Question 1

What makes a valve cryogenic-rated and what temperature range do LNG valves cover?

Accepted Answer

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 from standard valves: (1) extended bonnet — moves the stem seal gland out of the cold zone so packing operates at ambient temperature, preventing frost from forming on the seal and maintaining consistent gland pressure; (2) materials — bodies and bonnets in ASTM A352 LCB or LCC (to −46 °C), A351 CF8/CF8M austenitic stainless steel (to −196 °C), or ASTM A333 Gr.6 carbon steel pipe-bore designs; (3) seat materials — PTFE or stainless overlays suitable for cryogenic temperatures; (4) low-temperature impact testing — Charpy impact tests at −46 °C or −196 °C depending on design classification. Saudi Aramco's Jafurah gas development and LNG terminal projects in the Kingdom specify cryogenic-rated valves wherever gas is liquefied, stored, or transported at temperatures below −29 °C.

Question 2

What is the difference between ASTM A352 LCB and LCC for cryogenic valve bodies?

Accepted Answer

Both ASTM A352 LCB and LCC are cast low-temperature carbon steel alloys used for valve bodies in sub-zero service. LCB (Mn-C-Si) is rated to −46 °C and is the most common material for general low-temperature service in gas processing plants operating in the −29 °C to −46 °C range. LCC (Mn-C-Si-Mo) has higher tensile strength (minimum 485 MPa vs 450 MPa for LCB) and slightly better low-temperature toughness — also rated to −46 °C but preferred in higher-pressure designs or where pressure class demands greater wall strength. For true LNG temperatures (−160 °C), neither LCB nor LCC is suitable. Austenitic stainless steels such as ASTM A351 CF8 (304 SS equivalent) or CF8M (316 SS equivalent) are specified instead, as austenite retains ductility at cryogenic temperatures down to −196 °C. Gulf Union Ozone stocks LCB and LCC gate and globe valves in Class 150, 300, and 600, and CF8M ball valves for deeper cryogenic service.

Question 3

Are cryogenic valves used on Saudi Aramco projects SAEP-347 compatible?

Accepted Answer

Yes. SAEP-347 includes material numbers for low-temperature and cryogenic service valves. The Annex 4 material tables cover 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 will specify the SAEP-347 material number in the valve data sheet — and the supplier must provide EN 10204 3.1 Mill Test Certificates tracing the chemistry and mechanical properties (including Charpy impact results at the rated minimum temperature). 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.

Question 4

What types of cryogenic valves are available — gate, globe, or ball?

Accepted Answer

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 service. Extended bonnet designs allow the stem seal to operate at ambient temperature. Wedge gate or parallel slide designs are available in LCB, LCC, CF8, and CF8M. Globe valves with extended bonnets are used for throttling and flow control in cryogenic lines — typically smaller bore (NPS ½ to 4) where precise flow regulation is needed. Ball valves (API 6D, ASME B16.34) in CF8M with cryogenic-tested PTFE seats are used for isolation in LNG transfer lines. Top-entry designs are preferred in buried or insulated service because they allow seat replacement without removing the valve from the pipeline. Gulf Union Ozone stocks gate and globe valves in LCB/LCC from Class 150 to 600, and CF8M ball valves for cryogenic service from Jeddah — with other types available to order.

نوع الخدمة	درجة الحرارة التصميمية الدنيا	المادة
معالجة الغاز منخفض الحرارة	−29 °C to −46 °C	A352 LCB/LCC
استخراج الغاز الطبيعي المسيل	−100 °C	A333 Gr.6 / CF8
LNG service	−160 °C to −196 °C	CF8 / CF8M SS

صمامات التبريد العميق في المملكة العربية السعودية — خدمة الغاز الطبيعي المسال ودرجات الحرارة المنخفضة

ما الذي يجعل الصمام مُقيَّماً للتبريد العميق — الغطاء الممدود ومواد درجات الحرارة المنخفضة

مخزون صمامات التبريد العميق — المواصفات الفنية

الأسئلة الأكثر شيوعاً — صمامات التبريد العميق

اطلب عرض سعر لصمامات التبريد العميق — خدمة الغاز الطبيعي المسال، مخزون في جدة