Guide for LNG Maintenance and Operation – Standards, Systems, and Safety

LNG maintenance and operation are essential aspects of managing liquefied natural gas systems safely and efficiently. These processes encompass routine inspections, equipment servicing, system performance monitoring, and strict compliance with safety and environmental regulations. Effective LNG maintenance and operation help prevent system failures, reduce operational downtime, and ensure the longevity of onboard and shore-based infrastructure.

As global demand for LNG grows, proper maintenance and operation practices play a critical role in supporting sustainable and reliable energy transport.

General

Scope and Application

Application of this Guide is optional. However, compliance with requirements of the Guide is compulsory when seeking the optional LNG Bunkering notation, see 1/7.1. This Guide has been developed to outline the requirements for the design, construction, and survey of liquefied gas carriers and barges fitted with dedicated LNG transfer arrangements and intended to operate in regular LNG bunkering service. This Guide is focused on the requirements for bunkering of LNG, the remainder of the vessel is to comply with the applicable edition of the ABS Rules.

Users of this Guide are advised that the process of bunkering LNG involves a number of interested parties, including a vessel’s flag Administration, national regulatory bodies and port authorities. Therefore proposals are subject to review and approval by the applicable authorities with respect to installed safety equipment, operational practices, crew training, bunkering safety distances, simultaneous operations, etc. Accordingly ship designers, shipyards, ship owners/operators and other interested stakeholders are encouraged to determine the full applicable requirements and obtain the necessary approvals as early as possible in any LNG bunkering new construction or conversion project.

Objectives

The objective of this Guide is to provide criteria for the design, construction, installation, survey and operation of LNG transfer arrangements, associated machinery, equipment and systems in order to minimize risks to the vessel, crew and the environment. Detailed requirements are provided to achieve this objective in accordance with the following key principles and requirements:

• Vessel construction is in accordance with the ABS Rules for Building and Classing Steel Vessels (Steel Vessel Rules), ABS Rules for Building and Classing Steel Vessels Under 90 Meters (295 feet) in Length (Under 90 m Rules), ABS Rules for Building and Classing Steel Barges (Barge Rules) or the ABS Rules for Building and Classing Steel Vessels for Service on Rivers and Intracoastal Waterways (River Rules), as applicable.
• LNG containment systems are designed in accordance with Chapter 4 of the IGC Code, as incorporated by Section 5C-8-4 of the Steel Vessel Rules.
• LNG tank pressure, temperature and loading/filling limits are maintained within the design limits of the tank at all times.
• Means are provided to evacuate, purge and gas free the LNG tanks.
• LNG tanks are in a protected location.
• LNG containment spaces, bunkering stations and machinery spaces containing LNG or gas processing equipment are located and arranged such that the risk of any release of liquid or vapor will be minimized. Arrangements are provided for safe access during operations and inspections.
• LNG piping, systems and arrangements provide safe handling of liquid and vapor under all operating conditions. Means are provided to inert and gas free piping and systems.
• Bunker stations are arranged to provide compatible LNG transfer.
• Automation, instrumentation, monitoring and control systems are provided to minimize the risks with carriage, distibution and bunkering of LNG.
• Operation and maintenance manuals are provided for all LNG containment and transfer equipment and systems covering operation, maintenance and repair procedures

Definitions

Breakaway Coupling. Breakaway Coupling means an LNG bunkering line coupling designed to separate at a pre-determined load to prevent damage to installed LNG Transfer Arms and Manifold Draining, Purging and Disconnection ProcedureLNG transfer equipment; typically incorporates a dry-break feature to avoid unwanted LNG release.

Bunkering. Bunkering means the transfer of fuel to a vessel or facility in the form of LNG or traditional marine fuels such as residual or distillate fuel oils.

Cargo Machinery Space. Cargo Machinery Space are the spaces where cargo compressors, pumps or processing units are located.

Dual Fuel Diesel Engine. Dual Fuel Diesel Engine is a diesel engine that can burn natural gas as fuel with liquid (pilot) fuel and also have the capability of running on liquid fuel only.

Enclosed Space. Enclosed Space means any space within which, in the absence of artificial ventilation, the ventilation will be limited and any explosive atmosphere will not be dispersed naturally. See also 4-8-4/27 of the Steel Vessel Rules.

Emergency Release Coupling (ERC). ERC means emergency release coupling; typically incorporates a dry-break feature to avoid unwanted LNG release. May be termed PERC for powered emergency release coupling.

Emergency Shutdown (ESD). ESD means emergency shutdown. ESD (otherwise known as ESD-1) is the emergency shutdown of the LNG transfer in a controlled manner. ESD-2 is the automatic activation of the Emergency Release System. For further information refer to SIGTTO «ESD Arrangements and Linked Ship/Shore Systems for Gas Carriers».

