vent and drain valves

[struggling]

I am involved in an effort to "re-draw" all the P&ID's at the plant. On the drawing, a valve symbol is "blacked in" to represent a closed valve. Several questions have been asked concerning the normal alignment of vents and drains. We have identified a significant number of discrepancies. Should they be shown open, or closed?? Of course, these valves, in most cases, must be "closed" during normal plant operation - but what guidance should I use to determine how to show them on a drawing?

I've called myself reading the ANSI/ASME standards concerning vents and drains, and have a clear understanding of the requirements for caps and blind flanges for drains, vents and test connections, but have found no guidance for standardized valve positioning on drawings.

Help!

 

[MortenA]

1) Dont try to include to many information re. physical layout in a P&ID (physical orientation, no. of pipe bends etc). However drain and vent could be shown as drain "going down" and vents "going up" for quick reference. I always try to limit my no. of "installation notes" because the tend to stick to the drawing. Several generations (and projects and years) it will still say "min. distance" even though this has been installed long ago. Some times they are however required.

2) The idear using black and "non filled" symbols is widespread but not universal. Some companies even uses filling for totally different purposes such as a black ball like symbol for a ball valve and "non filled" for gate valves. I prefere write NC/LC/CSC (Normally Closed, Locked closed or Car Sealed Closed) next to the valve.

3) I think that special requirement during shut down could be added as notes but not directly on the drawing.