Combustible Dust Webinar Handout

1

Protecting Worker Health

Welcome Introduction to Combustible Dust Hazards and Mitigation for IHs

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Webinar

Introduction to Combustible Dust Hazards and Mitigation for IHs

2


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• Board of Certified Safety Professionals (BCSP)

• American Board of Industrial Hygiene (ABIH)


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Introduction to Combustible Dust Hazards and Mitigation

for Industrial Hygienists

Gary Q. Johnson, P.E.

Workplace Exposure Solutions LLC

December 10, 2013

4

Agenda

Conditions for dust deflagrations

Combustible dust tests

Explosion protection equipment

Dust collection equipment

Combustible dust procedures

Summary

7 Combustible Dust Hazards and

Mitigation

8

What Dusts Are Combustible?

OSHA Website general description (www.osha.gov/dts/shib/shib073105.html)

“The vast majority of natural and synthetic organic materials, as well as some metals, can form combustible dusts.”

“A combustible dust explosion hazard may exist in a variety of industries, including: food (e.g., candy, starch, flour, feed,) plastics, wood, rubber, furniture, textiles, pesticides, pharmaceuticals, dyes, coal, metals (Al, Cr, Fe, Mg, Zn,) and fossil fuel power generation.”

Combustible Dust Hazards and Mitigation

5

9

Dust Explosion Pentagon

Oxidant (Air)

Heat or Ignition

Fuel

Chemical Chain Reaction

New Fire Triangle

“Fire Triangle” plus Two


Animation of Dust Explosion Hayes Lemnertz Incident

10 US Chemical Safety Board


6

11

FLASH FIRE SEQUENCE WITH FLAMMABLE VAPORS ~ 3 SECONDS DURATION

SERIOUS BURNS BECAUSE CLOTHES IGNITE (~500 F) FROM FLASH FIRE (>1500 F)


Combustible Dust Hierarchy of Controls

Design it out – substitution? Not likely

Engineering controls – explosion protection and dust collection equipment

Administrative controls – housekeeping, hot work, equipment maintenance, Management of Change, emergency response, training

PPE – flame resistant garments


Mitigation

7

13

Light weight Flame Resistant Garments

Protection comes from preventing ignition of clothing in a flash fire – undergarments should also be flame resistant so the elastic will not melt into your skin from the heat

Work with vendors to determine what heat flux rating (ie, kcal/sq.cm.) FRG is appropriate. FRG after fire – fabric did not

support burning

Courtesy Bulwark Protective Apparel

Combustible Dust Testing Defines These Hazards

Ease of ignition of dust cloud

Minimum Explosible Concentration

Minimum Ignition Energy

Minimum Ignition Temperature, Layer, Cloud

Pressure consequences of a dust deflagration

Kst, deflagration index (Pmax, dP/dt)


Mitigation

8

15

Hazard Class

Kst

(bar-m/sec)

Pmax

(bar)

Some examples

ST-1 <200 Moderate (?)

explosion

10

powdered milk, charcoal, sulfur,

zinc

ST-2 200-300 Strong

explosion

10 cellulose, wood flour, methyl acrylate

ST-3 >300 Very strong explosion

12

anthraquinone, aluminum, magnesium

Example combustible dusts (NFPA 68) (higher number higher pressure explosion)

20 liter sphere

Greater hazard? Small qty ST-3 or Large qty ST-1

Courtesy Fauske Assoc.


16

Source: Dust Explosions in the Process Industries, Second Edition, Rolf K Eckhoff

Minimum Explosible Concentration The minimum concentration of combustible dust suspended in air, measured in mass per unit volume that will support a deflagration.

(lower concentration higher hazard)

Dust

Deposit Explosible

Range

IH

Range

10-3 10-2 10-1 1 10 101 102 103 104 105 106

MASS OF POWDER/DUST PER UNIT VOLUME [g/m3]

Dust MEC Dust MEC

Sugar 200 Aluminum 30

Cellulose 80 Magnesium 30


9

17

Static Electrical Ignition Potential? (lower MIE easier ignition)

Minimum Ignition Energy range, mJ

Example materials

25 - 50 ABS resin, aluminum, cellulose, cinnamon, coal, corn flour, paper dust, sugar, wheat starch

10 - 25 Aluminum stearate, epoxy resin, sulfur

< 10 Bisphenol-A, red phosphorus, polyethylene, thorium, zirconium

MIE Tester, Mike 3 apparatus



Minimum Ignition Energy (MIE) (mJ)

Predicts the ease and likelihood of ignition of a dispersed dust cloud. Lower number is greater risk of ignition.

MIE (mJ) Recommended Precaution per BS 5958

500 Low sensitivity to ignition. Ground plant below this level.

100 Consider grounding personnel below this level.

25 The majority of ignition incidents occur below this level.

10 High sensitivity to ignition. Consider restrictions on the use of high resistivity non-conductors below this level.

1 Extremely sensitive to ignition at this level. Handling operations should be such that they minimize the possibility of suspending the powder in air. Dissipate or discourage charge operations.