Hazardous Area. Hazardous Area means an area in which an explosive gas atmosphere is, or may be expected to be, present in quantities such as to require special precautions for the construction, installation and use of equipment. See also 4-1-1/1.9.4 and 4-8-4/27 of the Steel Vessel Rules.

Non-Hazardous Area. Non-hazardous Area means an area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of equipment.

International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code). IGC Code means the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, as amended.

Lower Explosive Limit (LEL). LEL means the lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source.

Liquid Cargo Cooling. A Liquid Cargo Cooling system is a system that lowers the LNG temperature by an indirect cooling system, for example, by coolant circulated through coils fitted either inside the cargo tank, onto the external surface of the cargo tank or by a remote system.

Liquefied Natural Gas (LNG). LNG means liquefied natural gas.

LNG Containment System. LNG Containment System is the arrangement for containment of LNG including, as applicable, a primary and secondary barrier, associated insulation and any intervening spaces, and adjacent structure if necessary for the support of those elements. The spaces around the LNG containment system are defined as:

• Hold Space is the space enclosed by the vessel’s structure in which a LNG containment system is located.
• Interbarrier Space is the space between a primary and secondary barrier, whether or not completely or partially occupied by insulation or other material
• Insulation Space is the space, which may or may not be an interbarrier space, occupied wholly or in part by insulation.

LNG Spraying. LNG Spraying means the process whereby LNG liquid is sprayed into the top of a LNG tank to cool the vapor phase and the tank and thereby reduce pressure in the tank.

Maximum Allowable Relief Valve Setting (MARVS). MARVS means Maximum Allowable Relief Valve setting.

Natural Gas. Natural Gas (dry) is defined as gas without condensation at common operating pressures and temperatures where the predominant component is methane with some ethane and small amounts of heavier hydrocarbons (mainly propane and butane). The gas composition can vary depending on the source of natural gas and the processing of the gas.

Primary Barrier. Primary Barrier is the inner element designed to contain the LNG when the Membrane Sheet Welding Procedure for LNG Containment SystemsLNG containment system includes two boundaries.

Purging. Purging is the process of introducing an inert gas, such as nitrogen, into a LNG tank, hose or piping system already in the inert condition with the objective of further reducing the existing oxygen content and/or reducing the existing hydrocarbon gas content to a level below which combustion cannot be supported if air is subsequently introduced into the system.

Recognized Standard. A Recognized Standard is an international or national specification or criteria acceptable to ABS.

Re-Liquefaction Unit. A Re-liquefaction Unit is a system used for taking the boil-off gas from LNG tanks and condensing it in a refrigeration system. LNG is then returned to the tanks.

Rules. Rules means the applicable edition of the ABS Steel Vessel Rules, Barge Rules, River Rules, Under 90m Rules, etc.

Secondary Barrier. Secondary Barrier is the liquid-resisting outer element of a LNG containment system designed to afford temporary containment of any envisaged leakage of LNG through the primary barrier and to prevent the lowering of the temperature of the vessel’s structure to an unsafe level.

Classification Notations

LNG Bunkering. When a liquefied gas carrier or barge is arranged for regular LNG bunkering service, the optional LNG Bunkering notation may be assigned. For application of the notation the arrangements and LNG bunkering systems are to be designed, constructed, and tested in accordance with the requirements of this Guide.

Example – ✠ A1, Liquefied Gas Carrier, LNG Bunkering, Ⓔ, ✠ AMS …

Vapor Return System. Where a vessel assigned the LNG Bunkering notation incorporates an optional Vapor Return System, the VRS notation may be assigned.

Associated Notations. Where a vessel assigned the LNG Bunkering notation incorporates additional equipment such as a Re-Liquefaction Unit, Gas Combustion Unit or Dual Fuel Diesel Engine designed, constructed and tested in accordance with the applicable requirements of the applicable sections of Part 5C, Chapter 8 of the Steel Vessel Rules, the additional notations RELIQ, GCU or DFD may be assigned.

Materials of Construction

Materials in general are to comply with the requirements of the ABS Rules for Materials and Welding (Part 2).

Materials used for piping and other components in contact with cryogenic liquids or gases, including materials used in potential leakage locations such as gratings, spray shields, drip trays, etc., are to be in compliance with Section 5C-8-6 of the Steel Vessel Rules.

Operating and Maintenance Instruction Manuals

Detailed instruction manuals are to be provided onboard covering the operations, safety and emergency procedures, maintenance requirements, personal protective equipment and occupational health hazards relevant to the containment and distribution of LNG.

The manuals are to include, but not be limited to, the regular test and maintenance procedures for the monitoring systems, gas detection systems, safety shut-off systems and the integrity of backup systems together with identification of the relevant responsible parties.

