What Are Cryogenic Valves?
As their name suggests, cryogenic valves are designed to be used in very cold applications. They are commonly used by companies that work with Liquefied Natural Gas (LNG) or liquid Nitrogen. For instance, the oil and gas industry frequently uses cryogenic temperature ranges starting at -238 degrees Fahrenheit . Additionally, some gases aren't labeled 'cryogenic' because of their temperature, but rather because they require more than a simple pressure increase to compress their volume. Cryogenic valves are built to help transport and store such cryogenic gases safely and efficiently.
Cryogenic valves differentiate from other standard valves in the modern market due to their ability to be fully functional both in temperatures as low as -320 degrees Fahrenheit and at pressures ranging from low distribution levels to over 3,000+ psi.
How Cryogenic Valves Work
Cryogenic valves can be operated manually or automatically via actuators to control, isolate, or regulate freezing media. To survive extreme thermal contraction, these valves feature extended bonnets (stem extensions). This design moves the stem packing gland away from the freezing liquid, allowing a warm vapor buffer to protect the packing seal from freezing and leaking. Additionally, specialized soft seats or metal-to-metal seals are used to maintain a bubble-tight shutoff even as component metals contract in sub-zero temperatures.
Why Other Valves Can't Cut It
Cryogenic fluids are extremely volatile. Having it leak in an unwanted place can cause severe freeze damage, fire hazards, or costly product loss. Standard valves cannot withstand these extreme temperatures because their internal components and body materials contract at different rates, leading to seat deformation, stem binding, and catastrophic seal failure.
Choosing the Right Cryogenic Valves
Five types of valves are ideal for cryogenic media. Each of these types has its own set of characteristics that make them suitable in some applications and unsuitable in others.
- Globe Valves. Called such due to their spherical shape, these valves have an internal movable disc that moves up and down. These cryogenic valves offer greater reliability for long-term sealing performance but are susceptible to moisture and aren't good in situations where flow rate is paramount.
- Ball Valves. These valves utilize a ball and generally include a PTFE body seat. They have better flow characteristics than globe valves but are more prone to wear and tear along their seals and the ball itself. They also have an upstream cavity relief hole to prevent explosive over-pressurization. Cryogenic ball valves are most valuable in applications in which an unrestricted flow path is necessary.
- Top Entry Ball Valves. Similar to standard ball cryogenic valves, this newer model has a one-piece design with butt-welded connections that makes maintenance easy. The lack of mechanical joints also makes it a preferred option in fire-safe applications.
- Gate Valves. Gate valves utilize a wedge-type gate that moves linearly to reach the mating body seat. They're similar to ball valves in that they offer good flow characteristics but are hampered by wear and tear.
- Butterfly Valves. Butterfly valves are a part of the quarter-turn family and utilize a circular disk at their center. This disc allows butterfly cryogenic valves to be shorter in length than the aforementioned choices, making them lighter and cheaper as well as quick and simple to operate. But over-use leads to their shorter lifespan.
Conclusion
Cryogenic valves are not the same as standard valves and have specific design features that allow them to successfully function at cryogenic temperatures. If you're in the market for cryogenic valve solutions for your design, you've come to the right place. Contact ValveMan today and let our experts help you find the answers you need!