Mitigation

10

Layer and Dust Cloud Ignition Temperature (ºC) Examples (Lower Temp Easier ignition)

Layer

Cloud Page 19



Measured Properties of Combustible Dusts and how the data is used – sample sizes 0.5 -2.0 kg

Property Definition ASTM Test Method

Application

KSt Dust deflagration index, bar-m/sec

ASTM E 1226 Measures the relative explosion severity & pressure compared to other dusts.

Pmax Maximum explosion overpressure generated in the test chamber

ASTM E 1226 Used to predict the severity of the explosion consequences and to design explosion protection for enclosures

(dp/dt)max Maximum rate of pressure rise

ASTM E 1226 Predicts the violence of an explosion. Used to calculate Kst

MIE Minimum ignition energy, milli-Joules

ASTM E 2019 Predicts the ease and likelihood of ignition of a dispersed dust cloud.

MEC Minimum explosible concentration, gm/m3

ASTM E 1515 Measures the minimum amount of dust, dispersed in air, required to spread an explosion. Analogous to the lower flammability limit (LFL) for gas/air mixtures but there is no UFL test for dusts.

MIT-Layer Minimum Ignition Temperature – Dust layer

ASTM E 2021 Measures surface temperature that will ignite a layer of dust

MIT-CLoud Minimum Ignition Temperature - Cloud

ASTM E 1491 Measures surface temperature that will ignite a dispersed dust cloud.

Page 20 Combustible Dust Hazards and

Mitigation

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21

Sieved Sample – As received, through 40 mesh screen (420 um)

Material larger than 20 mesh

Material passing through 20 mesh but not through 40 mesh screen

Material passing through 40 mesh but not through 200 mesh screen

Material passing through 200 mesh screen


Factors that Change Dust Ignitability

Property & Change Risk increases as the value:

Kst

MIE

Particle size distribution DECREASES

Dust chemistry (ie, PVC vs polyethylene)

Dust moisture content INCREASES

Dust concentration optimal range

Dust cloud turbulence INCREASES

Oxygen content INCREASES

Dust cloud temperature INCREASES

Initial dust cloud pressure INCREASES

Hybrid mixtures dust cloud with flammable vapors or gases


Mitigation

12

Combustible Dust Hazards and Mitigation 23

Questions – CD Hazards, Testing

OSHA CD Inspections & Violations Issued Oct. 2007-Oct. 2012

24

7625

2356

14321827

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Serious Other Than Serious

Federal

State

2272

653

0

500

1000

1500

2000

2500

Federal State

INSPECTIONS

VIOLATIONS


13

Distribution of Federal Violations


Mitigation

Some Combustible Dust NEP Findings

1. Hazardous dust accumulations

2. Unrated electrical equipment and Powered Industrial Trucks

3. Dust collectors inside buildings - no explosion protection systems.

4. Deflagration isolation systems not provided

5. The horizontal surfaces not minimized to prevent accumulation of dust on surfaces.

26


14

27

Explosion Vent Problems


Some Combustible Dust NEP Findings 6. Dust collector exhaust recycled through duct work back

into the work area without protection.

7. Magnetic separators and tramp metal separators not installed or not functioning to prevent foreign material entering into process stream.

8. Explosion vents on bucket elevator(s) and dust collectors were directed into work areas and not vented to a safe, outside location.

9. Equipment (such as grinders and shakers) not designed to minimize escape of dust into the surrounding work area.

10. Ductworks used in transporting combustible dust were not constructed of metal, not bonded or grounded.

28 Combustible Dust Hazards and Mitigation

15

Some Combustible Dust NEP Findings

11. Hot work performed in the combustible dust handling areas without hot work procedures.

12. Silos, legs of bucket elevators were not equipped with explosion relief venting.

13. Enclosureless dust collection systems were allowed indoors where they were connected to sanders having mechanical feeds and did not follow other reqmts.

14. Compressed air used to clean up the combustible dust accumulation in the presence of ignition sources.

15. Portable Vacuum Cleaners were not approved for Class II locations.


Mitigation

Welding on Outside

of Duct Wall

Dust Deposit on

Inside of Duct Wall

30

Set Explosion Control Strategy Process Hazard Analysis NFPA 654

Based on hazardous characteristics of dust

PHA-documented, thorough analysis and risk mitigation strategy for:

The facility

The process

Associated fire and explosion hazards

Retain PHA for life of process

Update PHA every 5 years

Other NFPA Stds: 664 Wood, 484 Metal, 61 Agriculture & Food Combustible Dust Hazards and

Mitigation

16

31

Accident Scenarios to Assess Explosion within process equipment

Ignition sources (frictional heating, smoldering dust layers, electrostatic sparks)

Equipment with dust clouds > MEC (blenders, driers, size reduction) Dust collectors have dust clouds > MEC (> 40% of incidents))

Explosion propagation – interconnected equipment (spark or deflagration)

Secondary explosions (fuel in dust accumulations, often more significant than primary explosion)

{Zalosh, et al, “Safely Handle Powdered Solids,” Chemical Engineering Progress Magazine, Dec. 2005}

NEW: ADD FLASH FIRE SCENARIO AND DETERMINING OPERATOR PROTECTION


NFPA 654-2013 Key Definition Changes (Ch.3) Flash Fire. A fire that spreads rapidly through a diffuse fuel,

such as dust, gas, or the vapors of an ignitable liquid, without the production of damaging pressure.

