Colour Coding is very important in a chemical plant- it discourages confusion and allows early identification during normal and during emergency conditions. Guidelines are given below on Colour Coding- the IS standard may be consulted for further detail.
The system of colour coding consists of a ground colour and colour bands superimposed on it.

The ground colour identifies the basic nature of the fluid carried and also distinguishes one fluid from another.
Colour bands are superimposed on ground colour to distinguish:
a) One kind or condition of a fluid from another kind or condition of the same fluid or
b) One fluid from another belonging to the same group

4.1 Ground Colour
Ground colour shall be applied throughout the entire length
4.2 Colour Bands
  • Colour bands shall be superimposed on the ground colour and shall be applied near the valves, flanged joints, tappings, junctions, points where the pipe line passes through walls, the valve station
  • The minimum width of the narrowest colour band shall be 25 mm
  • Whenever more than one colour band is indicated, the bands shall be arranged in the sequence given and the sequence follows the direction of flow
  • The relative proportional widths of first colour band to the subsequent bands shall be 4 :1
When further identification is required to supplement the colour codes, this may be done by the particular industry or plant for its own use.

5.1 Lettering
The recommended size of lettering for pipes of different diameters is given below :
O.D. of the pipe Size of Lettering
up to 30 mm 10 mm
above 30 - 50 mm 20 mm
above 50 - 80 mm 30 mm
above 80 - 150 mm 40 mm
above 150 - 250 mm 63 mm
above 250 mm 90 mm

5.2 Direction of flow
Where it is required to indicate the direction of flow, arrows or lettering (e.g., brine supply -BRS, chilled water return -CHWR) may be painted near valves, junctions, wall openings etc. and at suitable intervals along the pipe, in a manner best suited to local conditions. These shall be black or white in colour in contrast to the colour on which they are superimposed.

5.3 Visibility of markings
Attention should be given to the visibility of colour markings and the letterings. Where the pipelines are located above the normal line of vision of the operating personnel, the lettering should be placed below the horizontal line of the pipes at proper location so that the operator can easily notice and identify them from the floor level.