchor Windlass Design and Testing (IACS)

BS 6349-1-1 Maritime Works General Code of Practice for Planning and Design for Operations (BSI}

Cl-1500: Test Methods for Fiber Rope Physical Properties (Cordage Institute)

Cl-1502: Test Methods for High - Modulus Reduced Recoil Risk Rope (Cordage Institute) Cl-2001: Fiber Rope Inspection and Retirement Criteria (Cordage I nstitute)

Cl-2002: Determination of Cordage Institute Minimum Break Strengths (Cordage Institute)

Cl - 2003: Fibers for Cable, Cordage, Rope and Twine (Cordage Institute)

Common Structural Rules (CSR) for Bulk Carriers and Oil Tankers (IACS)

Criteria for Movements of Moored Ships in Harbour: A Practical Guide (PIANC}

DNV RP C205 Environmental Conditions and Environmental Loads (DNV}

EEMUA 191 (3rd Edition, 2013): Alarm Systems: A Guide to Design, Management and Procurement

(The Engineering Equipment and Materials Users Association)

Effective Procedural Practices (ASM Consortium) F1166, 2007 Standard Practice for Human Engineering Design for Marine Systems, Equipment, and Facilities (ASTM International)

Guidance Notes on Review and Approval of Novel Concepts (ABS)

Guidance Notes on the Application of Ergonomics to Marine Systems (ABS)

Guidance on Human Factors Safety Critical Task Analysis (Energy Institute)

Guidelines for Offshore Tanker Operations (OCIMF)

Guidelines for the Design, Operation and Maintenance of Multi Buoy Moorings (OCIMF) Guidelines for the Purchasing and Testing of STM Hawsers (OCI MF)

ISO 3730 Shipbuilding and Marine Structures -Mooring Winches (ISO}

ISO 4309 Cranes - Wire Ropes -Care and Maintenance, Inspection and Discard (ISO)

ISO 7825 Shipbuilding -Deck Machinery - General Requirements (ISO)

ISO 9241:210 Ergonomics of Human-System Interaction -Part 210: Human-Centred Design for Interactive Systems (ISO)

ISO 9554 Fibre Ropes -General Specifications (ISO) Jetty Maintenance and Inspection Guide (OCI MF/SIGTTO)

Marine Terminal Operator Competence and Training Guide (OCIMF)

Maritime Labour Convention (ILO)

MSC.1/Circ.1175 Guidance on Shipboard Towing and Mooring Equipment (IMO)

MSC.1/Circ.1455 Guidelines for the Approval of Alternatives and Equivalents as Provided for in Various IMO Instruments (IMO)

MSC.35(63) Guidelines for Emergency Towing Arrangements on Tankers (IMO)

Recommendations for Liquefied Gas Carrier Manifolds (SIGTTO/OCIM F)

Recommendations for Oil and Chemical Tanker Manifolds and Associated Equipment

A note on new terminology

A note on new terminology

Terminology can be confusing and common terms that are used across industry can mean different things to different groups In the years since the Mooring Equipment Guidelines, Third Edition (MEG3) was published, there has been a misunderstanding of mooring line strength terminology One example is Minimum Breaking Load (MBL)

In MEG3, OCIMF defined MBL as "the minimum breaking load of a new dry mooring line or chain as declared by the manufacturer" But industry has also used MBL to mean test and calculation methods for mooring line break force This has led to confusion between line users and manufacturers, and to differences between expected and actual mooring line performance

Due to the use of the term Minimum Breaking Load, many mooring line users have come

to the misunderstanding that lines can be safely loaded up to their MBL with no failures

or degradation This is not the case and OCIMF wants to make sure people understand the importance of safety margins on mooring lines There is also confusion among some ship owners who incorrectly believe that mooring line certificates must exactly match the MBL requested

To resolve this confusion, OCIMF has collaborated closely with Eurocard, the Cordage

Institute, shipping industry organisations and OCIMF members to clearly define a set of terms and test methods for mooring line MBL that can be used consistently by both line users and manufacturers when designing, specifying, testing and operating mooring lines These new terms will align the cordage and the tanker industries to a common language

Ship design MBL MBL Line Design Break Force (LDBF)

Working Load Limit (WLL)

