-196 Celsius degree Cryogenic Globe Valves

Description

PETROL STEEL CO.,LTD always adheres to the quality policy of "all for the user", abides by the corporate philosophy of "customer-centered, quality-based survival, technology-based development". The service tenet of "Excellence, Integrity, Integrity and Week", PESCO -196 Celsius degree Cryogenic Globe Valves are committed to becoming one of the most professional cryogenic valve suppliers in China, providing customers with higher quality products, more competitive prices, and faster and more complete services. Continuously improve the quality of products, we are willing to work with users, relying on our honest labor, to carry out extensive and various forms of sincere cooperation to create a brilliant tomorrow for cryogenic valves.

In recent decades, with the development of modern science and technology, the demand for cryogenic valves in engineering projects has increased. PETROL STEEL CO.,LTD's -196 Celsius degree Cryogenic Globe Valves are widely used in fertilizer, LNG and petrochemical fields. Valves suitable for medium temperature -40°C～-250°C are called low temperature valves. Cryogenic valves include cryogenic ball valves, cryogenic solenoid 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, cryogenic electric control valves, cryogenic pneumatic valves Except for liquid nitrogen and other liquid inert gases, most of the media controlled by low-temperature valves such as regulating valves are not only flammable and explosive, but also gasify when heating up or flashing, resulting in rapid volume expansion, which is easy to cause leakage and leakage. explode. Based on the characteristics of the medium and the requirements for the valve to be used at low temperatures, the design, manufacture, test and installation methods of low temperature valves are different from ordinary valves.

1. Standards and definitions of PETROL STEEL CO.,LTD's -196 Celsius degree Cryogenic Globe Valves
Different standards have different definitions for cryogenic valves.
1) British valve standard BS6364 "Valve for low temperature" is suitable for medium temperature range of -50°C~-196°C;
2) The US standard MSSSP-134 "Requirements for Cryogenic Valves and Their Valve Body/Bonnet Extensions" interprets the low temperature as "for standard practice, the low temperature range is between -100 °C ~ -195 °C";
3) The Chinese national standard GB/T 24925 "Technical Conditions for Low Temperature Valves" is applicable to the medium temperature range of -29°C~-196°C;
4) Shell valve standard SHELL MESC SPE 77/200 "Valve for low temperature and ultra-low temperature" is suitable for medium temperature range of -30°C~-196°C.
5) Foreign countries are generally divided into six temperature grades according to the liquefaction temperature of various gases under normal pressure.
Level 1 is 0~ -46°C
Level 2 is -47~-60°C
Level 3 is -61~-70°C
Level 4 is -71~-101°C
Level 5 is -102~-196°C
Level 6 6 is below -253°C

Generally, -46~-150°C is called low temperature, and below -150°C is called ultra-low temperature. The petrochemical industry defines cryogenic valves according to the design temperature of the conveying medium. Generally, the valves used in the medium temperature below -40 °C are called low temperature valves, and the valves used in the medium temperature below -101 °C are called ultra-low temperature valves.

2. Design characteristics of PETROL STEEL CO.,LTD's -196 Celsius degree Cryogenic Globe Valves.
1. Material selection of cryogenic valve
The working medium of the cryogenic valve is not only low in temperature, but also has high permeability, which determines many special requirements for valve materials. The mechanical properties of steel at low temperature are different from those at normal temperature. In addition to strength, the important index of low temperature steel is its low temperature impact toughness. The low temperature impact toughness of the material is related to the brittle transition temperature of the material. The lower the brittle transition temperature of the material, the better the low temperature impact toughness of the material. Metal materials with body-centered cubic lattice such as carbon steel have low temperature cold brittleness, while the impact toughness of metal materials with face-centered cubic lattice such as austenitic stainless steel is basically not affected by low temperature.

The materials of PETROL STEEL CO.,LTD's low temperature valve body, valve cover and other pressure parts are usually made of tough materials with good low temperature strength, and factors such as weldability, machinability, stability and economy must also be considered. When designing, three low temperature grades of -46°C, -101°C and -196°C are commonly used. -46°C low temperature grade generally uses low temperature carbon steel, -101°C and -196°C low temperature grade generally uses 300 series austenitic stainless steel, which has moderate strength, good toughness and good processing performance.

2. Structural design of petrochemical PETROL STEEL CO.,LTD's cryogenic valves
1) Bonnet structure design
A notable feature of -196 Celsius degree Cryogenic Globe Valves is that the bonnet is generally a long-neck structure, and it is also clearly stipulated in GB/T24925 "Technical Conditions for Cryogenic Valves" that "the bonnet of cryogenic gate valves, globe valves, ball valves and butterfly valves should be used according to different applications. The temperature requirements are designed to be a long-neck bonnet structure that is convenient for cold insulation, so as to ensure that the temperature at the bottom of the stuffing box is kept above 0°C.” The design of the extended bonnet structure is mainly to keep the valve operating handle and the stuffing box structure away from the low temperature area, which can not only avoid the frostbite of the operator caused by the temperature too low, but also ensure that the stuffing box and the gland are used at normal temperature to prevent the packing.