Dust Explosion Hazard Area. A room or building volume where an unvented deflagration of the entrainable dust mass can result in a pressure exceeding the strength of the weakest structural element not intended to fail.

Dust Flash Fire Hazard Area. An area where combustible dust accumulation on exposed or concealed surfaces, outside of equipment or containers, can result in personnel injury from thermal dose during a dust deflagration, as well as any areas where dust clouds of a hazardous concentration exist during normal operation. A propagating deflagration yields a flash fire through the hazard area.

32


17

33

Dust overhead, over an ignition source Dust MEC = 30

grams/cubic meter

Dust cloud 2 meters diameter, 5 meters long

Mass of dust in perfectly distributed dust cloud? V =pi x D2/4 x

L=3.14 x 22/4 x 5= 15.7m3

Mass =15.7 m3 x 30 gr/m3=471 gm x 1#/454gm= 1.04 pounds

How Little Dust for an Explosion?


34

Dust Explosion Pentagon: Multiple Strategies to Reduce Risk

Heat or ignition source:

prevent flames static

electricity, sparks,

smolders

Confinement of dust

cloud: building &

equipment designed

to safely contain or

vent

Oxidizer (oxygen

in air): reduce O2

with inert gas

Combustible dust

(fuel): prevent

accumulation –

design,

housekeeping

Dispersion of

dust particles:

prevent dust

layer getting

airborne – relief

device vent path


18

Ignition Sources

Stronger Open flame Welding arc Gas or dust

explosion Electrical short or

arc Friction Mechanical spark

(tramp metal)


Mitigation

Static Electricity Types

36

Spark discharge Brush discharge

Corona discharge

Propagating brush discharge

Bulk brush discharge

Courtesy Crohmiq Co.

Up to 1000 mJ Up to 40 mJ

Up to 1000 mJ

Up to 1000 mJ

Up to 1 mJ Combustible Dust Hazards and

Mitigation

http://images.google.com/imgres?imgurl=http://www.thisischurch.com/images/candleburning.jpg&imgrefurl=http://www.thisischurch.com/lectionarybiblenotesyearb/secondsundayofadventyearb.htm&h=309&w=232&sz=9&hl=en&start=1&tbnid=G0Us2VoYkgj-jM:&tbnh=117&tbnw=88&prev=/images?q=candle+burning&gbv=2&hl=en

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Ignition Sources Less strong

Static sparks

Cigarettes

Hot surfaces – internal combustion engines

Smoldering embers

Overheated electrical equipment

©Sierra Pacific Infrared Thermography


Mitigation

38

Grounding , Bonding-Dissipate Static Electrical Charges

Metal strip under rubber Courtesy Morris Coupling Co.

Jumper Wire – Courtesy J.O.A.

Clamp together Courtesy Jacob Tubing

Flanges and bolts on metal ducts < 106 ohms – British study

Dust drum bonding cable with alligator clip


20

Big Bags or Flexible Intermediate Bulk Containers (FIBC) Applications (consider contents, environment)

Type FIBC Comb. Solids?

Flam. Vapors?

MIE, mJ Exclusions

A OK No > 1000 Conductive solids

B OK NO > 3 Conductive solids

C (grounding tab, < 108 Ω)

OK, conductive solids OK

OK if present > 0.14 Ground resist. < 25 Ω

D (static dissipating construction)

OK OK flammable atmospheres

> 0.14 Conductive solids

39

TYPES B, C, & D: tested & verfied safe for intended use by recognized organization in accordance with IEC 61340-4-4, Electrostatics Part 4-4, Standard Test Methods for Specific Applications – Electrostatic Classification of FIBC’s


40

Electrical Classification – Class II for Combustible Dusts

Class II Group

Type Dust Temp. Lim., Normal Opns, oF/oC

Temp. Lim., F, Abnormal Opns, oF/oC

E Metal 392/200 392/200

F Carbonaceous 302/150 392/200

G Flour, grain, wood, plastics, chemicals

248/120 329/165

Division 1: combustible dust normally present that could product explosive or ignitable mixtures, mechanical failure might cause mixtures, electrically conductive dusts

Division 2: airborne combustible dust not normally present, comb.dust layer on electrical equipment may interfere with heat dissipation


21

Class II Electrical Equipment Enclosures

41

Division 1 – dust incendive proof? (NEMA 12) Courtesy Crouse Hinds Division 2 –

dust tight?

