What is a Bellows Seal Globe Valve？
WHAT IS A BELLOWS GLOBE VALVE?
A bellows globe valve is a type of globe valve that uses a metal bellows as the core dynamic seal between the valve stem and valve bonnet. It adopts a "bellows + packing" double sealing structure to completely solve the external leakage problem of traditional packing valves, making it particularly suitable for the shut-off and precise regulation of toxic, flammable, explosive, or high-purity media.
CORE STRUCTURE AND WORKING PRINCIPLE
Bellows: An axially expandable thin-walled metal tube, with one end welded to the valve stem and the other end welded to the valve bonnet/body, forming a dynamic sealing barrier that isolates the valve stem from the medium to achieve zero external leakage.
Double Sealing: The bellows serves as the primary seal, and the upper packing acts as a backup seal. Even if the bellows fails, the packing can still prevent leakage, improving safety redundancy.
Opening and Closing Method: The handwheel/actuator drives the valve stem to drive the valve disc to lift vertically, fitting or separating from the valve seat to realize shut-off and conduction. The flow channel is straight-through, and the valve disc and valve seat are mostly conical or flat seals, reaching ANSI Class VI leakage class.
KEY FEATURES
Feature | Description |
Zero External Leakage | The bellows isolates the valve stem from the medium, eliminating external leakage at the packing and meeting environmental and safety requirements |
Double Sealing | Bellows + packing form primary and secondary levels, ensuring safety even in case of failure |
Temperature and Pressure Resistance | Suitable for PN1.6～16MPa, -29～350℃; bellows materials can be 304/316L/Inconel, etc. |
Long Service Life | The bellows absorbs thermal expansion and contraction stress, reducing wear of the valve stem and packing; the sealing surface is often overlay welded with Co-based cemented carbide for wear and corrosion resistance |
Applicable Media | Toxic, flammable, explosive, valuable, or high-purity media, such as in chemical, pharmaceutical, power, petroleum, and other industries |
APPLICATION AND SELECTION POINTS
Main Uses: Shut-off and precise regulation of pipeline media (not recommended for frequent regulation).
Connection Methods: Flange, welding (butt weld/socket weld), threaded, selected according to working conditions.
Actuation Methods: Manual, electric, pneumatic; electric/pneumatic is suitable for remote control and automation systems.
Selection Parameters: Nominal Diameter DN15～200, Nominal Pressure PN16～320, medium temperature, corrosiveness, viscosity, and whether it contains particles, to match the bellows material and structure.
DIFFERENCES FROM TRADITIONAL PACKING GLOBE VALVES
Comparison Item | Bellows Globe Valve | Traditional Packing Globe Valve |
Sealing Method | Double sealing (bellows + packing) | Packing-only sealing |
External Leakage Risk | Extremely low, suitable for hazardous media | Relatively high, easy to leak when packing ages |
Maintenance Frequency | Low, long bellows service life | High, regular packing replacement required |
Applicable Working Conditions | Severe working conditions, hazardous/valuable media | Ordinary working conditions, low leakage requirements |
SUMMARY
The bellows globe valve achieves dynamic sealing of the valve stem through a metal bellows, combined with a double sealing design, solving the external leakage problem of traditional globe valves. It has significant advantages in industrial scenarios with high safety and environmental requirements. During selection, focus on the bellows material, pressure and temperature range, and sealing class to ensure long-term stable operation.
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