In addition, there is further guidance regarding the contents of the LNG bunkering operating and maintenance manuals in Subsection 3/5 of this Guide and Section 5C-8-18 of the Steel Vessel Rules. Inspection and maintenance of certified safe electrical equipment is to be in accordance with the applicable requirements of Section 9 and 10 of IEC 60092-502.

Alternatives

Equipment, components, and systems for which there are specific requirements in this Guide, or its associated references, may incorporate alternative arrangements or comply with the requirements of alternative recognized standards, in lieu of the requirements in this Guide. This, however, is subject to such alternative arrangements or standards being determined by ABS as being not less effective than the overall safety requirements of this Guide or associated references.

Where applicable, requirements may be imposed by ABS in addition to those contained in the alternative arrangements or standards so that the intent of this Guide is met. In all cases, the equipment, component or system is subject to design review, survey during construction, tests and trials, as applicable, by ABS for purposes of verification of its compliance with the alternative arrangements or standards. The verification process is to be to the extent as intended by this Guide.

Certification

Design review, survey, testing, and the issuance of reports or certificates constitute the certification of machinery, equipment and systems; see also 4-1-1/3 of the Steel Vessel Rules. There is guidance on the certification requirements for LNG bunkering machinery, equipment and systems see below. The applicable edition of the ABS Rules is to be used in association with this Guide.

Vessel Arrangements and System Design

General

While this Guide is focused on the requirements for bunkering of LNG, the remainder of the vessel is to comply with the applicable edition of the ABS Rules.

This Section details the general requirements for vessel arrangements and system design of liquefied gas carriers or barges intended to operate in regular LNG bunkering service and applying the LNG Bunkering notation.

Plans and Data to be Submitted

Plans and specifications covering the vessel arrangements are to be submitted and are, as applicable, to include:

• General arrangement;
• LNG containment arrangements;
• LNG bunkering station arrangements;
• BOG management arrangements;
• Cargo machinery space arrangements;
• Cargo piping arrangements;
• Hazardous area classification plan;
• Vent mast and venting arrangements.

BOG Management/Utilization, LNG Temperature Control, LNG Tank Loading and Vapor Return Management

Utilization or Management of Boil-off Gas and LNG Temperature Control

Unless the LNG tanks are designed to withstand the full gauge vapor pressure of the gas under conditions of the upper ambient design temperatures, as specified in 5C-8-7/2 of the Steel Vessel Rules, means are to be provided to maintain the tank pressure below the MARVS by consuming or managing the natural LNG boil-off at all times, including while in port, maneuvering or standing by.

Systems and arrangements that may be used for this purpose include one or a combination of the following methods:

1. Pressure accumulation, whereby the LNG is allowed to warm up and increase the tank pressure. The tank insulation, design pressure or both are to be adequate to provide for a suitable margin for the operating time and agreed cargo loading temperatures involved.
2. A cargo vapor re-liquefaction system. Re-Liquefaction Units are to be designed, constructed and tested in accordance with Appendix 5C-8-A5 of the Steel Vessel Rules. BOG compressors are to be in accordance with 5C-8-A5/3.1 and 5C-8-A5/5.5 of the Steel Vessel Rules.
3. The burning of natural or forced BOG in an approved consumer such as a Gas Combustion Unit, dual fuel diesel engine or other approved combustion unit. Gas Combustion Units are to be designed, constructed and tested in accordance with Appendix 5C-8-A6 of the Steel Vessel Rules. Dual fuel diesel engines are to be designed, constructed and tested in accordance with Appendix 5C-8-A7 of the Steel Vessel Rules. Dual fuel diesel engines may be considered a primary means of BOG management and utilized as part of the BOG management strategy, when available under all operating conditions.
4. Liquid cargo cooling. Liquid cargo cooling systems are to be designed, constructed and tested in accordance with the applicable requirements for Re-liquefaction Units in Appendix 5C-8-A5 of the Steel Vessel Rules.

LNG Tank Loading

LNG containment systems are to be designed in accordance with Section 5C-8-4 of the Steel Vessel Rules. The sloshing loads requirements detailed under 5C-8-4/14.3 are to be assessed for all partial loading conditions expected in LNG Bunkering Guidelines: Comprehensive Insights and Best Practices for OperatorsLNG bunkering service such that there are no significant operational limits on partial loading.

Such operational limits are to be detailed within the LNG Bunkering Operations Manual referenced under Section 3/5 of this Guide. Any operational limits from partial loading that would affect the vessels ability for unrestricted service will be subject to special consideration.

