Is there any logic or principle behind determining the placement of different levels in a PID pipeline?
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@In the case of AI, for example, the exhaust pipes in the reaction kettle are made of stainless steel, while the main exhaust pipe is lined with PTFE; should it be placed before or after the flame arrester? For example, the feed pipeline is made of a lower-grade stainless steel, while the part closest to the reactor is made of a higher-grade stainless steel. There are switch valves and isolation valves on the feed pipeline – where should I place them? And so on; I asked many people about this. Sometimes it’s necessary to protect valves, and other times it’s necessary to prevent pipes from being contaminated (such as nitrogen pipes). In short, it’s quite confusing. Is there any general principle? I don’t know whether the pipe grade change should be placed before or after the valve, nor which valve it should be placed at. In other words, it’s unable to analyze processes and problems independently. Is there anyone who can help sort this out?…
Indeed, these specifications mention it very little. From my past experience, I have opted to make the change in pipe material/grade before or after the valve; this prevents welding between pipes of different grades/materials. As for whether to place it before or after the valve, that is another consideration. It is generally preferred that the valves match pipes with higher grade requirements.