FACryogenic Valve
Introduction to cryogenic Valve
Cryogenic valve is a valve designed for very cold liquids at low temperatures. Piping systems for transporting liquid hydrogen, oxygen, helium, nitrogen and liquefied natural gas or very cold liquids require the use of cryogenic valves. The term cryogenic refers to materials and processes that operate at minus 1010 degrees Celsius or (-2390 degrees Fahrenheit). Therefore, cryogenic valves, or cryogenic valves, must be designed considering features that can withstand very low temperatures. The main difference between cryogenic valves and standard valves is that they are able to work at low temperatures and high pressures.
The main problem in using cryogenic valves is the leakage of liquids into the atmosphere through the gasket or seal, which reduces the performance of the valve and related equipment. Also, any leakage in the valve stem can cause local ice formation that may cause problems in the valve mechanism. Therefore, cryogenic valves should be designed according to API 598 for high performance and zero leakage.
Regarding cryogenic Valve
The use of cryogenic valves is very important because of their special features, such as developing skills in temperature control, resistance to contraction and expansion at low temperatures, and helping to maintain the stability of the flow of gases and liquids at low temperatures.
Appearance of cryogenic Valve
- Cryogenic valves are generally designed with extended caps, because if the seal is prevented from contacting the cold source, less heat transfer occurs and they maintain their insulating ability.
- In these types of valves, the seal in the valve stem has a relatively higher temperature than its surrounding environment.
- Also, in cryogenic valve design, sufficient space should be considered between the pipeline and the valve lever, in order to create proper insulation.
The size and pressure level of the cryogenic valve
Cryogenic valves or cryogenic valves are complex industrial parts that are produced in different sizes and pressure classes. The precision in the production of these valves has caused that their sizes usually vary from 1/8 inch to 88 inches (3 mm to 2240 mm). On the other hand, the pressure level of cryogenic valves varies from vacuum pressure to 700 bar.
Also, many types of cryogenic valves have the ability to work at temperatures up to -2540 degrees Celsius (-4250 degrees Fahrenheit).
Cryogenic valve type
One of the most important features in the production of cryogenic valves is their gender. To make a cryogenic valve, it is necessary to consider special features in their design and special materials for their production that can withstand very low temperatures.
For this purpose, materials such as aluminum, Monel, brass, bronze, stainless steel, Incoly, zirconium, etc. are used to make these valves. Materials such as PTFE or graphite are also commonly used as sealing materials.
Features of cryogenic valve (refrigerated valve)
1- High efficiency: Cryogenic valves must have high efficiency, because in industrial processes, heat is injected into the system and causes an increase in temperature. Therefore, acceptable efficiency in these valves is of great importance.
2- compatibility with low temperatures: cryogenic valves should be designed and built to work at low temperatures. To deal with volume contractions that occur at low temperatures, these valves are specially designed.
3- Resistance to freezing: At low temperatures, there is a risk of freezing that can close the valves. To avoid this problem, cryogenic valves must be designed to withstand freezing.
4- Materials: Cryogenic valves must be made of materials that can withstand low temperatures. For example, the use of stainless steel and alloys that are more resistant at low temperatures are used in the manufacture of cryogenic valves.
5- Compliance with standards: Cryogenic valves must be compatible with relevant industrial standards. For example, the use of valves that conform to the ANSI/ASME B16.34 standard ensures that these valves have the proper characteristics for use in cryogenic processes.
Important points when buying cryogenic valve
Cryogenic valves are very important in terms of application and are widely used in industries such as food, medicine, alcohol and petroleum. When buying cryogenic valves, it is very important to pay attention to the following points:
1- Choosing the right quality raw materials: High quality and standard raw materials should be used to make cryogenic valve. These materials include stainless steel with high chemical stability, copper, aluminum, etc.
2- Choosing the type of valve: In the market, cryogenic valves are sold in different types. To choose the right type, one should pay attention to factors such as the temperature used, line pressure, flow, and the type of consumables in the purchase process.
3- Ensuring the product standards: To ensure the quality and standard of the product, it is necessary to receive the necessary approvals, including the certificate of the manufacturing company, certificates and industrial standards.
4- Attention to security factors: cryogenic valve may be associated with risks. Therefore, when buying, you should pay attention to security factors such as how to transport, storage temperature, how to store and how to use the valve.
5- Price: Finally, the final price of the product is one of the important points that should be considered when buying a cryogenic valve. Considering the quality and standard of the product, you should check the price carefully and look for the right option with a competitive price.
Common valves for refrigeration applications
Often, the valves that are used for cryogenic applications are special wing valves, butterfly valves, gate valves, and butterfly valves. Therefore, it is necessary to choose the right type of cryogenic valve for the required application. There are no 100% exact instructions for the type of valve in freezing service. But there is a way to choose four-turn ball valves and triple-offset butterfly valves.
Selection of triple offset butterfly valves for freezing services:
Triple butterfly valves are high performance valves that are widely used for refrigeration services. Movement in such valves causes wear between the seat and the seal.
The triple offset design features a flexible stainless steel ring mounted in the disc assembly to create a zero leakage seal for cryogenic applications. The seal and contact surface of the seat is conical. These cones are steep and the contact angle between the seat and the seal creates a slight wedge effect that bends and radially compresses the disc seal ring. Regardless of flow direction or line pressure, the valve provides excellent shut-off capability.
Ball valves for refrigeration applications:
Piping and pipeline systems for LPG, LNG, thermal liquids and liquid oxygen, nitrogen applications use double seal ball valves. They can be reduced and complete. Cryogenic ball valves have a vapor space of sufficient height that allows gasification in the Glendra area. This causes packing of the gland at near ambient temperature.