Hazardous areas, often referred to as classified or explosive atmospheres, are locations where the presence of flammable gases, vapors, dust, or ignitable fibers creates a risk of fire or explosion. In such environments, selecting the right materials for equipment, instruments, and construction is critical to ensure safety and prevent potentially catastrophic incidents. Here's an overview of hazardous area materials and considerations:
Materials for Hazardous Areas:
Enclosures and Housings: Materials used for enclosures and housings of electrical equipment and instrumentation in hazardous areas must be non-sparking and able to contain any potential explosions. Common materials include cast aluminum, stainless steel, and glass-reinforced polyester (GRP). The choice of material depends on factors like the classification of the hazardous area and environmental conditions.
Sealing Glands: Cable glands and sealing fittings are used to prevent the ingress of hazardous gases or dust into equipment. Materials like nickel-plated brass, stainless steel, or plastic are chosen based on the specific hazard type and environmental conditions.
Wiring and Conductors: Wiring and conductors used in hazardous areas should be flame-resistant and have low electrical resistance to prevent sparking. Conductors are typically made of copper or aluminum, and insulation materials include polyethylene, polypropylene, or Teflon (PTFE).
Fasteners: Nuts, bolts, screws, and other fasteners must be made of materials that do not generate sparks, such as brass, stainless steel, or non-ferrous alloys. The choice of fastener material depends on the specific hazard type and classification.
Lighting Fixtures: Light fixtures in hazardous areas require robust construction and sealed enclosures to prevent the entry of flammable substances. Materials like die-cast aluminum, stainless steel, or plastic are often used for lighting fixtures.
Seals and Gaskets: Seals and gaskets used in hazardous areas should be made of materials that are resistant to the presence of hazardous gases or dust. Materials like silicone, Viton, and EPDM are commonly used for sealing applications.
Switches and Controls: Switches and control devices in hazardous areas should be designed to minimize sparking. Materials for these components typically include plastic or non-sparking materials like bronze or stainless steel.
Cable Insulation and Jacketing: Cables in hazardous areas require specialized insulation and jacketing materials to prevent the spread of fire. Common materials include thermosetting plastics (e.g., cross-linked polyethylene) and halogen-free compounds.
Ex-Approved Equipment: In many cases, equipment and materials used in hazardous areas should be certified to meet specific international standards, such as ATEX (in Europe) or NEC (in the United States). These certifications ensure that materials and equipment meet safety and performance criteria for use in explosive atmospheres.
Considerations for Hazardous Area Materials:
Hazard Classification: The type and classification of the hazardous area, such as Zones or Divisions, influence the selection of materials.
Environmental Conditions: Factors like temperature, humidity, and exposure to chemicals can impact the choice of materials.
Installation and Maintenance: Proper installation and regular maintenance are critical for ensuring the integrity of materials and equipment in hazardous areas.
Safety Standards and Regulations: Adherence to local and international safety standards and regulations is essential to ensure that materials and equipment meet safety requirements.
Selecting appropriate materials for hazardous areas is a complex task that involves considerations of not only material properties but also the specific hazard type and environmental factors. Proper material selection, along with adherence to safety standards, plays a vital role in mitigating the risks associated with explosive atmospheres and ensuring the safety of personnel and assets in these environments.
