Required paint quantity for painting of a pipe depends on following factors :
- Surface area to be painted.
- Required Dry Film Thickness (DFT).
- Percentage of Solids content in a given paint.
- Wastage of paint during painting which is based on type of painting method used.
Wet Paint Thickness
When paint is applied to steel structure, it is in wet condition with volatile organic compounds. When it dries, all volatile components goes away leaving only solids component behind. So to achieve particular dry film thickness, higher thickness of wet film is required is is calculated as :
Wet Film Thickness (WFT) = DFT/Fraction of Solids.
Theoretical Paint Quantity
Theoretical Paint quantity is calculated by multiplying total surface area to be painted with wet film thickness.
Theoretical Paint Quantity = Surface Area X WFT.
During painting process, some amount of paint gets wasted which depends on method of paint application. Typical wastage percentages are :
- Brush or Roller Painting : 10%.
- Airless Spray Painting : 20%.
- Conventional Spray Painting : 30%
So, we have to add wastage to calculated paint quantity to get actual paint quantity.
Actual Paint Quantity = Theoretical Paint Quantity / Fraction of Solids in Paint.