What are Cryogenic Valves?

What are Cryogenic Valves?

As its name suggests, cryogenic valves are designed for extremely cold applications. They are most commonly used by companies that work with Liquefied Natural Gas (LNG) or Compressed Natural Gas (CNG). For instance, the oil and gas industry frequently operates at cryogenic temperatures starting at -150°C (-238°F). Additionally, some gases are termed 'cryogenic' not just because of their temperature, but because they require more than a simple pressure increase to compress their volume. Cryogenic valves facilitate the safe and efficient transportation and storage of such cryogenic gases.

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Cryogenic valves are constructed to store these gases safely and perform efficiently during transportation, functioning in pressures up to 52 bar (750 psi) and temperatures as low as -196°C (-320°F).

Working Cryogenic Valves

Cryogenic valves are kept in a naturally closed position to ensure cryogenic gases or other media are secure and safely contained. They are designed to react to high pressure, which pushes the valve into the open position, allowing the gas or media to flow through. The flow will continue until the pressure decreases, at which point the valve will close again using a special metal seat for a bubble-tight shutoff to prevent leaks.

Testing Cryogenic Check Valve

Why Are Other Valves Not Suitable?

Cryogenic gases and media are extremely sensitive. Leaks can cause serious and costly damages, especially as transforming standard temperature gases into cryogens is an expensive process.

Standard valves are unsuitable because they contract and expand at different rates when exposed to extreme temperatures, which can break the seal and cause leaks. These heat gains have long been a problem in the study, transport, and storage of cryogenic gas processing.

Why Do Cryogenic Valves Have an Extended Bonnet?

Ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, and liquefied petroleum are flammable and explosive. They can gasify and expand hundreds of times when the temperature rises. Therefore, cryogenic valves are equipped with an extended bonnet or stem for several reasons:

1. The extended bonnet prevents the stuffing box, crucial in both cryogenic and other valves, from low temperature damage. As temperatures drop, the packing loses elasticity and its ability to prevent leaks. The medium then freezes between the packing and the stem, hindering stem movement and scratching the packing, causing severe leaks. An extended stem ensures the packing remains warm enough, at least above 8°C.
2. The extended structure makes it convenient to wrap the valve with special materials to prevent cold energy loss.
3. Pipes and valves are often installed in a 'cold box,' but the 'long neck' can go through the 'cold box' wall. This makes it easy to dismantle or replace the valve's main parts quickly through the bonnet.

Hence, the valve body and the pipeline are welded together to minimize leaks from the cold box and ensure the valve’s sealing performance.

Types and Differences of Cryogenic Valves

Various shapes and sizes of cryogenic valves are available, suitable for different pressure ranges. Common types include Ball, Butterfly, Gate, Globe, Check, and Relief valves. They can be manual or automatic, essential in large systems.

Cryogenic Ball Valve has a polytetrafluoroethylene body, offering better flow rates than globe valves. They are efficient when a tight seal is needed. However, they can wear around the seals and the ball, making them best for systems with unrestricted flow paths.

Cryogenic Butterfly Valves have a circular disc in the center, giving them a shorter length. They are lightweight, economical, and simple to operate, ideal for systems needing quick opening and closing actions.

Cryogenic Gate Valves have a wedge-shaped gate that closes in line with the body mounting, resulting in minimal pressure drop even when fully open.

Cryogenic Globe Valves have a spherical shape and an internal moving disc that rotates at a 90-degree angle to the body mounting plane, making them effective for long-term sealing. They are not recommended for high flow systems.

Cryogenic Relief Valves protect against overpressure by allowing steam to escape if safety limits are exceeded. Similarly, cryogenic check valves maintain pressure and prevent backflow.

Remark(s) of the Author...

Cavity Relief Ball Valve

Years ago, while working for Shell, I first heard about a Cavity relief ball valve in cryogenic service. But what could it be?

SHELL MESC stipulates a pressure equalizing hole of at least 3 mm in the ball, requiring an automatic way to relieve overpressure. The cryogenic standard BS mentions the same.

The use of self-venting ball seats according to EEMUA 182 specifications is another solution, where the surplus pressure spews out around the ball seat.

Cryogenic gases are very sensitive, and leakage can pose serious risks. Thus, a cryogenic valve is essential for the proper functioning of the system.

Reference(s) for this page:
www.dvsvalve.com
www.evergreenmidwest.com
valveman.com
www.cam-spa.it

A Guide on Cryogenic Valves Applications

What are Cryogenic Valves?

Often used in chemical and LNG (liquefied natural gas) industries, pipelines and valves are involved in the transmission of cryogenic liquids and gases. These are some cryogenic valves applications. Cryogenic valves are specially designed for these conditions. Cryogenic refers to materials and fluids handled below -101°C (-239°F), requiring materials that withstand extreme temperatures.

