Non-Electrical Equipment in ATEX

When people think of ATEX, they often picture electrical equipment—motors, switches, control panels. But mechanical equipment can be just as capable of causing ignition in an explosive atmosphere. The ATEX Equipment Directive (2014/34/EU) covers both, and in many industrial settings non-electrical ignition risks are every bit as significant as electrical ones.

What Counts as Non-Electrical Equipment?

Non-electrical equipment is any device with potential ignition sources that don't originate from electrical energy. In practice, this means equipment with moving parts, surfaces that can heat up through mechanical action, or components that can generate sparks through friction or impact. The EC ATEX Guidelines (§40-43) clarify that a wide range of mechanical equipment falls within scope.

Common examples include pumps and compressors, fans and blowers, gearboxes and drive systems, mixers and agitators, conveyor systems, brakes and clutches, and even hand tools designed for use in hazardous areas. If it moves, compresses, or has surfaces that can rub together in a potentially explosive environment, ATEX likely applies.

How Mechanical Equipment Creates Ignition Sources

Mechanical equipment can ignite an explosive atmosphere through several mechanisms, each of which must be assessed during design:

• Hot surfaces: Friction in bearings, seals, or brakes generates heat. Gas compression creates heat. Even normal operation can produce surface temperatures above the auto-ignition temperature of some substances if not properly managed.
• Mechanical sparks: Metal-on-metal contact—whether from normal operation, a bearing failure, or foreign objects entering rotating machinery—can create incendive sparks. The energy in a mechanical spark depends on the materials involved; light metals like aluminium and titanium can produce particularly energetic sparks.
• Static electricity: Non-metallic components such as drive belts, plastic fans, or rubber seals can build up electrostatic charge. If that charge discharges in the presence of a flammable atmosphere, ignition can occur.
• Adiabatic compression: Rapidly compressing gas raises its temperature. In pneumatic systems or compressors, this can create temperatures well above ignition thresholds if not controlled.

The Relationship Between Electrical and Non-Electrical Parts

In many installations, a piece of equipment has both electrical and non-electrical ignition risks. A pump driven by an electric motor is a classic example: the motor is assessed under electrical protection standards, while the pump itself—with its seals, bearings, and impeller—is assessed for non-electrical ignition risks. Each part needs its own appropriate certification, and the combination must be considered as a whole.

Categories and Conformity Assessment

Non-electrical equipment uses the same category system as electrical equipment—Category 1, 2, or 3 depending on the zones where it will be used. The conformity assessment procedures also follow the same module structure: Category 1 and 2 equipment generally require a notified body to examine the design and monitor production, while Category 3 may allow manufacturer self-certification.

The key standards for non-electrical equipment are EN ISO 80079-36 (general requirements) and EN ISO 80079-37 (specific protection concepts). These cover constructional safety (c), control of ignition sources (b), liquid immersion (k), and flow restricting enclosure (fr).

Marking Differences

The ATEX marking for non-electrical equipment follows the same structure as electrical equipment, but with one notable practical difference: instead of a temperature class (T1-T6), non-electrical equipment often shows the actual maximum surface temperature in degrees Celsius. This is because the T-class system was developed primarily for electrical equipment, and a direct temperature value is more meaningful for mechanical items where the heat source is friction or compression rather than an electrical circuit.

Practical Considerations

Non-electrical equipment assessment requires a different mindset from electrical assessment. Where electrical engineers think about spark energy and thermal effects of circuits, mechanical assessment focuses on friction, impact energy, surface temperatures under fault conditions, and material compatibility. A thorough ignition hazard assessment must consider both normal operation and reasonably foreseeable faults—a bearing seizing, a seal failing, a foreign object entering a fan.

Maintenance is particularly important for non-electrical equipment because mechanical wear directly affects ignition risk. A bearing that's within tolerance today might overheat next month. Vibration monitoring, temperature monitoring, and regular lubrication programmes are practical measures that complement the equipment's designed-in safety features.