Vapor Return System

It is envisaged that a number of different bunkering techniques will be developed that are dependent on the installed LNG tank types, installed equipment, flow rates, receiving facility arrangements, etc. These bunkering operations may use differential pressure or pumped loading combined with LNG spraying for control of LNG tank temperatures and pressures together with the use of re-liquefaction of cargo vapors, cargo cooling, pressure accumulation or consumption of the excess vapor.

Therefore, the installed equipment and arrangements will vary on a case-by-case basis. The intent of this Guide is not to exclude any established or novel arrangements.

Vapor Return Connection. LNG bunkering vessels are to be arranged with a vapor return connection on the manifold(s) as per 5C-8-5/6.3 of the Steel Vessel Rules.

Optional Vapor Return System. Vessels may also optionally be arranged with a vapor return system designed to manage the maximum vapor return flows without over pressurizing the LNG tanks. Where fitted, the vapor return system is to be designed, constructed and tested in accordance with this Guide; see 1/7.3 of this Guide for the VRS notation. See also Subsection 3/5, 3/7.7iii) and 3/7.9 of this Guide for the operational and design requirements for managing vapor return in LNG bunkering operations.

Cargo Machinery Space. Cargo machinery spaces are to be arranged in accordance with 5C-8-3/3 of the Steel Vessel Rules.

LNG Bunker Station

1. The bunkering station(s) and manifold(s) are to be located on the open deck so that sufficient natural ventilation is provided.
2. The bunker manifold and connections are to be visible from the bunkering control station and cargo control station or bridge, as applicable. Remote video arrangements may be accepted where direct line of sight from the aforementioned locations is not possible.

Personnel Protection. Suitable personnel protective equipment in accordance with 5C-8-11/6 and 5C-8-14/1 through 5C-8-14/3 of the Steel Vessel Rules is to be provided onboard.

LNG Bunkering Systems

General

The purpose of this Section is to define the on-board requirements for LNG bunkering systems to enable effective transfer of LNG from the LNG bunkering vessel to the receiving vessel or facility and to minimize risks to the vessel, crew and the environment.

The relevant aspects of related standards such as ISO 28460, EN 1473, EN 1474, etc., and the ISO Technical Specification ISO/TS 18683:2015 “Guidelines for systems and installations for supply of LNG as fuel to ships” may be used in addition to the Guide requirements.

Plans and Data to be Submitted

Plans and specifications covering the LNG bunkering system with all of the accessories are to be submitted and are, as applicable, to include:

• General arrangement of the LNG bunkering system including location of the gas detectors, electrical equipment and lighting;
• Detailed drawings and specifications of the bunkering station(s), manifolds, valves, couplings, transfer arms, hoses, transfer system working envelope, lifting and hose handling cranes, additional hull protection and control stations;
• Calculations for the transfer system foundations;
• LNG piping systems including details of piping and associated components, design pressures, temperatures and insulation;
• Purging equipment and arrangements including oxygen concentration calculation;
• Vapor return system arrangements and procedures including capacity calculations;
• Material specifications for LNG manifolds, valves and associated components;
• Calculations for the LNG manifold design loads;
• Fabrication procedures, weld procedures, stress relieving and non-destructive testing plans;
• Ventilation system;
• Fixed gas detection and alarm systems, and associated shut-off and shutdown systems;
• Descriptions and schematic diagrams for control and monitoring systems including set points for abnormal conditions;
• Details of all electrical equipment in the bunkering and control stations;
• Equipotential bonding and insulating flange arrangements;
• Failure Modes and Effects Analysis (FMEA) to determine possible failures and their effects in the operation of the LNG bunkering control system;
• Emergency shutdown (ESD) arrangements and ESD flow chart together with communication arrangements;
• Specifications and details of the emergency release system including emergency release couplings and breakaway couplings;
• Operating and maintenance instruction manuals;
• Testing procedures during sea/gas trials.

LNG Bunkering Operation Manuals

In accordance with Subsection 1/11 of this Guide, detailed instruction manuals are to be provided onboard containing the operations, safety and emergency procedures, maintenance requirements and occupational health hazards relevant to LNG bunkering operations.

The manuals are to include, but not be limited to, the instructions for ship-ship compatibility verification, hazardous area evaluation, connecting, leak testing, inerting, gassing up, cooling down, pumping LNG, LNG spraying, vapor return management, draining, purging, disconnecting, emergency shutdown procedures, bunker manifold load limits, any limitation to personnel engaged in bunkering operations, the identification of vessel specific bunkering limitations, appropriate personal protective equipment, flowcharts and ESD valve characteristics.