Div. 1 or 2 – purge retrofit as per NFPA 496? Courtesy Pepprl-Fuchs

TEFC-courtesy wegelectrical motors

Cour. Thomas.net



Questions – Regulatory, Ignition Sources

22

43





smolders

Confinement of dust

cloud: building &

equipment designed


vent

Oxidizer (oxygen

in air): reduce O2

with inert gas

Combustible dust

(fuel): prevent

accumulation –

design,

housekeeping

Dispersion of

dust particles:

prevent dust

layer getting

airborne – relief

device vent path


44

Explosion Pressure Profile

Explosion pressure rapidly builds beyond typical vessel yield strength

Vent or suppress –pressure less than Preduced to 2/3 yield strength –

no deformation

Yield strength - allow deformation

Pre

ssu

re

Time

Pmax

Vessel strength

Vent too small

Preduced

Pstat

Correct Vent

Unvented


23

Important to Get the Design Right the First Time!

45 Courtesy Rembe Co. Combustible Dust Hazards and

Mitigation

46

Explosion Containment

Pressure CONTAINMENT 10-12 bar (150-180 psig) Pros

no additional protection on vessel

indoor applications

Cons still need to isolate

connected equipment with high pressure design to isolation device

ASME pressure vessel & high capital costs

Courtesy Glatt Air Techniques Combustible Dust Hazards and

Mitigation

24

47

Venting - Explosion Doors

door safety cage if near walkway

Door weight = 2.5 #/sq.ft (NFPA 68) so its mass does not impede venting

Adv: Does not need to be replaced after venting

Disadv: Door sizes maybe larger than panels/membranes

Courtesy Philadelphia Safety Door Combustible Dust Hazards and

Mitigation

48

Venting – Explosion Panels, Rupture Disks

Domed panel, courtesy Fenwal

Rupture discs, courtesy Fike

Domed panels resist pressure cycling better than flat panels – 4-20x longer

Courtesy BS&B Safety Systems


25

Vented Explosions Are Violent!


Mitigation

50

Explosion Vent Design – Safe Discharge Zone

D = K(V/n)1/3

D – dist. in front, m K – flame length factor, K=10

(metal dust), K=8 (chem., agric. dusts)

V – volume vented enclosure, m3

n – number of vents Flame width = ½ D

Example: 2 vents V= 60 m3 (1980 ft3) Chemical dust, K = 8 D=24.5 m = 80 ft in front of

vent Courtesy Fenwal Combustible Dust Hazards and Mitigation

26

51

Indoors Venting Considerations Prevent ice & snow from adding weight to vent – vendor options

Max vent duct length as per NFPA 68, (<10 ft)

Blast Deflector Plate Design (NFPA 68, section 6.6)

-size: 175% vent area

-45-60o angle , centered on vent

-Distance, 1.5x vent diameter

-Strong mounting

-Limited to enclosures smaller than 20 m3 (706 ft3)


Safe Vent Discharge Location?

Page 52

Explosion Venting

Emergency Exit Doors

Rotate dust collectors, blast deflector plates


27

Don’t Make Your Own Explosion Vent Panels! (Plastic bags too strong)


Mitigation

Building Damage Limiting Construction – Wall Vent Panels

54

Courtesy BS&B Safety Systems


28

55

Flameless Vent

Two parts of device

• Rupture disk to relieve pressure

• Mesh screen to contain and quench flame front

Advantages:

• Indoor protection

Disadvantages:

•capital cost

•may not be suitable for high Kst dusts

• building pressure impact?

• hot gases safety zone 6-12 ft

Courtesy Fenwal


Flameless Vent Operation

56

Courtesy Rembe Co.


29

57

Fire Sprinklers in Dust Collector

Risk decision – puts out fire without operator intervention

Collector rated for 20”w.c. – filled with sprinkler water it would collapse!

Water dump valves to drain water

Challenge – getting an air tight dump valve

Courtesy Donaldson Corporation

3” dia. check valve


58

Active Protection – requires sensors & high speed control to initiate

Advantages:

• Indoor applications

• Prevents growth of explosion and aftermath

Disadvantages:

• Product contamination (perhaps moot with fire)

•Ongoing vendor inspection and maintenance costs -Quarterly -2 hr downtime -$800-1000/day

Explosion Chemical Suppression

Interlock suppression controls with equipment protected – permissive on

Courtesy Fenwal


30

Reinforce Mounting for Suppression Canisters


Mitigation Courtesy Fenwal

60

Chemical Suppression Lockout

- Remove permissive insert – magnetic switch

- Install lockout blank flange

- Install lockout cable and locks

Courtesy Fenwal


31

Explosion Suppression vs. Venting

Equipment indoors vent duct not practical

Not enough vent area on equipment High Kst or hybrid dust

Low Preduced

No safe place to vent

Toxic dusts cannot be discharged to atmosphere via a vent

Flame propagation through interconnection suppression on equipment -

isolation suppression controlled by same controls

61

Courtesy Fike


62

Spark Detection & Extinguishing

Courtesy BS&B Wide belt sanders generate sparks


32

Abort Gates

63 Courtesy Imperial Systems Combustible Dust Hazards and

Mitigation

64 Combustible Dust Hazards and Mitigation

33

65

Equipment DEFLAGRATION ISOLATION Isolation devices

needed:

To protect workers working near dust controlled equipment

To prevent pressure piling on upstream equipment such as a cyclone before a baghouse

One of the most common gaps in explosion protection equipment

Courtesy Fenwal Combustible Dust Hazards and Mitigation

66

Passive ISOLATION: Flame Front Diverter

Passive device

-Locate close to collector

-Vent to safe location

Advantages:

-Passive

-Self closing possible

Disadvantages:

-Directional

-System d/p

-Kst < 200

-Not tight seal

Courtesy J.O.A.


