The pipe number is unique, but it is not primarily relevant from the electrical viewpoint. He is asking for labeling 'electric heat trace circuits' numbering. The panel designation and circuit number is relevant from the troubleshooting viewpoint and (hopefully) conscise enough for troubleshooting. Crossreference to the pipe designation - as I pointed out before - is helpful. I have not seen, and I have seen enough, lineunbers used as an ID in any physical location, it is used on P&ID's, linelists, ISO's and very rarely on 3D models.
Originally Posted by petersonra