In industries such as LNG, hydrogen, and air separation, equipment must operate reliably at temperatures as low as −196°C. Standard industrial valves cannot maintain toughness or sealing performance under such extreme conditions. This is where cryogenic valves—including LNG valves, low temperature valves, cryogenic ball valves, cryogenic gate valves, and cryogenic globe valves—play a crucial role.

Cryogenic valves are engineered for extreme cryogenic applications, ensuring safe flow control, minimal leakage, and long-term reliability inside critical piping systems. This guide explains what cryogenic valves are, how they work, key valves design features, and why materials such as stainless steel are essential for low-temperature service.

1. What Are Cryogenic Valves?

Cryogenic valves are highly engineered industrial valves designed to operate at temperatures typically ranging from −50°C down to −196°C, the boiling point of liquid nitrogen. These valves ensure stable operation and safe isolation of liquefied gases.

Cryogenic valves are widely used in:

• LNG terminals and LNG storage tanks
• Air separation units (LOX, LIN, LAR systems)
• Hydrogen production and fueling systems
• Chemical and petrochemical low-temperature processes
• Cryogenic pump and compressor protection systems

Because cryogenic media expands rapidly during vaporization, even minor leakage can lead to safety hazards. This is why cryogenic valves must withstand extreme thermal shock and deliver high sealing integrity.

2. Why −196°C Matters: Extreme Operating Conditions

At −196°C, most metals lose ductility and become brittle. Sealing materials may harden, deform, or crack. To overcome these challenges, cryogenic valves must provide:

Material toughness at −196°C

Cryogenic valves typically use stainless steel (304, 316, 316L) because it maintains:

• High impact resistance
• Structural integrity
• Corrosion resistance
• Anti-brittle performance

Carbon steel, by contrast, becomes fragile below −60°C and is not suitable for cryogenic service.

3. Extended Bonnet / Extended Stem Design

One of the most distinctive features of cryogenic valves is the extended bonnet (also known as an extended stem).

Why an Extended Bonnet Is Necessary

The extended bonnet ensures:

• The packing gland stays above the cold zone
• Heat transfer reduces the chance of packing freezing
• Valve operation remains smooth
• Ice formation around the stem is minimized

This special valves design is essential for:

• LNG pipelines
• Vertical cryogenic tanks
• LOX/LIN/LAR gas lines
• Hydrogen temperature control systems

Without the extended stem, valve packing would freeze, preventing the operator from opening or closing the valve safely.

4. Critical Leakage Class Requirements

Cryogenic media (LNG, LOX, hydrogen) requires extremely tight sealing to prevent:

• Product loss
• Ice formation
• Oxygen enrichment
• Explosion risks (especially hydrogen)

Cryogenic valves often follow:

• ISO 28921 for cryogenic valve testing
• Leakage Class VI (soft-seated ball valves)
• Class IV–V for metal-seated valves
• Helium mass spectrometer leak detection

Ensuring zero external leakage is a core requirement for safe cryogenic applications.

5. Types of Cryogenic Valves

Cryogenic valves come in multiple valve type categories to meet different process needs.

5.1 Cryogenic Ball Valve

A cryogenic ball valve offers:

• Fast on/off operation
• Excellent sealing
• Minimal pressure drop
• Reliable performance at −196°C

It is widely used in:

• LNG transfer lines
• Hydrogen loading/unloading
• Industrial gas storage tanks

Their robust design allows them to maintain leak-tight performance even after repeated thermal cycling.

5.2 Cryogenic Gate Valves

Cryogenic gate valves provide:

• Full-bore flow when fully open
• Low flow resistance
• High structural stability in large pipelines

These valves are commonly used in:

• LNG plant inlet/outlet lines
• Air separation distribution pipelines
• LOX/LIN/LAR filling stations

They are recommended for systems requiring full open/full close without throttling.

5.3 Cryogenic Globe Valves

Cryogenic globe valves offer precise flow regulation and excellent throttling performance.

They are the preferred choice for:

• Vent lines
• Purge lines
• Bypass piping
• Pressure control systems

In air separation and hydrogen plants, globe valves are essential for accurate flow adjustment.

5.4 Cryogenic Check Valve

A check valve ensures one-way flow, preventing dangerous backflow that can damage:

• Cryogenic pumps
• LNG compressors
• Hydrogen transfer systems

Backflow prevention is critical to maintaining system safety.

6. Why Stainless Steel Is the Preferred Material

Cryogenic valves are typically manufactured from stainless steel because it provides:

• Excellent low-temperature toughness
• High corrosion resistance
• Structural strength at −196°C
• Compatibility with LOX and hydrogen systems

Materials such as Monel, Inconel, and duplex stainless steel may also be used for specialized conditions.

7. How Cryogenic Valves Integrate Into Piping Systems

In cryogenic plants, valves must work seamlessly with insulated piping systems designed to handle:

• Thermal contraction
• Cold shock
• Vaporization effects
• Pressure fluctuations

Cryogenic valves are installed in:

• Transfer lines
• Tank withdrawal lines
• Pump suction systems
• Vapor return lines
• Hydrogen fueling modules

8. Mecco’s Cryogenic Valve Testing Capabilities

To guarantee performance in −196°C environments, Mecco performs rigorous cryogenic testing, including:

Liquid nitrogen immersion tests (−196°C)

Valves are submerged and cycled to evaluate:

• Stem performance
• Sealing integrity
• Material contraction behavior

ISO 28921 cryogenic testing

Ensures valves meet global LNG and hydrogen safety standards.

Helium Leak Detection

Measures internal and external leakage with extremely high sensitivity.

Seat leakage tests (Class IV, V, VI)

Ensures valves meet customer requirements for both soft and metal-seated designs.

Tensile and impact testing for stainless steel materials

These capabilities allow Mecco to supply reliable LNG valves, cryogenic valves, and low temperature valves for global markets.

FAQ: Cryogenic Valves

1. What temperature range do cryogenic valves handle?

Cryogenic valves typically operate from −50°C to −196°C, depending on the application (LNG, LOX, hydrogen, etc.).

2. Why do cryogenic valves need an extended bonnet?

The extended bonnet keeps the packing area warm enough to prevent freezing and ensures smooth valve operation.

3. Which valve type is best for LNG?

Cryogenic ball valves are common in LNG transfer lines due to fast operation and excellent sealing.

4. Do cryogenic valves require special materials?

Yes. Stainless steel (304/316/316L) is the most widely used due to its toughness at low temperatures.

5. What leakage class is required for cryogenic valves?

Many systems require ANSI Class V or Class VI, depending on whether the seat is metal or soft.

6. Are cryogenic gate valves suitable for throttling?

No. Gate valves should be fully open or fully closed. For throttling, choose cryogenic globe valves.

7. What tests must cryogenic valves pass?

Cryogenic testing under −196°C, helium leak test, seat leakage test, and functional cycling.

8. Where are cryogenic check valves used?

They are used to prevent reverse flow in LNG, hydrogen, and industrial gas piping systems.