Integrating Fans and Component Selection for Safety
Designing electronic systems for environments with potentially explosive atmospheres is a critical challenge that requires careful consideration of safety from the outset. For engineers, this means understanding how each component—from microcontrollers to mechanical parts like fans—can affect system safety and compliance.
While regulatory standards like DSEAR and ATEX/UKCA are essential, the design phase should focus first on eliminating ignition risks through intelligent component selection, thermal management, and enclosure integration. Among these, fans play a particularly nuanced role, offering essential thermal control but introducing potential ignition sources if improperly specified.
This guide focuses on how to integrate fans and other key components safely and effectively into electronics intended for hazardous zones.
The Role of Fans in Hazardous Electronics Design
In electronic systems for hazardous environments, thermal control is crucial. Overheating can lead to ignition through high surface temperatures or component failure. Fans provide an efficient means of:
- Managing heat dissipation from power electronics
- Circulating air within enclosures to prevent hotspots
- Assisting external cooling of sealed or pressurised enclosures
However, using fans in explosive atmospheres introduces new considerations, since they contain moving parts and (often) motors that can generate sparks or heat.
Selecting Explosion-Safe Fans: Design Priorities
When incorporating fans into hazardous area electronics, you must consider:
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Zone Compatibility
Determine where the fan will be installed: inside the hazardous area, outside but connected via ducting, or within a pressurised enclosure. For internal use, the fan must be certified for the corresponding zone (Zone 0/1/2 for gases, or Zone 20/21/22 for dust).
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Ignition Risk Management
Fans can become ignition sources through:
- Sparking motors: Use brushless DC motors with certification, such as SUNON’s range of ATEX-approved EC fans, or isolate motor windings entirely outside the zone.
- Hot bearings or windings: Select fans rated for the correct T-class (e.g., T4 ≤ 135°C).
- Friction and blade strike: Use anti-sparking blade materials (e.g., aluminium or plastic with carbon loading) and ensure mechanical clearances to prevent contact with housings.
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Fan Certification
Use ATEX/UKCA-certified fans for hazardous zones. SUNON’s range of ATEX-approved EC fans has documentation verifying compliance with BS EN 60079-0 and other relevant standards (e.g., 60079-7 for increased safety, 60079-31 for dusts). In our opinion Sunon’s ATEX fans are the market leaders.
Integrating Fans into Thermal and System Design
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Start with Thermal Modelling
Before selecting a fan, perform a thermal analysis of the system. Consider:
- Component heat generation (power supplies, processors, FETs)
- Enclosure material and insulation properties
- Ambient temperature and airflow availability
Use tools like CFD to model air movement and identify stagnation zones.
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Determine Airflow Requirements
From thermal modelling, calculate required airflow (CFM or L/min). Factor in:
- Pressure drop through filters and grills
- Dust accumulation over time (especially in Zone 20/21 environments)
- Redundancy if fan failure would breach T-class limits
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Specify Redundant or Monitored Fans
To improve reliability:
- Use dual fans in critical systems (N+1 redundancy)
- Integrate tachometer feedback or stall detection into control systems
- Use PWM or temperature-based fan control to reduce wear and extend lifespan
- EMI and Electrical Design
Fans with motors can introduce electrical noise. For Ex i systems, ensure:
- Power to the fan is isolated or outside the hazardous zone
- Filters and ferrites are used on power lines
- Fan control logic (PWM, temperature sensing) is galvanically isolated if entering the hazardous zone
Conclusion
Incorporating fans into electronics designed for explosive atmospheres is a balancing act between cooling efficiency and ignition prevention. The key lies in designing safety in from the start – using certified components, managing thermal loads through modelling, and isolating potential ignition sources.
By making thoughtful, safety-first design decisions early in the process—especially around thermal management and airflow—engineers can create electronics that are not only effective and reliable but also safe and certifiable for even the most demanding environments.
Currently available in frame sizes of 120x38mm, Gelec offers a range of ATEX-approved EC fans from SUNON with multiple speeds and options with either flying leads or spade terminals. These CF series fans are dual voltage as standard, making them suitable for all markets.
