Regulations and Guidance for Liquefied Natural Gas Shipping

In today’s industrial and trade landscape, LNG plays an increasingly vital role in the energy sector. However, due to its specific properties and high safety standards, strict adherence to regulations and guidance is paramount.

In this article, we delve into the key aspects of the regulatory environment and guiding documents such as the International Gas Carrier Code (IGC Code), as well as the roles of classification societies and flag states in ensuring the safety of LNG operations.

Reference: SIGTTO “LNG Shipping Suggested Competency Standards”, Sections:

1 Have an awareness of the applicable regulations:

• IGC Code (Reference 1);
• Classification Society Regulations;
• Flag State Regulations;

2 Know the relevant regulatory requirements for containment system and cargo related operations:

• IGC Code (Reference 1);
• Classification Society Regulations;
• Flag State Regulations;
• Code of Safe Working Practices for Merchant Seafarers (Reference 2);

3 Have an awareness of industry and organisational guidance publications available:

• Liquefied Gas Handling Principles on Ships and in Terminals (Reference 3);
• International Safety Guide for Oil Tankers and Terminals (ISGOTT) (Reference 4);
• Tanker Safety Guide – Liquefied Gas (Reference 5);
• Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases (Reference 6);
• Safety Management System;
• Guidance for the Prevention of Rollover in LNG Ships (Reference 7);
• Liquefied Gas Carriers: your personal safety guide (Reference 8);
• Crew Safety Standards and Training for large LNG Carriers (Reference 9).

4 Have an awareness of industry sources of guidance and advice:

• LNG operations in port areas (Reference 10);
• Ship vetting and its application to LNG.
• Liquefied Gas Fire Hazard Management (Reference 11).

IGC Code

The International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) has been mandatory under SOLAS Chapter VII since 1st July 1986. It applies to ships carrying liquefied gases with the characteristics described in the Code (listed in Chapter 19 of the 2016 edition)

The Code includes design and construction standards, and equipment requirements. Gas carriers constructed prior to 1st July 1986 should comply with the requirements of the older Code for the Construction Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) and the Code for Existing Ships Carrying Liquefied Gases in Bulk (EGC Code).

The IGC Code 2016 edition has 183 pages and covers the following areas:

• Chapter 1 – General.
• Chapter 2 – Ship survival capability and location of cargo tanks.
• Chapter 3 – Ship arrangements.
• Chapter 4 – Cargo containment.
• Chapter 5 – Process pressure vessels and liquid, vapour and pressure piping systems.
• Chapter 6 – Materials of construction and quality control.
• Chapter 7 – Cargo pressure/temperature control.
• Chapter 8 – Vent systems for cargo containment.
• Chapter 9 – Cargo containment system atmosphere control.
• Chapter 10 – Electrical installations.
• Chapter 11 – Fire protection and extinction.
• Chapter 12 – Artificial ventilation in the cargo area.
• Chapter 13 – Instrumentation and automation systems.
• Chapter 14 – Personal protection.
• Chapter 15 – Filling limits for cargo tanks.
• Chapter 16 – Use of cargo as fuel.
• Chapter 17 – Special requirements.
• Chapter 18 – Operating requirements.
• Chapter 19 – Summary of minimum requirements.

Recent amendments

Two amendments to the IGC Code entered into force on 1st January 2020. The first of these was approved in November 2016 (Resolution MSC.411(97)) to include new ship and Properties and hazards of shipping LNG, LPGfire integrity arrangements. The other was approved in May 2018 (Resolution MSC.441(99)) to include a revised model form of the Certificate of Fitness.

Classification Societies

Classification Societies are recognised organisations that establish and apply rules and technical standards in relation to the design, construction and survey of marine related facilities, including ships and offshore structures. These are issued by the Classification Society as published rules. A ship that has been designed and built to the appropriate rules of a society may apply for a Certificate of Classification from that society and the society will issue a certificate on completion of the relevant surveys and formalities.

Such a certificate does not imply, and should not be construed as, an express warranty of safety, fitness for purpose or seaworthiness of the ship. The issuance of a certificate by a Classification Society only implies that the ship was in compliance with their standards at the time it was issued. Certificates are subject to periodic renewal following appropriate surveys.

