Food and beverage

Flour mills, silos, sugar refineries and plants handling combustible dusts

Flour mills, silos and sugar plants need ATEX equipment for combustible dust in Zones 20, 21 and 22 that withstands washdown. Maffioletti supplies it.

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Stainless steel tanks in a food processing plant

Where the hazardous areas are

In food processing the main hazard is combustible dust: flour, sugar, starch, grain, milk powder and cocoa. Hazardous areas include silos, bucket elevators, mills, filters, pneumatic conveying and bagging. Zone 20 is common inside silos, filters and elevators, Zone 21 around filling and discharge points, and Zone 22 where a dust cloud is not expected in normal operation and, if it forms, lasts only briefly. These non-conductive dusts are Group IIIB.

Gas and vapour hazards can also arise: distilleries, ethanol stores and ammonia refrigeration plants, since ammonia is toxic but also flammable (IIA T1).

Typical requirements

Temperature and dust layers: compare equipment temperature with the ignition temperature of both cloud and layer; thick layers need specific checks under IEC/EN 60079-14.
Dust protection: IP5X or IP6X depending on zone and group, plus water-jet resistance where areas are washed down (for example IP66).
Housekeeping: settled dust fuels secondary explosions, and smooth, easy-to-clean surfaces reduce deposits.
Static electricity: pneumatic conveying and bagging generate charge, so pipework, containers and FIBCs must be selected and earthed appropriately.
Standards: Directives 2014/34/EU and 1999/92/EC; IEC/EN 60079-10-2 for classification and IEC/EN 60079-14 for selection and installation.

Products for this sector

Lighting: LED high bay and linear luminaires for grinding towers, warehouses and silo rooms.
Enclosures, junction boxes and control stations: junction boxes and control stations with dust protection suited to the zone.
Sensors: capacitive sensors for flour and granule levels, and inductive sensors and encoders to monitor elevator speed.
Static grounding: Newson Gale systems for big bags, drums and bulk powder tankers.
Gas detection: detectors for ammonia in refrigeration plants and for alcohol vapours.

How we help

We design and assemble custom Ex enclosures, junction boxes and control stations in-house, and our 72-hour Express service on junction boxes and control stations helps when you need to restart quickly.

For silos and warehouses we prepare a lighting calculation, and the energy-saving calculator estimates what switching to LED is worth. Through Atex Italia we offer consulting, training and inspections. Contact us to talk it through with our technical team.

FAQ

Frequently asked questions

What ATEX zone is the inside of a flour silo?

The inside of a flour silo, where a dust cloud is present frequently or for long periods during filling, is usually classified Zone 20. Areas around filling and discharge points are generally Zone 21 or 22, depending on how well the system is sealed, extracted and cleaned.

Is sugar dust explosive?

Yes: finely divided sugar is a non-conductive combustible dust in Group IIIB and can form explosive clouds during grinding, conveying and bagging. That is why sugar grinding, filters and silos need area classification under IEC/EN 60079-10-2.

In a flour mill, what is the difference between Zone 21 and Zone 22?

In Zone 21 a combustible dust cloud is likely to form occasionally in normal operation, for example near filling points; in Zone 22 it is not expected in normal operation and, if it forms, lasts only briefly. This sets the equipment category: 2D for Zone 21 and 3D for Zone 22, or a higher category.