Whenever we are dealing with piping and vessels that use nuts and bolts as their joining method, there was always this “rule of thumb” about “short-threading” and “3-threads showing.” But now these “rules of thumb” may be no more, based on ASME PCC-1–2019, 8.2 Bolt Lengths. I was raised/trained in this as a fundamental in process safety, and we have cited short-threading many times during audits and investigations. But now, there is language stating neither “short-threading” nor “3-threads showing” may no longer be “fundamental”. I almost believe this is another case of “dumbing down” our RAGAGEPs. It seems when OSHA and EPA begin to understand process safety matters better and issue citations on some critical, albeit small in size ONLY matters that the RAGAGEP used in the citation gets a revision to make it more difficult for OSHA/EPA to use in their citations. For example, take these two statements from PCC-1:
- However, it has been shown that the full strength in a threaded fastener can be developed with one thread less than complete thread engagement (see para. 16.15 references), a potential consideration in certain post-construction situations.
- Excess thread protrusion beyond the nut should be minimized.
Let’s discuss what these revisions mean…