The corrugated metal pipe is also called corrugated metal pipe, metal spiral pipe, concrete-filled pipe, and corrugated pipe for footing bolts. The corrugated metal pipe is made of high-quality steel strip through the process of wave rolling, tube forming, nibbling, and cutting into a round and flat corrugated pipes. This article mainly introduces the causes of damage to corrugated steel pipes.
Anticorrosive corrugated steel pipe
The first form of damage is mainly related to acid dew point corrosion. The flue gas of the catalytic cracking unit usually contains sulfur trioxide, which is combined with water vapor in the flue gas to form sulfuric acid steam. At this time, the acid dew point temperature of the flue gas is 90 ~ 180 C, if the actual wall temperature of the corrugated steel pipes is too low (such as below 120 C, the reason is improper insulation in the corrugated steel pipes or the actual temperature change of the corrugated steel pipes caused by equipment start and stop), the acid will condense on the surface of the corrugated steel pipes, in the displacement stress, pressure stress, and even more sulfuric acid under the joint action, the corrugated steel pipes occur along the crystal stress corrosion cracking when there is When the presence of Cl - stress corrosion cracking will accelerate.
The second damage is mainly caused by the catalyst containing a high flow rate of flue gas into the corrugated steel pipes and the guide tube between the high-speed erosion of the corrugated steel pipes or the formation of turbulent flow in the wave abrasion corrugated steel pipes, so that the corrugated steel pipes wall thinning and local high temperature, resulting in its pressure-bearing capacity decreased until damage occurs.
The service life of corrugated steel pipes refers to the short working period or the number of cycles that can guarantee normal work when used under working conditions. Its rated life is the expected service life set out in the product design, requiring that the bellows do not allow fatigue, failure, damage, and other phenomena during this period.
The elastic sealing system composed of bellows often works under the conditions of variable load and large displacement with more cycles, the fatigue failure of corrugated steel pipes will make the system fail, so it is important to ensure the service life of bellows.
The traditional life is mainly obtained by the method of estimation using the empirical formula in the EJMA standard. This calculation method deviates a lot, and the life under complex working conditions is often only corrected by the safety factor, which can not well meet the needs of engineering applications, therefore, it is necessary to find a more advanced life analysis method to carry out fatigue life analysis of corrugated steel pipes.
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