Ship design Minimum Breaking Load (Ship design MBL) The MBL of new, dry mooring lines

for which a ship's mooring system is designed, which meets standard environmental criteria restraint requirements (defined in section three) 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

Line Design Break Force (LDBF) The minimum force at which a new, dry, spliced mooring line will break 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 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 The LDBF for nylon (polyamide) mooring lines should be specified as break tested wet, because nylon lines change strength characteristics once exposed to water and generally do not fully dry to their original

construction state

Working Load Limit {WLL) The maximum load that a mooring line should be subjected to in operational service, calculated from the standard environmental criteria (defined in section three) 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 analyses During operation, the WLL should not be exceeded In the same way that SWL is a limit for fixed equipment, the WLL value is used as a limit with the standard environmental criteria and mooring layout when designing mooring systems in establishing mooring system designs Steel wire ropes have a WLL of 55% of the ship design MBL and all other cordage (synthetic) has a WLL of 50% of the ship design MBL Although technically more accurate to relate the WLL to the specific mooring LDBF, the differences between ship design MBL and LDBF of varying manufacturers will be negligible Using the ship design MBL allows for a single value for analysis and comparison

Design Basis Load (DBL) The design load on a fitting, calculated by multiplying the ship design MBL by the Geometric Factor (GF)

xix

xx

Mooring Equipment Guidelines (MEG4)

Introduction to the Mooring System Management Plan and the Line Management Plan

What is the Mooring System Management Plan?

While updating the Mooring Equipment Guidelines, OCIMF became aware that across the marine industry there are inconsistencies in the methods used for maintaining mooring equipment information The Mooring System Management Plan (MSMP) has been created by OCIMF to help ship owners and operators keep consistent information about a ship's mooring equipment

It is not unusual to find the ship's original design data, records for permanent equipment (e.g winches and fittings), loose equipment (e.g mooring lines) and risk assessments kept

in separate locations Consequently, information useful to ship's personnel that is important for their understanding on the safe operation of the equipment is not easy to locate and can become misplaced, particularly when ownership of the ship changes

It is recommended that all information relevant to the mooring of the ship is considered together as a complete system It is also recommended that guidance is provided on the development of an MSMP that would complement the ship's Safety Management System {SMS) It is anticipated that ship operators will develop their own MSMPs that will provide

all necessary information to ensure the mooring system is fully assessed at build against set industry criteria, properly inspected and maintained while in service, and operated safely

A framework for the development of the MSMP is provided using a goal-based approach, which aligns with the IMO approach to goal-based standards Core elements of the system are divided into parts against which high level goals are supported by more detailed functional requirements

This, in turn, will become transferrable across ships and fleets and become easily understood

by ship's personnel, with a supplementary Mooring System Management Plan Register (MSMPR) providing the lifecycle record of where information is kept and who is responsible for its update

What is the Mooring System Management Plan Register?

The MSMPR is where all of the information identified in the MSMP is either kept or recorded

It is recommended that the MSMPR is available to ship's personnel and others authorised

to review or monitor the equipment status All stakeholders have a responsibility in collaborating to ensure the MSMPR is appropriately created

It is recommended that the MSMPR is kept as an up-to-date record of the mooring system, and any amendments undertaken with minimal delay The MSMPR should be integrated into the ship's document control system and be subject to change management controls to ensu re

a complete history is available for future ship personnel and operators

It is fu rther recommended that a backup copy of the MSMPR is kept separate from the ship

in case of damage or loss and that shore-side responsibility is identified to maintain these records along with the relevant ship's continuous synopsis record

Each ship is encouraged Exa mple of where the

to use this column to relevant i nformation identify what mooring may be kept Each

system component is ship is encouraged applica ble, and/or what to use this column relevant information is to identify where

is kept and who

is responsible for maintaining those records

Table 0.1: Example section of the MSMP What is a Line Management Plan?

