Bellow Seal Safety Valve

Technical Summary

Nominal Size: ½” to 8”

Pressure Class: Class 150 to Class 2500

Temperature Range: -29°C to 538°C

Design Standards: API 526, ASME Section VIII, ASME B16.34

Face to Face: As per manufacturer standard

Set Pressure Range: As per system requirement

End Connections: Flanged / Butt Weld

Construction and Materials

Body and Pressure Retaining Parts

• ASTM A216 WCB
• ASTM A351 CF8M
• ASTM A217 WC6
• ASTM A217 WC9
• ASTM A182 F316

Internal Components

• Disc: ASTM A182 F316 / Hard faced (Stellite)
• Seat: Stainless Steel / Stellite faced
• Stem: ASTM A182 F316
• Bellows: Stainless Steel (SS316 / SS321 / Inconel on request)

Sealing System

• Bellows Seal: Multi-layer metallic bellows providing leak-tight isolation of process fluid from spring chamber
• Gasket: Spiral wound gasket with graphite filler

Functional Design

Bellow Seal Safety Valve is designed to provide reliable overpressure protection while ensuring zero leakage of process media into the spring chamber. The metallic bellows isolates the bonnet assembly from the process fluid, preventing corrosion, contamination, and fugitive emissions.

When system pressure exceeds the set limit, the valve lifts automatically to discharge excess pressure. Once normal conditions are restored, the valve reseats to maintain system integrity. The bellows design enhances safety in applications involving hazardous, toxic, or high-purity media.

Material and Grade

Standard Materials

Component	Material	Grade	Typical Application
Body	Carbon Steel	ASTM A216 WCB	General steam and utility services
Body	Stainless Steel	ASTM A351 CF8M	Corrosive and chemical media
Body	Alloy Steel	ASTM A217 WC6 / WC9	High temperature steam service
Disc & Seat	Stainless Steel with Stellite overlay	ASTM A182 F316	Wear resistance and tight shut-off
Bellows	Stainless Steel	SS316 / SS321	Isolation and emission control

Extended Materials (On Request)

• Hastelloy C276 for aggressive chemical service
• Inconel 625 / 718 for high temperature and pressure applications
• Duplex Stainless Steel (F51) for chloride environments

Additional Information

Valve Type	Bellow Seal Safety Valve
Pressure Function	Overpressure protection
Operation	Spring loaded safety valve
Bellows Design	Metallic bellows for bonnet isolation
Leakage Control	Designed to minimize fugitive emissions
Installation	Vertical installation required
Service Media	Steam, gas, vapour, hazardous fluids

End Connections

• Flanged as per ASME B16.5
• Butt weld as per ASME B16.25

Applications

• Oil and gas industry: pressure relief in hydrocarbon systems where emission control is critical
• Chemical processing: handling of toxic and corrosive fluids requiring zero leakage to atmosphere
• Power generation: steam safety applications where spring protection and long service life are required
• Refining and petrochemical industry: relief systems in high temperature and hazardous service lines
• Pulp and paper industry: steam pressure protection in high temperature operations
• Gas processing plants: overpressure protection with containment of volatile gases