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Combustible Dust ProceduresCombustible Dust Procedures

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Gary Q. Johnson, P.E.Gary Q. Johnson, P.E.Workplace Exposure SolutionsWorkplace Exposure SolutionsNCNC--IVC IVC –– Raleigh, NCRaleigh, NCApril 30, 2010April 30, 2010

Agenda - Procedures Housekeeping Ignition Source Control Hazard Communication Training

Administrative Procedures

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Personal Protective Equipment Equipment Maintenance Management of Change Emergency Procedures & Incident

ReportingCopyright Gary Q. Johnson 2010

Back to the Dust Explosion Pentagon:Back to the Dust Explosion Pentagon:Multiple Strategies to Reduce Cleanup RiskMultiple Strategies to Reduce Cleanup Risk

Heat or ignition source: prevent static electricity, prevent static electricity, sparkssparks

Confinement of dust cloud: building & equipment building & equipment designed to safely contain or designed to safely contain or ventvent

Dispersion of dust particles: prevent dust prevent dust layer getting airborne layer getting airborne –– clean up method?clean up method?

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Oxidizer (oxygen in air): reduce Oreduce O22with inert gas (asphyxiation with inert gas (asphyxiation hazard?)hazard?)

Combustible dust (fuel): prevent accumulation prevent accumulation ––housekeepinghousekeeping

••Chemical Engineer Chemical Engineer –– Ohio State Univ.Ohio State Univ.••Professional Engineer Professional Engineer –– OhioOhio

••Industries: Industries: pharmapharma, laundry, paper, health , laundry, paper, health care, bar soap, paint, plastics compounding, care, bar soap, paint, plastics compounding, plastic film, auto parts, metal fabrication, plastic film, auto parts, metal fabrication, tree resins, printing, wood products, trainingtree resins, printing, wood products, training

How We Got Here Page 4

••7+ yrs Consultant 7+ yrs Consultant –– Dust Collection Systems, Dust Collection Systems, Combustible DustCombustible Dust••27 yrs Procter & Gamble 27 yrs Procter & Gamble –– HSE Exposure HSE Exposure ControlControl5 years US Navy 5 years US Navy –– nuclear submarinesnuclear submarines

••ACGIH Ventilation Committee (past)ACGIH Ventilation Committee (past)••Intl.Soc.Pharm.EngrsIntl.Soc.Pharm.Engrs –– Baseline GuidesBaseline Guides

Imperial Sugar Imperial Sugar –– Dust accumulations Dust accumulations were fuel for building wide deflagrationswere fuel for building wide deflagrations

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Dust Cloud Density > MECDust Cloud Density > MEC

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Pneumatic conveying system leak like dust cloud from compressed air blow down –cannot see 3-4 feet thru cloud

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Dust coating overhead piping and Dust coating overhead piping and conduit is knocked down (forktruck, conduit is knocked down (forktruck, supersack, supersack, earthquakeearthquake) over an ) over an ignition sourceignition source Dust MEC = 30 grams/cubic meterDust MEC = 30 grams/cubic meter Dust cloud 2 meters diameter, 5 meters Dust cloud 2 meters diameter, 5 meters

longlong

How Little Dust for an Explosion?

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longlong What mass of dust (specific What mass of dust (specific

gravity=1) in perfectly distributed gravity=1) in perfectly distributed dust cloud?dust cloud? V =pi x D2/4 x L=3.14 x 22/4 x 5= V =pi x D2/4 x L=3.14 x 22/4 x 5=

15.7m315.7m3 Mass =15.7 m3 x 30 gr/m3=471 gm x Mass =15.7 m3 x 30 gr/m3=471 gm x

1#/454gm= 1#/454gm= 1.04 pounds1.04 pounds

Housekeeping

The hazards associated with cleaning Safe cleanup methods

Manual

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Manual Vacuum cleaning Housekeeping procedures