Items

Lists the information that could be considered for the MSMPR record It

is recommended that information

is recorded as temporary if that information is only for the cu rrent ship operations, or permanent if it is intended to remain with the ship for its lifecycle The ship owner wil l assign their own designation within this column

Comments

Provide additional guidance on the types

of information that may be requ i red It is recommended this

is annotated where

it is not intended

that the information will be handed over with changes of shi p operators

The LMP is used to manage the operation and retirement of mooring lines and tails The LMP also documents the requirements, assumptions and evaluation methods used in determining the line retirement criteria The LMP is specific to an operator, ship type and trade route, but this publication gives general guidance on establishing an LMP

Typical components include:

• Records of mooring hours

• Line inspection records and plans

• Manufacturer and operator retirement criteria

• Test/inspection reports

• Manufacturer's recommendations following tests or inspections

xxi

one

I ntrod uction to moori ng

© Copyright OCIMF 2018

1.1 General 2

2

Mooring Equipment Guidelines (MEG4)

1.1 - General Mooring is the securing of a ship to a marine facility, terminal, berth or another ship using mooring lines It is one of the most important and frequently undertaken activities on board any ship For the purposes of this publication, mooring is considered to be an integrated system that factors in the role that each component in the system plays, resulting in a securely moored ship

Most tankers are moored to conventional piers and sea islands However, tankers may be moored to facilities that may not be connected to the shore, including Multi Buoy Moorings (MBMs), Single Point Moorings (SP Ms}, Floating (Production) Storage and Offloading units (F(P)SOs) and other offshore loading/discharging facilities

Ships may engage in a broader range of mooring operations when undertaking emergency towing, tug handling, barge mooring, canal transit, Ship to Ship (STS) transfer and anchoring, some of which may require specialised fittings or equipment

Anchoring equipment is covered by Classification Society rules and is not included in this publication

Loading platform

'

I

Cf_

Figure 1.1: A typical mooring pattern ot o conventional tanker terminal

The use of an effective mooring system is essential for the safety of the ship, its crew, the terminal and the environment In order to know how to optimise the moorings so that they can resist the various forces that will act upon the ship (which may impact the effectiveness of the mooring system}, the following three questions will need answers:

1 What are the forces applied on the ship?

2 What general factors determine how the applied forces are distributed to the mooring lines?

3 How can the answers to questions 1 and 2 be applied in establishing a good mooring system?

The most important principle of mooring is that no mooring arrangement has an unlimited capability It will be necessary to understand precisely what the mooring system of the ship is expected to encounter, and then design and equip to achieve it

Section one: Introduction to moori ng

1.2 - Objectives

Guidance in this section is intended for all stakeholders in the design and safe operation

of a ship, including ship and equipment designers, ship builders, surveyors, ship

operators/owners/managers, equipment manufacturers and suppliers, ship's personnel and marine terminal personnel

It establishes the principles covering all aspects of the mooring system, from initial ship design and mooring equipment arrangements (including fixtures and fittings and associated ship structural strength), to the factors influencing the selection of mooring lines and their safe handling, maintenance and retirement

Further guidance is provided on procedures for the safe operation and maintenance of the mooring system by ship's personnel, including the operational considerations and mooring management at the interface of the ship with the marine terminals that it visits

This section also provides guidance on the requirements for the mooring system that are

to be included in the ship's management system through a functioning Mooring System Management Plan (MSMP) An MSMP should cover all aspects of the mooring equipment, operation and maintenance (see section 1.9) These should be effectively managed from the ship's initial design through to end life

1.3 - Forces acting on the ship

The moorings of a ship must resist the forces due to some, or possibly all, of the following factors:

• Changes in draught, trim or list

This section deals mainly with the development of a mooring system to resist standard environmental criteria (defined in section three) involving wind, current and tidal forces on

a ship at a berth If the mooring system is designed to accommodate maximum wind and current forces, reserve strength may be sufficient to resist other moderate forces that may arise However, if significant surge, waves or ice conditions exist at a terminal, considerable additional loads can be developed in the ship's moorings These forces are difficult to analyse except through model testing, field measurements or dynamic computer programs

In planning for mooring at a terminal, consideration should be given to potential scenarios where the standard environmental criteria could be exceeded and deciding on what

appropriate measures will need to be implemented to avoid causing injury to personnel, damage to the environment or to assets

Forces on the moorings due to changes in ship elevation, from either tidal fluctuations or loading or discharging operations, must be addressed by diligent mooring line management

3

4

Mooring Equipment Guidelines (MEG4)

