The steam condensate pipe line is cracked; please help analyze the cause.

Possible causes of cracks in the steam condensate piping include: 1. **Water hammer phenomenon**: When steam in the steam system condenses rapidly, creating a local vacuum, the surrounding liquid or steam fills this space at extremely high speeds, generating a massive pressure surge known as water hammer. Such shock waves can cause fatigue in the pipeline material, ultimately leading to cracks. 2. **Freeze cracking**: Despite insulation measures, if the insulation is not effective or in extremely low-temperature conditions, the condensation water inside the pipes may freeze and form ice blocks. The expansion force of ice can cause pipes to crack. 3. **Material issues**: Although 304 stainless steel is corrosion-resistant, it may not be strong enough under conditions of high temperature and pressure cycles, especially if the material has defects such as intergranular corrosion or stress corrosion cracking. 4. **Design or installation issues**: If the pipe design is not sufficient to withstand the actual operating pressure, or if stress concentration occurs during installation (such as when the pipes are not properly aligned or the supports are not fixed correctly), this can also lead to cracking. 5. **Fatigue fracture**: Prolonged temperature and pressure variations can cause fatigue in materials, especially in straight sections without welds, as welds are typically reinforced. Based on the situation you described, this type of cracking in the straight section away from the weld is more likely to be caused by water hammer or design flaws. It is recommended to check the insulation condition and installation quality, as well as monitor whether water hammer occurs in the system; if necessary, a water hammer suppressor can be installed or the system’s pressure can be adjusted and optimized. .

This is likely to be corrosion beneath the insulation layer; due to the infiltration of water or steam, condensation, as well as accumulation, evaporation, and concentration in certain areas on the surface, chloride ions in the insulation material also become concentrated in those areas, thereby causing pitting and stress corrosion cracking. It is recommended to control the chloride content in the insulation material on one hand, and to apply an appropriate primer to the stainless steel pipes on the other hand.

On the premise that the composition of the material is confirmed to be qualified (a simple spectrometer can be used to determine whether it is 304), more consideration must be given to the concentration and temperature of the medium being transported

This post was last edited by CHANGBAISHI on 2024-4-18 08:34. It is recommended to cut off this section and check whether there is any corrosion inside. If there is corrosion inside, it is necessary to check whether the physical and chemical properties of the medium are related to the corrosion. It is also necessary to check whether the wall thickness of the outer curve of the elbow is uniform and whether there is any corrosion. For reference.

First, check the internal corrosion condition and take a sample of the condensate to analyze the ion content. From the images, it can be seen that the cracks are vertical and symmetrical on both sides near the lower part; I suspect it is due to localized electrochemical corrosion. I wonder if the cracks all occur at the lowest point of the straight pipe sections, and whether there were any instances of exceeding specified limits or of the pipeline being out of service in the past.

Thank you for sharing the information; the forum is even better with you!

Thank you; I will remove a section over the next few days and cut it open to take a look.