The sealing performance is reduced and the service life of the packing is extended. Because in the low temperature state, with the decrease of temperature, the elasticity of the packing gradually disappears, and the leak-proof performance decreases. The packing of the -196 Celsius degree Cryogenic Globe Valves will be scratched, causing serious leakage. Therefore, the low temperature valve must adopt the long-neck bonnet structure. In addition, the long neck structure also facilitates the winding of cold insulation materials to prevent cold energy loss. Since the low temperature pipeline generally has a thicker thickness of the cold insulation layer, the long-neck valve cover is convenient for cold insulation construction, and the packing gland is outside the cold insulation layer, which is conducive to tightening the gland bolts or adding packing at any time when necessary without damaging the cold insulation layer.

Bonnet extensions are specified in BS6364, MSS SP-134 and SHELL MESC SPE77/200 standards. Among them, BS6364 specifies the lengthened dimension of 15～500 with cold box, and stipulates that the minimum length of non-cold box should be 250mm; MSS SP-134 includes the lengthened dimension requirements of 15～300 with cold box and non-cold box, In comparison, the non-cold box extension is longer than the BS6364 specification, and the cold box extension is shorter than the BS6364 specification. SHELL MESC SPE 77/200 does not distinguish between cold box and non-cold box, and specifies the length of 15 to 1200 in different temperature ranges.

Taking into account comprehensively, SHELL MESC SPE 77/200 has a wide range of extended lengths, which is more convenient and reliable to use. If it is used in low-temperature critical occasions, it can be designed with reference to the SHELL MESC SPE 77/200 standard or according to the special length requirements of the design unit. In addition, when selecting the length, it is also necessary to consider whether the thickness of the designed cold insulation layer is greater than the length, if so, it should be lengthened to match the thickness of the cold insulation.

2) Structural design of drip board
Since the transmission in the valve is a low temperature medium, in order to avoid or reduce the transmission of the medium temperature to the filling material at the valve stem and its upper end, and prevent these materials from failing due to freezing, a drip plate structure can be added to the -196 Celsius degree Cryogenic Globe Valves. Some research institutions have carried out experimental verification on the valve with the drip plate structure, and proved that the upper end of the valve cover with the drip plate has a higher temperature. Due to the low temperature of the upper part of the extended valve cover, the valve is usually exposed to the air, and the water vapor in the air will liquefy into water droplets when it encounters the low temperature valve cover. The diameter of the drip plate exceeds the diameter of the middle flange, which can prevent low temperature liquefaction. Water vapor drips on the middle flange bolts to avoid bolt rust from affecting online maintenance. In addition, the drip plate needs to be set on the outside of the cold insulation layer, which can prevent the condensed water droplets from falling on the cold insulation layer and the upper part of the valve body, protect the cold insulation layer and prevent the loss of cooling capacity.

3) Structural design of pressure relief components
For -196 Celsius degree Cryogenic Globe Valves with a closed cavity structure, when used in flammable, explosive and easily vaporized media, there are special requirements for the valve sealing structure. Some low-temperature media will increase in volume after vaporization. For example, the volume of liquefied natural gas after vaporization is more than 600 times that of the liquid state. When the valve is closed and the ambient temperature is relatively high, the low-temperature medium in the valve body absorbs the environment. It is gradually vaporized by medium heat, and its volume rises rapidly, resulting in overpressure inside the valve, even threatening the safety of the valve, causing medium leakage or even a fire accident. The pressure structure enables automatic relief when the pressure in the inner cavity of the valve is abnormally overpressured. Such as low temperature gate valve and ball valve, due to different valve sealing principles, there will be obvious differences in pressure relief design. However, different manufacturers have their own different characteristics in the design of the pressure relief structure.

4) Anti-static and fireproof structure design
Since -196 Celsius degree Cryogenic Globe Valves are generally used in flammable and explosive media, anti-static design and fire protection design are particularly important. The anti-static design mainly uses a current-guiding method similar to a lightning rod to conduct the valve stem and the valve body, so as to export static electricity to eliminate potential safety hazards and ensure the supply safety of the entire system. For example, GB/T24925 clearly stipulates that "for valves with soft valve seats or soft closing inserts used for flammable vapors or liquids, the design should ensure that the valve body and valve stem have electrical continuity, and the large resistance of the discharge path should not exceed 10Ω.”. The design of the fireproof structure is mainly carried out for the problem of medium leakage caused by drastic temperature changes. The design of the fireproof structure is similar to the design requirements of ordinary valves.

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