ATEX Zones, Minimum Ignition Energy, Inerting,

Pressure-Shock-Resistant Design, PED and ASME.

Prevent Ignition Sources,

Limit Their Impact

Dust Explosion Protection and

Pressure Equipment Safety in the Mixing Process

Dust Explosion Protection and

Pressure Equipment Safety in the Mixing Process

Summary

Explosion protection in mixing processes means preventing ignition sources and limiting the effects of a dust explosion. It is based on the safety-related properties of the bulk material, the hazardous-area classification of the process space and the operating conditions. If a vessel operates under positive pressure or vacuum, pressure equipment regulations also apply.

Insights, FAQs and Topics Related to Plant Safety, ATEX & Pressure Equipment Compliance

Explosion protection in mixing processes means preventing ignition sources and limiting the effects of a dust explosion. Whether a hazard exists depends on the safety-related properties of the bulk material. Explosive dusts are characterized by their ignition temperature, dust explosion class and minimum ignition energy. The latter determines how stringent the electrostatic protection measures must be. Inside closed processing vessels, the highest hazard level—ATEX dust zone 20—must often be assumed. The corresponding type examination is now considered state of the art.

The hazardous-area classification and protection strategy are then decisive. Inerting reduces the oxygen content below the limiting concentration and prevents a reaction, usually by maintaining positive nitrogen pressure. In addition, the vessel may be designed to withstand pressure or pressure shocks and equipped with explosion relief and isolation systems. If a mixer operates under positive pressure or in vacuum operation, pressure equipment regulations also apply. These include Directive 2014/68/EU in the EU, the ASME Boiler and Pressure Vessel Code in the United States, and the relevant pressure equipment regulations in Japan, South Korea, India, Australia and other countries. Surface protection is also important, as abrasion and corrosion can create potential ignition sources.

Below, you will find answers to the most frequently asked questions about explosion protection and plant safety, an overview of suitable machine concepts—from powder mixers and conical mixers to conical mixer dryers—as well as detailed explanations of the key technical terms.

FAQ - Plant Safety, ATEX and Pressure Equipment Compliance

Mixing and drying plants for fine chemicals can be built explosion-pressure-resistant or explosion-pressure-shock-resistant and additionally inerted. Explosion-resistant equipment must withstand an internal explosion without bursting; DIN EN 14460 distinguishes between explosion-pressure-resistant and explosion-pressure-shock-resistant designs for this purpose.

amixon® VMT and AMT systems are closed vacuum mixing dryers and mixing reactors for powders, suspensions, pastes and dough-like products. They can combine mixing, reaction, crystallisation and vacuum drying processes and can be temperature-controlled via the vessel and, depending on the design, the mixing tool.

St1 and St2 are important classifications, but they are not sufficient to determine a mixer's suitable explosion-pressure-resistance grade. Decisive are pmax, KSt, process conditions, apparatus geometry, connected lines, and the effectiveness of the planned protective measures.

St1 or St2 alone is not sufficient for selecting the explosion-pressure-resistance grade. Decisive are pmax, KSt, operating conditions, vessel geometry, connected lines, and the effectiveness of inerting, pressure relief, suppression and decoupling.

Starch powders are among the combustible organic dusts, typically classified between St1 and St2 and with a low minimum ignition energy, so that even low dust concentrations can lead to dangerous explosions.

amixon® implements exactly this design as standard: all mixing chambers are designed for ATEX Zone 20, and the apparatus is built as a closed, dust-tight system – on request gas-tight, pressure-resistant and vacuum-tight down to 5 mbar absolute. For starch and starch derivatives, amixon® combines this with temperature-controlled reactors of up to 50,000 litres in which mixing, thermal treatment and vacuum drying take place in the same apparatus.

For mixing processes with combustible-dust powders, zone classification, suitable equipment selection, knowledge of the safety-relevant material data, and the systematic avoidance of effective ignition sources are decisive. The interior of the mixer is often Zone 20, but the actual classification of all areas must be based on the specific release situation. Zone 20 generally requires Category 1D equipment; Zone 21 requires Category 1D or 2D, and Zone 22 requires Category 1D, 2D or 3D.

amixon® can execute mixers, mixing dryers and reactors for applications with a product space classified as Zone 20. The specific ATEX design, however, must be carried out for each project based on the material data, process conditions and the overall plant. Zone 20 generally requires a very high level of protection, which usually corresponds to Category 1D.