As an independent and self-regulating body, a Classification Society has no commercial interests in the operation of the ship. In establishing its rules, each Classification Society may draw on the advice of members of the industry considered expert in their field. The principal Classification Societies are members of the International Association of Classification Societies (IACS). IACS establishes a set of common rules.

Classification rules are developed to ensure the structural strength and integrity of essential parts of the ship’s hull and its appendages, the reliability and function of the propulsion and steering systems, power generation and other features and auxiliary systems that have been built into the ship to maintain essential services on board.

A ship is maintained in “Class” provided that the relevant rules have, in the opinion of the society concerned, been complied with and that the appropriate surveys have been completed.

Flag State regulations

The role of the flag State is to ensure that its ships comply with the applicable international rules and regulations. Compliance is then enforced when the ship visits other States under what is known as Port State Control (PSC) inspections.

Most flag States ensure that ships comply with the applicable international rules and regulations, largely indirectly through recognised organisations, normally Classification Societies. The requirements of the flag State can be considered to complement the requirements in the IGC Code and Class Societies Rules for the Classification of Ships.

Read also: Safety Precautions and Measures on Gas tankers

• Thermal stress analysis for each cargo containment system/cargo tank and the cargo piping system, taking into account expansion, contraction, ship movement and flexing.
• Dynamic cargo pressure calculations based on hull accelerations at sea, indicating local maximum forces.
• Fatigue stress analysis caused by thermal stress and forces created by dynamic cargo pressures and induced forces from the hull.
• Sloshing calculations based on the impact forces borne by the cargo containment system due to the cargo free surface movement at sea.
• Transverse, longitudinal torsional and hull deflection analysis showing stress levels.
• Local stress analysis for tank domes and their pipe penetrations in addition to pipe supports within the tank and on the cargo deck.
• Any filling restrictions, in any or all of the cargo tanks, must be clearly stated in the ship’s documentation.

IGC Code regulatory requirements for containment systems and cargo related operations

Segregation of the cargo area

Cargo spaces should be located forward of the machinery space. When cargo is carried in a cargo containment system that requires a secondary barrier, the following rules apply:

• At cargo temperatures below minus 10 °C (-10 °C), the hold spaces should be segregated from the sea by a double bottom.
• At cargo temperatures below minus 55 °C (-55 °C), the ship should also have a longitudinal bulkhead forming side tanks (i. e. ballast tanks).

Secondary barrier

Where the cargo temperature at atmospheric pressure is below minus 10 °C (-10 °C), a secondary barrier should be provided to act as temporary containment for any leakage of liquid cargo through the primary barrier.

The secondary barrier should be designed so that it is capable of containing any leakage of LNG for a period of 15 days, unless different requirements apply for particular voyages.

Pipelines

All pipelines or components that can be isolated in a liquid-full condition should be provided with safety relief valves. Safety relief valves discharging liquid cargo from the cargo piping system should discharge back into the cargo tanks. A piping system should be provided to enable each cargo tank to be safely gas freed.

Ship’s cargo hoses

Liquid and vapour hoses used for cargo transfer should be compatible with the cargo and rated for the cargo temperature. Each new type of cargo hose, complete with end fittings, should be tested under cryogenic conditions and certified by a Classification Society.

Vapour return connections

Connections for vapour return lines to the shore installations should be provided. Pipes (seamless and welded), forgings and castings for cargo and process piping should have design temperatures below 0 °C and down to minus 165 °C (-165 °C).

Unless the entire cargo system is designed to withstand the full gauge vapour pressure of the cargo under conditions of the upper ambient design temperatures, maintenance of the cargo tank pressure below the Maximum Allowable Relief Valve Setting (MARVS) should be provided by one or more of the following means:

• A system that regulates the pressure in the cargo tanks by the use of mechanical refrigeration.
• A system where the boil-off vapours are utilised as fuel for shipboard use or a waste heat system. This system may be used at all times, including while in port and while manouvering, provided that a means of disposing of excess energy is provided, such as a steam dump system or gas combustion unit (GCU).
• A system allowing the product to warm up and increase in pressure. The insulation or cargo tank design pressure, or both, should be adequate to provide a suitable safety margin for the operating time and temperatures envisaged.

