Reliability of Corrugated Tube Compensator
Date：2018-08-30 / View：447
The reliability of corrugated tube compensator is composed of design, manufacture, installation and operation management. Reliability should also be considered from these aspects. Material selection for bellows used in heat supply networks should take into account not only the working medium, working temperature and external environment, but also the possibility of stress corrosion, the influence of water treatment agent and pipeline cleaning agent on the material, etc. In addition, based on the welding, molding and the ratio of performance and price of the corrugated pipe materials, the economical and practical corrugated pipe materials are selected.
In general, the selection of bellows shall meet the following conditions:
1.Good plasticity, easy processing and forming of bellows, and sufficient hardness and strength can be obtained by subsequent treatment (cold hardening, heat treatment, etc.).
2.High elastic limit, tensile strength and fatigue strength to ensure the normal operation of bellows.
3.Good welding performance to meet the welding process requirements of bellows in the manufacturing process.
4.Better corrosion resistance, to meet the requirements of bellows in different environments.
For the thermal pipe network laid in the trench, Rain Water or the accident sewage will soak the bellows when the pipeline in which the compensator is located is low, so we should consider the materials with stronger corrosion resistance, such as iron and nickel alloy, high nickel alloy and so on. Due to the high price of this kind of material, only one layer of corrosion resistant alloy can be added to the surface of the corrugated tube in contact with corrosive medium.
From the analysis of failure types and causes of bellows compensator, it can be seen that the plane stability, circumferential stability and corrosion resistance of bellows are related to their displacement, that is, fatigue life. Too low fatigue life will decrease the stability and corrosion resistance of bellows. According to the test and application experience, the fatigue life of bellows used in heating engineering should not be less than 1000 times.
The failure of most corrugated tubes is caused by external environment corrosion, so in the structural design of compensator, the contact between external corrosion medium and bellows can be considered. For the external pressure axial compensator, the packing sealing device can be added between the outlet ring and the outlet tube, which is equivalent to the sleeve compensator: it can resist the invasion of the external corrosive medium and add a safety barrier to the bellows compensator. Even if the bellows are damaged, the compensator can compensate and avoid the bellows failure.
The bellows cannot bear the load and should be hoisted separately, except for the pre-stretch or cold-tight pre-deformation required by the design, it is strictly prohibited to adjust the installation deviation of the pipe by the method of deforming the bellows. Welding slag shall not be allowed to spatter onto the surface of the bellows and be subjected to other mechanical damage during the installation process; all active components of the bellows shall not be trapped by external members or their active parts shall operate normally; water for hydraulic testing shall be clean and non-corrosive, And should be timely discharge of water in the ripple, and so on.
The main problems of compensator are the stability and corrosion of bellows.The stability of bellows can be solved by reasonable design of corrugated pipe waveform parameters, fatigue life, correct installation and pipe system stress analysis.Corrosion problems can be solved in two ways: (1) reasonable selection of corrugated pipe materials and structural design of compensator to block the corrosion source. (2) strengthening the management of chamber water accumulator to fundamentally solve the corrosion problem.
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