Bunker Station

General:

1. The bunkering system is to be arranged so that no gas is discharged to the environment during normal LNG bunker transfer operations.
2. Means are to be provided to relieve residual pressure and for draining the liquid from the bunkering lines at bunkering completion.
3. Bunkering lines are to be arranged for inerting and gas freeing.
4. Suitable arrangements are to be provided for the collection of any spilled LNG. Accordingly drip trays are to be fitted below LNG bunkering connections and where leakage may occur. The drip trays are to be made of stainless steel or another material suitable for the containment of LNG. Drip trays are to be provided with a means of draining rainwater, seawater, etc., at periodic intervals.
5. The bunker station area, manifold, transfer connections and control station are to be adequately illuminated.
6. Cargo sampling connections in accordance with 5C-8-5/6.5 of the Steel Vessel Rules are to be provided.

Manifold Design

1. The bunkering manifold(s) is/are to be designed to withstand the external loads during bunkering and to consider the applicable emergency release arrangements.
2. The maximum permitted external loads are to be detailed in the operation manuals referenced by 3/5 of this Guide and to be clearly displayed in the vicinity of the manifold.

Additional Hull Protection

1. A water distribution system, or equivalent, is to be fitted below the bunker manifold(s) connections and associated transfer system to provide a low pressure water curtain for additional protection of the hull and vessel’s side structure within the operating envelope of the bunker transfer system.
2. The water curtain system may be part of the fire main system provided the required fire pump capacity and pressure are sufficient for operation of the required numbers of hydrants, hoses and water spray systems simultaneously and the water curtain system is fitted with isolating valves.

Manifold Connections

1. All pipelines, hoses or components which may be isolated in a liquid full condition, or where liquid may accumulate, are to be protected by relief valves. The outlet from these pressure relief valves is to be led to the LNG tanks. Alternatively, they may discharge to the vent mast if means are provided to detect and dispose of any liquid cargo which may flow into the vent system.
2. A manually operated stop valve and a remote operated shutdown valve in series, or a combined manually operated and remote valve, are to be fitted in every bunkering line close to the manifold connecting point. The remote valve is to be operable from the control location for bunkering operations and/or another safe location. The remote valve may also be the ESD valve.
3. Provision for LNG vapor return connections are to be provided at the bunker manifold(s).
4. Strainers are to be fitted to protect control valves and systems.
5. Manifold connections not being used for bunker transfer operations are to be blanked with blind flanges rated for the design pressure of the pipeline system.

Vapor Return System, VRS Notation

1. The vapor return system, as applicable, is to be capable of accepting the maximum volumetric vapor flow and excess vapor required to meet the loading rate without over pressurizing the LNG tank(s).
2. Calculations for the maximum vapor return flow rate, pressure and corresponding tank pressure management details, are to be submitted for verification purposes and summary information detailed in the operation manuals referenced by Subsection 3/5 of this Guide.
3. The vapor return piping system and equipment are to be adequately separated and protected to avoid over pressurizing the LNG tank(s).
4. Control and monitoring of the vapor return system is to be integrated into the control and monitoring system required by Subsection 3/17 of this Guide and to be capable of varying LNG delivery rates in consideration of the monitored vapor return system parameters.
5. An ESD valve is to be fitted to the vapor return connection and incorporated within the ESD system required by 3/17.5 of this Guide.
6. The vapor return system is to be included within the scope of the FMEA required by 3/17.1ii) of this Guide.

Electrical Bonding/Isolation

1. Electrical isolation of the transfer system is to be achieved by the installation of insulating flanges at one end of the connection hoses for all transfer or vapor return connections. Insulation flange specifications and arrangements are to be in accordance with recognized industry standards such as ISGOTT “International Safety Guide for Oil Tankers and Terminals” and SIGTTO “LNG Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases”.
2. The bonding connection is to be located away from the manifold area in a non-hazardous area.

Fire Extinguishing Systems

1. A water spray system in accordance with 5C-8-11/3 of the Steel Vessel Rules is to be provided for each bunker manifold area.
2. A dry chemical powder fire extinguishing system in accordance with 5C-8-11/4 of the Steel Vessel Rules is to be provided for each bunker manifold area.

LNG Bunker Delivery

General. It is envisaged that a number of different bunkering techniques will be developed that are dependent on the installed LNG tank types and equipment on both bunkering and receiving vessel. This Subsection details the requirements for the bunkering vessel LNG delivery equipment and systems.

LNG Pumps

1. Material used in the design of the LNG pumps is to be in accordance with 5C-8-6/2.2 of the Steel Vessel Rules except that witnessed material testing is not required.
2. Each size and type of pump is to be prototype tested in accordance with 5C-8-5/13.1.3(a) of the Steel Vessel Rules.
3. All LNG pumps are to be hydrostatic tested in the presence of the Surveyor in accordance with 5C-8-5/13.1.3(b) of the Steel Vessel Rules.