34

67

Passive ISOLATION: Back Draft Damper

Normal flow direction (conceptually a check valve)

Tested for up to Kst = 300 dusts (ST-2 class) depending on duct diameter

Heavy duty damper slams shut with deflagration pressure wave – normally hangs open 60o against 25o valve seat

Routinely inspect for cleanliness – potential for dust fouling

Courtesy Rembe


Backdraft Damper Operation

68

Courtesy Rembe Combustible Dust Hazards and Mitigation

35

69

Passive Isolation: Mechanical Path

Rotary airlock valve (tight construction, 6 vanes or more)

Screw conveyors

Powder chokes

Rotary Air Lock Valve Combustible Dust Hazards and

Mitigation

70

Isolation – Fast Acting Valves

Gate valve – full opening design Located far enough from collector

to allow for time delay between sensing an explosion and sending a signal to close the valve.

Advantage Full isolation of flame front Prevent product cross contamination

Disadvantage Capital cost ($1200-1400/inch

diameter) – MAX SIZE 24” Stronger duct between valve and

collector (3-8 meters) Routine test cycling of valve may

require replacement parts

Courtesy Fenwal


36

71

Active Isolation: Pinch Valves

Courtesy CV Technologies

How it works 1. Housing installed into ductwork. 2. Inflatable bladder rapidly activates to close the line. 3. Air receiver tank provides inflation energy. 4. Controller manages and monitors valve operation. 5. Sensor (not shown) triggers activation of valve closing. - Clean side application - Lower differential pressure rating than float valve

Courtesy Rembe Combustible Dust Hazards and

Mitigation

Explosion Protection Design Standards

NFPA 68-2012

Explosion vent doors, vent panels, flame arresting vents, flame front diverters

NFPA 69-2008

Explosion prevention: chemical suppression, limiting oxidants (inerting)

Explosion isolation: high speed valves, rotary airlock valves

Fire prevention: spark detection and extinguishing, abort gates


Mitigation

37

73





smolders

Confinement of dust

cloud: building &

equipment designed


vent

Oxidizer (oxygen

in air): reduce O2

with inert gas

Combustible dust

(fuel): prevent

accumulation –

design,

housekeeping

Dispersion of

dust particles:

prevent dust

layer getting

airborne – relief

device vent path


74

Oxidant Concentration Reduction (NFPA 69: Explosion Prevention)

Inerting gases to reduce oxygen from normal 19.5% to 8-10% (actual value depends on dust Limiting Oxidant Concentration test)

Nitrogen most common, some use of carbon dioxide

Requires oxygen monitor and controls to ensure continual low oxygen level

Advantages Preventive technique

Avoids product contamination

Disadvantages

Asphyxiation hazard next to inerted equipment if it goes positive– adequate alarms and controls?

Nitrogen use operating expense if no recycling possible

Nitrogen molecule


38


Questions – Explosion Protection Equipment

Jahn Foundry – Phenolic Resin

76





smolders

Confinement of dust

cloud: building &

equipment designed


vent

Oxidizer (oxygen

in air): reduce O2

with inert gas

Combustible dust

(fuel): prevent

accumulation –

design,

housekeeping

Dispersion of

dust particles:

prevent dust

layer getting

airborne – relief

device vent path


39

Housekeeping Blowdowns for inaccessible or

unsafe locations (precautions to prevent flash fire)

Clean accessible areas with vacuum, etc. so dust accum. < threshold dust accum.

Compressed air hoses – pressure relief nozzles 30 psig max pressure

All energized electrical equipment NEMA 12

Ignition sources, hot surfaces shutdown or removed from area

Housekeeping procedures documented

77 Courtesy Rembe Co.


78

Safe sweeping

Sweep gently to minimize airborne dust

Natural bristles (no synthetic)

Aluminum or conductive polymer dust pans

Courtesy Rembe Co.


40

79

Static dissipating features -Drum grounding cable -Conductive vacuum and air hoses -Conductive wheels

Courtesy Vac-U-Max


Electric with Explosion Proof blower and control switches

Portable Vacuum Cleaners with Combustible Dust Protection

courtesy Ruwac

80

Central Vacuum Cleaning Systems

System components -High vacuum producer (6-12”Hg = 82-164” w.c.) -Filter/receiver -Pre-separator (optional) -Tubing branches to use zones -Hoses and tools

Courtesy Gardner Denver


41

Housekeeping Procedures

Layer Depth Criterion (LDC) – dust thickness (density x area)

Hazard if > 5% of floor area of confined area – include overhead horizontal surfaces – up to 1,000 sq.ft.

