Design and Material Selection for Low Temperature Valves

 
low temperature valves are indispensable components in the management systems of low-temperature liquid storage and transportation equipment. Low temperature valves are characterized by flexible operation and reliable sealing, making them suitable for a wide range of low-temperature and cryogenic media management systems. Particularly for ultra-low temperature valves, their operating temperatures are extremely low, requiring adherence to a set of special requirements and principles during design and material selection.
 

1. Design Requirements for Low Temperature Valves

 
Long-term Working Capability: Low temperature valves must have the ability to work stably for extended periods in extremely low-temperature media and surrounding environments, ensuring the system's normal operation and safety.
 
Prevention of Heat Source Formation: Valves should not become heat sources in low-temperature systems to prevent heat influx, which may lead to abnormal pressure buildup and safety hazards.
 
Non-interference with Operation and Sealing Performance: Low-temperature media should not adversely affect the handwheel operation and packing sealing performance of valves, ensuring their reliability and stability.
 
Explosion-proof and Fireproof Design: Valve assembly components directly in contact with low-temperature media should possess explosion-proof and fireproof structures to address potential safety risks.
 
Friction Prevention Measures: Since lubrication is ineffective at low temperatures, special structural measures, such as surface treatments, are needed to prevent frictional damage to valve components.
 

2. Material Selection for Low Temperature Valves

 
Selection of Main Materials: Material selection for valve bodies needs to consider metallurgical factors. For instance, ordinary steels exhibit low-temperature brittleness at low temperatures, necessitating the use of materials with excellent low-temperature properties, such as nickel-containing steels and austenitic stainless steels.
 
Selection of Other Component Materials: Depending on the operating temperature, appropriate materials should be selected for valve bodies, bonnets, valve seats, and discs. For temperatures above -100°C, ferritic steels are preferred, while austenitic steels are suitable for temperatures below -100°C.
 
Selection of Stem and Fastener Materials: Stem and bolt materials should be alloys like Ni and Cr-Mo at temperatures above -100°C, undergoing suitable heat treatment to enhance tensile strength. Below -100°C, austenitic stainless acid-resistant steels are utilized.
 
Selection of Gasket and Packing Materials: Careful consideration is required for gasket and packing materials to avoid issues such as shrinkage and swelling at low temperatures, with materials like fluoroplastics and asbestos packings needing special attention.
 

3. Special Processes and Structural Design

 
Valve Structure Design: Special structural designs, such as long-necked bonnet structures, should be employed to ensure that packings operate close to ambient temperatures, thereby guaranteeing sealing performance.
 
Surface Treatments: Surface treatments, such as hard chromium plating or nitriding and nickel-phosphorus plating, are essential to prevent frictional damage to stem surfaces under low temperatures.
 
Through meticulous design and material selection, forged steel low temperature demonstrate superior performance in extremely low-temperature environments, safeguarding the safe and stable operation of industrial production systems.