Contractor cleanup Summary

Cleanup Dust Explosion Scenario

Overhead settled dust –create dense dust cloud > MEC during cleaning

Static electrical spark –hose to building structure

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g– ignite this dense dust cloud (other ignitiion sources possible – hot surface, flame)

Exploding cloud dislodges other settled dust to propagate deflagration

Expanding deflagration gases destroy building

NFPA 654: Annex DAssessing Dust Layer Hazard

Dust layer allowable thickness varies with dust bulk density: 1/32” layer basis for

Proportion of building with layer Floor area > 5% up

f 2

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/ yhazardous condition Density 75 #/ft3, MEC=350

gm/m3

1/32” cover floor => dust cloud 10 feet high, dense enough for dust deflagration

AT(inches)=((1/32)*75#/ft3)/(actual density#/ft3) BD = 36: AT= 1/8” BD = 18: AT = ¼”

to 20,000 ft2, 1000 ft2 maximum?

Overhead dusty areas 5-10% floor? Bar joists and beams Walls Piping and conduit

NFPA 654: Allowable Dust Accumulation, table A.6.6.2

Accumulation frequency: Infrequent (2-3 episodes/year) Frequent (>3 episodes/yr or within 24 hours) Continuous (faster than 24 hours)

Housekeeping frequency:/ ” / ” f

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<1/32” 1/8” – infrequent – SAME SHIFT <1/32” 1/8” – frequent – OFTEN ENOUGH TO KEEP

LAYER AVG 1/16” > 1/8” – SHUT DOWN AND CLEAN UP IMMEDIATELY

Electrical classification: Infrequent - at least dust tight 1/32 -> 1/8” – frequent – Class II, Div. 2 > 1/8” – infrequent - Class II, Div 2 > 1/8” – frequent - Class II, Div 1

FM 7-76 (Prevention and Mitigation of Combustible Dust Explosions and Fire): Assessing Dust Layer Hazard

Hazard exists in 10 ft high building if: > 5% of area has >1/16” dust layer Dust bulk density assumed = 36 #/ft3

Equation for different conditions for

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Equation for different conditions for suspendible dust above floor or floor dust that could be disturbed Tex = HxAtot/(87.5xBDxADust)

H = height of room, ft Atot = total area, 20,000 ft2 upper limit ADust = area with suspendible dust (bar joists,

beams, piping, conduit, light fixtures can be 5-10% of floor area)

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Clean Design Concepts to Minimize Clean Design Concepts to Minimize Overhead Dust AccumulationsOverhead Dust Accumulations

60o slopes on horizontal surfaces

Enclose structural steel

Electrical Cable Tray

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Solid deck plates versus open grating

Enclosed I-Beam

Spills from one level to the next through open grating become fugitive dust

Dust Layer Where, How Much?Dust Layer Where, How Much?Lightly discolored ~ 1/64” layer

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¼”

1/32”1/16”3/32”

Use settling pans to determine rate of fugitive dust accumulation.

Dust Layers on Process Equipment?

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Dust Layers on Overhead Structure, Conduits, Piping?

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Dust above ceiling tiles?Dust above ceiling tiles?

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Dust Accumulations in Ventilation Ducts?Dust Accumulations in Ventilation Ducts?

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Cleanup Methods

Safe conditions for compressed air blow down

Sweeping

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Sweeping Water wash down Vacuum cleaning

Portable vacuum cleaners (PVC) Central vacuum cleaning systems (CVC)

Safe compressed air blow down NFPA 654: Section 8.2

Vacuum all accessible dust – vacuum cleaners listed for use in Class II locations

De-energize any electrical equipment not rated for

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equipment not rated for Class II locations

Cool any hot surfaces capable of igniting dust cloud

Use 15 psi steam or compressed air

Vacuum up remaining dust

Safe sweeping

Sweep gently to minimize airborne dust

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Natural bristles (no synthetic)

Aluminum or conductive polymer dust pans

Water wash down Water wash down –– what pressure?what pressure?

