Overview
ISO 18154:2017 - Ships and marine technology - Safety valve for cargo tanks of LNG carriers - Design and testing requirements - defines design, test and inspection methods for diaphragm-type pilot‑operated safety valves used on cargo tanks of LNG carriers. Its purpose is to ensure that safety valves reliably keep tank pressure below the maximum allowable working pressure, addressing components, materials, production testing, performance (including low‑temperature and vacuum conditions), sizing, marking and sealing.
Keywords: ISO 18154:2017, LNG carrier safety valve, pilot operated safety valve, diaphragm‑type, cargo tanks, pressure relief, performance test, leakage test.
Key topics and requirements
- Scope and definitions: Terms such as set pressure, reseating pressure, blowdown, lift, and theoretical discharge capacity are defined to standardize terminology.
- Main valve components: Requirements and roles for body, nozzle, disk, cover and diaphragm are specified to ensure functional integrity in LNG service.
- Design requirements: Design considerations to ensure safe pressure relief operation under LNG carrier conditions (pilot‑operated, diaphragm actuated).
- Materials: Selection criteria for materials suitable for cryogenic and marine environments are addressed.
- Production testing and inspection:
- Impact testing and non‑destructive inspection
- Pressure testing (including fluid, duration and equipment considerations)
- Surface and visual inspection
- Performance testing:
- Ambient temperature performance and leakage tests
- Low‑temperature performance and leakage tests, with preparation and safety requirements
- Vacuum testing to verify valve behavior under negative tank pressures
- Type testing, sizing and performance determination: Methods to determine discharge capacity and proper sizing for specific tank applications.
- Marking and sealing: Requirements for traceability and tamper evidence after testing/installation.
Applications and who uses it
ISO 18154:2017 is used by:
- Valve manufacturers designing and certifying diaphragm‑type pilot‑operated safety valves for LNG service
- Shipbuilders and marine system integrators specifying relief devices for LNG carrier cargo tanks
- Classification societies and regulatory bodies verifying compliance with cargo containment safety rules
- Marine and offshore engineers, testing laboratories and surveyors conducting production, performance and vacuum tests
Practical uses include selecting and sizing safety valves, performing production and commissioning tests, ensuring cryogenic compatibility and documenting conformity for regulatory acceptance.
Related standards
- ISO 4126‑4 - Safety devices for protection against excessive pressure - Part 4: Pilot operated safety valves
- IMO IGC Code - The International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk
- API STD 527 - Seat Tightness of Pressure Relief Valves
- ASME B16.34 - Valves - Flanged, Threaded and Welding End
ISO 18154:2017 complements these documents by focusing specifically on diaphragm‑type pilot operated safety valves for LNG carrier cargo tanks and the specific testing and inspection regimes required for safe cryogenic maritime service.