Introduce a typical case of thermal corrosion

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A typical case of thermal differential corrosion is introduced: in an olefin dehydrogenation reactor, the gas temperature ranges from 440 to 560°C and it is in a dry state, resulting in minimal corrosion of the stainless steel vessels. But the designed pressure gauge tube is tilted upward and not insulated on the outside. As a result, the gas in the pressure tube condensed to form hydrochloric acid, which flowed back downward, causing corrosion and perforation at the weld between the pressure tube and the container wall within just 48 hours. Obviously, this design is unreasonable; this corrosion problem can be solved by designing the pressure gauge tube to slope downward, insulating it from the outside to prevent heat loss, and installing a drain valve at the lowest point. Analysis: This case is what is known as \"cold spot corrosion\" (temperature difference corrosion). When designing and constructing insulation for containers and piping systems that handle high-temperature gases, it is essential to consider avoiding the formation of \"cold spots\". If it is not possible to provide proper insulation for the attachments on the outer surfaces of equipment and pipelines, then effective protective measures should be taken for the inner surfaces of the shells beneath those attachments, such as surfacing them with corrosion-resistant alloys.