ATEX STANDARDS FOR EXPLOSION PREVENTION

EXPLOSION PROTECTION IN DEDUSTING PLANTS

© BETH® Filtration GmbH 2008 . Seite 2

BETHPULS Bag Filter prototype explosions pressure test

Explosion pressure shock resistant design in combination with explosion pressure venting



Explosion pressure shock resistant design in combination with explosion pressure venting Photo page 2

Place of testing: Bergbau – Versuchsstrecke / Dortmund – Derne

Kind of dust : Lignite ( 500 g / m3 ) Dust explosion class : St 1 Vessel volume : 22 m3 Vent area : 2 m2 Reduced explosion pressure : 1.18 bar ( 0.18 bar overpressure ) Number of tests : 36 Max. explosion overpressure : 0.44 bar


Explosion Protection in Dedusting Plants

Dedusting plants are in operation for the

collection and separation of dust.

Consideration different kind of dust in dedusting plants concerning the applications and industrys

For example:

Wood, wood products Food, grain, cereal Coal, coal products

Secondary fuelPlastic, rubber

Chemical products, Metal etc.


Vattenfall Europe Mining AG dedusting of the actual largest lignite mill of world

Source of dust : Vertical roller milType of dust : LigniteCapacity of the mill : 88 t/hBulk density dust : 0.35 – 0.5 t/m3Dust capacity : max. 293.3 m3/h Raw gas volume : max. 150,000 Am3/hOperating temperature : 55 – 80°C (short peaks 100°C) Dew point : 30.9°C Raw gas dust content : max. 587 g/m3Operating pressure : - 45 mbar (rawgas inlet filter)



Vattenfall Europe Mining AG dedusting of the actual largest lignite mill of world BETHPULS Bag Filter 6.90x10.7.20 (double line)



Explosion Protection in Dedusting PlantsVattenfall Europe Mining AG dedusting of the actual largest lignite mill of world

BETHPULS Bag Filter 6.90x10.7.20 (double line)

Filter type : BETHPULS 6.90x10.7.20Operation method : On-lineNumber of filter bags : 900Dimensions filter bags : ø160 x 5,200 mm Filter cloth : PEAC 600 Si Filtering surface area : 2,400 m2 Air to cloth ratio : max. 1.044 m3/m2 x min Admissible operating pressure: - 140 mbar Main dimensions filter : 7.28 m x 10.2 m x 12.4 m


Dust characteristics

Kind of dust LigniteDust explosion class St 1KSt- value 150 bar x m x s-1

Explosion overpressure pmax 9.0 bar

Protective measures

Prevention of effective ignition sourcesExplosion pressure shock resistant up to1.4 bar Explosion venting according VDI 3673 Venting device BETH Explosion doorsNumber / size 16 / 0.53m2per each Disengagement Diverter/rotary valves

Explosion Protection in Dedusting PlantsVattenfall Europe Mining AG dedusting of the actual largest lignite mill of world

BETHPULS Bag Filter 6.90x10.7.20 (double line)



Defination of dust according VDI 3677 part 1 = Particle < 500 μm

This definition of dust are also valid in the explosion protection

VDI 2263 „ Dust Fires and Dust Explosions Hazards – Assessment – Protective Measures“

Exception: Flock = Short staples which are generated by cutting

endless fibers, grinding etc.

Length: 0,5 – 2,5 mm Weight:0,5 bis 22 dtex = gram / 10 km fiber lenght

Source: BMFT Band 64 „Humanisierung des Arbeitslebens“



For the Recognition of Hazards according

DIN EN 1127-1 „Explosive atmospheres – Explosion prevention and protection – Part 1: Basic concepts and methodology

German version EN 1127-1 : 1997“

in dedusting plants and the required

Analysis of Hazards

is it very important to know

Safety Characteristics of Dust ( Burning and Explosion Behaviour )



Burning and Explosion Characteristics of Dust

according BIA – report 12/97and / or BIA data bank GESTIS-STAUB-EX

or tests according

VDI 2263 Part 1 „Test Methods for die Determination of the Safety Characteristic of Dust“

through authorize test / proof institute



A dust explosion is possible when the hazard triangle is closed

Dust content in air higher the explosive limits ( lower dust concentration ) Oxygen concentration in the dust/air mixture higher limiting concentration Effective ignition source

