Rough surfaces are prone to dust deposition and that is why we require smooth and rounded (easily cleanable) surfaces in the cleanroom, be it pipes, vessels, equipment, walls, floors or ceiling. In the case of pipes, this can be an overkill but generally it is 180 grit external finish.
It is true that my client's spec asks for 180 grit external surface finish. This applies to all exposed SS pipes, SS cladding for CS pipes, SS outer layer for insulation and even for supports as well.
I had a discussion with my client about this matter. I just wonder if there are some international rules to guide this application. My client just told me probably it is for esthetical purpose while my feeling likes you that it is for clean purpose.
