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What is a cryogenic valve?
The valve suitable for medium temperature -46°C~ -196°C is called cryogenic valve.
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., which are mainly used in ethylene, liquefied natural gas devices, natural gas LPG LNG storage tanks, receiving bases and satellite stations, air separation equipment, petrochemical tail gas separation equipment, liquid oxygen, liquid nitrogen, liquid argon, carbon dioxide cryogenic storage tanks and tankers, pressure swing adsorption oxygen production and other devices. The output liquid cryogenic media such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc., 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 LNG 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. Resulting in a leak in the LNG medium causing an explosion. Therefore, in the process of developing, designing and developing LNG valves, the material is the primary and key issue.
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Cryogenic Valve Standards and Product Structure:
1.设计：API6D、JB/T7749
2. Routine inspection and test of valves: according to API598 standard.
3. Valve low temperature inspection and test: according to JB/T7749.
4. Drive mode: manual, bevel gear transmission and electric drive device.
5. Valve seat form: The valve seat adopts a welded structure, and the sealing surface is welded with cobalt-based cemented carbide to ensure the sealing performance of the valve.
6. The ram adopts an elastic structure, and the pressure relief hole is designed at the inlet end.
7. The valve body of the one-way seal is marked with the flow direction mark.
8. Cryogenic ball valves, gate valves, globe valves, and butterfly valves adopt a long neck structure to protect the packing.
9.超低温球阀标准:JB/T8861-2004
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Cryogenic valve product specifications and design parameters:
1.压力等级:150, 300, 600Lb, 900LB, 1500LB(45MPa)
2. Valve diameter: 15~1200mm(1/2~48").
3. Connection type: flange type, welded type, threaded.
4.阀门材料：LCB, LC3, CF8。
5. Operating temperature: -46°C, -101°C, -196°C, -253°C
6. Applicable medium: LNG, ethylene, propylene, etc.
7. Drive mode: manual, bevel gear transmission, electric.
One of the key issues that must be considered when designing and selecting materials for valves is the operating temperature of the valve. In order to standardize the suitable working temperature of the main material of the valve, the material properties of various types of valve steel and alloy grades have made clear provisions on the suitable working temperature and related requirements of the main material of the valve used in the petrochemical, chemical, fertilizer, electric power and metallurgical industries of the mainland, which are used in the design, manufacture and inspection of valve products. In addition, from the aspects of technical management and production management and material procurement, each type of steel should be selected with good comprehensive performance, and too many steel grades and alloy grades should not be selected to prevent confusion.
Ultra-low temperature valve material selection:
Ultra-low temperature valve ( - 254 (liquid hydrogen) ~ - 101 °C (ethylene) ) The main material must be austenitic stainless steel, copper alloy or aluminum alloy with a cubic lattice, and its low-temperature mechanical properties after heat treatment, especially the low-temperature impact toughness, must meet the requirements of the standard. The following austenitic stainless steels can be used in the manufacture of ultra-low temperature valves. ASTM A351 CF8M, CF3M, CF8, and CF3, ASTM A182F316, F316L, F304, and F304L, and ASTM A433 316, 316L, 304, 304L, and CF8D. The body, bonnet, ram or disc of the ultra-low temperature valve must be cryogenic in liquid nitrogen (-196 °C) before finishing.
Cryogenic valve material selection:
The main materials suitable for cryogenic valves ( - 100~ - 30 °C) are low-temperature austenitic stainless steel and ferritic and martensitic steel for low-temperature pressure parts. Austenitic stainless steels for low temperature use are ASTM A351 CF8M, CF3M, CF8 and CF3, ASTM A182 F316, F316L, F304 and F304L, ASTM A433 316, 316L, 304, 304L and CF8D. Ferritic and martensitic steels for low-temperature pressure parts are ASTM A352 LCA (-32 °C), LCB, LCC (-46 °C), LC1 (-59 °C), LC2, LC211 (-73 °C) and LC3 (-100 °C). The materials in the ASTM A352 standard have a low initial price, but their chemical composition must be smelted according to reliable and very strict factory internal control standards. The heat treatment process is complex, and it needs to be quenched and tempered many times to meet the requirements of the low temperature impact toughness required by the standard, and the production cycle is long. When the low-temperature impact toughness does not meet the standard requirements, it is not allowed to be used as low-temperature steel. Therefore, it is only used when the production batch is large and can be smelted in furnaces, and austenitic stainless steels are generally selected.
When the working medium of the valve is non-corrosive substances such as water, steam, air and oil, carbon steel is generally used. Carbon steel for valves refers to WCB, WCC cast steel, and ASTM A105 forged steel in accordance with ASTM A216. The suitable working temperature of carbon steel for valves is -29~425 °C. However, for the sake of safety, considering that the working temperature of the medium may fluctuate, therefore, the general use temperature of carbon steel should not exceed 400 °C.
The main material of the valve is becoming more and more diversified and highly parameterized. The working medium corresponding to the valve is also more complex, and the working temperature requirements are higher. Understanding the properties of various types of valve steels and alloys and their suitable working temperatures is the knowledge that relevant technical personnel and operators who design, manufacture, purchase and use valves must master. In particular, the use temperature of the material should not exceed its suitable working temperature, otherwise it will cause a terrible serious accident.