Hydroforming bellows expansion joint minimum diameter can be to a few millimeters in diameter, up to 4 to 5 m, are rarely more than 4 mm wall thickness, the applicable scope is bigger.

Injection pipe hydroforming is to use the pump (oil or water) in the medium pressure, forcing the tube billet bulging in the limit module, and then down positioning between the module and the use of hydraulic press equipment, or other related similar effect on the compression pipe to the required length, eventually down the module, and corrugated pipe forming.

The features of the hydroforming is: the forming process, the tube billet uniform compression, moderate amount of thinning, longitudinal seam in the forming process of tube billet by forming pressure test. But hydraulic forming technology to the mold demand is high, especially for machining large diameter of the bellows, mold cost increased sharply, the intensity of labor is big, have a high request for hydraulic press tonnage and pillar. For large and super large bellows, choose rolling, from technical and economic point of view, a more reasonable.

Multi convolutions bellows expansion joint fills the tube billet in the process of forming a forming pressure medium as oil or water. Sealed oil viscosity, easy to achieve, but hard to avoid the leakage will cause environmental pollution, the cost is high; The characteristics of water medium instead. Both oil charge and water filling, forming system should be independent, separated from hydraulic press hydraulic system, its role is to ensure that the tube billet pressurized drum zhang bumps, synchronize the forming pressure medium in the process of discharge at the same time.

Forming, the first to start the pump the liquid filling the tube billet, when after reaching certain pressure, between modules of tube billet shell bulge, stop the pump pressure, down template positioning, starting hydraulic press, pipe, axial compression at the same time open booster pump, pipe end cover and module under the axial thrust of the hydraulic press to continue moving, waveform expands unceasingly, until the template is on board, and mold, as this should monitor the slippage of the template, to ensure uniform clearance between each other, avoid deviation. And die, general booster about 0.1 MPA, the holding 10-15 points, can discharge pressure, open mode, remove the bellows, forming the end.