Explosion protection for extraction systems

How can explosive dusts be extracted safely?

Industrial processes release not only visible but also invisible dusts which, together with oxygen, can form an explosive dust-air mixture. To trigger an explosion, all that is needed is an ignition source, for example a spark, which can be caused by electrical components or friction.

Ignition sources for explosive dusts

  • Discharge of static electricity
  • Electrical malfunctions
  • Hot surfaces
  • Grinding/friction sparks

ATEX compliant explosion protection

In connection with explosion protection, the term »ATEX« is often used, which stands for the abbreviation of the French term for explosive atmospheres »ATmosphères EXplosibles«.

Which substances can form explosive atmospheres?

For an explosive atmosphere to form, the substances must be flammable and can be in the form of powder, gas or liquid. These flammable or explosive substances are usually explosive as a dust-air mixture, if their grain diameter is less than 500 μm. However, some dusts are still explosive up to a grain diameter of 1 mm.

Flammable solids:

  • Plastics
  • Organic substances (flour, coffee, starch, cellulose …)
  • Metals (aluminum, magnesium …)

Flammable gases:

  • Natural gas
  • Hydrogen
  • Acetylene

Flammable liquids:
Disinfectants, organic solvents, fuels.

What are the explosion protection techniques?

Primary explosion protection:
The primary explosion protection principle means the preventive avoidance of an explosive dust air mixture and the use of special protective measures. Primary explosion protection is considered the most reliable technique to avoid explosions.

All extraction systems from ABSAUGWERK are built according to the primary explosion protection principle and can also be operated indoors.

  • Correct interpretation of the recording according to BGR 109-001
  • Air speeds over 20 m/s (collection, pipe system, extraction system)
  • Correct planning of the pipe system (smooth pipe, radii for branches and pipe bends)
  • Material separation by cyclone
  • Offline cleaning
  • Precoat unit

Secondary explosion protection
With this principle, ignition is prevented by any ignition source in the hazardous area, but the explosive atmosphere (dust-air mixture remains in an explosive concentration) exist.

  • Avoiding sources of ignition, e.g. due to static charging
  • Grounding of pipe system and extraction system
  • No sucking in of metallic objects
  • Components free of ignition sources, e.g. ATEX motor according to Zone 22

Tertiary explosion protection
The term refers to constructive explosion protection. Measures and protective devices are used here to limit the effects of an explosion, e.g. bursting discs. In the case of extraction systems with this technology, high follow-up costs for spare and wear parts are usually to be expected.

What is the ATEX directive?

The ATEX Product Directive 2014/34/EU applies to the placing on the market of equipment and products in potentially explosive atmospheres.. The directive applies to all equipment and protective systems for potentially explosive atmospheres sold in the EU area since 2014. To comply with the regulations, extraction systems must be designed to be free of ignition sources and conductive, and special ATEX components (e.g. motor) must be installed. The manufacturer is responsible for compliance with the regulations.

What are zones?

Potentially explosive atmospheres are classified into zones on the basis of the frequency and duration of their occurrence/presence. On this basis, the necessary measures are determined, which apply in all EU member states in accordance with Directive 1999/92/EC.

For dusts, zones 20, 21 and 22 are relevant:

Zone 20
is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, for long periods or frequently.

Zone 21
is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.

Zone 22
is a place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

In which technical rules are there specifications for explosion protection?

The following Technical Rules for Industrial Safety (TRBS) and for Hazardous Substances (TRGS) contain information on explosion protection (ATEX):

TRBS 1112 Part 1:
Explosion hazards during and due to maintenance work – Assessments and protective measures.

TRBS 1122:
Modifications of gas filling plants, storage facilities, filling stations, service stations and airfield refueling facilities – Determination of the inspection obligation according to Annex 2 Section 3 BetrSichV and the permit obligation according to § 18 BetrSichV.

