Generally, electrical safety is ensured by the implementation of one of two considerations, i.e. that electrical apparatus be located where reasonably practicable outside Explosive Atmospheres, and that electrical apparatus be designed, installed and maintained in accordance with measures recommended for the area in which the apparatus is located.

The selection of equipment for use in Explosive Atmospheres will depend upon a number of variable factors including but not limited to the Zone of Use, the Hazard Category, the Gas Group or Combustible Dust data, the rating of equipment for the operating conditions, the Temperature Classification requirement of the equipment (determined by the T Rating of the flammable mixture), any construction material considerations including reliability against chemical attack, the Ingress Protection Rating required, the protection against possible damage from vibration, reduction in the risk of thermite sparking, the possibility of static charge formation, and perhaps several other factors related to the electrical characteristics of the installation.

In order to ensure that the preferred type of equipment is used on a plant or project, the responsible engineers may prefer to specify the apparatus by make and model or generic type. Bearing in mind that the most progressive and forward thinking manufacturers are continuously developing their products the task of specification must also be a continuous process.

Here are a few of the basic factors which may affect specification of electrical equipment for Explosive Atmospheres :-

  • Clear definition of the acceptable form(s) of certification,
  • Acceptable Certification Standards,
  • Acceptable Gas Groups,
  • Zone of Use requirement,
  • Form of Protection preferred,
  • Temperature Classification,
  • Any environmental conditions,
  • Any particular material requirements,
  • Minimum Ingress Protection,
  • Additional Deluge Test Certification, if required,
  • Additional Marine approvals, if required,
  • Minimum and Maximum Ambient Temperature rating.

Prior to selection being finalised and equipment being earmarked for purchase the relevant engineering personnel should review the availability of the preferred or specified equipment, verifying that it has the necessary Explosive Atmospheres certification to meet the conditions prevailing. This review of certification should cover any special conditions for safe use that may be included in the certification documents to avoid subsequent non-conformities arising when the equipment is ready to be installed, commissioned, operated, inspected or maintained.

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