Survey – dust deposition rates

Written procedure

Responsibilities

Safe methods

Routine and special cleanup

Recordkeeping


Mitigation

Dust collection system design 1 – Minimize fugitive dust

Open hoods have lowest collection efficiency

Better - Enclosed process under dust collection

Design as though OEL < 1 mg/m3

Control smaller dust sources – discarding bags at bag dump 82


42

83

Dust collection system design 2-adequate conveying velocity

Dust Control Systems: 3500 to 4500 fpm (higher for some dusts.)

Aerosol or other small particle Control Systems: 2500 to 3500 fpm.

(ft/min)duct in airstream of velocity V

min)/(ft lumeexhaust vo Q

(inches)diameter duct D

)(ftduct of area sectional-crossA

: where ) 576/*_(/

3

2

2

DAAQV

Hayes – Lemnertz ducts


84

1) Duct does not get larger after branch entry

2) Unneeded ducts blanked

3) Poor duct transitions or merges

4) Excessive use of flexible ducts

5) High dust collector d/p

6) Blast gates changed

7) No system technical documentation

8) No system monitoring

8 visible clues of inadequate duct conveying or transport velocity


43

85

Complete Dust Collection System Explosion Protection Overview

Static grounding

Conveying velocity

Static grounding

Internal, external

Inlet

isolation

Explosion

vent,

suppress,

or contain

Spark

resistant?

Recirculation?

return air isolation

Hood

design

Housekeeping to prevent

dust accumulations

Electrical

Classification


86

Review - Can a Dust Collector Be Indoors?

YES IF ONE OF THESE IN PLACE

Pressure containment

Short explosion vent duct to outdoors

Flameless vent

Chemical or Water Suppression

Volume < 8 cubic feet with no explosion protection – carefully considered risk decision

Sources: NFPA 654, 68, 69


44

Combustible Dust Procedures

Ignition Control: enhanced hot work permits, static grounding integrity, electrical enclosures

Housekeeping

Equipment maintenance: explosion protection, dust collection, vacuum cleaning

Emergency response: fighting dust fires

Management of Change: internal design standards, Process Hazard Analyses, change procedures

Flame Resistant Garments

Employee training


Mitigation

Summary Treat dust as guilty of being combustible unless

proven innocent

Conduct PHA’s for your process – “live” as long as your process

Apply hierarchy of controls where a deflagration hazard exists as per NFPA stds.

Maintain explosion protection and dust collection equipment as per NFPA stds.

Implement a Combustible Dust Program

Use Management of Change

Reference materials follow 88 Combustible Dust Hazards and Mitigation

Copyright Gary Q. Johnson 2013

45


Final Questions

Gary Q. Johnson

December 2013

Reference: Other Combustible Dust Regulations, Standards, Guidelines

46

Literature to ID Comb. Dusts (Use for setting direction, not design)

OSHA CD Safety Poster

NFPA 61 (Food, Agric.) table A.6.2.1

NFPA 68 (Expl.Vent) Annex F

NFPA 484 (Metals) in Annexes

NFPA 499 (Haz. Area Elec.) Table 4.5.2

BGIA (Europe – table of ~ 4600 matls.) http://www.dguv.de/ifa/Gefahrstoffdatenbanken/GESTIS-STAUB-EX/index-2.jsp


Mitigation

US Chemical Safety Board (http://www.csb.gov/combustible-dust-hazard-investigation/)

Combustible Dust Hazard Investigations Hayes Lemnertz (aluminum dust) CTA Acoustics (auto insulation – phenolic resin) West Pharmaceutical (polyethylene) Jahn Foundry (phenolic resin) Rouse Polymerics (rubber) Ford River Rouge Coal Explosion

Imperial Sugar Company Dust Explosion and Fire (sugar dust)

Hoeganaes Corporation Fatal Flash Fires (iron dust)


Mitigation

http://www.dguv.de/ifa/Gefahrstoffdatenbanken/GESTIS-STAUB-EX/index-2.jsp








http://www.csb.gov/combustible-dust-hazard-investigation/







47

Page 93

OSHA Technical Manual Section III: Chapter 3 - Ventilation Investigation

(http://www.osha.gov/dts/osta/otm/otm_toc.html)

Contents: I. Introduction II. Health Effects III. Standards and Codes IV. Investigation Guidelines V. Prevention and Control VI. Bibliography Apdx III:3-1. Ventilation Primer Apdx III:3-2. Glossary Apdx III:3-3. OSHA, Consensus Standards Apdx III:3-4. Troubleshooting an Exhaust System


OSHA Ventilation Regulations

29 CFR 1910.94

A) – Abrasive Blasting

B) – Grinding, Polishing, and Buffing

C) - Spray Finishing

29 CFR 1910.106 – Flammable and Combustible Liquids

29 CFR 1910.1450 – Laboratory Chemical Safety


Mitigation

48

OSHA Resources

Website: http://www.osha.gov/dsg/combustibledust/index.html

Combustible Dust National Emphasis Program

Status Report on Combustible Dust National Emphasis Program, October 2009

Other useful documents – see last slides of presentation – copies of complete document in web posting

