Cryogenic valves are among the most technically demanding valve categories in industrial use. Operating at temperatures as low as -196°C, they require specialized material selections, unique design features like extended bonnets, and rigorous low-temperature testing — all governed by standards including BS 6364, API 6D, and ASME B31.3.
This guide covers everything engineers and procurement teams need to know when specifying or sourcing cryogenic valves for LNG, liquid nitrogen, liquid oxygen, or other low-temperature service applications.
1. What Qualifies as "Cryogenic" Service?
In valve engineering, cryogenic service refers to operating temperatures below -50°C. The most common cryogenic temperature ranges encountered in industry are:
| Service / Fluid | Operating Temperature | Notes |
|---|---|---|
| LNG (Liquefied Natural Gas) | -162°C (-260°F) | Most common LNG terminal service |
| Liquid Nitrogen (LN₂) | -196°C (-321°F) | Lowest common industrial cryogenic temp |
| Liquid Oxygen (LOX) | -183°C (-297°F) | Requires oxygen-clean service valves |
| Liquid Argon (LAr) | -186°C (-303°F) | Air separation plant service |
| Ethylene | -104°C (-155°F) | Petrochemical refrigeration service |
| LPG / Propane (refrigerated) | -50°C (-58°F) | Low-temperature carbon steel suitable |
2. Key Design Features of Cryogenic Valves
2.1 Extended Bonnet (Cold Box Extension)
The most visible distinguishing feature of a cryogenic valve is its elongated bonnet — also called a cold box extension or neck. The extended bonnet serves several critical functions:
- Temperature gradient: Creates a warm zone where the stem packing operates near ambient temperature, preventing packing embrittlement
- Personnel protection: Keeps actuators and handwheels at a safe temperature for operator contact
- Ice formation prevention: Reduces moisture condensation at the packing gland
- Actuator compatibility: Ensures electric or pneumatic actuators operate within their rated temperature range
The minimum bonnet length is calculated based on the service temperature and valve size, per BS 6364 requirements. For LNG service at -162°C, bonnet lengths of 150mm to 600mm are typical depending on valve size.
2.2 PTFE / Nylon Seats
Standard elastomeric seats (NBR, EPDM, Viton) become hard and brittle at cryogenic temperatures, losing their sealing ability. Cryogenic valves use:
- PTFE (Teflon) seats: Maintain flexibility down to -200°C, the most common choice
- Nylon seats: Acceptable to -80°C, suitable for less extreme cryogenic service
- Metal seats: For cryogenic service where fire safety or particle contamination of soft seats is a concern
2.3 No Cavity Trapping
A critical design consideration for cryogenic ball valves is the risk of cavity lock-up. When a ball valve is closed with cryogenic liquid trapped in the ball cavity, the liquid may warm up and expand — building up pressure that can damage seats or body. Cryogenic ball valves use one of two solutions:
- Self-relieving seats: Seats designed to vent excess cavity pressure back into the inlet
- Body cavity vent (bleed hole): A small hole in the ball that connects the cavity to the inlet bore, preventing pressure lock-up
3. Material Selection for Cryogenic Service
| Material | Min. Temperature | Typical Use |
|---|---|---|
| CF8M (SS 316 casting) | -196°C | LNG, liquid nitrogen, cryogenic ball/gate valves |
| CF8 (SS 304 casting) | -196°C | LNG, cryogenic applications |
| A182 F316 (SS 316 forging) | -196°C | Forged cryogenic valves, small sizes |
| LCC (Low Temp Carbon Steel) | -50°C | Refrigerated LPG, propane, sub-zero gas service |
| LCB (Low Temp Carbon Steel) | -46°C | Light cryogenic applications |
| 9% Nickel Steel | -196°C | LNG storage tanks, large bore cryogenic |
| Hastelloy C276 | -196°C | Corrosive cryogenic media |
4. Applicable Standards for Cryogenic Valves
- BS 6364 — The primary standard for cryogenic valves. Covers design, testing, materials, and marking requirements. Specifies low-temperature tests at design temperature
- API 6D — For cryogenic pipeline valves. Requires low-temperature shell and seat tests at the design temperature
- ASME B16.34 — Pressure-temperature ratings for valves (all materials including cryogenic grades)
- MSS SP-134 — Valves for cryogenic service including design, material, and testing requirements
- ASME B31.3 — Process piping code governing the design of cryogenic piping systems
5. Cryogenic Valve Testing Requirements
Beyond standard hydrostatic testing per API 598, cryogenic valves undergo additional qualification tests:
- Low-temperature body test: Shell hydro test with the valve body cooled to design temperature using liquid nitrogen immersion
- Low-temperature seat test: Seat leakage test at design temperature — both with valve body cooled
- Operational test: Full open/close cycles at design temperature to confirm operability (no ice-seizing, no stem freeze-up)
- Extended bonnet warm zone test: Confirmation that bonnet temperature remains above the packing's minimum rated temperature
6. LNG Industry Applications
LNG (Liquefied Natural Gas) facilities require cryogenic valves at every stage of the value chain:
| LNG Facility Area | Valve Type | Key Requirements |
|---|---|---|
| Liquefaction trains | Cryogenic ball valves, gate valves | SS 316 body, PTFE seats, BS 6364 tested |
| LNG storage tanks (in-tank) | Cryogenic ball valves, safety valves | -196°C rating, extended bonnet, fire-safe |
| LNG loading arms | Ball valves, butterfly valves | Quick-connect, fire-safe, top entry |
| LNG regasification | Control valves, check valves | Flow control at cryogenic temps |
| BOG (Boil-Off Gas) systems | Gate valves, globe valves | Low-temp rating, tight shut-off |
7. Novel Valves Cryogenic Valve Range
Novel Valves India Pvt. Ltd. manufactures a comprehensive range of cryogenic valves for LNG and low-temperature industrial service:
- Cryogenic Ball Valves: Trunnion-mounted and floating, -196°C service, extended bonnet, PTFE seats, BS 6364 tested. Sizes ½" to 24", classes 150# to 2500#
- Cryogenic Gate Valves: Bolted bonnet and pressure seal designs, extended bonnet, -196°C service
- Cryogenic Globe Valves: Angle and straight pattern for flow control in cryogenic service
- Cryogenic Check Valves: Swing and dual-plate designs for low-temperature gas/LNG service
Need cryogenic valves for your LNG or low-temperature project? Our team specializes in cryogenic valve specifications and can provide BS 6364-tested, API 6D-certified cryogenic ball valves and gate valves for your exact service conditions.
Request Cryogenic Valve Quote