The forming method which Bellowman adopted for the Metal expansion joints is Hydroforming, followed by finish rolling. Firstly, rectangular metal sheets are sheared and rolled into tubes, which is then the longitudinal seam welding will be carried out.

“Bellows”, of course, once the welding is completed, all of the convolutions of the bellow elements will be formed in integral by hydro forming machine. Finally, the required “U” shapes of the convolutions are implemented by the use of rollers. The bellows are then trimmed on the basis of needed dimensions, and ready for installation of end connections or other accessories.




       Ribbon material                              Shearing                                      Rolling                           Longitudinal welding

               Forming                                 Re-forming                              Final assembly                             Inspection