Cryogenic valves are not only suitable for low temperatures but also for handling fluids under high pressure. Generally, a cryogenic valve can handle fluids at temperatures as low as -320°F and pressures as high as 750 psi.

Features of Cryogenic Valves

Cryogenic valves differ significantly from standard valves used in normal temperatures. Some of their features include:

• They handle temperatures ranging from 37°F to -320°F, varying from one valve to another.
• Cryogenic valves often have long stems to keep the valve stem seal away from the cold fluid.
• They have excellent bubble-tight shutoff features to prevent leakage, as transported fluids are often chemicals that can cause extreme issues if leaked.
• These valves are mainly used in chemical, LNG, CNG, and other oil and gas industries.
• Compared to standard valves, cryogenic valves are lightweight and must be clean and lubricant-free.

How Do Cryogenic Valves Work?

Cryogenic valves store and transport cryogenic liquids and gases like liquid oxygen, liquid hydrogen, liquefied natural gas, and liquefied petroleum. Their operation depends on external pressure. Cryogenic valves are usually kept in a closed position to ensure the media inside does not escape into the atmosphere.

These valves react to increasing pressure by opening, allowing the media to flow. The flow continues until the pressure decreases, at which point the valve closes again.

Design

Cryogenic valves are made from special materials like LCB, LC3, CF8, etc., selected based on the temperature range the valve can withstand. Using inappropriate materials can lead to internal and external leaks, cracks, and other major issues.

The standout design feature of cryogenic valves is the extended stem, which keeps external heat out and the packing gland above 0°C. The stem also prevents parts above the valve's bonnet from freezing.

Impressive Sealing

Cryogenic valves have extreme sealing properties due to the media they carry. Leakage of stored chemicals can cause disastrous consequences as many chemicals are inflammable at higher temperatures.

Gasification is another issue with rising temperatures. If the fluids inside a cryogenic valve gasify, their volume increases significantly, potentially causing a pipeline blast.

Challenges

Improperly designed cryogenic valves can pose extreme risks. External heat, pressure, and other dangers constantly challenge these valves. Therefore, they must be made from quality materials.

Standards and codes for cryogenic valves include BS, MSS SP-134, ISO, and ASME B16.34.

Types of Cryogenic Valves

Not all standard valves can be used as cryogenic valves. Common types include ball, butterfly, globe, and relief valves. Quarter-turn valves are preferred for their tight shut-off capability.

• Cryogenic Ball Valve

Belonging to the quarter-turn family, these valves are excellent for cryogenic fluid transport and storage due to their great flow characteristics and excellent shut-off quality.

• Cryogenic Butterfly Valves

These valves have a shorter length due to the circular disk at the center. They are cheaper, lighter, and provide quick opening and closing actions.

• Cryogenic Globe Valves

These valves have an internal disk that rotates perpendicularly to the seat, offering long-term operation, durability, and long-lasting sealing.

• Cryogenic Gate Valves

These valves have a structure that can be lowered to stop the media flow. They endure with a tight shut-off capability and can be lifted to resume flow.

• Cryogenic Relief Valves

These valves maintain a particular pressure range inside a pipeline and prevent overpressurization, releasing excess pressure when needed.

Common Cryogenic Valves Applications

Cryogenic valves are primarily used in the oil and gas industry, but they are also employed in various other sectors. Some common applications include:

• LNG Plants and Terminals
  Liquefied Natural Gas (LNG) requires cryogenic pipelines and valves due to the risk of vaporizing and expanding under pressure. The right type of cryogenic valve can be chosen based on the requirement.
• Food and Beverage Industry
  Cryogenic valves are widely used in processing food items and beverages transported to and from freezers using cryogenic pipes and valves.
• Chemical and Petrochemical Industry
  These industries often need to transport liquified gases and other chemicals, done using cryogenic valves.
• Aerospace Storage
  Cryogenic valves are common in the aerospace industry, used throughout constructions and turbines.
• Medical Industry
  Cryogenic valves are increasingly used in the medical industry, found in pipelines transmitting gases like oxygen and in storage spaces housing medical instruments.
• Air Separation Plants
  These plants use cryogenic valves in various pressure techniques to separate different gases in the air.

Conclusion

Cryogenic valves have wide-ranging applications, suitable for many industries due to their ability to handle extremely low temperatures and high pressures.

When choosing a cryogenic valve manufacturer, consider the materials used in production and ensure necessary certifications. DomBor is a leading manufacturer, supplying cryogenic valves to various industries for over two decades.

Get in touch with us today and choose the perfect cryogenic solution to meet your needs.