Advanced Notice of Proposed Rule Making Combustible Dust Postings: Docket # 2009-0023 (178 postings)

http://www.regulations.gov/ - search on “Combustible Dust” and there are over 1700 postings


Mitigation

Safety and Health Information Bulletin www.osha.gov

Purpose Background Elements of a Dust Explosion Facility Dust Hazard Assessment Dust Control Ignition Control Damage Control Training References 9 pages

Issued 7/2005


Mitigation

http://www.osha.gov/dsg/combustibledust/index.html

http://www.regulations.gov/

49

OSHA Combustible Dust Safety Poster

97

1 page Issued 2008


OSHA Fact Sheet

Explosions overview

Prevention

Dust Control

Ignition Control

Injury and Damage Control

2 pages

Issued 3/2008


Mitigation

50

Combustible Dust Hazard Communication

99

Introduction OSHA’s Hazard Communication Standard Identifying and Controlling the Potential for Dust Explosions MSDS Preparation Product Labels Training & Information References OSHA Assistance Regional Offices 21 ½ size pages

Issued 2009 Combustible Dust Hazards and

Mitigation

OSHA Guidance Combustible Dust Fire Fighting (2013)

100

Inform firefighters of hazards from Combustible Dust fires Useful tool for site emergency planning and fire department interaction


51

Page 101

National Fire Protection Association (NFPA) Standards GENERAL: 68: Guide for Venting of Deflagrations 69: Std. on Explosion Prevention Systems 91: Std. for Exhaust Systems for Air Conveying of

Vapors, Gases, Mists, and Noncombustible Particulate Solids (incorporated by reference into NFPA 61, 484, 654, 655, 664)

499: Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas


Page 102

INDUSTRY SPECIFIC 61: Standard for the Prevention of Fires and Dust Explosion

in Agricultural and Food Processing Facilities 85: Boiler and Combustion Systems Hazards Code 86: Standard for Ovens and Furnaces 484: Standard for Combustible Metals 654: Std. for the Prevention of Fire and Dust Explosions

from the Manufacturing, Processing, and Handling of Combustible Particulate Solids

655: Standard for Prevention of Sulfur Fires and Explosions 664: Standard for the Prevention of Fires and Explosions in

Wood Processing and Woodworking Facilities

National Fire Protection Association (NFPA) Standards


52

Standards – Combustible Dust • NFPA 652 (NEW) –

Fundamentals (in development)

• NFPA 61 – Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities.

• NFPA 484 – Standard for Combustible Metals

• NFPA 654 – Standard for the Prevention of Fire and Dust Explosions from Manufacturing, Processing, and Handling of Combustible Particulate Solids

• NFPA 655 – Standard for Prevention of Sulfur Fires and Explosions

• NFPA 664 – Standard for the Prevention of Fire and Explosions in Wood Processing and Woodworking Facilities. 103

NFPA 652

NFPA 664

NFPA 61

NFPA 484

NFPA 655

NFPA 654


Page 104

ANSI/AIHA Z9 Standards (http://www.asse.org/shoponline/standards.php)

Z9.1 – Open Surface Tanks Ventilation and Operation

Z9.2 - Fundamentals Governing the Design and Operation of Local Exhaust Systems

Z9.3 - Standard for Spray Finishing Operations — Safety Code for Design, Construction, and Ventilation

Z9.4 - Abrasive-Blasting Operations — Ventilation and Safe Practices for Fixed Location Enclosures

Z9.5 - Standard for Laboratory Ventilation

Z9.6 - Exhaust Systems for Grinding, Polishing, and Buffing

Z9.7 - Recirculation of Air from Industrial Process Exhaust Systems Combustible Dust Hazards and

Mitigation

http://www.asse.org/shoponline/standards.php

53

ANSI/AIHA Z9 Standards (http://www.asse.org/shoponline/standards.php)

Z9.9 BSR/AIHA (Draft) Portable Ventilation Systems

Z9.10 ANSI/AIHA -2008 Fundamentals Governing the Design and Operation of Dilution Ventilation Systems in Industrial Occupancies

Z9.11 ANSI/AIHA 2008 Laboratory Decommissioning Standard

Z9.12 BSR/AIHA Design, Operation, and Maintenance of Combustible Dust Collection Systems (in process)

Z9.13 BSR/AIHA Design, Operation, Testing, and Maintenance of Laminar Flow Fume Hoods

Z9.14 BSR/AIHA Methodology for Certification of a Biosafety Level - 3 (BSL-3) Lab


Mitigation

Industrial Ventilation, A Manual of

Recommended Design, 28th Edition, ACGIH,

2013 (Now in Imperial and SI Units)