Hoses, Bunker Transfer Systems, Lifting and Hose Handling Equipment

1. Hoses used in LNG bunker transfer systems are to be in accordance with 5C-8-5/11.7 of the Steel Vessel Rules.
2. Cranes, loose gear, supports, etc., are to be provided for hose handling and bunkering operations and are to be designed, arranged and surveyed in accordance with the applicable requirements of the ABS Guide for Certification of Lifting Appliances.
3. Hose supports or cradles are to be used where necessary to keep hose bends within the design limits, as per manufacturer’s recommendations.
4. Fixed LNG bunker transfer systems are to be designed and tested in accordance with recognized standards such as EN1474-3 (offshore transfer system) and/or EN1474-2 (transfer hoses). LNG bunker transfer systems and hoses are to be arranged to provide sufficient flexibility over the range of expected relative vessel motions.
5. Calculations for the transfer system foundations, as applicable, together with details of any hose support arrangements and working envelope are to be submitted.

Emergency Release System

1. The LNG bunker delivery system is to be capable of being rapidly disconnected by the use of dry-break emergency release couplings (ERC) or breakaway couplings or similar protective devices. Breakaway couplings are to operate when exceeding design loads in any direction.
2. This emergency release system is to be designed to prevent damage to the bunkering system components (in particular the risk of surge in the system is to be considered), prevent damage to the ship’s structure, transfer arms or hose handling cranes, be operable under ice formation conditions prevalent during LNG bunkering, prevent spark generation and to operate with minimum release of LNG when activated. Refer also to the requirements for the Emergency Shutdown (ESD) System detailed under 3/17.5 of this Guide.
3. The ERC is to be capable of operation and releasing all bunker transfer lines at all times including immediately following a ship blackout condition.
4. Where the ERC incorporates powered release capability, the system may be connected to the ESD system but is to be only operable under ESD-2 (As applicable, reference should be made to the requirements under relevant standards such as SIGTTO “ESD Arrangements and Linked Ship/Shore Systems for Gas Carriers”) conditions. However, manual activation of this powered emergency release coupling (PERC) is still to be possible. Manual or automatic activation of the PERC is to be inhibited without prior operation of the ESD system. The release system is to incorporate suitable means to prevent accidental operation. Manual or automatic operation of the PERC is to be indicated by the control and monitoring system referenced by 3/17.3 of this Guide.

Communication Equipment

1. Effective internal communication equipment is to be provided between the bunker control station and cargo control station or bridge of the LNG bunkering vessel, as applicable.
2. Two means of voice communication between the LNG bunkering vessel and the receiving ship are to be provided (i. e., main and back up voice communications).
3. Portable communication equipment is to be of a certified safe type.

LNG Piping System. Installed LNG and gas piping is to be in accordance with Section 5C-8-5 of the Steel Vessel Rules.

Inerting System

1. An arrangement for inerting LNG bunkering lines, supply lines and, as applicable, the receiving vessel, with nitrogen or other suitable inert gas is to be provided. The dewpoint of the gas is to be taken into consideration.
2. Where the inert gas is produced onboard then the equipment and arrangements are to be in accordance with 5C-8-9/5 of the Steel Vessel Rules.
3. Inert gas pressure vessels are to be in accordance with Section 4-4-1 of the Steel Vessel Rules.
4. Where an inert gas generator or inert gas pressure vessels are located in a dedicated enclosed space then the space is to be equipped with a mechanical forced ventilation system providing a minimum of 6 air changes per hour.
5. Inert gas piping is not to pass through accommodation spaces, service spaces or control stations.
6. Inert gas generators and storage vessels may be located in machinery spaces provided the space is equipped with oxygen deficiency monitoring equipment and a calculation is submitted to demonstrate that the oxygen concentration will not be below 19 % by volume, even if the total quantity of inert gas is accidently released in the space.

Gas Detection. Gas detection equipment is to be in accordance with 5C-8-13/6 of the Steel Vessel Rules and in addition is to have a permanently installed system of gas detection and audible and visual alarms in the LNG bunkering manifold area. Monitoring and safety shutdowns are to be in accordance Table 1 see below.

Control, Monitoring and ESD Safety Systems

General:

1. The bunkering control and monitoring system may be connected to an integrated control system or be a stand-alone system.
2. A Failure Modes Effects Analysis (FMEA) is to be carried out for the bunkering control system identifying component criticality.
3. The bunkering control and monitoring system design is to meet the single failure criteria (i. e., no single control system component failure or single fault condition is to lead to loss of control of bunkering operations or result in an unsafe situation). For the purpose of the FMEA, any excessive transient surge pressure is to be treated as a single fault. For further guidance on implementing FMEA requirements for classification purposes, refer to the ABS Guidance Notes on Failure Mode and Effects Analysis (FMEA) for Classification.
4. Control of bunkering is to be possible from a safe location in regard to bunkering operations.

