Jacketed pipe length

Correction: It is heat transfer oil that serves as the medium in the outer jacket, while the melt is in the inner jacket

Under normal circumstances, heat tracing using heat transfer oil is not recommended unless there is no other alternative, as heat transfer oil tends to leak at high temperatures. In other words, leaks can occur due to imperfections in the tubing or manufacturing defects, not to mention weld issues； Even with 100% radiographic inspection of the welds, minor leaks of heat transfer oil cannot be guaranteed to be detected.

It’s a fully jacketed pipe, with 304 stainless steel used for the tubing; polyester pipes generally require stainless steel tubes as well. I’d like to know at what distance partitions need to be installed in the jacket. . .

There are concerns regarding the operating temperature when using heat transfer oil with 304 pipes; it is recommended to use 321 material instead； It is recommended that the welded sections serve as partitions; in other words, the straight pipe sections should not exceed 6 meters in length, with thinner pipes used to connect them.

At least the melt pipe is 304, as stated in the book published by the China Textile Research Institute. . . Other media might work better with 321; perhaps I didn’t express myself clearly. Firstly, melts are generally quite sensitive to temperature. For tubular concealed types, the jacket is welded directly, so it’s not possible to use a spacing of 6 meters between units. What I’d like to ask is: at what length intervals is it necessary to reinstall the inlet and outlet for heat transfer oil on the jacket? (I think the main purpose of this is to ensure uniform temperature reduction.) I saw in this post https://bbs.hcbbs.com/thread-1226780-1-1.html that it’s 30 meters, and after consulting someone else, I was told that it’s possible to follow the approach used for steam. . . I still decided to make heat transfer oil inlet and outlet ports on the 30m jacket.