Ignition source Oxygen

Explosive dust



Safety Characteristics of Dust and the Explosion Hazards

are content of the Explosion Protection Document

according article 8 Directive 1999/92/EG ( ATEX 137 )

Responsible for the safety : Operating management of the plant Consideration : National law

Example : Germany

Betriebssicherheitsverordnung BetrSichV § 6 BGR 104 ( alt ZH 1 / 10 ) „Explosionsschutz-Regeln Regeln für das Vermeiden der Gefahren durch explosionsfähige Atmosphäre mit Beispielsammlung“ E 6



Inertial separators VDI 3676 Filtering separators VDI 3677 Electrostatic precipitators VDI 3678 Wet separator VDI 3679

if required in combination including

Ducts with all partsFans, silencerDischarge devices ( rotary valves etc. )Screw conveyors Silos etc

All parts of the dedusting must be consider for the recognition of Explosion Hazards

Possible parts of a dedusting plant can be



Consideration and assessment of the different separator types

Example: Filtering separators acc. VDI 3677 Part 1

Bag filters, Envelope filters ( pocket ), Cartridge filters, Candle filters, Laef filters

Arrangement filter elements: Vertical or horizontal

Operation: Suction or pressure Regeneration divices



Typical examples of dedusting plants

1.) Bag filter for mill dedusting

Rawgas : Ducts, cyclone, bag filter, screw conveyor, rotary valvesCleangas : Bag filter, ducts, fan, silencer, stack



Typical examples of dedusting plants

1.) Object dedusting combination cylone – bag filter

Rawgas : Ducts, cyclone, bag filter, rotary valvesCleangas : Bag filter, ducts, fan, silencer, stack



All parts of the dedusting plant must be consider and a assessment in zones is required:

0, 1 and 2 for gas 20, 21 and 22 for dust

Consideration of the location and installation of the dedusting plant. A influence of zones through apparatus etc. they are no part of the dedusting plant, but they are installed in the near of the dedusting plant, is possible and to consider by the selection and installation of the required protective measures.

Analysis of Hazards Explosion Protection Document

Plant operating management – supplier of the plant



Protective Measures

Possibilities of Explosion Protection Measures:

Preventive and through Design Measures

Preventive:

Prevention of Explosible Dust/Air Mixtures

Prevention of Dust Explosions through Inerting

Prevention of Effective Ignition Sources



Protective Measures

Design Measures:

Explosion pressure resistant design for the max. explosion pressure

Explosion pressure resistant design in combination with explosion venting (pressure relief)

Explosion pressure resistant design in combination with explosion suppression

Explosion Disengagement, Explosion Interruption

Explosion resistant:Pressure resistant = Safety factor 1.5

Pressure shock resistant = Safety factor 1.0




Clean gas housing

Raw gas housing

Hopper

Screw conveyor

Venting openings for rupture disks orExplosion doors

Stage of erection




Hazards during the venting process in surrounding areas outside p red 0.53 bar g p red 0.64 bar g

Flames pressure




Result of exceeding the existing explosion pressure shock resistance damaged filter housing by p red 0.75 bar g

Raw gas housing:

Side panels

End panels

Hopper:

End panels

Side panels

Note: The result of incorrect sizing and design in particular concerning pressure shock resistance, flame tightness, calculation of venting area,venting devices (explosion doors, rupture disks), venting efficiency, explosion values of dust etc is the same



EC suitability test of BETH explosion door according directive 94/9/EC (ATEX 95)

Beginning of the venting process

End of the venting explosion door closed

During venting process explosion door open pressure und flame propagation outside



Certificate EC suitability test BETH explosion door according directive 94/9/EC



Required QS certificates to supply EC suitability tested BETH explosion door acc 94/9/EC


Explosion Protection in Dedusting PlantsScheme of execution examples of explosion protected filters proofed by notified body



BETH diverter based of the VDI report 701 (real execution) test of disengagement by a notified body

Test field stage of erection



Pressure and flame

Diverter DN 1000

Ductwork DN 1000

BETH diverter based of the VDI report 701 (real execution) test of disengagement by a notified body

Cover fixed in the cage

Disengagement process during the test



Possible Design Measures by Example Plant Item 1.)

