Welded Metal Bellows
A welded metal bellows is a zero leakage dynamic seal capable of a great range of motion. The metal bellows is manufactured from sheet stock. The material of construction may be stainless steel, high nickel alloys, titanium or other alloys to suit the application requirements. The material thickness may range from 0.001” to 0.025” thick.
Welded Bellows Technology
- GTAW & CO2 laser welding
- Thickness (0.001 to 0.025 inches)
- Sizes, diameters (0.125 to 23 inches)
- Round and non-round
- Materials
- Stainless steels
- High nickel alloys
- Titanium
- Mass spectrometer leak tight
- 1 × 10-10 std cc/sec He capability
(1 cc in 320 years)
- Zero leakage dynamic seal
Bellows Performance
- Bellows should mostly work in compression, 20% extension max. For maximum life, always work in compression
- Nested height of bellows should have a minimum of .002” between max weld bead size for 3 ripple configuration
- Avoid imposing lateral offset while axial stroking. Severely degrades life
- Max pitch 1/3 of span
- Bellows free length will typically stabilize at 15 to 25% of as welded length
Bellows Configurations
Nested Ripple
- Long stroke capability
- Compact nested length
- Good linearity
- Moderate pressure capability
- High cycle life
Flat Plate
- Limited stroke capability
- Excellent linearity
- Good pressure capability
- Excellent effective area control
Crescent
- Good stroke capability
- Compact nested length
- Good linearity
- Good pressure capability
Welded Bellows Capabilities
Zero leakage through a range of motion in extreme operating conditions
- Axial Deflection
- Angular Deflection
- Lateral Deflection
Bellows Performance Parameters
Spring Rate
- Function of material thickness, material type, cross-sectional geometry, pitch, span and number of convolutions
- +/- 5% material thickness equates to +/- 10% change in spring rate in ripple geometry
Effective Area
- 2D Area of bellows exposed to pressure differential
- Function of OD/ID and installation geometry
Life
- Function of deflection and pressure (membrane) stresses
- Variables in life determination include:
- Spring Rate
- Pressure Differential
- Stroke/Convolution
- Bellows Span
- Material Fatigue Strength
Engineering Capabilities
- 3-D Solid Modeling
- Bellows Device Design and Analysis
- Pressure Vessel Design and Analysis
- Finite Element Structural Analysis
- Flow Simulation
- Gas Charged Accumulator and Reservoir Thermodynamic Sizing
- Complex real gas analysis
- Development, Qualification, and Acceptance Testing
- Comprehensive Technical Documentation
