How to design a P&ID ? Part-1

Designing a P&ID Part-1

In this part we will see the legend and symbols using in P&ID now days. Please note that the legend and symbols may vary from one process designer to another and the reader should understand that. Following sections will give a brief idea about P&ID representation.

Pipe line number

X” – AB – CDEF – GHI – J

X = Pipe line size.

AB = Service Code (Arbitrary for Chlorine I can take as CL).

CD = Last two digits of drawing number.

EF = Line sequence number.

GHI = Line material of construction.

J = Insulation thickness.

Example:

                6” – CL – 0102 – CS – 40H

The above line is 6 inch pipe in chlorine service present in a drawing whose number ends with 01 and it is second such line in the drawing. Also the material of construction is Carbon Steel with 40mm thick hot insulation.

Service code, pipe material, insulation notation varies from one company to another. Some companies also use color coding to easily differentiate the lines in colored P&ID.

Area numbers

In order to easily review a section in P&ID it is always better to allot specific number for that particular unit. Consider the following example.

31: Raw material processing section.

32: Reacting section.

33: Purification section.

34: Storage/Packing/Drumming section.

So if I say, I am using a roll crusher in 31 section, I am actually referring roll crusher present in raw material processing section.

Equipment tag format

In a process industry we use lot of process equipments (pumps, vessels, exchangers, reactors etc,). Calling a pump with its true name like “Propylene glycol distillation column bottom pump” may create confusion. Also it is cumbersome enough to mention with its original name all times. So we use a notation which conveys the equipment name tidy. Generally the equipment tag name will be of the form

AN – EQ – SN

AN: Area Number

EQ: Equipment type code

SN: Sequence Number

For Example

03 C 3204

The above tag name corresponds to a fourth (04) column (C) in reacting section (32), whose area number is three (03).

Again some companies follow three digit tag number and some four digits. It is purely based on the company discretion. For equipments we can use the following notation.

Code	Equipment
A	Agitator
C	Distillation columns, absorption columns, scrubber, packed columns
D	Drums
E	Exchangers
EJ	Ejectors
F	Filter
G	Decanters, Centrifuges
H	Hydro cyclones
J	Hoppers, Bunkers
K	Compressors, Blowers
L	Vacuum pumps
M	Mixers
P	Pumps
R	Reactor
SM	Static Mixers
T	Tanks
V	Vessels