Control and Monitoring System

1 Automatic control, alarm and safety functions are to be provided to maintain operations within preset parameters for all LNG bunkering operations. Operation outside the preset parameters or activation of the safety functions is to provide audible and visual alarms in the bunkering control location.

2 The temperatures, pressures, flow rates and functions of the LNG bunkering system are to be controlled as follows:

1. A control and monitoring system is to be provided in the bunkering control location.
2. The design of the control system is to be such as to identify faults in the equipment, as well as the process system. The control and monitoring systems are to comply with the requirements of 4-9-2/3.1 of the Steel Vessel Rules, as applicable
3. Indications of parameters necessary for the safe and effective operation of the process are to be provided, as per Table 1 of this Guide see below.
4. All computer-based control systems are to comply with the applicable requirements of Section 4-9-3 of the Steel Vessel Rules.

3 At the bunkering control location the tank pressure and tank level are to be monitored. Overfill alarm and automatic shutdown are also to be indicated at this location.

4 Local reading manifold pressure gauges and transmitters with isolation valves are to be fitted to indicate the pressure between stop valves and hose connections.

ESD System

1 The LNG bunker transfer system is to be fitted with a linked and compatible emergency shutdown (ESD) system, which is independent from the installed control and monitoring system, to stop bunker flow in the event of an emergency. The ESD system is to be operational during bunker operations and is to be controllable from both the LNG bunker vessel and the receiving ship to enable a safe shut down in the event of an emergency during bunker delivery. The ESD actions are to be coordinated. The bunker transfer ESD system is to be part of the LNG bunkering vessel ESD system.

The ESD function is the controlled cessation of bunker liquid/vapor transfer to or from the vessel upon detection of an unsafe condition. The bunkering process is to be stopped immediately and thereafter LNG will not be transferred. The bunker transfer system of the bunkering vessel as well as that of the receiving vessel will be transferred to a safe static status so that any remedial action can be taken.

The design of the ESD system it to be such as to identify faults in the system and it is to be possible to passively test the ESD system prior to commencing LNG transfer. Refer also to the requirements for the Emergency Release System detailed under 3/9.7 of this Guide.

2 The ESD link is to be established as a pre-requisite to the commencement of LNG transfer operations. Arrangements are to be provided such that transfer of LNG is only to be possible after having established this ESD communication link. This ESD link is to be fail-safe. The purpose of the ship/shore or ship/ship link is to transmit, without delay, a signal from one party to the other.

3 The design of the ESD system is to consider the potential generation of surge pressures within bunker transfer pipe work.

4 The ESD system is to be activated by the manual and automatic inputs listed in Table 1 see below. Any additional inputs are only to be included in the ESD system if it can be shown their inclusion does not reduce the integrity and reliability of the system overall.

5 A functional flow chart of the ESD system and related systems is to be provided at the LNG bunkering control station and cargo control station or bridge, as applicable.

6 One ESD valve is to be provided at each manifold connection. The ESD valve may also be the remote operated valve required by 3/7.7ii) of this Guide.

7 ESD valves are to be arranged in accordance with 5C-8-18/10.2.1 of the Steel Vessel Rules.

8 As a minimum, the ESD system is to be capable of manual operation by a single control at the cargo control station or bridge, the safe control position required by 3/17.1iv) of this Guide and at least two strategic positions around the bunker delivery area.

The monitoring and safety shutdowns for the LNG bunkering system are to be in accordance with Table 1 see below.

Surveys During Construction

General. This Subsection pertains to surveys during fabrication at the manufacturer’s facility and installation and testing of LNG bunkering components, piping and associated systems onboard the vessel. For surveys at the manufacturer’s facility, the scope of the survey will be confined to only those items that are supplied by the manufacturer.

Surveys at Manufacturer’s Facility

Construction and testing of LNG bunkering components and associated piping is to be in accordance with 5C-8-5/8, 5C-8-5/9, 5C-8-5/13 and 5C-8-6/5of the Steel Vessel Rules, as applicable.

Certification of the complete LNG bunkering system cannot be accepted based solely on the ABS Type Approval Program, and therefore ABS Surveyor’s attendance is required during fabrication for unit certification. However, component parts of the unit can be certified in accordance with the ABS Product Quality Assurance (PQA) Certification system outlined in Appendix 1-1-A3 of the ABS Rules for Conditions of Classification (Part 1).

When Surveyor’s attendance at the shop of the manufacturer and at the assembly site is required by the applicable Rules or this Guide, the manufactured/assembled system components will be verified to be satisfactorily in compliance with the aforementioned Rules or Guides.

