Can stainless steel expansion joints be used in high-temperature tar pipelines?

I have a question for experts: in the structure of a tubular furnace, where the furnace bottom is connected to the collection pipe, it is necessary to prevent heating-induced thermal expansion stresses in the furnace tubes. I am considering using stainless steel expansion joints to connect the branch pipes to the collection pipe – I wonder if this is feasible. Are there any proven examples of such use? Some people say that these joints can wear out and cause leaks within a few months. The material is 400-degree tar. Thank you

This post was last edited by Shutong on 2020-8-26 at 21:11. Tar has an impact on elbows and pipe bends; high-speed fluids, or those containing bubbles, continuously strike the metal surface, resulting in more severe impact erosion. This type of corrosion is known as impact corrosion. Impact corrosion is the result of the combined destructive effects on metal of mechanical damage from high-speed fluids and electrochemical corrosion. Due to the presence of certain amounts of moisture in the tar, it is pumped into the radiant section of the tubular tar furnace under pressure using a two-stage tar pump; as a result, the moisture and light components in the tar vaporize to form numerous small droplets that become entrained within the tar. Consequently, areas such as the two-stage elbows in the tar system and the asphalt extraction outlets are primarily subject to impact corrosion. Impact corrosion is the main cause of corrosion in elbow thermocouples. Pipes and other accessories are generally also made of stainless steel, but with a higher grade of material. Another measure taken is to add soda ash to the tar. In terms of the manufacturing process, efforts should be made to reduce moisture and ammonium salts as much as possible.

400 degrees is a bit high in tar processing; I’m not sure. But we use them quite a lot in the 360-380 range; expansion joints are used at both the inlet and outlet of the tubular furnace circulation pump, and as long as the right type is selected, there are no problems.