1.3.1 Wind and current drag forces

The procedures for calculating wind and current drag forces are covered in appendix A Calculations carried out on a range of ship sizes have shown that the wind and current drag coefficients are not significantly dependent on ship size Consequently, the ship drag coefficients in appendix A may be used for bridge-aft ships with similar geometry, down to 16,000 DWT

Figure 1.2 demonstrates how the resultant wind force on a ship varies with wind velocity and direction For simplicity, wind forces acting on a ship can be broken down into two components: a longitudinal force acting parallel to the longitudinal axis of the ship and a transverse force acting perpendicular to the longitudinal axis The transverse force generally produces a yawing moment

Wind force on the ship also varies with the exposed area of the ship Since a head wind only strikes a small portion of the total exposed area of the ship, the longitudinal force is relatively small A beam wind, on the other hand, exerts a very large transverse force on the exposed side area of the ship For a given wind velocity the maximum transverse wind force on a VLCC

is about five times as great as the maximum longitudinal wind force For a 50 knot wind

on a ballasted 250,000 DWT tanker, the maximum transverse forces are about 300 tonnes (2,943kN), whereas the ahead longitudinal forces are about 60 tonnes (589kN)

Table 1.1: Maximum longitudinal and transverse wind forces on a 250,000 DWT tanker, Sm trim, 50 knot wind

If the wind is from any quartering direction between the beam and ahead (or astern), it will exert both a transverse and longitudinal force since it is acting on both the bow (or stern) and the side of the ship For any given wind velocity, both the transverse and longitudinal force components of a quartering wind will be smaller than the corresponding forces caused by the same wind acting abeam or head on

Note the sign convention used in this section is aligned with the sign convention used by the scientific community, such as research establishments and designers, where a force from directly astern is considered to be from 0 degrees and the compass angles proceed

in an anti-clockwise direction This convention is also adopted in appendix A when discussing wind and current forces (This is different to the normal interpretation used by mariners, whereby force from directly ahead is considered to be from 0 degrees and the compass angles proceed in a clockwise direction)

Section one: Introd uction to mooring

E 'iii e Cl

45 • 90° 135•

Direction of wind off bow 180°

With the exception of wind that is dead ahead or astern or directly abeam, the resultant wind force does not have the same angular direction as the wind For example, for a 250,000 DWT tanker, a wind 45 degrees off the bow leads to a resultant wind force of about 80 degrees

off the bow In this case, the point of application of the force is forward of the transverse centreline, producing a yawing moment on the ship

Degree Off Force 5 x Draught 3 x Draught 1.10 x Draught 1.02 x Draught

Table 1.2: Example of the effect of under keel clearance versus draught (assuming 2 knat current)

Current forces on the ship must also be considered when evaluating a mooring arrangement

In general, the variability of current forces on a ship due to current velocity and direction follows a pattern similar to that for wind forces Current forces are further complicated by the significant effect of under keel clearance Table 1.2 shows the impact on force due to reduced under keel clearance The majority of terminals are orientated more or less parallel to the current, thereby minimising current forces Nevertheless, even a current with a small angle (such as 5 degrees) off the ship's longitudinal axis can create a large transverse force and must

be taken into consideration

5

These components will comprise:

• Mooring equipment and arrangements

• Mooring equipment strength

• Mooring pattern

While components will be discussed separately below, they are interlinked and must be considered jointly during the design phase of the ship This will ensure the ship can both moor safely and achieve the design capacity to meet or exceed the requirements of the standard environmental criteria as defined in section 3.2

1.4.1 Mooring equipment and arrangements

Early in the ship design process the selection and location of mooring equipment and their arrangement on the deck of the ship must be determined to ensure that the ship can moor safely alongside berths and meet the standard environmental criteria

Areas that should be considered when designing mooring equipment and arrangements are outlined throughout this publication and take full account of the safety and exposure of personnel during mooring operations They include:

• The need for sufficient deck space and equipment to enable effective oversight and supervision of operations, adequate lighting and avoidance of impairments that degrade communications capability, such as from machinery noise

• The number, location and size of deck winches, mooring lines, bollards and fairleads to provide an effective, balanced mooring pattern

• Industry requirements including applicable IMO regulations, recognised industry standards (e.g IACS, ISO) and associated industry guidance and recommendations as they apply to mooring and towing equipment

• The application of human factors in the design to ensure crews are not exposed to avoidable risks during mooring operations

