piping pitting corrosion

In gas pipelines where the medium is hydrogen and nitrogen, at temperatures of 180°C and pressures of 23 MPa, point corrosion occurring due to the deposition of condensed water does pose certain safety risks. First, the original thickness of the pipe was 35 mm, which decreased to 25 mm after corrosion; this means that corrosion resulted in a loss of approximately 28.6% of the original thickness. Under high-temperature and high-pressure operating conditions, the strength and corrosion resistance of pipelines are particularly crucial. Under high-temperature conditions, the corrosion rate of metal materials generally increases, as high temperatures can accelerate chemical reactions and enhance the activity of corrosive agents. Furthermore, if the pipe surface is in prolonged contact with water vapor, especially in the presence of condensed water, an electrochemical corrosion environment is created, which accelerates the occurrence of localized corrosion. Taking these factors into account, it is recommended to take the following actions: 1. **Inspect and repair the air deflector**: Ensure that condensation water does not drip back onto the pipes, thereby preventing further corrosion. 2. **Regularly measure pipe thickness**: Use ultrasonic thickness measurement tools to check the thickness of the entire pipe as well as specific areas affected by corrosion, in order to assess its safety. 3. **Strengthen monitoring and maintenance**: Regularly inspect and maintain the pipeline system, especially in areas showing signs of damage or corrosion. 4. **Consider safety margins**: Assess the impact of the current thickness loss on the overall strength and safe operation of the pipeline. If the corrosion is severe or occurs in critical areas, more aggressive repair measures may be necessary, such as local replacement of pipe sections or the use of lining repair techniques, to ensure safe operation. .

Do water droplets falling on high-temperature pipes cause pitting corrosion on the pipe surface more easily?

Judging from the appearance, corrosion is not necessarily caused during operation. I suspect that this pipeline has been out of use for a long time, at least for several years. It originally had an insulating layer on its surface; during the period it was not in use, water absorbed by this insulating layer caused corrosion beneath it. It must have been several years already

This constitutes local thinning, and it is necessary to evaluate it in accordance with 3.2.4 of TSG D7005-2018 \"Rules for Periodic Inspection of Pressure Piping – Industrial Piping\"; other data are also required :)

The pipeline is in operation for a long time; it has no insulation on its outer surface, and the problems are mainly caused by dripping water

This is actually a case of localized corrosion, but it remains uncertain whether it can be treated according to the provisions for localized thinning in TSG D7005-2018, as the corrosion occurs in multiple locations; the distance between these pits also needs to be taken into consideration.

For 20# steel at 180°C and 23 MPa, with an allowable stress of 126 MPa at operating temperature, a wall thickness of 23.03 mm is already quite dangerous