Overview
ISO 16259:2025 - Ships and marine technology - Performance test procedures of LNG BOG re-liquefaction system on board a ship defines standardized test requirements and procedures to verify the mechanical performance of onboard liquefied natural gas (LNG) boil-off gas (BOG) re-liquefaction systems. Applicable to LNG carriers, LNG bunkering vessels and LNG-fuelled ships, the standard is intended for both factory acceptance and on-board tests. It establishes an objective, commonly accepted test method for stakeholders while excluding manufacturer‑specific functions and any extra client‑requested tests.
Key topics and technical requirements
- Scope and applicability
- Verifies mechanical features of LNG BOG re-liquefaction systems used to liquefy BOG and reduce fuel consumption and emissions.
- Excludes manufacturer‑specific functions and client‑specific additional tests.
- Test fluids
- LNG is the principal test medium. Substitutes (e.g., liquefied nitrogen) may be used when LNG is impractical, with correction factors applied per ISO 6976.
- Inspection and tests (examples included in Annex A)
- Design appraisal - drawings and approvals from classification society or flag administration (see Annex B).
- Equipment safety function testing - alarms, emergency shutdown (ESDS), valves and safety devices at ambient and minimum working temperatures; review of FMECA and accessory certificates (PSV, gas detectors).
- Hydrostatic (or pneumatic) testing - connecting components (casings, flanges) tested at not less than 1.5× design pressure (pneumatic alternative 1.3×); pressure held for at least 30 minutes to check for leakage or deformation.
- Cryogenic function tests, emergency shutdown tests, performance tests at cryogenic conditions, instrument signal inspection, and visual inspection.
- Deliverables
- Marking requirements and comprehensive test reports (samples in Annex C).
- Informative annexes
- Annex A–E: inspection procedure, document list for design appraisal, sample test report forms, system concept models (including FGSS interaction), and natural gas composition examples.
Practical applications
- Standardizes how to assess and document the mechanical performance of LNG BOG re-liquefaction systems for:
- Factory acceptance testing (FAT)
- On-board commissioning and performance verification
- Contractual acceptance between ship owners and equipment providers
- Helps reduce disputes, supports classification society approval, and promotes system reliability and marine GHG reduction.
Who should use this standard
- Ship owners and operators of LNG carriers, bunkering and LNG‑fuelled vessels
- Equipment manufacturers and system integrators
- Shipyards performing installation and commissioning
- Classification societies and flag administrations
- Naval architects and marine systems engineers
Related standards and references
- IMO IGF Code, IMO IGC Code
- ISO 6976 (gas properties/corrections)
- IACS requirements and national flag administration regulations
- ASME BPVC (referenced abbreviated term in document)
Keywords: ISO 16259:2025, LNG BOG re-liquefaction system, performance test procedures, boil-off gas, hydrostatic test, cryogenic test, LNG ships, on-board tests.