Formed Bellows
High-precision flexible solutions for thermal expansion, vibration compensation, and pressure-containing motion in demanding industrial environments.
Product Overview
Formed Bellows are elastic, thin-walled components produced through specialized hydraulic (hydroforming) or mechanical expansion of seamless stainless steel tubing. The forming process creates a convoluted geometry that delivers exceptional flexibility while maintaining the full pressure-containing integrity of the parent tube — with no circumferential weld seams. This makes formed bellows the preferred choice for high-pressure, large-diameter, and industrial-grade applications where the premium cost of edge welded bellows is not justified by the vacuum requirements.
Unlike edge welded bellows built up from individual diaphragms, formed bellows offer inherently higher burst pressure, superior buckling resistance under external pressure, and a more economical price point — particularly in larger diameters and higher production volumes. For a side-by-side performance comparison, see our Edge Welded Bellows Technical Guide which includes a detailed formed vs. edge welded comparison table.
Technical Specifications
| Specification | Technical Details |
|---|---|
| Materials | AISI 304, 316L, 321, Monel, Inconel 625/718, Hastelloy C-276/C-22 — see Material Selection Guide |
| Forming Process | Seamless Hydraulic (hydroforming) / Mechanical Expansion from tube stock |
| Vacuum Integrity | High Vacuum (HV) to 10⁻⁸ mbar; not recommended for UHV <10⁻⁹ mbar applications (for UHV, use our Copper Gasket Sealed UHV Bellows) |
| Operating Temperature | Cryogenic (-200°C) to +800°C (material-dependent; Inconel grades for extreme high-temperature service) |
| Multi-Ply Option | 2-ply and 3-ply configurations available — higher pressure rating and lower spring rate than single-ply of equivalent wall thickness |
Core Advantages
- Superior Fatigue Life: Engineered for millions of flex cycles under rated pressure conditions — multi-ply designs further extend cycle life by reducing per-layer stress amplitude.
- Hermetic Sealing: Seamless tube construction with zero circumferential welds — the continuous grain structure provides inherent leak-tightness for toxic, high-purity, or hazardous media containment.
- Multi-Ply Technology: Optional 2- and 3-layer walls balance high pressure capacity with low spring rates — each ply carries a portion of the pressure load, enabling thinner individual layers and greater overall flexibility.
- Vibration Damping: The multi-convolution structure effectively isolates mechanical noise and high-frequency oscillations in piping systems — protecting downstream equipment from pump-induced and flow-induced vibration.
- Cost-effective at scale: The hydroforming process becomes highly economical at production volumes above 100 units, making formed bellows the go-to for OEM series production.
