IMSML Website Article 3/2026: Resolution MSC.551(108) – Amendments to the International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels (IGF Code)
These amendments to the IGF Code deal with suction wells for fuel tanks below the lowermost boundary of tank and discharge from pressure relief valves. The IGF Code amendments also contain updated requirements for hazardous zone radius for fuel tanks vent mast outlet. The IGF Code amendments came into force earlier this month on 1 January 2026.
Note that the IGF Code is mandatory under Chapters II-1 and II-2 of the International Convention for the Safety of Life at Sea, 1974.
What is the Meaning of Ships Constructed on or after 1 January 2026?
First, it is for building contracts placed on or after 1 January 2026. Second, if there was no building contracts placed, it then means the keels of which are laid or which are at a similar stage of construction on or after 1 July 2026. Third, it refers to the delivery of which is on or after 1 January 2030.
Must Risk Assessment be Conducted?
YES, see Paragraph 4.2.2.
PART A-1: Specific Requirements for Ships Using Natural Gas as Fuel
Ship Design and Arrangement
How are Protective Distance for Independent Tanks Measured?
It is measured to the tank shell (the primary barrier of the fuel containment system), see new Paragraph 5.3.3.3.
How are Similar Measurements Made for the Membrane Tanks?
The distance is measured to the bulkheads surrounding the tank insulation, see new Paragraph. 5.3.4.4.
How are Airlocks Regulated for Ships Constructed on or After 1 January 2026?
A new Paragraph 5.12.1 is applicable for ships constructed on or after 1 January 2026. First, it regulates air locks enclose by gas tight bulkheads with two substantially gas tight doors spaced at least 1.5m, and not more than 2.5m apart. Second, the sill height of the door leading to the hazardous area shall not be less than 300mm, unless subject to the requirements of the International Convention on Load Line. Third, the doors shall be self-closing without any holding back arrangements.
Fuel Containment System
How are the Tanks Designed?
There is a mathematical formula in Paragraph 6.4.15.3.1.2 which has to be followed for Type C independent tanks. It designates the minimum vapour pressure. It takes into account the following:
[1] Primary and dynamic membrane stress;
[2] Height, width, length of tank;
[3] Relative density of the fuel at design temperature.
Regulations for Pressure Relief System
How is the Sizing of the Pressure Relieve System Determined?
Paragraph 6.7.3.1.1 deals with the sizing of pressure relief valves (PRV). It is applicable to ships constructed on or after 1 January 2026. First, regardless of the state of any one PRV, the capacity of the residual PRV must meet the combined relieving capacity requirements of the system. Second, the combined relieving capacity shall be greater of the following, with no more than 20 percent rise in liquefied gas fuel tank pressure above the MARVS (note, the acronym refers to the ‘maximum allowable valve setting’ for ships carrying liquefied gas. It is the highest pressure a cargo tank can safely withstand before a relief valve opens to prevent over-pressurisation). Third, the tank shall not be loaded until the full relieving capacity is restored.
A new Paragraph 6.7.3.1.1.2 now provides for vapours generated under fire exposure. First, it takes into account the minimum required rate of discharge of air at standard conditions. Second, it accounts for fire exposure factor for different liquefied gas fuel tank types, for example, even for tanks without insulation located on deck.
Regulations for Maintaining of Fuel Storage Condition
How is Tank Pressure and Temperature Controlled?
There is a new Paragraph 6.9.1.1 for ships constructed on or after 1 January 2026. Liquified gas fuel tank pressure and temperature shall be maintained at all time within their design range by means acceptable to IMO or its national regulators. The exception to this is liquefied gas fuel tanks designed to withstand the full gauge vapour pressure of the fuel under conditions of the upper ambient design temperature.
Material and General Pipe Design
How is General Pipe Design Regulated?
A new Paragraph 7.3.2.1 regulated minimum wall thickness for ships constructed on or after 1 January 2026. It takes into account the following factors:
[1] Theoretical thickness;
[2] Design pressure;
[3] Outside diameter;
[4] Allowable stress;
[5] Efficiency factor, ie for earless pipes and for longitudinally or spirally welded pipes;
[6] Allowance for bending;
[7] Corrosion allowance;
[8] Negative manufacturing tolerance for thickness.
