The reliability of metal bellows compensator is composed of design, manufacturing, installation and operation management. Reliability should also be considered from these aspects.
Material selection:
For the material selection of bellows used for heating pipe network, in addition to the working medium, working temperature and external environment, the possibility of stress corrosion, the impact of water treatment agent and pipeline cleaning agent on the material, etc., should also be considered. On this basis, combined with the welding and forming of bellows materials and the performance and price ratio of materials, the economical and practical bellows manufacturing materials should be selected.
Generally, the material of bellows shall meet the following conditions:
(1) High elastic limit, tensile strength and fatigue strength ensure normal operation of bellows.
(2) Good plasticity facilitates the processing and forming of bellows, and sufficient hardness and strength can be obtained through subsequent treatment processes (cold work hardening, heat treatment, etc.).
(3) Good corrosion resistance, meeting the working requirements of bellows in different environments.
(4) Good welding performance, meeting the welding process requirements of bellows in the manufacturing process. For the heating pipe network laid in the trench, when the pipeline where the compensator is located is low, the corrugated pipe will be soaked by rainwater or accidental sewage, and the materials with stronger corrosion resistance, such as iron-nickel alloy and high-nickel alloy, should be considered. Due to the high price of such materials, it can be considered to add a layer of corrosion-resistant alloy only on the surface in contact with corrosive media when manufacturing bellows.
The fatigue life design can be seen from the failure type and cause analysis of the bellows compensator that the plane stability, circumferential stability and corrosion resistance of the bellows are all related to its displacement, namely, the fatigue life. Too low fatigue life will lead to the deterioration of the stability and corrosion resistance of metal bellows.