You can have too much of these. I've been doing a few in the last week or so, and I'm just about all PIDed out. Where I'm working they don't have a standard, so we went with a bunch of symbols that the engineer liked the look of on a previous job. He did not particularly like the ones that I have posted on my site at http://bilrocad.com
There seems to be all sorts of ways of doing a valve unsurprisingly: the ones on my site have little bits of line on the ends of the valves, and they have actuators built in. On his ones, the actuators come as a separate block. Some of them have invisible attributes, some don't.
They are also plainly "old autocad" in that there are no dynamic blocks at all. I have not been a fan of dynamic blocks for normal drafting, but I think they might be the best for PIDs.
If I get enthusiatic enough, I hope to post a set that could do pids.
It looks like a fertile field for lots of lisp macros. On that springs immediately to mind is a routine where you specify 2 points and a line is drawn between the two with maybe a continuation tag at one end and a valve in the line, already inserted.
You can pay for such things, but it seems most people don't, preferring to slog it out with plain Autocad.
There are all sorts of ways of doing pids- I like the tanks drawn in a heavy line-the engineer likes them in grey or very light so that the lines are the emphasis.
Anyone interested in a CAD standard? I have a very lightweight one that just covers the basics.
Maybe next post......