Bunkering
How are Manifolds Regulated?
This is now regulated by a new Paragraph 8.4.1 using the following principles:
[1] Bunkering manifolds shall be designed to withstand the external loads during bunkering;
[2] Connections at the bunkering station shall be arranged in order to achieve a dry disconnected operation;
[3] Dry-disconnect / connect coupling in accordance with or equivalent to acceptable IMO standards, see ISO 21593:2019;
[4] Manual connect coupler or hydraulic connection coupler. Note, this is used to connect the bunker system to the receiving vessel bunkering manifold presentation flange;
[5] A bolted flange to flange assembly.
A new Paragraph 8.4.2 makes provision for the following:
[1] The Ultimate aim is to ensure a dry-disconnect;
[2] Special consideration should be informed by a bunkering arrangement risk assessment;
[3] The aseessment should be conducted at the design stage, taking into consideration dynamic loads at the bunkering manifold (in accordance with recognised standards);
[4] Consideration must also be given to safe operation of the ship and other hazards that may be relevant to the ship during bunkering operations;
[5] Fuel handling shall include documentation that the bunkering arrangement risk assessment was conductd and special consideration was granted under this requirement.
A new Paragraph 8.4.3 also provides for the following:
[1] It is mandatory for the provision of an emergencies release coupler (ERC) / emergency release system (ERS), or its equivalent;
[2] An exception would be to enable a quick physical disconnection ‘dry berak-away’ of the bunker system in an emergency event.
Fuel Supply to Consumers
How is the Redundancy of Fuel Supply Regulated?
A new Paragraph 9.3.1 provides for ships contucted on or after 1 January 2026:
[1] The provisions regulate single fuel installations;
[2] The fuel system shall be arranged with redundancy and segregation;
[3] The system prevents leakage in one system, or failure of one of the fuel essential auxiliaries, thus not leading to an unacceptable loss of power;
[4] Should there be a leakage or failure, IMO may accept a partial reduction in propulsion capability from normal operation (Note, this has to be done in accordance with SOLAS Regulation II-1/26.3).
How do the Regulations on Safety Function of the Gas Supply System Operate?
A new Paragraph 9.4.7 makes the following provisions for ships constructed on or after 1 January 2026:
[1] Applicable where the master gas valve is automatically shut down when the safety system is activated;
[2] Automatic venting of the following is required:
[a] The complete gas supply pipe between the master fuel valve and the double block and bleed valves; AND …
[b] The double block and bleed valves.
A new Paragraph 9.4.8 is applicable to ship constructed on or after 1 January 2026 and provides:
[1] There shall be one manually operated shutdown valve in the the gas supply line to each gas consumer upstream of the double block, AND …
[2] Bleed valves to assure safe isolation during maintenance on the gas consumer.
What is the Regulatory Provision for Fuel Supply to Gas Consumers in Gas-Safe Machinery Spaces?
A new Paragraph 9.6.1.1 contains the following:
[1] Completely enclosed gas fuel piping in gas-safe machinery spaces;
[2] Using double pipe or duct;
[3] Gas fuel piping shall be a double wall piping system with the gas fuel contained in the inner pipe;
[4] The space between the concentric pipes shall be pressured with inert gas at a pressure greater than the gas fuel pressure;
[5] Suitable alarms shall be provided to indicate a loss of inert gas pressure between the pipes.
Are there Regulations for the Design of Ventilated Ducts, Outer Pipe Against Inner Pipe Gas Leakage?
A new Paragraph 9.8.1 is applicable to the following:
[1] Only applicable to ships constructed on or after 1 January 2026;
[2] Applicable for the design pressure of the outer pipe or duct fuel systems;
[3] Not less than the maximum working pressure of the inner pipe.
A new Introductory Part of the Text in Paragraph 9.8.2 provides for:
[1] Applicable to ships on or after 1 January 2026;
[2] Provides an alternative to Paragraph 9.8.1;
[3] The design pressure of the outer pipe or duct shall be taken as the higher of a list.