If a ship operator requests enhanced flexibility with ship mooring, which may be outside a standard mooring arrangement, the following may also be considered:

• Residual capacity to ensure the ship can berth, or remain berthed, in the event of unscheduled occurrences such as winches being out of service

• Lines unable to be deployed from optimal locations due to incompatibility with berth facilities

• Equipment redundancy, including critical equipment and spares

• Other influencing factors, such as locations with peculiar environmental operating

parameters, e.g.:

- Exposed locations

- Operating envelope limits of loading arms at berth

- Extraordinary strong tide, current or other phenomena (tidal bore)

Section one: I ntrod uction to moori ng

1.4.2 Mooring equipment strength

In considering the design of the mooring equipment and arrangements in section 1.4.1, this publication also establishes principles for equipment strength, many of which are interrelated and should also be taken into consideration These include:

• System design will establish, from standard environmental criteria, the effective

ship design MBL for each mooring line in the standard mooring pattern

• System design will ensure that the mooring fittings and machinery, and the structure to which they are attached, do not suffer structural damage or failure before the mooring line; i.e the SWL of fittings should be at least equal to or exceed the ship design MBL

• Loads to which mooring lines are exposed do not exceed the stated WLL

The relationship between SWL, WLL and ship design MBL of loose and permanent equipment

is explored in figures 1.3 and 1.4

7

Mooring Equipment Guidelines (MEG4)

All values are percentage values of the ship design MBL

t;, Operational brake render

□ Safe Working Load (SWL)

= Ship design MBL

.o1 Max rated pull

Design Basis Load (DBL)

Specified Minimum Yield Stress (SMYS) Max design brake render (ISO-Holding load)

Note: Stress (SMYS) is force per unit area, so cannot

strictly be shown against the same scale as the other load

Single Bollard;

Recessed Bitt

-�

Winch Foundation

values The value shown represents the load that

would cause the stress

Winch Drum, Shafts, Bearings

Ship Mooring System Component

-Winch Brake

Figure 1.3: Relative percentage values of mooring system components based on ship design MBL

Mooring Line Type/Component

accidental load condition

-o- US - Mooring structure SWL

� fittings will be sized according ,_

to the largest ship design MBL that the berth is designed for

Note 2: These values are examples only and are based on PIANC Report No 153 - 2016, Section 7.5.5 which, explains different approaches Onshore mooring designs vary according to applicable codes and standards in the location Additionally, the type of materials used, the anticipated >-

-metocean conditions and the design operating philosophy all impact design loads This diagram illustrates SWL values comparing US standards and the EU risk based approach, where normal, >- extreme and accidental conditions are taken into account in structural design Additional factors of

safety are taken into account to determine yield values and test loads, but these are

,-omitted for clarity

Single Hook/ Bollard Mooring Point 2 Hook Mooring Point 3 Hook Mooring Point 4 Hook

Shore Mooring Point Type

9

10

Mooring Equipment Guidelines (MEG4)

% ship design MBL

Operational brake holding load

50 synthetics At nominal heaving speed winch motor

rendering (max stall) load (50% ship design MBL) (ISO)

33 Winch motor - pull - between 22-33% at

nominal heaving speed (ISO)

22

0

Figure 1.4: Illustration of operational and limiting values for mooring lines

1.4.3 Mooring pattern The term mooring pattern refers to the geometric arrangement of mooring lines between the ship and the berth Industry has previously standardised on the concept of a generic mooring pattern (see figure 1.1), taking into account standard environmental criteria The generic mooring pattern is mainly applicable to a multi-directional environment and to the design of

a ship's mooring system

For ships regularly trading to terminals with a directional environment, a site-specific pattern (such as one including head and stern lines and/or extra breast and spring lines) may be more effective Consideration may be given to the provision of additional or higher capacity mooring equipment

The most efficient line lead for resisting any given environmental load is a line orientated

in the same direction of the load This would imply that, theoretically, mooring lines should all be orientated in the direction of the environmental forces and be attached at such a longitudinal location on the ship that the resultant load and restraint act through one location Such a system would, however, be impractical since it has no flexibility to accommodate the different environmental load directions and mooring point locations encountered at various terminals

