Different types of fire need different types of protection:

• Cellulosic fires; burning building products such as wood, paper, fabrics and small amounts of flammable liquids. Applies to commercial and public buildings.
  Thin film intumescent coatings like Steelmaster to be used.
• Hydrocarbon fires; burning liquid and/or gaseous hydrocarbon products, temperature increasing to 1100°C in 10 minutes. Applies to offshore installations, FPSO’s and petrochemical plants.
  Thick film intumescent epoxy to be used.
• Jet fires; as above products under pressure, temperature increasing to 1300°C in 5 minutes.
  Thick film intumescent epoxy to be used.

Normal appearance

Intumescent coatings may well look like conventional paints. However in a fire they swell to become a meringue-like substance which provides vital insulation for the structural steelwork.

The degree of fire protection needed is normally defined by building regulations and the thickness

After a fire

of the coating is specified to satisfy those requirements.

Fire resistance is an expression of time in minutes - generally 30, 60, 90 and 120.

The heating rate of the member is one of the contributory factors to the fire resistance. This governs the time taken to reach its specific failure temperature.

The heating rate of each section will vary depending on its dimensions.

A short heavy section will heat up more slowly than a tall light section.

This effect is stated as the ‘Section Factor’ and is denoted as the Hp/A value of the steel section.

The Hp/A value is calculated from the dimensions of the steel section:

Hp = the perimeter of the steel exposed to the fire
A = the cross sectional area of the section

Section Factor (Hp/A) = Heated Perimeter / Cross-Sectional Area

The larger the surface area relative to the cross sectional area is, the higher Hp/A value. Therefore more material is required with a higher Hp/A value.

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