A new Paragraph 9.8.4 makes provision for the following:
[1] Applicable to ships constructed after 1 January 2026;
[2] Duct shall be pressure tested;
[3] Ability to withstand the expected maximum pressure at the fuel pipe rupture.
Fire Safety
How is Fire Protection Regulated?
There is now a new Paragraph 11.3.1:
[1] Applicable to ships constructed on or after 1 January 2026;
[2] Applicable to fuel preparation rooms;
[3] Applicable due to SOLAS Regulation II-2/9;
[4] Regarded as a machinery space of Category A.
How is Dry Chemical Powder Fire Extinguishing System Regulated?
Provisions of a new Paragraph 11.6.2:
[1] Applicable to other portable fire extinguishers required elsewhere in IMO instruments;
[2] One portable dry powder extinguisher of at least 5 kg capacity shall be located near the bunkering station;
[3] Also applicable to the fuel preparation room;
[4] For ships constructed before 1 January 2026, the portable dry powder extinguisher shall be provided in the fuel preparation room;
[5] The above shall be not later than the first survey on or after 1 January 2026.
Explosions Prevention
What is Hazardous Area Zone 1?
There is a new Paragraph 12.5.2.1:
[1] For ships constructed on or after 1 January 2026;
[2] Applicable to tank connection spaces; AND …
[3] Fuel storages hold spaces.
Control, Monitoring and Safety Systems
What are Level Indicators for Liquefied Gas Fuel Tanks?
A new Paragraph 15.4.1.3 contains the following:
[1] Applicable to ships on or after 1 January 2026;
[2] Applicable to any of the following types of liquefied gas fuel tank liquid level gauges, could be any of the following types:
[a] Indirect devices. These determine the amount of fuel, eg weighing or in-line flow metering;
[b] Closed devices which do not penetrate the liquefied gas fuel tank. E.g. Devices using radioisotope or ultrasonic devices;
[c] Closed devices which penetrate the liquefied gas fuel tank but form part of a closed system. Note, these keep the gas fuel from being released.
[d] The devices in [c] above are considered tank connections.
[e] If the closed gauging device is not mounted directly onto the tank, it shall be provided with a shut off valve. Note, this shall be located as close as possible to the tank.
PART B-1 - Manufacture, Workmanship and Testing
Welding of Metallic Materials and Non-Destructive Testing of the Fuel Containment System
What Precautions are taken for Production Weld Tests?
There is now a new Paragraph 16.3.5.1:
[1] Generally for all fuel tanks and process pressure vessels;
[2] The exception are membrane tanks;
[3] Production weld tests shall be performed for approximately each 50m of butt-weld joints;
[4] It shall be representative of each weld position;
[5] For secondary barriers, the same type of production tests are required for primary barriers shall be performed;
[6] The exception is that the number of tests may be reduced subject to agreement with IMO or the Regulators;
PART C-1 - Operation
Regulations for Bunkering Operations
What are the responsibilities during bunkering operations?
A new Paragraph 18.4.1.1.1 now provides for the following: The master of the receiving ship (or their representative) and the representative of the bunkering sources (ie the person in charge) shall do the following:
[1] Transfer procedure to be agreed in writing;
[2] Cooling down and gassing up (if necessary);
[3] Min and Max transfer rate at all stages;
[4] Min and Max limiting transfer pressure and temperature;
[5] Bunkering line PRVs settings;
[6] Volume to be transferred.
Thank you for reading IMSML Website Article 3/2026
Stay tuned for the next IMSML Website Article 4/2026: Resolution MSC.552(108) – Amendments to the International Code for the Safe Carriage of Grain in Bulk under Resolution MSC.29(59)
Signing-off for today,
Dr Irwin Ooi Ui Joo, LL.B(Hons.)(Glamorgan); LL.M (Cardiff); Ph.D (Cardiff); CMILT
Professor of Maritime and Transport Law
Faculty of Law
Universiti Teknologi MARA Shah Alam
Selangor, Malaysia
Tuesday, 20 January 2026
Note that I am the corresponding author for the IMSML Website Articles. My official email address is: uijoo310@uitm.edu.my