For general applications, the mooring pattern must be able to cope with environmental forces from any direction This can best be approached by splitting these forces into a longitudinal and a transverse component and then calculating how to most effectively resist them It follows that some lines should be in a longitudinal direction (spring lines) and some lines

in a transverse direction {breast lines) This is the guiding principle for an effective mooring pattern for general application, although the locations of the actual fittings at the terminal will not always allow it to be put into practice

The decrease in efficiency caused by deviating from the optimum line lead is shown in figures 1.5 and 1.6 (compare with cases 1 and 3 in figure 1.7, where the maximum line load increases from 57 (559kN) to 88 tonnes (863kN)) However, for a 60 knot head wind the highest loaded

Section one: Introduction to mooring

line for the generic pattern is 39.5 tonnes, whereas it is 28.6 tonnes for the site-specific

pattern For terminals located where the environment forces are directional, the site-specific pattern is actually more effective See sections 1.7, 1.8, 3.3 and 3.4 for further details

Designers and operators must fully understand the basic difference between spring lines and breast lines:

• Spring lines restrain the ship in two directions (forward and aft)

• Breast lines are deployed perpendicular to the ship and restrain against transverse motion

away from the berth

On-berth direction restraint is provided by the pier or facility through fenders, breasting dolphins or other restraint mechanism Whereas all breast lines will be stressed under an off-berth environmental force, only the aft or the forward spring lines will generally be

stressed depending on the direction of the force at a given time Requirements for line tending therefore differ between spring and breast lines

If spring lines are pre - tensioned, the effective longitudinal restraint is provided by the

difference between the tension in the opposing spring lines Too high a pre-tension can significantly reduce the effectiveness of the mooring system Likewise, differences in vertical angles between forward and aft springs can lead to ship surge along the jetty

Mooring patterns for a directional environment may incorporate head and stern lines that are orientated between a longitudinal and transverse direction This optimises restraint for the longitudinal direction where the dominant environmental force acts, while maintaining some lateral restraint for the less dominant lateral environmental directions

Another option for mooring patterns with dominant longitudinal forces is to add more spring lines

The effectiveness of a mooring line is influenced by two angles: the vertical angle the line forms with the pier deck and the horizontal angle the line forms with the parallel side of the ship The steeper the orientation of a line, the less effective it is in resisting horizontal loads

As an example, a line orientated at a 45 degree vertical angle is only 75% as effective in restraining the ship as a line orientated at a 20 degree vertical angle Similarly, the larger the horizontal angle between the parallel side of the ship and the line, the less effective the spring line is in resisting a longitudinal force

Lines are 90° to ship tonnes = 1 x WLL x Cos(angle)

Angle Number of lines WLL Cos(angle)

12

Mooring Equipment Guidelines (MEG4)

Simple 4 Line Mooring Pattern

Simple 4 Line Mooring Pattern

Transverse Restraint Capacity

Line WLL Sin1 .,.1 Transverse restraint (t)

Figure 1.6: Effect of horizontal angle on transverse restraint

For the total effect of both horizontal and vertical angle on transverse restraint, further calculation is required to arrive at the resultant transverse restraint value

w

All loads are in tonnes

✓ Recommended

CASE 1 Generic All Wire Mooring

(All wires the same construction and diameter)

60 knot wind 45 ° off bow 56.7

60 knot beam wind 56.7

x Not Recommended

CASE 2 Generic Mixed Moorings

(Mooring arrangements as above except that lines 2, 4, 11 and 13 are polypropylene)

Illustrates lack of contribution of fibre lines

to overall mooring strength

11.3

57.1 56.7

60 knot head wind

60 knot wind 45 ° off bow

60 knot beam wind

Ofri:IM!il CASE 3 Site-specific

(All wires the same construction and diameter)

Showing effect on line tensions as consequence of non-ideal leads

15.9 5.0 91.6 6.8

60 knot wind 45 ° off bow 52.6 49.9 48.5 43.5 83.9 19.5 19.0 5.0 5.0 36.7 30.4 40.8 24.9 24.0

60 knot beam wind 56.2 54.0 53.l 48.1 88.4 17.7 17.2 11.8 12.2 70.3 49.9 70.3 46.3 45.8

Note: Computer program assumes line does not yield or break Examples are based on ballasted 250,000 DWT ship Loads are for conditions shown

