Views: 0 Author: Site Editor Publish Time: 2025-05-23 Origin: Site
In the field of industrial valves, zero leakage technology has always been the goal pursued, especially when dealing with hazardous media or working conditions with high requirements. METAL SEALING OF TRUNNION BALL VALVES and soft sealing of GATE VALVES are two common sealing methods, and there are many differences in their performance, application scope, and standard requirements. Based on the BS 6364 standard, this article will conduct a detailed comparative analysis of these two sealing technologies to help practitioners better choose suitable valve types.
I. BASIC PRINCIPLES OF METAL SEALING OF TRUNNION BALL VALVES AND SOFT SEALING OF GATE VALVES
(1) Metal Sealing of Trunnion Ball Valves
The METAL SEALING OF TRUNNION BALL VALVES is achieved through the close contact between the metal seat and the ball. This sealing method usually adopts a metal-to-metal hard sealing structure and can maintain good sealing performance under harsh working conditions such as high temperature, high pressure, and those containing particles. Metal-sealed trunnion ball valves are usually suitable for occasions that require frequent opening and closing and have extremely high sealing requirements, such as in the petroleum, chemical, and natural gas industries.
(2) Soft Sealing of Gate Valves
The soft sealing of GATE VALVES is achieved through the close fit between the sealing ring made of soft materials (such as PTFE, nylon, etc.) and the gate or valve seat. The advantage of soft-sealed gate valves lies in their excellent sealing performance with an extremely low leakage rate, which can even reach zero leakage. This sealing method is usually suitable for working conditions with clean media and lower temperatures, such as water, steam, and some chemical reagents.
II. REQUIREMENTS OF THE BS 6364 STANDARD FOR THE TWO SEALING TECHNOLOGIES
BS 6364 is an international standard for cryogenic valves. It puts forward strict requirements on aspects such as the sealing performance, structural design, material selection, and testing methods of valves. The following is a comparative analysis of the metal sealing of trunnion ball valves and the soft sealing of gate valves according to the BS 6364 standard:
(1) Comparison of Sealing Performance
Items | Metal Sealing of Trunnion Ball Valves | Soft Sealing of Gate Valves |
Leakage Class | Usually complies with ISO 5208 Class D, allowing a very small amount of leakage | Can reach ISO 5208 Class A, zero leakage or close to zero leakage |
Applicable Media | Harsh media with high temperature, high pressure, and containing particles | Clean media, such as water, steam, chemical reagents |
Applicable Temperature Range | -196 °C to high temperature (depending on materials) | Generally below 250 °C |
Durability | Higher, suitable for frequent opening and closing | Lower, frequent opening and closing may cause wear of sealing materials |
(2) Comparison of Structural Design
Items | Metal Sealing of Trunnion Ball Valves | Soft Sealing of Gate Valves |
Valve Seat Material | Metal (such as stainless steel, cemented carbide) | Soft materials (such as PTFE, nylon) |
Sealing Principle | Metal-to-metal hard sealing | Close fit between soft materials and metal components |
Operating Torque | Higher, requiring a larger operating force | Lower, with flexible operation |
Anti-static Design | Usually requires anti-static measures | Requires anti-static measures (for flammable media) |
(3) Comparison of Testing Methods
Items | Metal Sealing of Trunnion Ball Valves | Soft Sealing of Gate Valves |
High-pressure Sealing Test | Conduct the test according to the cold working pressure (CWP), allowing a very small amount of leakage | Conduct the test according to the cold working pressure (CWP), and the leakage rate needs to comply with ISO 5208 Class A |
Low-temperature Soaking Time | Soak for at least 1 hour after the valve body and valve cover reach the test temperature | Soak for at least 1 hour after the valve body and valve cover reach the test temperature |
Operation Test | Open and close 20 times without load, and test the opening and closing operating forces for the first and last times | Open and close multiple times without load and test the sealing performance |
III. ANALYSIS OF APPLICATION SCENARIOS
(1) Application of Metal Sealing of Trunnion Ball Valves
• Petroleum and Natural Gas Industry: Used for transporting media such as crude oil and natural gas containing particles, and can maintain sealing performance under harsh working conditions.
• Chemical Industry: Suitable for occasions dealing with high-temperature, high-pressure, and corrosive media, such as sulfuric acid and nitric acid.
• High-temperature Steam System: Can withstand the impact of high-temperature steam and maintain stable sealing performance.
(2) Application of Soft Sealing of Gate Valves
• Water Treatment System: Used for tap water, sewage treatment and other occasions, and can achieve zero leakage to ensure water quality safety.
• Pharmaceutical Industry: Suitable for handling clean, particle-free chemical reagents to ensure the purity of drug production.
• Food Processing Industry: Used for transporting food raw materials or finished products to prevent pollution and ensure food safety.
IV. SUMMARY AND SUGGESTIONS
Both the METAL SEALING OF TRUNNION BALL VALVES and the soft sealing of GATE VALVES have their own advantages. The choice should be determined according to specific working conditions and media characteristics. If the working conditions require maintaining sealing performance in a harsh environment with high temperature, high pressure, and containing particles, it is recommended to choose the METAL SEALING OF TRUNNION BALL VALVES. For occasions with clean media, lower temperatures, and the need for zero leakage, the soft sealing of GATE VALVES is a better choice. In practical applications, it is also necessary to combine the requirements of relevant standards such as BS 6364 to ensure that the selection and use of valves comply with the specifications, so as to achieve the goal of zero leakage.