Surveyor’s attendance is required typically to:

1. Confirm that the facility to manufacture, fabricate or repair LNG bunkering systems or its components does have and maintains a quality-control program effectively covering design, procurement, manufacturing and testing, as applicable, and meeting the requirements of a recognized standard applicable to their product.
2. Qualify or verify welder’s qualifications, welding procedure specifications and corresponding weld procedure qualification records to the extent deemed necessary by the attending Surveyor.
3. Verify material certificates/documentations, particularly for materials of piping, main pressure retaining parts of valves, including safety valves that have flanged or threaded ends or other specialty fittings. Witness of material testing where required by the Steel Vessel Rules.
4. Survey final weldments.
5. Witness, as far as deemed necessary and in accordance with the approved fabrication procedures, weld nondestructive examination tests and to review records of nondestructive examinations.
6. Witness pressure and/or proof-load testing of equipment components and as a unit, as applicable and as called for in the approved fabrication procedures and test plans.
7. Witness testing of subassemblies and completed units as called for in the fabrication procedures.
8. Verify all certified safe systems, motor controllers, consoles and instrumentation and control panels are in compliance with approved drawings.
9. Carry out other inspections and to witness the final Factory Acceptance Test (FAT) as agreed upon during prefabrication meeting.

Surveys During Installation

The following surveys are to be carried out to the satisfaction of the attending Surveyor on the LNG bunkering components, piping and associated systems during installation and testing:

1. Piping systems are to be visually examined and pressure-tested, as required by 5C-8-5/13.2 of the Steel Vessel Rules.
2. Electrical wiring, connections and bonding arrangements are to be in accordance with Part 4, Chapter 8 of the Steel Vessel Rules and checked for continuity and proper workmanship.
3. Instrumentation is to be tested to confirm proper operation as per its predetermined set points.
4. Pressure relief and safety valves are to be tested.
5. Control system, alarms, safety functions and shutdowns are to be tested for proper operation, as noted see above, Table 1 of this Guide.
6. The LNG bunkering systems are to be checked for proper operation.
7. Availability of operation manuals onboard to be verified.

Surveys During Trials. During the initial cryogenic/gas trials, the LNG bunkering components and associated systems are to be confirmed for satisfactory operation, including associated controls, alarms and shutdowns. The tests are to be conducted in accordance with the approved testing procedure during gas trials.

Table below has been prepared for guidance only and annotated to agree with the Steel Vessel Rules, IMO IGC Code and other IMO requirements. The list is not to be considered exhaustive; should additional equipment not listed be fitted onboard, same will be subject to special consideration for compliance with the Steel Vessel Rules, the IGC Code and other IMO requirements. This list is not to be considered as substitutive or integrative of the content of the Steel Vessel Rules and/or other applicable Regulations. In case of conflict between the content of this list and the applicable Steel Vessel Rules and regulations, the latter are to be considered applicable. See also 4-1-1/3 of the Steel Vessel Rules.

Surveys After Construction and Maintenance of Class

General. This Section pertains to periodical surveys after construction for the equipment described see above of this Guide.

Definitions. For definitions related to the surveys of equipment covered by this Guide, see above and 7-1-1/3 of the ABS Rules for Survey After Construction (Part 7).

Read also: Security Zones in LNG Bunkering: A Guide to Meaningful Protection

Modifications. When it is intended to carry out any modifications to the LNG containment or distribution systems and associated components, which may affect classification, including substitutions of material differing from that originally installed, the details of such modifications are to be submitted for review. If ABS determines that the modification will affect classification, the affected system or component to be modified will be subject to the review, testing and survey requirements in accordance with this Guide.

Survey Intervals. Annual, Intermediate and Special Periodical Survey intervals, or survey under the Continuous Survey Program, are to be in accordance with the applicable parts of Sections 7-2-1 and 7-6-2 of the ABS Rules for Survey After Construction (Part 7). Machinery survey based upon Preventative Maintenance Techniques is to be in accordance with 7-6-1/5 of the ABS Rules for Survey After Construction (Part 7).

Surveys. The hull and machinery surveys after construction are to be in accordance with the applicable requirements as contained in 7-3-2/5.11, 7-6-2/1.5, 7-6-2/1.9, 7-6-2/3.3.3, 7-6-2/3.9 and associated references of the ABS Rules for Survey After Construction (Part 7).

Alternative Surveys. ABS is at all times amenable to consider alternative survey arrangements which can be shown, through either satisfactory service experience or a systematic analysis based on sound engineering principles, to meet the overall safety, serviceability and standards of the Steel Vessel Rules and this Guide. Alternative to requirements particularly contained in Subsection 4/5 of this Guide, an In-Service Inspection Plan (ISIP) may be developed by the Owner and submitted to the Assistant Chief Surveyor’s office for review. A stamped copy of the ISIP placed onboard the LNG bunkering vessel is to be referenced during all of the scheduled surveys.