As we have discussed before, this old saying is one that has stuck with me from the mid-1990’s when I learned it a process piping course. Catchy phrase – easy to remember. And I still use it, although my 2023 post made it clear it may be a thing of the past. So I asked AI to explain the saying “3-threads showing,” and I was delighted to see its response:
In the world of piping and pressure vessel inspection, seeing “3-threads showing” is a common rule of thumb, though the technical requirements often allow for more flexibility than the field-standard “safety margin.”
Here is the breakdown of how this is typically handled in industrial codes: