ATEX and explosion safety in powder processing

Dust explosions are an underestimated risk in the powder processing industry. A cloud of fine organic or metallic dust combined with an ignition source can trigger a devastating explosion within milliseconds. For engineers, buyers and QA managers in pharma, chemicals, food and the battery industry, ATEX-compliant process equipment is therefore not an option but a legal and operational necessity. HECHT supplies powder handling systems that build explosion safety into every design.

What ATEX means for your process

ATEX refers to two European directives: 2014/34/EU for equipment in explosive atmospheres and 1999/92/EC for the protection of workers. For powder processing companies this means all equipment in contact with combustible dust must be certified for the correct zone and explosion group. Non-compliant equipment leads to audit failures, insurance complications and, in the worst case, personal injury.

The core of ATEX compliance is breaking the explosion triangle: combustible dust, oxygen and an ignition source must never be present simultaneously in dangerous proportions.

Dust explosions: the mechanism

A dust explosion requires five elements, captured in the explosion pentagon:

Combustible dust — organic substances (sugar, starch, milk powder), metals (aluminium, lithium) or pharmaceutical APIs
Sufficiently fine particles — typically below 500 microns, with explosivity rising as particle size falls
Suspended dust cloud — a dispersion at a concentration above the lower explosion limit
Oxygen — from the ambient air
Ignition source — sparks, hot surfaces, static electricity or mechanical friction

Dust explosion characteristics are expressed in Kst value and Pmax. These determine the explosion class (St 1, St 2, St 3) and thereby the construction requirements.

Zoning: classifying ATEX zones

Zoning divides your installation according to the likelihood of an explosive dust atmosphere forming. Correct zone classification is the basis of the explosion protection document (EPD).

Zone 20 — dust cloud present continuously or for long periods, for example inside a mixer or silo
Zone 21 — present occasionally in normal operation, such as at filling and discharge points
Zone 22 — present rarely and briefly, typically in the immediate vicinity of equipment

HECHT equipment is available in category 1D, 2D and 3D versions, matched to the zone in which the equipment is installed.

Earthed design and static electricity

Static charging is one of the most common ignition sources in powder transport. Friction between powder and hose walls, or between powder and equipment surfaces, builds up charges that discharge as a spark. An earthed design prevents this.

HECHT consistently applies:

Continuous earthing — all conductive parts electrically bonded to an earth potential below 10⁶ ohm
Conductive or antistatic hoses and seals — to prevent charge build-up in flexible sections
Earthing control — monitoring systems that verify earthing continuity before a process starts

Explosion protection: preventing and controlling

ATEX recognises two strategies that HECHT combines: explosion prevention (avoiding ignition) and explosion protection (controlling the consequences). Where prevention cannot be fully guaranteed, constructive measures are applied.

Pressure-shock-resistant design — equipment built to withstand the full explosion pressure without failing
Explosion pressure relief — bursting discs that vent pressure in a controlled way to a safe area
Explosion suppression — fast-acting suppressant injection that smothers the explosion at its source
Decoupling — fast-closing valves that prevent an explosion propagating through pipework

Integration in dust-free and closed systems

Explosion safety and operator protection reinforce each other. A closed, dust-free process design not only limits operator exposure to powder but also reduces the chance of an explosive atmosphere outside the equipment. HECHT integrates ATEX compliance into vacuum transport, containment filling heads and dosing systems, so a single installation meets both safety and GMP requirements.

Inerting with nitrogen is a complementary measure: by bringing the oxygen content below the limit value, explosion becomes impossible regardless of dust concentration or ignition source.

Frequently asked questions about ATEX

When is ATEX equipment mandatory?

As soon as a combustible dust atmosphere can form in your process, ATEX applies. The zone classification determines the equipment category you need.

What is the difference between Kst and Pmax?

Kst indicates the rate of pressure rise and determines the explosion class; Pmax is the maximum explosion pressure. Both are needed to size protective measures.

Is earthing sufficient as protection?

Earthing prevents static ignition but does not cover all ignition sources. A complete ATEX concept combines prevention with constructive protection.

What is inerting?

Replacing oxygen with an inert gas such as nitrogen, making combustion impossible. This is especially relevant for lithium and reactive APIs.

How is zoning determined?

Based on the likelihood and duration of an explosive atmosphere, recorded in the explosion protection document. HECHT advises on this together with your safety officer.

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Tailored advice from HECHT

Explosion safety starts with the process design, not with a bursting disc added afterwards. HECHT analyses your powder properties, zone classification and handling process and delivers an ATEX-compliant system that aligns with your GMP and operator protection requirements. Contact our engineers for a no-obligation risk analysis and a concept tailored to your installation.