GBC nested bellows have controlled radii at both O.D. crown and I.D. root of each convolution. Thus, as the bellows is extended there are no crevices to open and release particles. Also, the controlled radii allow accurate prediction of stresses, which leads to accurate life prediction. Edge-welded bellows, in contrast, incorporate unavoidable crevices, which lead to difficult cleaning and less predictable stress levels.
Nesting Convolute Bellows
Conventional Welded Bellows
No Crevices Close inspection of sample parts will show deliberately-engineered radii at both the O.D. crown and the I.D. root of each convolution. Thus, as the bellows is extended there are no crevices to open and release entrapped particles. By contrast, an Edge-Welded Bellows incorporates unavoidable crevices. Cleaning of the Hydroform Nesting Bellows is readily accomplished by presently accepted methods.
Welding A seventy convolution, 13.5 in. O.D. Gardner Hydroform Nesting Bellows has only a single longitudinal butt-weld, for the fabrication of the initial tube. This contrasts with the 500 ft. of welding which an Edge-Welded version of this bellows would have. The inspection procedures for this single weld are covered by MIL-W-8611. The use off seamless tubing eliminates all welds except end fitting attachment.
Fewer Convolutes Because of a greater active span, a Hydroform Nesting Bellows needs fewer convolutions than an Edge-Welded Bellows. This means less weight and involves fewer natural frequencies. It also usually means that additional volume can be accommodated in the same envelope, in the event that design requirements are upgraded.
Engineered Design The design expertise for this bellows is based upon well-founded Gardner Bellows experience. Customer design parameters are computer-analyzed for design optimization and accurate life prediction.
Minimal Wall Thinning The techniques used to fabricate a Hydroform Nesting Bellows involve hydraulic forming and shaping that result in minimal wall thinning, approximately 12% maximum.
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Last Updated October 28, 2003