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) has been in force since 1 January 2026. Draft IGC amendments were approved at MSC 111 subject to formal adoption at MSC 112; an anticipated date is not yet legally fixed. MSC 111 adopted a new consolidated version of the liquefied-hydrogen interim recommendations, but no number appears in the current official index and none is invented here.
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.
- Treat the MSC 111 package as approved pending MSC 112 adoption and the hydrogen recommendations as an adopted interim outcome without an available official number.
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 |
| Tank gas-freeing and inerting procedure not correctly completed before entry for maintenance or survey | 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
- No invented number for new hydrogen resolution
FAQ
Related Topics
Last substantive revision of this page: 31 August 2026 · page fingerprint 840118495052