Technical Drawings

[dogtop]

Does anyone know of a recommended or suggested practice, standard, or guideline that describes how to put together a P&I Diagram? Things that I am looking for are: pieces of equipment per sheet, layout, line types and sizes, required descriptions, and any other details to make the diagram readable and understandable by any engineer in the world.

TIA

 

[Ashereng]

This is just a guess, but P&ID would vary from industry to industry, client to client, etc.

I don't know about standard practices or standards, other than ISA symbology, but here are some good practices:
- direction arrows on process lines
- direction arrows on signal lines (especially soft signals)
- entry/exits out of the lefthand/righthand sides of the sheet only (none out the top, and definitely none in the middle of a dwg)
- equipment name in the same location on each drawing (the top, bottom, side, whatever, but consistent)
- notes in a notes section (again, consistent location)
- space the lines and text (there will be a lot of photocopying later that will "bleed" the lines and text)
- use ISA guideline on symbology
- name/lable all the lines (don't use thickness to denote line size)
- if the final deliverable size is 11x17, cad on 11x17 and expand later (don't do it the otherway and shrink)
- straight lines are good, bend/break only if you have to (and use 90° corners)
- use templates for identical things as much as you can
- people seem to not like arial format (I don't know why, but I do) even though it is a very clean format

Okay, enough ranting. Getting off of soapbox.

 

[Eltron]

Ash is right. Even though ISA Standard S 5.1 covers P&ID's, everybody has their own symbols and procedures. I try to stick as close to the ISA standard as possible, but sometimes clients request deviation.

Check this link:

http://engstandards.lanl.gov/drftman/appendix.htm.

L and L lists their standards online. AutoCAD has an inexpensive add on that follows ISA. You can find it at:

http://www.cadtoolsonline.com/pid.htm.

The best advice that I can give you is to pick a method and stick to it. Make your drawings look pretty. After all, the idea is that your process can be followed legibly on paper. Nobody wants to spend the whole day trying to decipher a drawing that looks like the one my son made on his bedroom wall with his mother's eyeliner.

Hope that helps.