Pressure relief system

All cargo tanks should be provided with a pressure relief system appropriate to the design of the cargo containment system and the cargo being carried. Hold spaces, Safety, Risks and Security Aspects in Liquefied Natural Gas Industryinterbarrier spaces, cargo piping and machinery, which may be subject to pressures beyond their design capabilities, should also be provided with a suitable pressure relief system. The pressure relief system should be connected to a vent piping system designed to minimise the possibility of cargo vapour accumulating on the decks or entering accommodation spaces, service spaces, control stations and machinery spaces or other spaces where it may create a hazardous condition. Pressure control systems specified by Chapter 7 of the IGC Code should be independent of the pressure relief systems.

Each cargo tank over 20 m³ should be fitted with at least two pressure relief valves of approximately equal capacity. Pressure relief valves should not be set higher than the vapour pressure that has been used in the design of the tank. Pressure relief valves should be connected to the highest part of the cargo tank above deck level.

Sampling

Enough gas sampling points should be provided, for each cargo tank, to adequately monitor the progress of purging and gas freeing. Gas sampling connections should be fitted with isolating valves and capped above the main deck.

Interbarrier, insulation and hold spaces

These spaces, which are associated with cargo containment systems for flammable gases requiring full secondary barriers, should be inerted with a suitable dry IG and kept inerted with make-up gas provided by a shipboard nitrogen generation system or by shipboard storage (generally liquid N₂ and sufficient for normal consumption for at least 30 days).

Alternatively, the hold spaces may be filled with dry air provided that the ship maintains a stored charge of an IG (e. g. N₂) or is fitted with an IG generation system.

IGG plant. An IG generation plant should be capable of producing IG with an O₂ content that is no greater than 3 % by volume.

Level, pressure and temperature

Each cargo tank should be provided with a method of indicating level, pressure and temperature of the cargo. Pressure gauges and temperature indicating devices should be installed in the liquid and vapour piping systems, in cargo refrigerating installations and in the IG systems.

The secondary barrier should be provided with instrumentation that detects when the primary barrier has failed to be liquid-tight at any location or when liquid cargo is in contact with the secondary barrier at any location. This instrumentation should consist of certified, approved and calibrated gas detecting devices.

Each cargo tank is normally fitted with at least two independent liquid level gauging devices. However, the IGC Code makes provision for a single system provided it is capable of external maintenance. As per the IGC Code 13.3, each cargo tank should be fitted with a high liquid level alarm operating independently of other liquid level indicators.

No cargo tank should be more than 98 % liquid full at the reference temperature, except as permitted by a Flag State, supported by Class, that allows a higher filling limit.

Use of boil-off gas as ship’s fuel. LNG is the only cargo whose vapour or boil-off gas (BOG) may be utilised in machinery spaces such as boilers, IG generators, combustion engines and gas turbines.

Classification Society regulatory requirements for containment systems and cargo related operations

Classification Societies give their support to, and sometimes build on, the requirements detailed in the IGC Code, providing further clarification and occasionally additional requirements.

Classification requirements/containment system. These provide further details and information on:

• Dynamic and sloshing loads within cargo tanks;
• Strength of tank supports;
• Information on the insulation, including the types of compounds, construction and testing;
• Requirements for welded joints;
• Single cargo tank warm-up, inerting, purging, gassing up and cooldown while the other cargo tanks contain LNG or LNG vapour, without requiring the suspension of the burning of BOG. Separation of a single tank from the cargo system should be by two positive methods of isolation, e. g. a double valve or a valve and a spectacle blank.

