Bellows Expansion Joints
Bellows expansion joints are flexible connectors consisting of one or more corrugated bellows elements designed to absorb thermal expansion, contraction, and mechanical vibration in piping systems. Available in axial (single and universal), lateral, angular (hinged and gimbal), and pressure-balanced configurations, each type is engineered for specific movement patterns and system constraints.
Our bellows are hydroformed or mechanically formed from stainless steel sheet (SS304, SS316L, SS321, Inconel 625) with optimized convolution geometry for fatigue life. Multi-ply designs offer increased flexibility and cycle life while maintaining full pressure capability. Each joint can be supplied with tie rods, limit rods, hinges, gimbal rings, internal flow liners, and external protective shrouds as required by the application.
EJMA / GB/T12777
SS304/316L
DN25-DN4000
Applications
- Steam and condensate piping in power plants
- Chemical plant process piping
- District heating transmission lines
- Exhaust and flue gas ducting
- Cryogenic piping systems
Quality Assurance
All Bellows Expansion Joints products undergo NDT testing with MTC per EN 10204 3.1. Third-party inspection by SGS, BV, TUV available.
Bellows Expansion Joints Technical Specifications
Bellows expansion joints absorb thermal expansion, vibration, and misalignment in piping systems. The flexible bellows element compensates for axial, lateral, and angular movement while maintaining a pressure-tight seal.
| Parameter | Specification |
|---|---|
| Standard | EJMA / GB/T 12777 / ASME B31.3 Appendix X |
| Bellows Material | SS304, SS316L, Inconel 625, Incoloy 800, Hastelloy C276, Monel 400 |
| Size Range | DN25 (1 inch) to DN4000 (160 inch) |
| Pressure | Full vacuum to 40 bar (special designs to 100 bar) |
| Movement | Axial, Lateral, Angular, or Combined |
| Ply | Single-ply or Multi-ply (2-4 plies for enhanced flexibility) |
Types and Movement Capabilities
Expansion joints are designed for specific movement types. Selecting the correct type requires analyzing the piping system thermal expansion and support configuration:
- Axial Expansion Joint: Absorbs axial compression/extension along the pipe axis. Simplest and most economical, used in straight runs with proper guides.
- Lateral Expansion Joint: Absorbs lateral (perpendicular) movement in one plane. Uses tie rods to constrain movement and direct forces to anchors.
- Angular Expansion Joint: Absorbs angular rotation (bend) in one plane. Used in pairs to absorb lateral movement in Z-shaped or L-shaped piping.
- Universal (2-ply): Combines axial and lateral movement absorption, for complex systems.
- Hinged and Gimbal: Restricts movement to angular only, used in high-pressure systems to control bellows distortion.
- Pressure Balanced: Absorbs axial movement while eliminating pressure thrust loads on anchors. Used where anchors cannot withstand thrust.
Manufacturing & Design Standards
Bellows are manufactured by hydroforming or mechanical forming, with design per EJMA (Expansion Joint Manufacturers Association) standards:
- Bellows Forming: Thin-walled tube (0.5-3mm) hydroformed or roll-formed into convolutions. Multi-ply bellows use stacked tubes for redundancy and flexibility.
- Welding: Bellows welded to end fittings using TIG (GTAW) with full penetration, often with Inconel filler for high-temperature service.
- Bellows Design: Per EJMA, calculations include fatigue life (minimum 1000 cycles), stress analysis, and spring rate.
- Internal Sleeve: For flow turbulence reduction and liner protection, internal sleeves are welded in high-flow or abrasive service.
- NDT: 100% dye penetrant on bellows welds, helium leak test for critical service, burst pressure test at 1.5x design.
Typical applications: steam lines in power plants, refinery hot lines, HVAC chilled water systems, exhaust systems, and district heating. Fatigue life is designed for 1000-50,000 cycles depending on service requirements.