Page 106

1. Exposure Assessment

2. Preliminary Design

3. Principles of Ventilation

4. General Industrial Ventilation

5. Design Issues – Systems

6. Design Issues - Hoods

7. Fans

8. Air Cleaning Devices

9. LEV System Design Calculation Procedures

10. Supply Air Systems

11. Energy Considerations

12. Cost Estimating

13. Specific Operations


http://www.asse.org/shoponline/standards.php

54

Page 107

ACGIH Industrial Ventilation Manual Chapter 13 – Specific Operations

13.05-Battery Charging

13.10-Clean Rooms

13.15-Filling Operations

13.20-Foundry Operations

13.25-Gas Treatment

13.30-Kitchen Equipment

13.35-Laboratory Ventilation

13.40-Low Volume-High Velocity Exhaust Systems

13.45-Machining

13.50-Material Transport

13.55-Metal Melting Furnaces

13.60-Mixing

13.65-Moveable Exhaust Hoods

13.70-Open Surface Tanks

13.72 Push-Pull Ventilation

13.75-Painting Operations

13.80-Mech.Surface Cleaning and Finishing

13.85-Vehicle Ventilation

13.90-Welding and Cutting

13.95-Woodworking

13.99-Miscellaneous


Industrial Ventilation, A Manual of Recommended Practice for Operation & Maintenance, 1st Edit., ACGIH, 2007

Page 108

1. Construction & Project Management Phase

2. Commissioning and Proof of Performance

3. Testing and Measurement of Ventilation Systems

4. Balancing Duct Systems with Dampers

5. Ventilation System Monitoring & Maintenance

6. Monitoring & Maintenance – Air Cleaning Devices

7. Troubleshooting Ventilation Systems

8. Modifying Industrial Ventilation Systems

9. Operator Skills and Training


55

Page 109

Air Movement and Control Association (AMCA)

200: Air Systems

201: Fans and Systems

202: Troubleshooting

203: Field Performance Measurements of Fan Systems

410: Recommended Safety Practices for Air Moving Devices


Factory Mutual Global Property Loss Prevention Data Sheets

110

Insurance company guidance, not a standard. (Referenced in CD NEP.) Available for free download at: http://www.fmglobal.com/fmglobalregistration/

PLPDS pertinent to combustible dusts No. 7-76, Prevention and Mitigation of Combustible

Dusts and Explosions (2006) No.7-73, Dust Collectors and Collection Systems (2008) No. 10-3, Hot Work Management

Combustible Dust Hazards and

Mitigation

56

Page 111

National Institute for Occupational Safety and Health (NIOSH) Publications

Occupational Health Guidelines for Chemical Hazards http://www.cdc.gov/niosh/81-123.html

Hazard Control http://www.cdc.gov/niosh/hazcommn.html

Hazards Identification http://www.cdc.gov/niosh/hidlist.html

Site Index http://www.cdc.gov/niosh/siteindx.html#alpha


Page 112

Industrial Ventilation Design Guidebook

(1600 pgs,$200) (http://www.invent.hut.fi/)

1. INDUSTRIAL AIR TECHNOLOGY

2. TERMINOLOGY 3. DESIGN METHODOLOGY

OF INDUSTRIAL AIR TECHNOLOGY

4. PHYSICAL FUNDAMENTALS 5. PHYSIOLOGICAL AND

TOXICOLOGICAL CONSIDERATIONS

6. TARGET LEVELS 7. PRINCIPLES OF AIR AND

CONTAMINANT MOVEMENT INSIDE AND AROUND BUILDINGS

8. ROOM AIR CONDITIONING

9. AIR-HANDLING PROCESSES 10. LOCAL VENTILATION 11. DESIGN WITH MODELING

TECHNIQUES 12. EXPERIMENTAL

TECHNIQUES 13. GAS-CLEANING

TECHNOLOGY 14. PNEUMATIC CONVEYING 15. ENVIRONMENTAL

ASSESSMENT 16. ECONOMIC ASPECTS


57

Page 113

U.S.EPA Hazardous Air Pollutants

http://www.epa.gov/ttn/atw/hapindex.html

Maximum Achievable Control Technology (MACT) Rules Status http://www.epa.gov/ttn/atw/112j/info/112(j)-table2.html

Integrated Risk Information System http://www.epa.gov/iris/index.html

Pollution Prevention http://www.epa.gov/opptintr/p2home/

Pollutants/Toxics http://www.epa.gov/ebtpages/pollutants.html

Treatment/Control http://www.epa.gov/ebtpages/treatmentcontrol.html

EPA Method 204 – Criteria For and Verification of a Permanent or Temporary Total Enclosure



Thank you!

Upcoming AIHA Webinar

ISO 45001 – A Global OH&S Management System Standard

Monday, December 16, 2013

2:00 PM ET - 3:30 PM ET

This session will begin promptly at the scheduled start time. We appreciate your patience.

http://www.epa.gov/ttn/atw/hapindex.html

http://www.epa.gov/ttn/atw/112j/info/112(j)-table2.html



http://www.epa.gov/iris/index.html

http://www.epa.gov/opptintr/p2home/

http://www.epa.gov/ebtpages/pollutants.html

http://www.epa.gov/ebtpages/treatmentcontrol.html

Documents

Combustible Dust Webinar Handout