Classification requirements/piping arrangements. These provide further details and information on:

• Calculations for pipe thickness;
• Calculations for fluid velocity within the pipelines, so that they do not exceed 10 m/s for liquid and 30 m/s for vapour;
• Types of austenitic stainless steel suitable for cryogenic use;
• Provision of sufficient expansion loops or bellows in the liquid and vapour pipeline systems to allow for any thermal expansion and contraction of the pipes and the flexing of the ship. Bellows used in the cargo system should be of the multi-wall type, with flexible elements in the outer layer;
• Pipe joints and welding requirements to allow a sufficient number of flanges for any maintenance of equipment;
• Efficient drainage of marine loading arms (MLAs) and manifolds;
• How cargo liquid lines should encourage self-draining toward tanks;
• Relief valves on liquid pipelines relieving to at least two cargo tanks. Pipeline relief valves are not permitted to relieve to mast risers;
• Relief valves fitted to the outboard end of the liquid manifolds outside the ship’s manifold valves;
• Piping on the deck area outside of the cargo tanks. These should be insulated with rigid, self-extinguishing polyurethane foam or equivalent, suitable for temperatures up to +80 °C and should be covered to prevent ingress of moisture;
• Insulation thickness to limit cargo boil-off generated in the ship’s piping;
• Pipe securing points (anchors) to accommodate thermal and dynamic loading (including surge pressures) that may be induced in the ship’s piping;
• “U” bolts for securing pipelines, which are to be of stainless steel construction;
• Avoidance of metal to metal contact between all pipelines, supports and fittings by using pads, sleeves, etc;
• Provision of supporting evidence for the strength of pipelines and their supports, showing the design is suitable for all conditions of operation;
• Electrical bonding (grounding) of cargo pipelines;
• A requirement that all butt welds in the pipeline system should be 100 % radiographically inspected;
• That pressure testing should be by water ashore and by air or N₂ on board ship;
• That after manufacture and testing, pipes should be internally dried, cleaned and sealed before installation on the ship. After installation they should be blown through with dry air and it is recommended that the main cargo systems are inspected internally by means of a remote controlled camera.

Every safety valve in the ship’s cargo piping system must be supplied by a sing le approved manufacturer and allow for manual operation.

Note: Classification Societies are not the only organisation responsible for ensuring standards on LNGCs. An LNGC may also be liable to inspection or survey by Port State Control, Flag State, OC/MF (SIRE), or even a prospective Charterer (Ship Vetting).

A typical Classification Society survey may include:

1 Examination of all relevant certificates

Examples including:

• Certificate of Fitness;
• Safety construction;
• Safety equipment;
• Load line;
• International Oil Pollution Prevention (IOPP) and other environmental certification;
• Shipboard Oil Pollution Emergency Preparedness (SOPEP);
• Certificate of Class;
• Officers and crew certificates of competency;
• Official log books and records;
• Loading/stability information;
• Safety management certificate (ISM SMC);
• Company’s document of compliance (ISM DoC);
• Inspection of the company’s SMS format;
• On board copies available of the Gas Carrier/IGC Code (Controlled Documents), etc.;

2 Weather decks

From an LNGC perspective, this may include, but not necessarily be confined to, the following areas:

• Cargo tank gas dome sealing integrity;
• Wheelhouse closure and sealing arrangements;
• Accommodation ventilation, with associated controls/recirculation/shutdown provision;
• Integrity of air locks to appropriate cargo/work related spaces;
• Closing arrangements of any special enclosed spaces provided for protection against a major cargo/vapour release;
• Portable ventilation provisions for enclosed space entry;
• Condition of portable/fixed cargo/bunker drip trays;
• Cargo tank level gauging system/records/certificates;
• Cargo tank temperature sensing system/records/certificates;
• Cargo high-high level alarms;
• Cargo high/low pressure alarms;
• Cargo auto high level shut-off systems;
• Manual/automatic cargo emergency shutdown systems for pumps and compressors;
• Cargo/ballast vent arrangements;
• Cargo interbarrier/annular space integrity;
• Cargo space pressure/vacuum relief arrangements with associated alarms/trips;
• Integrity of electrical/electronic equipment in the “Gas Dangerous Zone”.

3 Hull survey (continuous)

This involves a general inspection of the hull, its closing appliances, mooring equipment, etc. From the LNGC perspective this encompasses inspection of the inner hull, cofferdams, duct keels and double bottoms as appropriate. Condition of ballast tank, cofferdam and hold space coatings and sacrificial anodes will all be subject to inspection. For the LNGC “Inner Hull Inspection” (IHI), records are particularly important. Class typically requires that all spaces surrounding the cargo containment system are inspected, with cargo on board, once every 6 months and records regarding their condition should be maintained accordingly.

