Hi hc,
Listen to the advice of experience given here; you’re right on the money. I was taught that support placement was part of my job. As Jop points out, the major structures, primarily the piperacks, has to be decided well ahead of time. The modern equivalent to what I used to do manually, and share with the structural group through study drawings, is temporary steel in the 3D models, or “white steel” as it’s sometimes referred to, placed by the piping designers for the structural designers to follow.
I remember a brief two year stint many years ago that I spent in the pulp and paper industry coming from the oil and gas industry. I was chastised for placing pipe supports and coordinating these with the structural group because there was a separate pipe support group that dealt with this. I saw the fruits of their labour when I went to the field; pipe hangers to the ceiling blocking the run of an overhead crane.