*mydirectindustry

Catalogs
R. STAHL AG
The basics of dust-explosion protection

The basics of dust-explosion protection

Product catalog summary

Dust as a Risk Factor
Dust explosions occur when combustible dust and air are ignited by a source such as sparks, open flames, or electrostatic discharges. These explosions can be more devastating than gas explosions due to the potential for chain reactions. Industries like food processing and pharmaceuticals are particularly vulnerable.

Definitions and Characteristics
Dust consists of small particles that can remain airborne. Key explosion characteristics include particle size, explosion limits, maximum explosion pressure, and minimum ignition energy. Particles larger than 400 µm are generally non-explosive, and moisture content affects ignition and explosive behavior.

Legal Basis and Standards
Regulations like the IEC 61241 series and European Directive 94/9/EC provide guidelines for dust explosion protection, including equipment requirements and testing methods.

Dust Explosion Protection Measures
Preventive measures include classifying hazardous areas, selecting appropriate equipment, and regular maintenance. Equipment must prevent ignition sources, and facilities should implement organizational steps to minimize risks.

Classification of Dust Explosion Hazardous Areas into Zones
Hazardous areas are classified into Zones 20, 21, and 22 based on the frequency and duration of explosive dust atmospheres. Proper classification aids in selecting suitable equipment and implementing safety measures.

Equipment Selection
Equipment in hazardous areas must meet safety standards to prevent ignition, including maintaining surface temperatures below dust ignition temperatures.

Installation and Maintenance
Proper installation and regular maintenance are crucial for safety, including checking for ignition sources and ensuring equipment operates within safe conditions.

Standards and Regulations
Standards like EN 50281-1-1 and EN 50281-1-2 align with IEC 61241 and European Directives to harmonize dust and gas explosion protection standards.

Dust Explosion Protection Measures
Preventive measures include reducing combustible substance concentration, avoiding ignition sources, and using explosion-resistant designs.

Types of Dust Explosion Protection
Protection types include "tD" (enclosure), "pD" (pressurization), "iD" (intrinsic safety), and "mD" (encapsulation), each with specific requirements for thermal endurance and mechanical stress.

Material Hardness Testing
Material hardness should not exceed a 20% difference between initial and final figures to maintain sealing properties.

Static Electricity
Electrostatic discharge is a significant ignition source. Materials must prevent surface charging to avoid discharges that can ignite dust.

Protection by Pressurization "pD"
This method is crucial for switch cabinets in Zones 21 and 22, requiring interior cleaning before pressurization.

Mechanical Stability
Equipment must withstand impact energy tests as per EN 50014.

Intrinsic Safety "iD"
Based on IEC 60079-11, this emphasizes preventing ignitable sparks through encapsulation or IP 6X ratings.

Encapsulation "mD"
Aligns with IEC 60079-18 standards, focusing on encapsulation for protection.

Equipment Selection
Criteria include hazardous zone category, dust properties, and temperature limitations.

Self-Ignition of Dust Deposits
Discusses risks of self-ignition and the importance of determining maximum permissible surface temperatures.

Determining Maximum Surface Temperature
Manufacturers determine maximum surface temperature under dust layers during type testing, with specific limits for dust clouds and layers.

Plugs and Sockets
In Zone 20, plugs and sockets are prohibited. In Zones 21 and 22, they must be interlocked or designed to prevent separation when energized.

Supplementary Requirements
EN 50281-1-1 outlines additional requirements for Category 2D equipment.

Radiation-Emitting Equipment
Optical radiation can ignite dust/air mixtures, with specific power and energy density limits.

Installation and Maintenance
Proper installation and maintenance are crucial, with cables and glands needing to be dustproof and compliant with EN 50014.

Documentation
EN 50281-1-2 requires maintaining site plans showing hazardous areas and equipment types, aligning with Directive 99/92/EC.

Product Overview
R. STAHL offers certified products for dust hazardous areas, compliant with Group 3D regulations for Zone 22.

