How to design a P&ID? Part-2

Pipe line representation

Pipe lines should be shown with an orthogonal arrow mark i.e, You should not mention the arrow mark in the middle of line. Always represent the arrow at the pipe right angles in the drawing.

 

Apart from process lines, we use various lines in P&ID to represent electrical signal, pneumatic signal, hydraulic signal, software link, mechanical link etc. Following representation is used in general to represent various lines in P&ID.

Whether a line is insulated or not, whether personal protective equipment is required to go near that line etc such details are mentioned in the line number itself. Some of the most commonly using traces and codes are as follows.

1. ET   : Electric Trace
2. FP   : Fire Protection
3. HC  : Heat Conservation
4. I      : Insulation
5. PP   : Personal Protective Equipment
6. S     : Steam Trace

In process lines we use various valves to control the flow and direction. Valves which we represent in the P&ID will only be procured by the respective companies. Depending on the type of valve several representations are available to denote the valves. Some of them are mentioned here as follows.

Some P&IDs also mention the tag number for valves. Apart from the above mentioned valves some special fittings are shown below.

These valves and fittings are connected to the process lines by thread joints, welded joints and flanges. They are also represented in different formats like

Even P&ID file name has also a special meaning. For Example

1234D567RN.DWG

Here 1234 represents the project code or number, D stands for P&I drawing, 567 stand for drawing number which may be based on first one or two digits of instrument loops.