Bellows Seal Globe Valve

Bellow seal globe valves are used where stem leakage must be minimized while maintaining controlled throttling and positive isolation. A welded metallic bellows forms the primary pressure barrier around the stem, while conventional packing provides secondary sealing if the bellows is damaged. African Valve is a leading Bellow Seal Globe Valve Suppliers in Nigeria, supplying valves in different pressure classes, body materials, bellows grades, end connections and actuation arrangements for steam, chemical, petrochemical and process services.

Where Are Bellow Seal Globe Valves Used?

Bellow Seal Globe Valves are selected for services where conventional stem packing alone may not provide the required leakage control. Typical installations include steam systems, power plants, chemical-processing units, petrochemical facilities, refineries, marine utilities and industrial process lines.

They are particularly useful for hazardous, high-temperature or emission-sensitive fluids where leakage through the stem sealing area must be controlled. Selection should consider fluid compatibility, operating pressure, temperature, required throttling duty and expected operating cycles because these conditions directly affect bellows material and fatigue life.

Engineering Design & Operation

The stem moves the disc linearly toward or away from the seat to regulate or isolate flow. During stem travel, the welded metallic bellows expands and compresses without allowing the process fluid to reach the conventional packing area.

The bellows normally acts as the primary stem seal, with gland packing retained as a secondary sealing arrangement. Multi-ply bellows may be used where greater flexibility and cyclic capability are required. Disc and seat profiles can be selected for isolation or controlled throttling, while Stellite-faced seating may be specified for elevated temperature or repeated operation.

Manual handwheel operation is common, while pneumatic or electric actuators can be supplied for automated systems.

Bellow Seal Globe Valve Features

• Metallic Bellows Seal: Forms the primary barrier around the stem
• Secondary Packing: Provides backup sealing behind the bellows
• Low Stem Leakage: Suitable for emission-sensitive and hazardous services
• Flow Regulation: Globe trim supports throttling and controlled flow adjustment
• Metal Seating: Suitable for elevated-temperature service
• Multi-Ply Bellows: Available where increased cycle capability is required
• Hard-Faced Trim: Available for erosion and repeated seating
• Actuation: Handwheel / Gear / Pneumatic / Electric

Technical Specifications

Materials & Components

• Body: ASTM A216 WCB / ASTM A352 LCB / ASTM A351 CF8 / CF8M / ASTM A217 WC6 / WC9
• Bonnet: Matching body material / Application-specific alloy
• Bellows: SS316L / SS316Ti / SS321 / Nickel Alloy
• Disc: Stainless Steel / Alloy Steel / Stellite-Faced
• Stem: AISI 410 / AISI 316 / 17-4PH / Application-specific alloy
• Seat: Stainless Steel / Stellite-Faced Metal Seat
• Packing: Flexible Graphite / PTFE / Low-Emission Packing
• Gasket: Spiral Wound / Graphite
• Fasteners: ASTM A193 B7 / B8 / B8M / ASTM A320 L7 with compatible ASTM A194 nuts

Bellows grade, number of plies and stroke capability should be selected according to fluid chemistry, temperature, pressure and expected operating cycles.

Applications

• Power Generation: Steam, boiler and plant utility systems
• Steam Service: High-temperature isolation and throttling
• Oil & Gas: Refinery and hydrocarbon process lines
• Chemical Processing: Compatible corrosive and hazardous fluids
• Petrochemical Plants: Process and utility piping
• Marine & Offshore: Utility and process systems
• Industrial Utilities: Thermal fluid and process services
• Process Plants: Applications requiring controlled stem leakage

Testing & Standards

Depending on construction and project requirements, applicable standards may include BS 1873, API 623, ASME B16.34, ASME B16.10, ASME B16.5, API 598 and EN 12266.

Testing may include shell pressure testing, seat leakage testing, bellows integrity testing, dimensional inspection and full-stroke operation. PMI, NDT and material traceability may also be specified for critical pressure, temperature or corrosion service.