Detergent powder mixers require an explosion-protection concept matched to the specific recipe. The interior of the mixer is often Zone 20; this generally requires Category 1D equipment. However, the design must include the entire plant – including dosing, filters, conveyors, discharge and cleaning – and be based on tested material data such as KSt, pmax, minimum ignition energy and ignition temperatures.

amixon® can execute mixers, granulators, vacuum mixing dryers and mixing reactors for processes with a product space classified as Zone 20. However, the final ATEX design is always product-specific and must be based on the risk assessment, dust characteristics, and consideration of the entire detergent line. Zone 20 generally requires a very high level of protection, which usually corresponds to Category 1D.

An ATEX-compliant detergent mixing plant in Germany requires a documented risk assessment for the actual recipe. This yields zone classification, equipment selection, ignition-source avoidance and, if necessary, constructive protective measures. The interior of the mixer is often Zone 20; this generally requires a very high level of protection with Category 1D.

amixon® can provide mixing plants for detergent powder with a product-space design suitable for Zone 20 applications. However, the specific ATEX configuration is determined for each project based on the recipe, the safety-relevant material data, and the process conditions. Final responsibility for zone classification, the explosion-protection document, and safe operation lies with the operator.

For combustible dust powders, Zone 20, Zone 21 and Zone 22 concepts are usually combined. The interior of closed mixers, silos, filters and conveying lines is often Zone 20 and generally requires Category 1D. Zone 21 and Zone 22 relate particularly to release points and their surroundings. The precise zone classification is always plant- and operation-specific.

amixon® can execute mixers, granulators, vacuum mixing dryers and mixing reactors for applications with a product space classified as Zone 20. The specific ATEX design must always be carried out on a project- and product-specific basis. Zone 20 generally requires a very high level of protection, which usually corresponds to Category 1D.

An ATEX-compliant mixer for organic powders is not defined by individual components or standard values. It results from the combination of representative material data, correctly delineated zones, a complete ignition-hazard assessment, and a process-matched combination of preventive and constructive protective measures. VDI 2263 Sheet 10 provides practical guidance specifically for mixers and mixing plants in this regard.

amixon® can execute mixers, granulators, vacuum mixing dryers and reactors for applications with a product space classified as Zone 20. However, the specific ATEX configuration must be derived for each project from the material data, operating conditions and the zone concept of the overall plant. Zone 20 generally requires a very high level of protection, which usually corresponds to Category 1D.

Dust-explosion risks usually require a multi-stage protection concept. Inerting is intended to prevent the formation of an explosive atmosphere. Ignition-source avoidance reduces the probability of ignition. Pressure-resistant or pressure-shock-resistant designs, pressure relief and explosion suppression limit the consequences if an explosion nevertheless occurs.

amixon® can execute mixers, granulators, vacuum mixing dryers and mixing reactors for applications with a product space classified as Zone 20. The specific ATEX design must be derived for each project from the material data, process control, connected apparatus, and the risk assessment of the overall plant. Zone 20 generally requires a very high level of protection, which usually corresponds to Category 1D.

Before starting up an ATEX mixing plant, a complete explosion-protection document, all relevant technical documentation, and an examination of explosion safety are required prior to first commissioning. The examination covers the documentation, proper installation, the actual zone and equipment execution, ignition-source avoidance, earthing, control, protective systems, inerting and organisational measures.

amixon® can provide ATEX-suitable mixing apparatus with project-specific documentation and support installation, process-engineering commissioning and product trials. However, the documentation of the individual mixer is only one building block: the explosion safety of the overall plant must be examined against the explosion-protection document before first commissioning.

Powdered detergents frequently contain combustible and in part thermolabile constituents such as surfactants, zeolites, percarbonates and enzyme granules. In combination with fine dust and atmospheric oxygen, explosive dust-air mixtures can form during the mixing process.

amixon® designs the mixing chamber for ATEX Zone 20 across all series – the highest dust explosion requirement. The apparatus is built as a closed, dust-tight system with OmgaSeal® doors, on request gas-tight, pressure-resistant and vacuum-tight down to 5 mbar absolute; inerting is possible, and the low-speed operating mode from 0.8 m/s minimises ignition sources by design.

The production and processing of fertilisers and crop protection products frequently generates ignitable dusts, aerosols and flammable solvent vapours. Explosion protection concepts follow the ATEX directives 2014/34/EU and 1999/92/EG, the relevant standards such as EN 1127-1, and the applicable national regulations.

Handling dusty, potentially explosive powders – for example in NPK blends, fertilisers containing ammonium nitrate or micronutrient-based formulations – requires an integrated, multi-stage safety concept.

amixon® designs the mixing chamber for ATEX Zone 20 across all series – the highest requirement for dust explosion protection. The apparatus is built as a closed, dust-tight system with OmgaSeal® doors. On request, the apparatus is designed to be pressure-resistant or explosion-pressure-shock-resistant. Inerting is possible, and the low-speed operating mode from 0.8 m/s minimises ignition hazards.