TRBS 1123:
Modifications of systems in potentially explosive atmospheres requiring testing – Determination of the need for testing in accordance with § 15 Para. 1 BetrSichV

TRBS 1201 Part 1:
Testing of systems in potentially explosive atmospheres

TRBS 1201 Part 3:
Repair of equipment, protective systems, safety, monitoring and control devices as defined by Directive 2014/34/EU

TRBS 2152/TRGS 720:
Hazardous explosive atmospheres – General

TRBS 2152 Teil 1/TRGS 721:
Hazardous explosive atmospheres – Assessment of explosion hazards

TRBS 2152 Teil 2/TRGS 722:
Prevention or limitation of hazardous explosive atmospheres

TRBS 3151/TRGS 751:
Avoidance of fire, explosion and pressure hazards at filling stations and filling plants for filling land vehicles

TRGS 407:
Activities involving gases – Risk assessment

TRGS 507:
Surface treatment in rooms and containers

TRGS 509:
Storage of liquid and solid hazardous substances in stationary containers and filling and emptying points for mobile containers

TRGS 510:
Storage of hazardous substances in portable containers

TRGS 529:
Activities in the production of biogas

TRGS 723:
Hazardous explosive mixtures – Measures of constructive explosion protection which limit the effects of an explosion to a harmless level

TRGS 724:
Hazardous explosive mixtures – Measures of constructive explosion protection, which limit the effects of an explosion to a harmless level

TRGS 725:
Hazardous explosive atmospheres – Measuring, control and regulating devices within the scope of explosion protection measures

TRGS 727:
Avoidance of ignition hazards due to electrostatic charges

Which standards must be observed?

VDI 2263:
Dust fires and dust explosions; hazards, assessment, protective measures

VDI 2263 sheet 1:
Dust fires and dust explosions; hazards, assessment, protective measures; test methods for determining safety-related parameters of dusts

VDI 2263 sheet 2:
Dust fires and dust explosions; hazards, assessment, protective measures; inerting

VDI 2263 sheet 3:
Dust fires and dust explosions; hazards, assessment, protective measures; explosion pressure shock resistant containers and apparatus; calculation, construction and testing

VDI 2263 sheet 4:
Dust fires and dust explosions; hazards, assessment, protective measures; suppression of dust explosions

VDI 2263 sheet 5:
Dust fires and dust explosions; hazards, assessment, protective measures; explosion protection in fluidized bed plants

VDI 2263 sheet 5.1:
Dust fires and dust explosions; hazards, assessment, protective measures; explosion protection in fluidized bed plants; instructions and design examples for manufacturers and operators

VDI 2263 sheet 6:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection at dust extraction plants

VDI 2263 sheet 6.1:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection on dust extraction systems; examples

VDI 2263 sheet 7:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection at spray drying plants

VDI 2263 sheet 7.1:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection at spray drying plants; examples

VDI 2263 sheet 8:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection on elevators

VDI 2263 sheet 8.1:
Dust fires and dust explosions; hazards, assessment, protective measures; fire and explosion protection on elevators; examples

VDI 2263 sheet 8.2:
Dust fires and dust explosions; hazards, assessment, protective measures; explosion suppression and combination of constructive protective measures on elevators

VDI 2263 sheet 9:
Dust fires and dust explosions; hazards, assessment, protective measures; determination of the dust behavior of bulk materials

VDI 3673 sheet 1:
Pressure relief of dust explosions

DIN EN 1127-1:
Explosive atmospheres, explosion protection,
Part 1: Basic principles and methodology

DIN EN 1127-2:
Explosive atmospheres, explosion protection,
Part 2: Basic principles and methodology in mines

DIN EN 1755:
Industrial trucks – Safety requirements and verification – Additional requirements for use in potentially explosive atmospheres

DIN EN 14491:
Protective systems for the pressure relief of dust explosions

DIN EN 14986:
Design of fans for use in potentially explosive atmospheres Avoidance of ignition hazards due to electrostatic charges