Views: 0 Author: J-VALVES Publish Time: 2024-02-29 Origin: Site
In the liquefied natural gas (LNG) industrial chain, low-temperature valves are crucial equipment to ensure the safe and stable operation during the processes of production, storage, transportation, and utilization. Among them, TRUNNION BALL VALVES have been widely used in LNG low-temperature working conditions due to their advantages such as simple structure, good sealing performance, and low flow resistance. However, due to the particularity of LNG working conditions, valves are required to maintain reliable performance at extremely low temperatures, which imposes extremely high requirements on valve selection and manufacturing processes. This article will focus on discussing the key points for selecting trunnion ball valves under LNG low-temperature working conditions and the technological breakthroughs in cryogenic treatment.
I. REQUIREMENTS FOR VALVES IN LNG LOW-TEMPERATURE WORKING CONDITIONS
The temperature of LNG is usually around -162 °C, which means that valves must be able to maintain their mechanical and sealing properties at extremely low temperatures. The following are the basic requirements for valves in LNG low-temperature working conditions:
• Material Selection: The main components of valves (such as valve bodies, valve covers, balls, valve seats, and valve stems) must be made of materials that can maintain good toughness and stability at low temperatures, such as austenitic stainless steel (304, 316, etc.).
• Cryogenic Treatment: All components in contact with the medium must undergo cryogenic treatment during the processing to eliminate the phase transformation stress and processing stress of materials at low temperatures.
• Sealing Performance: Valves should have bidirectional sealing capabilities and maintain reliable sealing performance at low temperatures.
• Structural Design: Valves should be equipped with long-neck valve covers, anti-static structures, pressure relief devices, etc., to adapt to the low-temperature environment and ensure safe operation.
II. TECHNOLOGICAL BREAKTHROUGHS IN CRYOGENIC TREATMENT OF TRUNNION BALL VALVES
Cryogenic treatment is a key technical link in the manufacturing process of TRUNNION BALL VALVES. Its purpose is to improve the microstructure of materials through low-temperature treatment and enhance the performance of valves under low-temperature working conditions. The following are the main steps and technological breakthroughs of cryogenic treatment:
(1) Process Flow of Cryogenic Treatment
• Pretreatment: Roughly machine components such as valve bodies, valve covers, balls, valve seats, and valve stems to remove surface defects.
• Cryogenic Treatment: Immerse the components in liquid nitrogen, lower the temperature to -196 °C, and maintain it for 1 - 2 hours, and then allow them to warm up to room temperature naturally. This process usually needs to be repeated 2 - 3 times.
• Finish Machining: After cryogenic treatment, perform finish machining on the components to ensure dimensional accuracy and surface finish.
• Inspection and Testing: Conduct low-temperature impact tests, dimensional inspections, and sealing performance tests on the treated components.
(2) Technological Breakthroughs in Cryogenic Treatment
• Improvement in Material Stability: Through multiple cryogenic treatments, the phase transformation stress and processing stress of materials at low temperatures are eliminated, ensuring the dimensional stability and sealing performance of valves under low-temperature working conditions.
• Optimization of Sealing Performance: Advanced sealing materials (such as PCTFE, PTFE, etc.) and surface hardening techniques (such as supersonic flame spraying) are adopted to further improve the sealing performance of valves at low temperatures.
• Improvement in Structural Design: The design of the long-neck valve cover effectively avoids the impact of temperature changes in the stuffing box on the sealing performance at low temperatures.
III. KEY POINTS FOR SELECTING TRUNNION BALL VALVES UNDER LNG LOW-TEMPERATURE WORKING CONDITIONS
Component Name | Material Options | Applicable Temperature Range |
Valve Body / Valve Cover | Austenitic Stainless Steel (304, 316) | -196 °C to Room Temperature |
Ball | Austenitic Stainless Steel (316, 316L) | -196 °C to Room Temperature |
Valve Seat | PCTFE, PTFE or Stainless Steel | -196 °C to Room Temperature |
Valve Stem | Austenitic Stainless Steel (316, 316L) | -196 °C to Room Temperature |
Sealing Surface | Supersonic Flame Spraying (WC, Nickel-Chromium Alloy) | -196 °C to Room Temperature |
Design Points | Explanation |
Long-Neck Valve Cover | Prevent the temperature of the stuffing box from being too low and ensure sealing performance |
Pressure Relief Device | Prevent the pressure in the valve cavity from being too high and ensure safe operation |
Anti-Static Design | Prevent the accumulation of static electricity and avoid potential safety risks |
Test Items | Test Standards | Explanation |
Low-Temperature Impact Test | ASTM A370 | Ensure the toughness of materials at -196 °C |
Sealing Performance Test | API 598 | Include high-pressure and low-pressure sealing tests |
Dimensional Inspection | ASME B16.10, ASME B16.5 | Ensure that the dimensions of components meet the standards |
IV. Conclusion
With the rapid development of the LNG industry, the demand for low-temperature valves is constantly increasing. TRUNNION BALL VALVES have been widely used in LNG low-temperature working conditions due to their excellent performance and reliability. Through the technological breakthroughs in cryogenic treatment, the material stability, sealing performance, and structural design of valves have been significantly improved, enabling them to better meet the requirements of LNG working conditions. During the selection process, users should reasonably select materials, structures, and performance testing standards according to specific working conditions to ensure the safety and reliability of valves.
In the future, with the further development and application of cryogenic treatment technology, trunnion ball valves will play a greater role in LNG low-temperature working conditions and provide a powerful guarantee for the safe and stable operation of the LNG industrial chain.
