Description
A Bellow Seal Valve uses a metallic bellows assembly to isolate the valve stem from the process fluid, eliminating stem leakage and reducing maintenance. The bellows acts as a dynamic seal while the valve controls flow (on/off or regulation). This design is especially suited for toxic, hazardous, high-temperature, or high-pressure service where tight sealing is critical.
Construction & Materials
Body Material: Carbon Steel (ASTM A216 WCB / A105)
Bonnet: Bolted Bonnet / Pressure Seal (for high-temperature service)
Bellows Material:
SS 304 / SS 316 / Inconel (for high temperature/corrosive applications)
Trim (Disc, Seat, Stem):
Stainless Steel (SS304 / SS316)
Hard-faced options (Stellite) for extreme wear resistance
Seat: Renewable / Hard-faced
Packing: Graphite / PTFE (additional to bellows seal for extra protection)
Valve Types / Configurations
Globe Valve (CS Bellow Seal Globe) – precise throttling & control
Gate Valve (CS Bellow Seal Gate) – tight shut-off with low pressure drop
Stop / Check Valve (with bellows) – prevents backflow with sealed stem
Standards & Specifications
Design Standards: ASME B16.34 / BS / API
Pressure Rating: Class 150 / 300 / 600 / higher on request
Temperature Range: Up to 450°C+ (bellows material dependent)
End Connections:
Flanged (ASME B16.5)
Butt Weld (ASME B16.25)
Screwed (for smaller sizes)
Key Features
Zero stem leakage: Bellows prevents any leakage along the valve stem
Enhanced safety: Ideal for toxic or hazardous fluids
Long service life: Durable bellows and rugged CS body
Reliable operation: Smooth movement with low maintenance
High temperature & pressure handling: Bellows and trim suited for severe conditions
Dual sealing: Bellows + gland packing for redundant protection
Typical Applications
Chemical & Petrochemical Plants
Refineries
Power & Steam Systems
Pharmaceutical & Fertilizer Industries
Toxic / Corrosive Fluid Lines
High-pressure steam & thermal oil systems
Benefits of Thermax/Thermax CS Bellow Seal Valves
✔ Eliminate fugitive emissions
✔ Comply with environmental & safety regulations
✔ Ideal for hazardous fluid services
✔ Extends service intervals
✔ Protects actuators and packing from process fluid
