As I have said many times before, the world of process safety can be a very confusing and strange sandbox to play in. There are so many rumors and innuendoes stemming from the fact that our PSM/RMP world is made up of a weave of RAGAGEPs, many of which practicing process safety professional can’t fully understand and apply. Just recently I was told by a piping contractor that “hex head/cap screw bolts” are prohibited from being used on flanged joints in HAZMAT service (e.g. PSM/RMP processes). This bolt is prohibited in PSM/RMP flanges?
Now as you can imagine, my mind goes way back to my days working in chemical and petrochemical plants where the vast majority of our joints were flanged connections; so the statement that hex head/cap screw bolts are prohibited from use caught me off guard. What was he talking about… “hex head/cap screw bolts are prohibited on chemical processes???” Has the world gone mad? Well, his statement does have quite a bit of support… although many will argue that hex head/cap screw bolts and nuts are NOT PROHIBITED – just not recommended either! Let’s discuss…
First let’s look at ASME B16.5, PIPE FLANGES AND FLANGED FITTINGS for what it says about this:
(emphasis by me)