Quick Answer
LNG (liquefied natural gas) valves must operate at cryogenic temperatures down to -162°C (-260°F), so they need special materials, extended bonnets, and cryogenic testing. Key requirements include stainless steel bodies, cold-box compatibility, fire-safe design, and compliance with BS 6364 or ISO 28921 cryogenic valve standards.
Why Cryogenic Valves Are Different
At -162°C, ordinary carbon steel becomes brittle, elastomers lose flexibility, and thermal contraction changes clearances. LNG valves are therefore designed with:
- Stainless steel bodies (CF8, CF8M) that stay ductile at cryogenic temperature
- Extended bonnets to keep the packing area at a workable temperature
- Cryogenic-compatible seats (PTFE, PCTFE, or metal) that seal at low temperature
- Fire-safe designs per API 607 for downstream safety
Key Standards for LNG Valves
| Standard | Scope |
|---|---|
| BS 6364 | Specification for valves for cryogenic service |
| ISO 28921 | Industrial valves — isolating valves for low-temperature service |
| API 6D / ASME B16.34 | Design and ratings |
| API 607 | Fire-safe testing |
Common Valve Types in LNG Plants
- Cryogenic ball valves — main process isolation (top-entry designs for easy maintenance)
- Globe valves — control and throttling
- Check valves — compressor discharge and pump protection
- Butterfly valves — large low-pressure lines
Selection Checklist
- Specify the design temperature (usually -196°C for nitrogen, -162°C for LNG)
- Choose stainless steel or other cryogenic-ductile body materials
- Require cryogenic seat materials and extended bonnet design
- Demand cryogenic testing (valve tested at design temperature, not just ambient)
- Verify fire-safe certification where required by the project
Frequently Asked Questions
What temperature rating do LNG valves need?
Most LNG valves are rated to -196°C (-320°F) to cover LNG (-162°C) and liquid nitrogen testing.
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Why do cryogenic valves have long stems?
Extended bonnets keep the stem packing and actuator away from the cold zone so the seal remains effective and icing is minimized.
Can standard ball valves be used for LNG?
No. Standard seats and materials fail at cryogenic temperature. LNG service requires specially designed and cryo-tested valves per BS 6364 or ISO 28921.
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Disclaimer: This article is provided for general educational and informational purposes only and does not constitute professional engineering advice. Valve applications vary with pressure, temperature, media, and applicable codes. Always verify specifications against the manufacturer’s data sheet and consult a qualified engineer before selecting, installing, or repairing any valve. Valve Knowledge Hub makes no warranties about the accuracy or completeness of the information on this site and assumes no liability for any use of it.
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