4 Cargo handling areas

This includes ensuring that such spaces contain only designated equipment/materials and are not used for stowage of extraneous items. It also includes an integrity check of:

• Electrical/electronic fittings;
• Bulkheads and associated penetration sealing arrangements;
• Cargo/vapour piping and associated segregation provision;
• Pumping arrangements, as appropriate;
• Gas detection and sampling equipment, including calibration records;
• Gas detection span/zero calibration gas availability;
• Temperature/pressure indicating systems, with test/calibration records;
• Critical instruments, with associated test/calibration records;
• Condition/operation of associated space ventilation/damper arrangements, with test records, etc.;

5 IG/dry air production systems

This involves a general inspection of plant, atmosphere and production changeover arrangements, associated piping and the integrated automation system (IAS). Again, record keeping is important for equipment testing and provision of a deck operations log and planned maintenance system confirms that production quality, in terms of O₂ and humidity, has been consistently achieved.

6 Protection of personnel

This inspection, from the LNGC perspective, ensures that protective clothing and equipment is provided, with stowage arrangements for all personnel involved in cargo operations, and is in compliance with the IGC Code (Chapter 14). The inspection should also encompass breathing apparatus (BIA) equipment with test/maintenance records and portable gas detection equipment, again with associated test/maintenance records.

7 Fire appliances and records

This involves a complete check of fixed and portable systems and associated test/maintenance records. Typically, fire/smoke detection arrangements will be inspected/tested, the fire main construction/condition checked and proof will be provided by operational test that each fire pump, including the emergency fire pump, can be operated independently so that the required jets of water can be produced simultaneously from different hydrants. Fan flaps, skylights and dampers also undergo inspection with their remote/automatic closure/stop facilities. Again, test/maintenance records are important and must be produced. Fireman’s outfits must also be prepared for inspection.

8 Specific features

Typically, for the LNGC, this includes inspection of the following equipment and the associated control, monitoring and alarm provisions:

• Cargo conditioning equipment;
• Vaporisers (LNG and forcing as applicable);
• Gas heaters;
• Critical cryogenic valves;
• Cargo custody transfer system (primary and secondary);
• Fuel gas burning equipment;
• Swept duct/canopy extraction fans (with auto cut-in and alarm systems);
• Master fuel gas sentinel valve (including associated safety chain);
• Gas compressors (including remote/auto shutdown circuits);
• Independent gas detection system;
• Nitrogen generating plant;
• Gas combustion unit (GCU);
• etc.;

Proof must be given that any equipment used for fuel gas burning, including the fuel gas master sentinel valve, can be remotely closed from within the machinery space. The safety devices fitted to shut off the fuel gas supply from the cargo area in the event of gas leakage, or swept duct/canopy vent system failure, should be tested and logged. The surveyor may also, confirm that any special arrangements noted on the Certificate of Fitness for survival or conditions of damage are in order.

9 Machinery survey (continuous)

This is based on a Class approved planned maintenance system (PMS),which in turn largely depends on condition monitoring (i. e. vibration analysis, performance monitoring, risk based inspection, etc). From an LNGC perspective, this includes gas compressors and air compressors for the N₂ generating plant, etc.

The in-tank fully immersed cargo pumps are removed, according to the survey cycle, during refit for overhaul by a specialist.

Else

Flag State regulatory requirements for containment systems and cargo related operations. These are issued by the maritime administration of the relevant flag State. A guidance document is provided for surveyors when assessing and surveying gas carriers for the issue of Certificates of Fitness.

This document indicates the procedures followed by the flag State’s marine administration in addition to specifying the conditions under which Certificates of Fitness are issued and validated. The instructions, which include internationally agreed interpretations, are not self contained but should be read in conjunction with the IGC Code and other relevant instructions of the marine administration

Liquefied Gas Handling Principles. This textbook, published by the Society of International Gas Tanker and Terminal Operators (SIGTTO),deals with the General Provisions, Rules and Requirements for Safe Carriages of Cargoessafe handling of bulk liquid gases (LNG, LPG and chemical gases) and emphasises the importance of understanding their physical properties in relation to the practical operation of gas handling equipment on ships and at terminals. The book has been written primarily for serving ships’ officers and terminal staff who are responsible for cargo handling operations, but also for personnel who are about to be placed in positions of responsibility for these operations.

