ATEX directive

The ATEX directive usually refers to EU Directive 2014/34/EU, which governs equipment and protective systems intended for use in potentially explosive atmospheres. It is the product directive for equipment placed on the EU market. A separate workplace directive, 1999/92/EC, governs employer duties for classifying hazardous areas and managing worker risk.

For industrial cleaning equipment, ATEX matters where combustible dust or flammable gas can be present: coal bunkers, biomass silos, grain or sugar handling, waste processing, filter houses, solvent areas and some chemical plants. Dust zones are normally described as Zone 20, 21 or 22 according to how often an explosive dust atmosphere is present.

Equipment implications

Equipment must be selected for the correct group, category, zone, ignition source risk, temperature class or maximum surface temperature, and dust ingress protection. Mechanical equipment can be an ignition source through hot surfaces, impact, friction, electrostatic charge or adiabatic compression, so ATEX is not only an electrical issue.

Acoustic-cleaning implications

Pneumatic sonic horns are often attractive in dust areas because they can avoid local electrical drives inside the vessel. That does not remove the ATEX duty. The horn, valve, accessories, earthing, surface temperature, materials and installation method still need to match the zone and dust properties. Compressed-air discharge can also disturb dust layers, so firing sequences should be assessed with the plant's explosion-protection basis.

Documentation and maintenance

Operators need certificates, declarations, equipment marking, zone drawings, inspection intervals and maintenance records. Replacing a valve, diaphragm or gasket with a non-equivalent part can invalidate the protection concept. Sylio-style installations should treat ATEX compliance as part of the cleaning-system design package, not as an afterthought.

Zone and equipment selection

ATEX selection starts with the hazardous-area classification prepared by the operator. Gas areas use Zone 0, 1 and 2. Dust areas use Zone 20, 21 and 22. The zone describes the likelihood and duration of an explosive atmosphere; it does not by itself describe how easily the material ignites. Dust layer behaviour, minimum ignition temperature, minimum ignition energy, conductivity, moisture and housekeeping all affect the final risk assessment.

Equipment marking must be read against that basis. Important details include equipment group, category, gas or dust marking, equipment protection level where used, temperature class or maximum surface temperature, ambient range and special conditions of use. A component that is suitable for one zone or dust may not be suitable for another. Assemblies also matter: a certified valve, horn and enclosure can still be non-compliant if the assembled system introduces an unassessed ignition source or an uncertified interface.

Mechanical ignition risks

ATEX is sometimes treated as an electrical enclosure issue, but mechanical cleaning equipment has its own ignition mechanisms. Impact between moving parts, friction from misalignment, hot bearings, electrostatic charge, adiabatic compression, overheated solenoids, non-conductive flexible hoses, unbonded nozzles and dust layers on warm surfaces can all matter. Pneumatic acoustic cleaners reduce some electrical risks inside a vessel, but they still need certified or assessed mechanical parts, suitable materials and correct installation.

Compressed air also changes dust behaviour. A firing event can lift settled dust, break a stable layer, or create turbulence near an ignition source. That is why acoustic-cleaning sequences in dust service should be reviewed against explosion isolation, venting, suppression and housekeeping arrangements. Cleaning may reduce long-term dust accumulation, but each pulse is still an event in the hazardous area.

Documentation and lifecycle

The compliance file should connect certificates, declarations of conformity, installation drawings, zone drawings, equipment markings, inspection schedules, spare parts and maintenance instructions. Sites often lose compliance through small changes: a substituted solenoid, an uncertified limit switch, a painted bonding point, a non-conductive gasket, a different diaphragm material or a repair that changes clearances. The person maintaining the equipment needs enough information to preserve the protection concept.

Periodic inspection checks for damaged markings, loose earth bonds, corrosion, dust layers, missing covers, incorrect glands, cracked housings, modified air lines and evidence of overheating or rubbing. In dusty plants, cleaning and housekeeping are part of the control system because a certified surface-temperature limit assumes dust layers are managed within the design basis.

Acoustic-cleaning specification

For Sylio-type systems, the ATEX requirement should be stated before layout is frozen. The specification should name the zone, dust or gas group where known, maximum surface temperature requirement, ambient range, materials, earthing requirements, valve location, control enclosure location and inspection access. If the horn penetrates a vessel wall, the boundary between internal zone and external area should be explicit.

The safest design is one that can be inspected without dismantling half the plant and maintained without improvising parts. Acoustic cleaning is often installed to reduce manual entry into dusty vessels; ATEX discipline helps ensure the online cleaning system does not introduce a different risk while solving the access problem.

Change control

ATEX compliance is vulnerable during small plant changes. Moving a valve package from a safe area into a zoned area, adding a non-certified junction box, changing a hose material, or replacing a metal horn part with a polymer part can change the ignition assessment. The same applies when housekeeping deteriorates and dust layers become thicker than assumed by the surface-temperature assessment.

For online cleaning systems, management of change should cover the complete assembly and the way it is operated. A new firing sequence can alter dust-cloud frequency. A new enclosure can affect heat dissipation. A new maintenance access point can change bonding or isolation practice. Treating these details as engineering controls keeps the installed system aligned with the hazardous-area file.

Inspection note

ATEX inspections should include the cleaning equipment in the same route as other hazardous-area assets. Inspectors should confirm markings remain legible, bonding is intact, dust layers are controlled, covers are fitted and no temporary repair has introduced an unassessed part. Pneumatic equipment is not exempt from that discipline.

Related terms

• IEC 60079
• Pneumatic acoustic cleaner
• Sonic horn