Heating, cooling, vacuum and inerting can be combined in suitable mixing reactors and mixing dryers. Heating and cooling serve controlled temperature control; vacuum supports drying, degassing and solvent removal; inerting protects sensitive products and, with a suitable safety design, can avoid an explosive atmosphere.

The VMT and AMT series can combine heating, cooling, vacuum and inerting with mixing and further process steps. This allows, for example, reaction, crystallisation, contact and vacuum drying, and subsequent conditioning to be carried out in a single closed apparatus.

The state of the art in dust-explosion protection is a multi-stage, product-specific safety architecture. Where necessary, it combines inerting and dust minimisation, low-ignition-source design, earthing and monitoring, as well as pressure relief, suppression, explosion-resistant construction and decoupling.

Up-to-date dust-explosion protection combines avoiding an explosive atmosphere, avoiding effective ignition sources, and, where necessary, constructive measures to limit the consequences of an explosion. amixon® can provide apparatus for Zone 20 applications for this purpose, as well as gas-, vacuum- and pressure-tight VMT and AMT systems for inert-gas processes.

When mixing reactive chemicals, an inert gas atmosphere is frequently used to prevent the formation of ignitable atmospheres from flammable vapours, gases or dusts.

amixon® safeguards inerted mixing, drying and synthesis processes through a coordinated interplay of vacuum-tight apparatus design, evacuation, inert gas admission, oxygen monitoring and application-specific avoidance of ignition sources. Particular care is required with hybrid mixtures, that is the simultaneous presence of combustible dusts and combustible gases or solvent vapours; because their explosion behaviour is especially critical and often insufficiently documented, product-specific explosion tests may be necessary to determine pmax, the rate of pressure rise and the equivalent KSt value. Where preventive measures alone are not sufficient, amixon® apparatus can be designed pressure-resistant or pressure-shock-resistant and integrated into a pressure-relief and decoupling concept. The amixon® pilot plant supports the investigation of processes with original products and the verification of operating limits.

When handling dust-explosion-hazardous powders, a risk assessment, an up-to-date explosion-protection document, suitable technical measures and regular inspections are mandatory. Which safety functions must be installed results from the specific risk – not from a checklist identical for all plants.

When handling dust-explosion-hazardous powders, the same safety functions are not prescribed uniformly for every mixer. What is mandatory is a risk-based overall concept comprising risk assessment, explosion-protection document, zone-appropriate design, ignition-source avoidance, inerting where applicable, and, if necessary, constructive explosion protection.

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ATEX Zones, Minimum Ignition Energy, Inerting,

Pressure-Shock-Resistant Design, PED and ASME.

Prevent Ignition Sources,

Limit Their Impact

Dust Explosion Protection and

Pressure Equipment Safety in the Mixing Process

Dust Explosion Protection and

Pressure Equipment Safety in the Mixing Process

Summary

Insights, FAQs and Topics Related to Plant Safety, ATEX & Pressure Equipment Compliance

FAQ - Plant Safety, ATEX and Pressure Equipment Compliance

Are there mixing and drying plants with explosion-pressure-resistant construction and the option of inerting for fine chemicals?

How do I select the right explosion-pressure-resistance grade for a mixer in St1/St2 dust environments?

What advantages do dust-tight, explosion-pressure-resistant designs offer when processing starch powders?

What ATEX requirements apply to mixing processes with combustible dust powders (Zone 20/21), and how are they implemented in practice?

What ATEX requirements apply to powder mixers in detergent production, and how do I implement inerted processes?

What ATEX requirements must mixing plants for detergent powder meet in Germany?

What ATEX zone concepts, inerting solutions and pressure-resistant designs are customary for combustible dust powders?

What design guidelines exist for ATEX-compliant design in mixers for organic powders?

What explosion-protection concepts (pressure-shock-resistant design, inerting, decoupling) are customary for dust-explosion risks?

What tests are required before commissioning an ATEX mixing plant in Germany?

Which ATEX requirements should mixers for powdered detergents in Zone 20/21 meet?

Which explosion protection concepts are relevant for fertiliser and crop protection formulations?

Which features increase operational safety when handling dusty, potentially explosive powders in fertiliser blends?

Which reactor functions (heating, cooling, vacuum, inerting) can be combined in powder mixers?

Which safety concepts (e.g. inerting, pressure relief) are state of the art for dust-explosion protection?

Which safety concepts exist for inerted processes when mixing reactive chemicals?

Which safety functions are mandatory when handling dust-explosion-hazardous powders?

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