What is a cryogenic valve, characteristics and material requirements of cryogenic valve?

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

Classified by medium temperature.

High temperature valve – t greater than 450'c.

Medium temperature valve - 120'c is less than t less than 450'c.

Normal temperature valve ——- 40'c is less than t and less than 120'c.

Cryogenic valve ——- 100'c is less than t less than -40'c.

Ultra-low temperature valve – t less than -100'c.

<> cryogenic valves have the following performance characteristics:

1. The bonnet is designed with a long neck structure, which can isolate the influence of low-temperature medium on the packing, prevent the performance of the cap seal from decreasing, and also make the valve open and close flexibly;

2. The filler adopts flexible graphite or PTFE combined structure, which has good low temperature resistance;

3. The cryogenic valve adopts the structure of opening a pressure reducing hole on the valve core. The gasket adopts stainless steel leather clip polyfluorine or flexible graphite winding structure; 4. When the valve is closed, in order to prevent the low-temperature medium in the valve cavity from rising due to the temperature rise, the pressure relief structure is provided on the high-pressure side of the ram or valve body;

5. The sealing surface of the valve is surfacing with cobalt-based cemented carbide, which has small deformation and wear-resistant at low temperature and can maintain good sealing performance. Because the output liquid low-temperature media such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum and other products are not only flammable and explosive, but also gasified when the temperature rises, and the volume expands hundreds of times when gasified. The material of the cryogenic valve is very important, and the unqualified material will cause external or internal leakage of the shell and sealing surface; The comprehensive mechanical properties, strength and stiffness of the parts cannot meet the requirements of use and even break; Caused by leakage of LNG media**.

Therefore, in the process of developing, designing and developing cryogenic valves, material treatment is the primary and key issue.

Cryogenic ball valves have a larger total flow orifice size. Cryogenic ball valves give faster power switching motion and are suitable for storage tank applications, cryopumps, pipelines or low-voltage trolleys. Cryogenic ball valves are available in a variety of sizes with operating temperatures from +120 to -196 tanla.

Cryogenic ball valves are widely used in very low temperature and ultra-low temperature, including but not limited to LNG natural gas, chemical gas, spiritual and steel service sales projects, mining, pharmaceutical industry, wastewater, sewage treatment, carbon dioxide introduction and blending, refrigeration and natural gas applications. There are many kinds of cryogenic ball valves, such as electric cryogenic ball valves, pneumatic cryogenic ball valves, short-shaft pneumatic cryogenic ball valves, etc.

In the ultra-low temperature environment, the metal material will undergo low temperature cold brittleness, that is, the strength and hardness will increase, and the plasticity and toughness will decrease significantly, which will seriously affect the safety of the valve. In order to prevent low-stress brittleness of the material at low temperatures, components such as the valve body and disc are often made of austenitic stainless steel. Such as l l and so on, among which 316l has the best stability.

Austenitic stainless steel has excellent strength, toughness, corrosion resistance and weldability, and a low coefficient of linear expansion. However, impurities such as S and P in austenitic stainless steel will reduce the strength and low-temperature impact toughness of the material, and their content should be strictly controlled.

The valve body, bonnet, disc, seat and stem and other parts of the large-diameter ultra-low temperature valve must be subjected to low-temperature cryogenic treatment to make the austenite converted into martensite and fully deformed before finishing, so as to reduce the influence of temperature on the sealing performance of the ultra-low temperature valve. The low temperature treatment temperature should be lower than the material phase change temperature and lower than the actual operating temperature of the valve. The processing time was 1 2 h, and then it was taken out and cooled to room temperature, and the cycle was repeated twice.

The opening and closing parts of the globe valve are plug-shaped discs, the sealing surface is flat or conical, and the disc moves in a straight line along the center line of the fluid. The movement form of the valve stem has a lifting rod type (the valve stem is lifted, and the handwheel is not lifted), and there is also a lifting and rotating rod type (the handwheel and the valve stem rotate and lift together, and the nut is located on the valve body). The shut-off valve is only suitable for full open and full closing, and is not allowed to be adjusted and throttled.

The globe valve has the following advantages: simple structure, easy to manufacture and maintain.

The working stroke is small, and the opening and closing time is short. The disadvantages of good sealing, small friction between sealing surfaces, and service life compared with globe valves are as follows

The fluid resistance is high, and the force required for opening and closing is high. It is not suitable for media with particles, high viscosity and easy coking. 7 y% |

Poor regulation performance.

The main characteristics of the ball valve are its compact structure, reliable sealing, simple structure, convenient maintenance, the sealing surface and the spherical surface are often in a closed state, not easy to be eroded by the medium, easy to operate and maintain, suitable for water, solvent, acid and natural gas and other general working media, but also suitable for the medium with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene, etc., which are widely used in various industries. The ball valve body can be integral or combined1 The fluid resistance is small, and the full-bore ball valve basically has no flow resistance. Simple structure, small size and light weight.

It is easy to operate, quick to open and close, and only needs to rotate 90° from full open to full closed, which is convenient for long-distance control. It can be used in a wide range of applications, from small to a few millimeters and several meters in diameter, from high vacuum to high pressure. The processing accuracy is high and the cost is expensive.

The shut-off valve is only suitable for full open and full closing, and is not allowed to be adjusted and throttled. The flow direction of the medium enters the valve cavity from the top of the valve disc, and at this time, under the action of the medium pressure, the force of closing the valve is small, and the force of opening the valve is large, and the diameter of the valve stem can be reduced accordingly.

Ball valves are suitable for general working media such as water, solvents, acids and natural gas, but also suitable for media with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene, etc., and are widely used in various industries. The ball valve body can be monolithic or combined.

Cryogenic valves include cryogenic ball valves, cryogenic gate valves, cryogenic globe valves, cryogenic safety valves, cryogenic check valves, cryogenic butterfly valves, cryogenic needle valves, cryogenic throttle valves, cryogenic pressure reducing valves, etc.

Cryogenic valves are suitable for medium temperatures -40 196.