Catalog excerpts

The basics of dust-explosion protection-2

R.STAHL Explosion protection >

Open the catalog to page 2

The basics of dust-explosion protection-3

1 > Dust as a Risk Factor Definitions and Characteristics Legal Basis and Standards4Dust Explosion Protection Measures5Classification of Dust Explosion Hazardous Areas into Zones6Dust Types of Protection7Equipment Selection8Installation and MaintenanceProduct Overview 4610 12 141622 2830 2 3 4 5 6 7 8 9 > R.STAHL Explosion protection size="-2">

Open the catalog to page 3

The basics of dust-explosion protection-5

Figure2: Ignition Sources of Dust Explosions Types of Dusts Involved in Dust Explosions R.STAHL Explosion protection Figure3: >

Open the catalog to page 5

The basics of dust-explosion protection-9

Figure 5: Modified Hartmann Tube R.STAHL Explosion protection >

Open the catalog to page 9

The basics of dust-explosion protection-12

12 4. Dust Explosion Protection Measures4.1 Preventive (Primary) Explosion Protectionby Avoiding an Explosive Atmosphere 4.2 Preventive Explosion Protection by Avoiding Effective Ignition Sources This measure prevents the hazardous explosiveatmosphere from being ignited. This can be achieved by: > Analysing potential ignition sources > Determining the necessary extent of protective measures The complexity of the processes that can lead to a dust explosion means that it is extremely difficult to assess the actual risks in dealing with explosive dust/air mixtures. This makes explosion prevention...

Open the catalog to page 12

The basics of dust-explosion protection-15

Table8: Housekeeping and Explosion Hazard Level of Thickness ofDuration of PresenceFire or HousekeepingDust Layerof a Dust LayerExplosion Riskgoodzero ornot presentnonenegligible fairnot negligibleshorter than thenonelength of 1 shiftpoor not negligiblelonger than the fire hazard and length of 1 shiftZone 22 if cloudsare created > Figure6: Example of the Classification into Dust Explosion Hazardous Areas According to IEC 61241-10 > Zone 20Inside the hopper of a bag emptying stationZone 21Immediate surround-ings (radius of 1m) around the manholeZone 22Area outside Zone 21due to accumulatios of...

Open the catalog to page 15

The basics of dust-explosion protection-21

The dust type of protection mDӔ in accordancewith IEC61241-18is to be based primarily on type of protection mӔ according to IEC60079-18, which is currently being revised.Further proceedings on the draft of IEC61241-18will therefore be determined by the development of the new IEC60079-18. > Temperature limits on all outer surfaces of apparatus or their parts whose power limits exceed the operational limits required in IEC61241-11. The surface may consist of an enclosure or an encapsulation.Workis continuing on the standard for the intrinsicsafety iDӔ ignition protection type, therefore we refer...

Open the catalog to page 21

The basics of dust-explosion protection-28

28 > > Cables with thermoplastic or elastomeric wireinsulation, screened or armoured cable and an outer sheath of PVC(poly-vinylchloride), PCP (polychloroprene rubber), or a similar material. Cables with a seamless aluminium sheath withor without armouring. 8. Installation and Maintenance > Mineral-insulated cables with metal sheath. Cabel installation Note: > When cables are externally provided with protection, or when there is no danger of me- chanical damage, cables with thermoplastic or elastomeric insulation and a sheath of PVC, PCP, or a similar material are permitted. These cables and...

Open the catalog to page 28

The basics of dust-explosion protection-30

30 > Some Examples of Dust Explosion Protected Products 9. Product Overview > Luminaire Series 6600and 6608, Compact Luminaire 6100 and 6108 > R.STAHL has a fully certified product range for dust hazardous areas in your installation. Wetakedust explosion protection just as seriously as gas explosion protection. We can offer you a specially adapted solution for almost every application. At a minimum, all dust explosion protection products comply with the regulations of Group 3D; that is, they can be used in Zone 22 (non-conductive dusts). The following equipment series and systems arecertified...

Open the catalog to page 30

The basics of dust-explosion protection-31

31 Your Safety Our Reality If your installation is faced with the risk of a dustexplosion, R.STAHLoffers the expertise you need.R.STAHL has decades of experience in the field ofelectrical explosion protection. We will be glad to help you solve your safetyproblems. In addition to a comprehensive range of electrical equipment, we offer you expert advice and training in the dust explosion protection field.Get in touch with us. You will find a downloadable list of our dustexplosion protection products in PDFform at: www.dust-ex.stahl.de > R.STAHL Explosion protection size="-1">

Open the catalog to page 31

The basics of dust-explosion protection-32

www.visuell.de R.STAHLAm Bahnhof 30, 74638 Waldenburg, Germany Phone +49 7942 943-0 Fax +49 7942 943-4333 www.stahl.de > ID-NR. 00 006 84 77 0S-PB-dustex-01-en-05/2008 Printed in the Federal Republic of Germany size="-1">

Open the catalog to page 32

All R. STAHL AG catalogs and technical brochures

Archived catalogs

*Prices are pre-tax. They exclude delivery charges and customs duties and do not include additional charges for installation or activation options. Prices are indicative only and may vary by country, with changes to the cost of raw materials and exchange rates.

Brand list