What is an explosion-proof control panel? Basic knowledge of control panels used in hazardous locations

Explosion-proof control panels are specialized control panels essential for safely controlling electrical equipment in hazardous locations where flammable gases or dust are present. This article provides an easy-to-understand explanation of the basic structure and applications of explosion protection.
1. What is an Explosion-Proof Control Panel? Basic Concepts and the Background for Its Necessity
An explosion-proof control panel (explosion-protected control panel) is a control panel installed in "hazardous locations" where flammable gases or combustible dust are present, designed to prevent ignition by sparks or high temperatures generated inside the panel.
In environments such as factories and plants, using a general-purpose control panel as is can lead to internal relays and switches becoming ignition sources, posing a risk of causing explosions. Explosion-proof control panels fundamentally avoid such risks and are important safety devices for protecting human lives, equipment, and production lines.
2. Types of Explosion Protection Structures and Applicable Environments
For explosion-proof control panels, several explosion protection structures exist depending on the operating environment and the type of hazardous material. The main ones are as follows:
- Flameproof enclosure (d): A structure that contains an explosion within the enclosure even if it occurs. Most widely used.
- Increased safety (e): Components are configured not to generate sparks, and insulation and clearances are enhanced.
- Intrinsic safety (i): A structure where the circuit itself does not possess enough energy to cause an explosion. Frequently used in instrumentation signal systems.
- Pressurized enclosure (p): Pressurized air is supplied into the enclosure to prevent flammable substances from entering.
The choice of structure is determined by the "zoning" (hazard classification) of the area where it is installed and the nature of the controlled equipment.
3. Design Requirements and Selection Points for Explosion-Proof Control Panels
Unlike ordinary control panels, explosion-proof control panels require the following design and structural considerations:
- Enclosure material and structure: Use aluminum alloy or steel plate to ensure airtightness and strength.
- Sealing of cable entry points: Use explosion-proof cable glands to achieve both airtightness and explosion protection.
- Heat dissipation measures: Ingenuity is required in internal layout and fan usage to prevent heat buildup.
- Component selection: Use explosion-proof certified relays, terminal blocks, switches, etc.
- Maintainability: A structure that considers safety during opening/closing and maintenance of certification is required.
Furthermore, at the design stage, it is necessary to clearly define the panel's installation environment (indoor/outdoor, temperature, humidity, corrosivity) and implement corresponding IP ratings and corrosion protection measures.
4. Basic Knowledge of Explosion Protection Certification and Legal Compliance
When explosion-proof control panels are used in Japan, they must comply with \-\-Domestic Explosion-Proof Certification (TIIS certification)\-\- based on the Industrial Safety and Health Act. For export, compliance with national and regional standards such as \-\-ATEX (Europe) and IECEx (international standard)\-\- is required.
For the design, manufacturing, inspection, and installation of explosion-proof control panels, the following laws and guidelines are relevant:
- Industrial Safety and Health Act (under the jurisdiction of the Ministry of Health, Labour and Welfare)
- Electrical Appliance and Material Safety Act (PSE)
- Explosion protection standards by the International Electrotechnical Commission (IEC)
- Various factory guidelines (chemical industry, painting lines, etc.)
If a panel that does not comply with these certifications and standards is installed in a hazardous location, there is a risk of legal liability in the event of an accident, so confirmation at the specification stage is essential.