Should the wind shift, lines without loads, as shown above, would assume some loadings, so all lines should be tended at all times

"'

;:; 0

C g._

0 ::,

14

Mooring Equipment Guidelines (MEG4)

A comparison of cases 1 and 3 in figure 1.7 demonstrates that, although the same number

of lines is used in each situation, Case 1 results in a better load distribution, minimising the load in any single line Therefore, ships will be most effectively moored using lines 'within the length' of the ship, through a combination of breast and spring lines, with:

• Breast lines orientated as perpendicular as possible to the longitudinal centreline of the ship and as far aft and forward as possible

• Spring lines orientated as parallel as possible to the longitudinal centreline of the ship 1.5 - Stiffness of lines

The stiffness of a mooring line is a measure of its ability to stretch under load Under a given load, a low stiffness line will stretch more than a high stiffness line Stiffness plays an important role in the mooring system It is covered in greater detail in section five This section deals with the role of stiffness in the mooring system The stiffness of mooring lines can affect the mooring system in a number of ways, including:

• Low stiffness lines can absorb higher dynamic loads For this reason, low stiffness is desirable for STS transfer operations, or at terminals subject to waves, swell or passing ship forces

• Extremely low stiffness (such as all nylon lines) on a ship can also mean that the ship will

move further in her berth and this could cause problems with marine loading arms or hoses

and operating envelopes

• Movement can also create additional energy in the mooring system Stored energy in a low stiffness line, if released on sudden failure, will 'snap-back' unpredictably and can cause injury to personnel and/or damage to equipment

• The different stiffness of multiple line materials may affect how forces are distributed into the mooring system

• Ensuring properly tensioned lines will reduce line failures from dynamic effects, e.g passing ship, seiche and wind gusting

The simple four - line mooring pattern shown in the upper portion of figure 1.6 is insensitive

to the stiffness of the lines and is only suitable for small ships such as tugs, small barges and coasters Larger ships will require more lines resulting in more effective load sharing and interaction between lines This becomes more complicated as the number of mooring lines increases

Optimum restraint is generally accomplished when load sharing is achieved and breast lines are loaded equally to the same percentage of their breaking strength

If, however, two parallel lines of different stiffness are connected to a ship at the same point, the stiffer one will always take a greater portion of the load (if the winch brake is set) even

if the orientation is the same This is because both lines must stretch an equal amount to ensure an even distribution of forces in each line and if not achieved, the stiffer line assumes

a greater portion of the load The relative difference between loads can be very large, and depends on the difference in line stiffness

The stiffness of a mooring line primarily depends on the following factors:

• Material type

• Construction

• Length

Section one: Introduction to mooring

Figure 1.8 demonstrates the significance of material type, construction and length on load distribution The most important points to note in this example are the appreciable difference

in stiffness between wire and fibre lines and the effect of line length on stiffness

• Case A shows an acceptable mooring where lines of the same size and material are used

• Case B indicates the sharing of loads between lines of the same material but of different size and each line is equally stressed to approximately the same percentage of its breaking strength

• Cases C and D are examples of mooring arrangements that should be avoided (mixed

mooring materials and lines of different lengths)

Wire mooring lines are very stiff Typical elongation of a wire line under load is about 1 % of wire length Under an equivalent load, a polypropylene rope may stretch ten times as much

as a wire Therefore, if a wire is run out parallel to a conventional fibre line, the wire will carry almost the entire load while the fibre line carries practically none

There are many varieties of fibre lines in use, and new product developments are introduced all the time These fibre lines include those made from High Modulus Synthetic Fibre (HMSF) which, like wire mooring lines, are also very stiff compared to conventional fibre moorings Stiffness also varies between different types of fibre lines and, although the difference is generally not as significant as that between fibre line and wire, the difference will affect load distribution HMSF lines will, for example, have much higher stiffness than other synthetic fibre lines and would carry the majority of the load if run out parallel to conventional

The effects of mixing wire and synthetic fibre lines are shown in figure 1.7 by comparison of cases 1 and 2 Note the low loads in fibre lines 2, 4, 11 and 13 in case 2 and the subsequent increase in load in the wire at line 1 (56.7 tonnes) in both the 60 knot 45 degree off bow and beam wind to 91.6 and 91.2 tonnes respectively Further, the load in the wire in line 12 also increases, from a high of 57.1 tonnes in the case 1 beam wind scenario to 88.0 tonnes in case 2

