Failure reason of metal corrugated pipe expansion joint

Oct. 08, 2019

Metal corrugated pipe, also known as expansion joints or compensators, is a type of compensating element. The effective telescopic deformation of the bellows of the working body is utilized to absorb dimensional changes caused by thermal expansion and contraction of pipelines, pipes, containers, etc., or to compensate axial, lateral, and angular displacements of pipelines, conduits, containers, and the like. It can also be used for noise reduction and vibration reduction.

Corrugated metal pipe is used in many industries, and is widely used in aviation, aerospace, petroleum, chemical, metallurgy, electric power, paper, wood, textile, construction, medicine, food, tobacco, transportation and other industries. In addition to good compensation, high reliability is the main reason. Its reliability is ensured through multiple links such as design, manufacturing, installation, operation management, etc. Any loss of control in one link will lead to the reduction or even failure of the life of the compensator.

After many years of statistics, the industry has found that the cause of the failure of the bellows compensator is nothing more than the above aspects: The design accounts for 10%, the manufacturer cuts the work by 50%, the installation does not meet the equipment requirements, accounting for 20%, and the rest is caused by improper operation management.

Pipe corrugated Metal

Failure of the corrugated steel pipe occurs during pipeline pressure testing and operation. There are three main types of problems during pipeline pressure test: due to improper temporary support of the pipeline system, or improper installation of the pipe system fixing bracket, the bracket is damaged, the bellows is excessively deformed and fails; the pressure or displacement considered by the bellows design is safe and affluent. Insufficient degree, the bellows is unstable and deformed when the pipeline is pressure tested; the quality of the compensator is manufactured, the manufacturer cuts the work, and the 5-layer stainless steel is changed to 3 layers or less. The failure of the bellows during operation mainly manifests in two forms of corrosion leakage and instability deformation, among which corrosion failure is mostly. Anatomical analysis of corrosion-infected bellows found that corrosion failure is usually characterized by point corrosion perforation and stress corrosion cracking, in which chloride stress corrosion cracking accounts for about 95% of the total corrosion failure. There are two types of bellows instability: strength instability and structural instability. The strength instability includes the internal and external pressure bellows plane instability and the external pressure bellows circumferential instability. The structural instability is the column loss of the internal pressure bellows compensator stable.

Corrugated Steel Pipe

Today, “Special Steel 100 Seconds” talks about the failure of the bellows expansion joint. In addition to considering the working medium, working temperature and external environment, the possibility of stress corrosion and the influence of the pipe cleaning agent on the material should also be considered. On the basis of this, the welding, forming and material cost-effectiveness of the bellows material are combined. Economical and practical corrugated pipe making materials.

Under normal circumstances, the material selected for the bellows should meet the following conditions:

(1) Good plasticity, facilitating the forming of the bellows, and obtaining sufficient hardness and strength by a subsequent treatment process (cold work hardening, heat treatment, etc.).

(2) High elastic limit, tensile strength and fatigue strength to ensure the normal operation of the bellows.

(3) Good welding performance, meeting the welding process requirements of the bellows in the manufacturing process.

(4) Good corrosion resistance and meet the requirements of bellows in different environments.

Once the bellows fails, it will increase the safety hazard of the pipeline. Therefore, for safety reasons, “Special Steel 100 Seconds” suggests that you should correct the correction after the bellows has the above-mentioned failure performance. Continue to use the cost, causing greater losses to the follow-up.

The cost of the product itself is small, and it is a big invisible loss for subsequent production. Don't take this small compensation component lightly.

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