Edge welded bellows
At Palatine, our Edge Welded Bellows are manufactured using precision welding processes to provide bellows that are high quality and uniform. Using hydraulic presses, we stamp diaphragms from stainless steel strip and form them with a corrugation across the span of the stamping. These metal diaphragms are then welded onto the inner and outer diameters. Welded together as a ‘stack’ or ‘element’ – and to almost any length – these can be built to suit almost all operating requirements.
All testing of our welded assemblies is carried out using a Vacuum leak test machine. Using Helium as our search gas, the machine will detect trace amounts of helium in the immediate area being tested and register the overall leak rate for the component which is recorded in mBar Litre/sec. Our target leak rate for UHV applications is better than 1×10-9 mBar Litre/sec.
Edge welded bellows are manufactured from strip material ranging from 0.076mm to 0.30mm in thickness. Diaphragms are formed and blanked from the strip material. A pair of diaphragms welded together on the inner diameter form a convolution. One or more convolutions welded together at the outer diameter form the bellows element.
The bellows diaphragms/convolutions are welded using micro-TIG. The process incorporates an autogenous (no filler material), fusion weld. The resulting weld beads are of a uniform shape, clean and can appear almost invisible to the eye.
Depending upon stroke requirement, angulation, lateral offset, temperature and pressure considerations: edge welded bellows can be constructed to almost any length, to suit a range of operating parameters and across a broad range of application.
With ultra-high vacuum applications, high leak rates are required. All bellows elements manufactured are subject to helium leak test on a mass spectrometer where the target leak rate for all welded components is (better than) 1.0 x 10-9 mBar litre/sec.
The Nested bellows design incorporates a one or more corrugations across the span of the diaphragm. The corrugation enhances the flexibility of the disc enabling bellows elements to achieve long stroke capability and large angular movements. Having good resistance to pressure in the closed condition the nested form also offers low spring rate characteristics. Generally available in 316L or Alloy 350 stainless steel.
The Omega design offers is capable of withstanding high external pressures. This patented construction is only available in a single size. Spring rates are high and axial movements per convolutions are small.
Available in either 316L stainless steel (upto 150 Bar at 300°C) or Nickel Alloy / Nimonic 90 (upto 193 Bar at 350°C).
Also blanked from strip material, these diaphragms have no corrugation (unlike their nested counterpart). We have tooling for the production of number of flat-plate options that complement our nested range, for situations where the required movement and space available may be more limited.
Generally available in 316L or Alloy 350 stainless steel.
Welded diaphragm bellows are used in the following applications:
- Flexible connectors in piping and ducting systems
- Compensators for accommodating changes in volume of fluids in sealed instruments
- Valve stem seals
- Rotating and reciprocating shaft seals
- Pressure sensors
- Hydraulic accumulators and shock absorbers
- Expulsion tanks
- Flexible shaft couplings
- Connectors for Ultra-High vacuum systems
In all of these applications one or more of the following characteristics are used to advantage:
- Long stroke per length unit
- Short nested length
- Large volumetric compensation for short free length
- Constant effective area with change in pressure
- Excellent spring characteristics and pressure deflection curves
- Ability to withstand high pressure and temperature
- High operating life
- Excellent corrosion resistance determined by choice of material
- Leak tightness to mass spectrometer sensitivity
- Reduced outgassing of assemblies because of welded construction