The reason why bellows expansion joints are widely used in many industries is that besides considering good compensation ability, reliability is the key of bellows expansion joints. Reliability is guaranteed by many links such as design and manufacturing. Negligence of any link will lead to reduction or even failure of the service life of the compensator.
Most bellows expansion joint manufacturers have analyzed the failure causes of bellows expansion joints, and found that during operation, the failure is mainly manifested in two forms: corrosion leakage and instability deformation, with corrosion failure being the majority. From the anatomical analysis of corrosion failure bellows, it is found that corrosion failure I is divided into pitting corrosion perforation and stress corrosion cracking, of which chloride stress corrosion cracking accounts for about 95% of the total corrosion failure.
Therefore, the safety and reliability of expansion joints of bellows compensators can be greatly improved by properly selecting the materials and structures of bellows, reasonably designing waveform parameters and fatigue life, and ensuring installation quality.
In design, the stability of bellows should be considered to prevent instability of bellows. Data show that the compensation amount of bellows depends on its fatigue life. The higher the fatigue life, the smaller the compensation amount of bellows per wave. In order to reduce the cost and improve the compensation amount of single wave, the lower the allowable fatigue life, the greater the meridional bending stress of bellows caused by displacement, the higher the comprehensive stress, which greatly reduces the stability of bellows. When the allowable service life of bellows design is low, not only its meridional comprehensive stress is high, but also its circumferential stress is high, which makes the bellows locally enter plastic deformation quickly, leading to failure caused by bellows instability.
In addition to the design, the material selection of bellows is also very critical. For the selection of corrugated pipe materials, besides the working medium, working temperature and external environment, the possibility of stress corrosion, the influence of water treatment agent and pipeline cleaning agent on the materials, etc. should also be considered. On this basis, combining the welding, molding and performance-price ratio of corrugated pipe materials, a practical corrugated pipe manufacturing material meeting the working conditions should be selected.
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