The contents cover the syllabus for the IMO Dangerous Cargo Endorsement (Liquefied Gas) as outlined in the IMO Standards of Training, Certification and Watchkeeping convention (STCW).The text is complementary to the ICS “Tanker Safety Guide (Liquefied Gas)” and the IMO Gas Carrier Codes. Where a point regarding ship design requires authoritative interpretation, reference should always be made to the IMO Codes. The importance of the ship/shore interface in relation to the overall safety of cargo handling operations is stressed throughout the text.

ISGOTT. The “International Safety Guide for Oil Tankers and Terminals” (ISGOTT) is the standard reference work on the safe operation of oil tankers and the terminals they serve.

ICS “Tanker Safety Guide – Liquefied Gas”. This publication is to provide those serving on ships carrying liquefied gas cargoes with information on recognised good practice. While the recommendations given may not fully cover every possible situation, they do provide the best general guidance currently available on safe procedures.

The guide deals primarily with operational matters and good practice. It does not make recommendations on the construction of gas ships or their equipment. The data sheets contained in this guide outline the main characteristics of individual cargoes.

Safety Management System (SMS). The function of the safety management system (SMS),which will be company specific, is to develop, implement and maintain a safety and environmental protection policy. It contains instructions and procedures to ensure safe operation of ships and protection of the environment. The SMS defines levels of authority and communication between, and among, shore and shipboard personnel. It establishes procedures for reporting accidents, for nonconformities with the provisions of the ISM Code, and to prepare for and respond to emergency situations and procedures for internal audits and management reviews.

LNG operations in port areas. This document, written for port administration, provides guidance on best practice for managing gas shipping operations within ports, including the profile of risks attached to gas operations.

Ship vetting and its application to LNG. Inspections and vetting carried out by charterers, buyers, terminal operators and sellers has been an integral part of ship operations in both oil tankers and LPG carrier operations for more than 25 years and has improved the operating standards. As LNG ships have tended to operate under long-term contractual arrangements they have not been exposed to vetting.

Recent changes in trading patterns have resulted in short-term freight contracts, involving vessels trading to new ports. As a result charterers, buyers, terminal operators and sellers must be sure that the condition, operation and ownership of the vessels are of an acceptable standard, by applying ship inspection and vetting systems to LNG shipping.

This publication draws on information learned from the oil industry and passes it on to all concerned parties involved in vetting LNG ships. It also contains information about the practices of some individual companies and these examples are purely for guidance only.

Liquefied gas fire hazard management. Brings together, in a single volume, the principles of liquefied gas fire prevention and fire-fighting. It covers a broad spectrum of the liquefied gas industry, including large refrigerated and smaller pressurised storage terminals, ships, cylinder filling plant and road and rail tanker loading racks. The book has been compiled for operational staff, such as plant supervisors and ships’ officers, who are involved in the handling of flammable liquefied gases. It is also of benefit to fire officers and emergency planners who have liquefied gas installations within their jurisdiction, or experience regular road or rail car traffic involving these products in their area.

Cargo operating manual. Chapter 18 of the IGC Code requires that a ship is provided with a copy of the IGC Code and suitably detailed cargo system operating manuals, as approved by the ship’s Administration. The cargo operating manual will set out how trained personnel can safely operate the ship to carry LNG. The content of the manual includes:

• Overall operation of the ship at all stages, including dry-dock, cooldown, warm-up, transfer, sampling, gas freeing, ballasting, tank cleaning, etc;
• The integrated automation system (IAS) and the cargo temperature and pressure control systems;
• Cargo system limitations;
• Nitrogen and IG systems;
• Fire-fighting arrangements;
• Fixed and portable gas detection system;
• Emergency shut down systems and emergency procedures.

The cargo operating manual is a primary source of reference for safe operations. Personnel should ensure they are familiar with and understand its contents, reading it in conjunction with the company SMS procedures, the IGC Code and the applicable cargo safety data sheet (SOS).