Metal bellows has good flexibility and temperature, pressure, corrosion resistance, suitable for steam, water, oil and various industrial gases, pharmaceuticals and other media delivery. Movement of the piping system, the heat expansion absorption, vibration absorption plays an important role. Metal bellows are wave-like shape of the pipe like a regular, common metal bellows have carbon steel and stainless steel, but also lined with a steel, aluminum and so on. Mainly for small bending radii required non-concentric axial drive, or irregular turning, stretching, or absorb heat pipe deformation, or not easy to install using the occasion to make a fixed connection elbow pipe and pipe or conduit and Connect the device to use. Prestressed metal bellows product performance: a rigid test: anti-concentrated load 0.75KN or uniform load when 1.5KN, radial deformation ≤0.1d. 2, permeability test: Spam or grout cement ratio of 0.5 for 30 minutes without leaking, leaking slurry. 3, tensile test: axial tension 5KN wall without damage. 4, anti-pull test: buried in concrete pullout design for bolt for bolt design pullout pullout of more than 2.3 times five, bending experiment: When the curvature radius of curvature for the 30d, no leakage , plasma leakage.