At this point, the container has two possible forms of failure. One is compression yield failure, the other is that when the external pressure reaches a certain value, the radial deflection of harmonic condenser manufacturing harmonic element CSG-25-80-2UH tends to increase sharply with the increase of compression stress, until the container is compressed. At this time, the stress of the compressed film has not reached the yield point of the material, or even much lower. This phenomenon is called instability or buckling of the external pressure vessel. To ensure the stability of external pressure vessel is a necessary condition for normal operation of chemical vessel. Vacuum-operated condensers, crystallizers, distillation towers and other enclosures are subjected to external pressure from the atmosphere, and the medium used for heating in jacked vessels also exerts external pressure on the inner shell, which are examples of external pressure vessels.

For thin-walled cylinders with very small wall thickness compared to diameter, the compressive stress in the wall of harmonic condenser is usually lower than the proportional limit of the material when the harmonic element CSG-25-80-2UH is unstable