Valve Applications in LNG (Liquefied Natural Gas) Terminals

Liquefied Natural Gas (LNG) terminals involve the receiving, storing, and regasifying of LNG at temperatures around -162°C (-260°F). Valves in LNG service must operate reliably at cryogenic temperatures, maintain sealing integrity through repeated thermal cycling, and resist material degradation from exposure to cryogenic temperatures. LNG valve applications include loading/unloading valves at the LNG carrier berth, storage tank isolation valves, cryogenic transfer pumps, vaporization systems, and emergency shutdown valves.

Cryogenic Valve Requirements for LNG

Valves for LNG service must meet the design and testing requirements of BS 6364 (Cryogenic Valve Standard) or ISO 28921 (Industrial valves for cryogenic service). The valve body and trim materials must be austenitic stainless steel (ASTM A351 CF8M, ASTM A182 F316) to avoid ductile-to-brittle transition at LNG temperature. The extended bonnet design raises the stuffing box and actuator connection above the cryogenic zone to keep the packing at a temperature where it maintains sealing resilience.

• BS 6364: British standard for cryogenic valves, specifies design and testing

• ISO 28921: international standard for industrial valves in cryogenic service

• Extended bonnet: raises packing above cryogenic zone, minimum 250 mm extension

• Austenitic stainless: CF8M, F316, maintains toughness at -196°C

• Cryogenic test: valve tested at operating temperature with liquid nitrogen

LNG Tank Isolation and Transfer Valves

LNG storage tanks require large-diameter isolation valves (typically 10 to 24 inches) for tank fill, withdrawal, and emergency isolation. These valves are typically cryogenic ball valves with extended bonnets, fire-safe design, and actuator systems qualified for cryogenic service. The valve actuator must operate reliably at ambient temperature while the valve body is at -162°C. Emergency shutdown valves for LNG tanks must close within the specified time (typically 30 seconds or less).

BOG (Boil-Off Gas) Handling Valves

Boil-off gas (BOG) is generated by heat ingress into LNG storage tanks, causing a small percentage of the LNG to vaporize. BOG is typically compressed and either returned to the liquefaction plant, used as fuel gas, or re-condensed and returned to the tank. Valves in BOG service handle natural gas vapor at low temperature and must be suitable for both cryogenic and ambient temperature operation.