Double-seat globe valve is a valve that realizes medium control through a double-seat sealing structure. The upper and lower ends of the valve core are equipped with independent valve seats, which can control the opening and closing of two flow channels simultaneously or in stages. This design is mainly used to solve the problem of excessive opening and closing torque of high-pressure and large-diameter valves, and has the functions of preventing mixed flow and safe isolation.
1. Structure and working principle
Double-seat linkage design
The main and auxiliary valve seats work together: the small valve seat (auxiliary valve seat) opens first to reduce the system pressure, and then the main valve seat opens easily when the pressure difference decreases, which is suitable for high-pressure (such as ≥PN40) or large-diameter (DN≥150) working conditions;
Double sealing surface configuration : The upper and lower valve seats use soft seals (such as PTFE) or metal hard seals to enhance sealing reliability and reduce leakage risks.
Actuator adaptation
It can be equipped with electric and pneumatic actuators (such as Alfa Laval pneumatic diaphragm actuators), support remote control and automatic operation, and meet the precise flow regulation needs of chemical, power and other industries.
2. Core application scenarios
High-pressure fluid control
In steam systems or oil and gas pipelines, the valve operating torque is reduced by staged pressure reduction to extend the life of the equipment;
Anti-mixing and safe isolation
Used in the pharmaceutical and food industries, the double valve seat is used to isolate different media to prevent cross-contamination (such as the Alfa Laval anti-mixing valve design);
In the cold storage hot fluorine defrosting system, the double valve seat structure can simultaneously control the refrigerant flow and safe pressure relief to avoid the risk of system overpressure.
3. Technical characteristics and limitations
Advantages
Low flow resistance and high flow volume: The double valve seat design expands the flow cross-sectional area and reduces pressure loss;
Anti-seismic stability: The double guide structure of the valve core enhances the ability to resist fluid impact and is suitable for high vibration environments.
Use restrictions
Maintenance complexity: The double sealing surface needs to be regularly inspected for wear, and the maintenance cost is higher than that of a single-seat valve;
Temperature sensitivity: The gray cast iron valve body (such as HT250 material) has a long-term applicable temperature of ≤250℃, and high-temperature scenes need to be upgraded to cast steel or stainless steel.
4. Selection and maintenance points
Material matching: Corrosive media should preferably use stainless steel valve bodies (such as 304/316) or surface coating treatment;
Sealing performance verification: Air tightness test should be carried out according to API 598 standard, and the leakage rate should be controlled at ≤0.01%×DN (mm/min);
Actuator compatibility: High-torque pneumatic actuators (such as ZMAN series) are recommended for high-pressure systems to ensure fast response and stable control.
Summary: The double-seat globe valve has unique advantages in high-pressure control, anti-mixing and safety isolation scenarios through the coordinated action of double valve seats and the design of multiple sealing surfaces, but its structural complexity requires strict matching of working conditions and maintenance specifications.