Hazardous Locations Explained

cbetton News

In electrical engineering, a hazardous location is defined as a place where potential hazards (fires, explosions etc.) may exist under normal or abnormal conditions due to concentrations of flammable gases, vapours, dusts or ignitable fibres. Electrical equipment installed in such locations is designed and tested to ensure it does not initiate an explosion due to arcing contacts or high surface temperature. According to the NEC (National Electrical Code) the three types of hazardous locations are categorized by:

  • Class I – (gases, vapours, and liquids)
  • Class II – (dusts)
  • Class III – (fibres and flying particles)

Class I is directly related to oil and gas market applications such as petroleum refineries, gasoline storage, dispensing areas and utility gas plants. According to the ignition temperature of the substance / explosion pressure / other flammable characteristics, the gases and vapours of Class I locations are broken into four groups and two sub-divisions:

  • Group A – Acetylene
  • Group B – Hydrogen, gases or vapours of equivalent hazard
  • Group C – Ethyl-ether vapours, ethylene, or cyclopropane
  • Group D – Gasoline, hexane, naphtha, benzene, butane, propane, alcohol, etc.
  • Division 1 – Normally explosive and hazardous
  • Division 2 – Not normally present in an explosive concentration (but may accidentally exist)

Temperature classes exist to designate the permissible surface temperature of electrical equipment which allows them to operate normally in the surrounding atmosphere:

  • T6 – 85  ~ 100°C (185 ~ 212°F)
  • T5 – 100 ~ 135°C (212 ~ 275°F)
  • T4 – 135 ~ 200°C (275 ~ 392°F)
  • T3 – 200 ~ 300°C (392 ~ 572°F)
  • T2 – 300 ~ 450°C (572 ~ 842°F)
  • T1 – 450°C + (842°F +)

For further information on solutions designed for use in extreme conditions, call ECA Services on +44 (0)118 929 4990.