15

16

Mooring Equipment Guidelines (MEG4)

Same size and type mooring line

Note: All loads are approximate

Figure 1.8: Effect of mooring stiffness on restraint copocity

300mm Polyamide = 37.5 tonnes (368kN) fi;J§+i,,i,,i§,Htli

3 tonnes (29kN) Polyamide = . ,, l tonne (l0kN)

x Not Recommended

:S 25 tonnes (245kN) 2:: 50 tonnes (490kN)

x Not Recommended

The effect of line length (from securing point on board to shore bollard) on load distribution must also be considered Line stiffness varies directly with line length and has a significant effect on line load As shown in scenario D (figure 1.8), a line 60m long will assume only about half the load of a 30m parallel and adjacent line of the material type, construction and diameter

Section one: Introduction to mooring

For a similar line diameter and construction, age can also impact on line stiffness Usually this factor is not an important consideration since the load relative to a line's strength is the governing factor rather than the absolute load

Synthetic tails are often used on the ends of wire lines to permit easier handling and to decrease line stiffness Tails may also be used to decrease the stiffness of low stretch ropes made from HMSF materials (see section 5.8)

If tails are used, the same size and type of tail should be used on all lines run out in the same service

The effect of attaching llm long tails, made from both polyester and polyamide, to steel wire and HMSF mooring lines is shown in figure 1.9 Longer tails will have a significant impact on the mooring system stiffness

The objective of a good shipboard mooring arrangement is to provide and arrange equipment

to accomplish the following:

• P rovide for a safe and effective mooring pattern at conventional piers and sea islands

• Facilitate safe and effective mooring, unmooring and line tending operations, including the handling of tug lines during harbour and escort towing operations, with minimum demand and risk to personnel

• Enable safe and effective mooring at anticipated non-conventional terminals such as SP Ms, MBMs and offshore terminals including F(P)SOs and Floating Storage and Offloading units (FSOs)

• Allow safe and effective operations at anticipated activities, such as STS transfers or

canal transits

The mooring equipment and arrangements should be designed to minimise the risk to those involved in the operation, taking account of human factors as laid out in section two and IMO resolution A947 (23)

17

18

Mooring Equipment Guidelines (M EG4)

1.6.2 Mooring line arrangements

These guidelines assume that the moored ship may be exposed to strong winds or current from any direction Consideration of the principles of load distribution in figure 1 7 leads to the following mooring guidelines which should be considered when planning mooring line arrangements:

• Mooring lines should be arranged as symmetrically as possible about the midship point of the ship A symmetrical arrangement is more likely to ensure a good load distribution than

be used because of the berth geometry

- Head and stern lines can sometimes be required for manoeuvring purposes, but that should not lead to their reliance when the ship is moored, when lines should be repositioned to form a more symmetrical arrangement

• Mooring facilities with effective breast and spring lines alone will allow a ship to be moored securely within its own length

• The vertical angle of the mooring line should be kept to a minimum The flatter the mooring line angle, the more effective the line will be in resisting horizontally-applied loads on the ship

• Mooring lines of the same size and material should be used for all leads If this is not possible, all lines in the same service, i.e breast lines, spring lines, etc should be the same size and type For example, all spring lines could be wire and all breast lines synthetic

• If used, mooring tails should be the same size and material

• All lines in the same service should be about the same length between the ship's winch and the shore bollard Line stiffness varies directly with line length and shorter lines will assume more load

In practice, final selection of the mooring lines to achieve a mooring pattern for a given berth is not something a ship can assess in isolation Consideration of local operational and weather conditions, pier geometry and ship design, will also need to be taken into account, and may often require input from local experts For example:

• While it is normal for spring lines to be used for manoeuvring a ship out of a berth, some pilots may request head and stern lines to assist in this purpose

• At berths where the mooring points are too close to the ship and effective breast lines cannot be provided, head and stern lines may be necessary

• Where the location of bollards means that lines will have an excessive vertical angle in the light condition, these excessive angles would considerably reduce restraint capability, requiring extra lines to provide additional restraint capacity