Liquefied Gases and Operational Notes on the IGC Code
Boil-off management uses systems approved for ship and cargo; venting is not a routine substitute for reliquefaction. MSC.523(106) has been in force since 1 January 2026, while the MSC 111 IGC package awaits formal adoption.
Operational Explanation
Pressure control may use reliquefaction, cargo as fuel, thermal oxidation/GCU or pressure accumulation within limits, depending on cargo, Certificate of Fitness and approved manuals. Venting and pressure-relief discharge are protections/means permitted only under Code conditions and approved safeguards, not routine boil-off management.
Regulatory Reference
IGC Code and Certificate of Fitness. MSC.523(106), in force from 1 January 2026, amends chapter 6 on materials, including high-manganese austenitic steel: it is not a new general boil-off management regime. The IGC revision approved at MSC 111 remains distinct from subsequent adoption at MSC 112. The Revised interim recommendations for liquefied hydrogen are now published as MSC.597(111). IMO MSC.597(111).
An inerted tank is not safe for entry: its atmosphere may lack sufficient oxygen. For maintenance or survey apply the required isolation, gas-freeing/ventilation, atmospheric testing, authorization and entry permit, attendance and rescue plan. Do not confuse explosion prevention with a breathable atmosphere. IMO MSC.581(110).
Risks depend on the product and containment system: not every gas carrier carries cargo at cryogenic temperature. Identify the applicable flammability, toxicity, asphyxiation, pressure and low-temperature hazards separately. IMO: IGC materials amendment.
Scope of Application
Gas carriers and cargoes listed/accepted under the IGC Code, Certificate of Fitness, ship systems and approved manuals. Hydrogen interim recommendations are not a general IGC requirement for every unit.
Procedure / How to Complete It
- Identify cargo, containment limits and approved pressure-control systems.
- Operate reliquefaction, use as fuel, GCU/thermal oxidation or pressure accumulation only under manuals.
- On failure apply ship-specific contingency procedure, reduce heat input/pressure by approved means and protect containment.
- Do not use venting or relief discharge as routine substitute; use only within authorised conditions, limits and safeguards.
- Treat MSC.523(106) as in force from 1 January 2026.
- Distinguish the IGC revision approved at MSC 111 from future adoption; for liquefied hydrogen check MSC.597(111) and Administration conditions.
Practical Example
Example: before loading LNG, the crew carries out gradual tank cooldown according to the cooling curve set out in the ship-specific operating manual, checking that the cooling rate does not exceed the structural limits set to avoid thermal-shock fractures.
What Typically Goes Wrong
Listing controlled release as a normal method, ordering venting when reliquefaction fails, describing MSC.523(106) as phased during 2026 or turning MSC 111 approval into adoption/entry into force.
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Tank cooldown carried out too quickly relative to the prescribed cooling curve | Risk of thermal shock and structural damage to the containment system | Strictly follow the gradual cooling curve specified in the ship-specific operating manual |
| Boil-off gas management not continuously monitored during the voyage | Risk of tank overpressure or unnecessary cargo loss | Continuously monitor tank pressure and temperature, not only at scheduled intervals |
| Personnel not specifically trained on the cryogenic characteristics of the cargo carried | Incorrect management of specific emergencies (freezing, cryogenic material embrittlement) | Ensure specialist training for personnel serving on gas carriers, distinct from generic tank-ship training |
| Gas detection systems not periodically calibrated according to manufacturer specifications | False negatives in the event of an actual gas leak, delaying detection of a hazardous condition | Calibrate gas detection systems according to the manufacturer's required schedule, not only after an obvious malfunction |
| Inerted tank mistaken for a space safe to enter | Residual hazardous atmosphere in the tank when personnel enter | Instrumentally verify the tank atmosphere according to the full procedure before any entry, regardless of the expected gas-freeing time |
| Loss of cryogenic insulation not detected promptly, exposing ordinary steel structures to very low temperatures | Risk of brittle fracture of the exposed structure, not designed for cryogenic temperatures | Systematically monitor the integrity of the cryogenic insulation and the temperature of structures adjacent to the containment systems |
What the PSCO Checks
Operational Tips
- Do not generalise chemical tanker procedures to gas carriers: cryogenic temperatures introduce specific risks (material embrittlement, thermal shock) not present when carrying chemical products at ambient temperature.
- Monitor boil-off gas as a continuous operational parameter, not as an occasional check.
- Check that crew training includes specific cryogenic emergency scenarios, distinct from generic firefighting scenarios.
Preparation checklist
- Approved pressure-control means identified
- Failure contingency procedure available
- Venting/relief limited to Code and approved procedures
- MSC.523(106) dated 1 January 2026
- MSC 111 approval separated from MSC 112 adoption
- MSC.597(111) checked for carriage of liquefied hydrogen
FAQ
Related Topics
Last substantive revision of this page: 15 September 2026 · page fingerprint 9908754339c1