1.) Object dedusting combination cylone – bag filter

Protective Measure Item 3 Vessel: Explosion pressure restistant design in combination with explosion venting (pressure relief) or explosion suppression. Explosion pressure resistant design for the maximum explosion pressure



Example BETHPULS Bag Filter for “Dedusting secondary fuel ” bunker

Diverter for explosion disengagement in the raw gas ductwork

BETHPULS Bag Filter “Explosion pressure shock resistant 1.4 bar with explosion venting”

Clean gas channel and duct

Fan

Vent duct behind the explosion flaps


Example BETHPULS Bag Filter for “Dedusting secondary fuel bunker”


Kind of dust Wood etc. Dust explosion class St 1KSt- value 200 bar x m x s-1

Explosion overpressure pmax 10 bar

Protective measures

Prevention of effective ignition sourcesExplosion pressure shock resistant up to1.4 bar Explosion venting according VDI 3673 Venting device BETH Explosion flapsDisengagement BETH diverter/rotary valve




Duct cyclone to bag filter

Example BETHPULS Bag Filter for “Dedusting plant for aluminium powder”

Cylindrical BETPULS – bag filter in combination with cyclone

Cyclone outlet

Cyclone inlet

Clean gas duct

Bag filter

Raw gas duct

Cyclone


Example BETHPULS Bag Filter for “Dedusting plant for aluminium powder”


Kind of dust Overspraypowder Dust explosion class St 2KSt- value 259 bar x m x s-1

Explosion overpressure pmax 9.9 barLower explosible limit 60 g/m3

Protective measures Prevention of effective ignition sources

Explosion pressure shock resistant up to11.0 bar Disengagement raw gas side Rapid action valve

clean gas side Rapid protection valve




Water-spray system

Example BETHPULS Bag Filter for “Dedusting a fuel-mixture preparation”

BETHPULS Single-line bag filter protected by preventive and design measures

Explosion flaps

Bag filter

Fan, silencer, and stack

Clean gas ductDiverter with raw gas duct

Maintenance platforms

Bag filter


Example BETHPULS Bag Filter for “Dedusting a fuel-mixture preparation”


Kind of dust Secondary fuel (house waste, wood)Dust explosion class St 1KSt- value 77 bar x m x s-1

Explosion overpressure pmax 7.0 bar

Protective measures

Prevention of effective ignition sourcesExplosion pressure shock resistant up to1.4 bar Explosion venting according VDI 3673 Venting device BETH Explosion flapsDisengagement BETH diverter/rotary valve




Conclusion

Correct operation according the range of use

The operation of explosion protected dedusting plants is only permissible with material and safety characteristics according

the documentation of the plant ( operating instructions, data sheet etc. )

Analysis of HazardsExplosion Protection Document

Maintenance acc. the service manual of the supplier Observance of the maintenance cylce time acc. service manual

By no consideration is the dedusting plant in operation not safe Dust explosion and the damaging of the plant is possible.

Danger for employees with all consequences for health and life



Example of damaged bag filter through a dust explosion of lignite

Reason: Operating mistake, no maintenance acc. instructions Material change ( dust with higher safety characteristics )



Example of damaged bag filter through a dust explosion of lignite

Reason: Operating mistake, no maintenance acc. instructions Material change ( dust with higher safety characteristics )


THANKS FOR YOUR ATTENTION Peter Stender Senior Engineer BETH®Filtration GmbH

BETH® Filtration GmbHBorsigstraße 823560 LübeckDEUTSCHLANDFon +49 451 5307-500 Fax +49 7151 [email protected]

BETH ®Filtration (Schweiz) AGBalz-Zimmermannstraße 7CH-8302 KlotenSCHWEIZFon +41 438133-380 Fax +41 [email protected]

WEIS ENVIRONMENTAL® LLCNiederlassung USA4445 Malone RoadP.O. Box 181070Memphis, TN 38118USAFon +1 901 531 6081Fax +1 901 531 6085 [email protected]

Documents

ATEX STANDARDS FOR EXPLOSION PREVENTION