What makes a valve cryogenic-rated and what temperature range do LNG valves cover?
A cryogenic-rated valve is designed and tested to operate at sub-zero temperatures without embrittlement, seat leakage, or stem seal failure. For LNG service, valves must function at −160 °C (the liquefaction temperature of natural gas at atmospheric pressure). Key design differences: (1) extended bonnet — moves the stem seal gland out of the cold zone so packing operates at ambient temperature; (2) materials — ASTM A352 LCB or LCC for −46 °C service, CF8/CF8M stainless for −196 °C; (3) low-temperature Charpy impact testing at the rated MDMT before delivery. Saudi Aramco's Jafurah gas project and LNG facilities in the Kingdom specify cryogenic valves for all service below −29 °C.
What is the difference between ASTM A352 LCB and LCC for cryogenic valve bodies?
Both ASTM A352 LCB and LCC are cast low-temperature carbon steel alloys for valve bodies in sub-zero service. LCB is the common grade for general low-temperature service to −46 °C in gas processing plants. LCC has higher tensile strength (minimum 485 MPa vs 450 MPa for LCB) and is preferred in higher-pressure designs or where wall strength margins matter. Both require Charpy V-notch impact tests at −46 °C. For true LNG temperatures (−160 °C), neither grade is suitable — austenitic stainless such as CF8 (304 SS equivalent) or CF8M (316 SS equivalent) is specified because austenite retains ductility down to −196 °C. Gulf Union Ozone stocks both LCB and LCC gate and globe valves in Class 150 through 900, and CF8M ball valves for LNG temperatures.
Are cryogenic valves used on Saudi Aramco projects SAEP-347 compatible?
Yes. SAEP-347 Annex 4 includes material numbers for low-temperature and cryogenic service valves — ASTM A352 LCB and LCC gate valves in Class 150 through Class 900, and CF8M stainless gate and globe valves for deep cryogenic applications. For Saudi Aramco projects involving NGL extraction, gas processing, or LNG facilities, the procurement engineer specifies the SAEP-347 material number in the valve data sheet. Gulf Union Ozone supplies cryogenic valves with full SAEP-347 documentation packages including impact test reports, PMI results for stainless valves, and fire test certificates where required.
What types of cryogenic valves are available — gate, globe, or ball?
All three types are used in LNG and cryogenic service, each for different functions. Gate valves (ASME B16.34, BS EN 13709) are the primary on/off isolation valve in cryogenic lines — extended bonnet designs move the gland above the cold zone. Globe valves with extended bonnets are used for throttling and flow control in cryogenic lines, typically NPS ½ to 4 where precise regulation is needed. Ball valves (API 6D, BS EN 13709) in CF8M with cryogenic-tested PTFE seats are used for isolation in LNG transfer lines — top-entry designs allow seat replacement without removing the valve from the pipeline. Gulf Union Ozone stocks LCB/LCC gate and globe valves (Class 150–900) and CF8M ball valves from Jeddah, with other types and sizes available to order.