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Hard spray Hard spray “pumps air” “pumps air” ––pumped air pumped air column create column create dust cloud?dust cloud?

Fog or mist Fog or mist wets dustwets dust

Water wash down versus dry?

Advantages Increases conductivity

of dust layer – reduce static electricity

Disadvantages Safe way - wet down

first, then spray downT i kl d

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static electricity If done right, minimizes

combustible dust cloud

Trickle down mess –widespread cleanup

Where does residue end up and can that area be cleaned?

How water tight is YOUR electrical system?

Portable Vacuum Cleaner Portable Vacuum Cleaner –– Air PoweredAir Powered

Static dissipating features

-Drum grounding cable

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cable

-Conductive vacuum and air hoses

-Conductive wheels

Courtesy Vac-U-Max

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Portable Vacuum Cleaner Portable Vacuum Cleaner -- ElectricElectric

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HEPA filter

Electrical Classification II, Div 1

Courtesy Vac-U-Max

Courtesy Gardner Denver

Portable Vacuum Cleaner Portable Vacuum Cleaner –– High KHigh Kstst and Explosive Materialsand Explosive Materials

--Incoming waste Incoming waste submerged in liquid submerged in liquid

--Air powered vacuumAir powered vacuum

--Bonding strap on reelBonding strap on reel

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-- Sight glass level, Sight glass level, sludge removalsludge removal

--Static conductive Static conductive wheels, hoseswheels, hoses

--Applications: rocket Applications: rocket propellant, toner, propellant, toner, gunpowder, sodium gunpowder, sodium azideazide

Courtesy Vac-U-Max

Bagging Vacuum Cleaner WasteBagging Vacuum Cleaner WasteAddress ergonomic issues for emptying the unit - break vacuum to empty the hopper

- Continuous liner cartridge –non-conductive plastic

- Static conductive plastic

Courtesy Vac-U-Max

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- Static conductive plastic individual liners

Central Vacuum Cleaning SystemsCentral Vacuum Cleaning Systems

System components

-High vacuum producer (6-12”Hg = 82-164” w.c.)

-Filter/receiver

-Pre-separator

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Pre separator (optional)

-Tubing branches to use zones

-Hoses and tools

Courtesy Gardner Denver

CVC Design PrinciplesCVC Design Principles Place multiple hose inlets on a tubing branch,

convenient to areas of need Layout tubing network branches to match

operating team usage Long radius elbows to minimize plugging

T bi j ti f id t

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Tubing junctions from side or top Tubing diameter

Adequate conveying velocity – 3500 to 4500 ft/min

Enlarge as necessary for vacuum expansion Filter/receiver and optional separator

conservatively sized for solids slug loading Size vacuum producer for reasonable number

of hoses

Use the CVC tools designed for your problem!Use the CVC tools designed for your problem!

Pipes

Floors

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Crevices

Open end of hose has limited reach – job takes longer –tools designed for high velocity “scrubbing power”

Equip-ment

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Elements of Effective HousekeepingElements of Effective Housekeeping

Survey – areas with unacceptable accumulation (FM 7-76 useful to assess hazard)

Designated responsibilities Adequate resources Safe cleaning methods Routinely document results

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Look for opportunities to eliminate dust sources (overhead accumulations greatest concern – ie, structural steel beams might have horizontal surface area 10% of floor)

Building clean design: 60o

sloped surfaces, box in structural steel, etc.

Routine management reviews of housekeeping schedule to ensure focus and continuous improvement

Determining Cleanup FrequencyDetermining Cleanup Frequency

Clean up area with care to avoid ignition risks – note areas where layer is thicker

Purchase 9x9 baking pans, weigh them and mark the tare weight

Suspend these pans in the areas where the dust was thicker

Routinely monitor pan dust layer to get data on how fast your dust settles

Clean up before the layer exceeds the allowable layer

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Ignition Source ControlIgnition Source Control

Hot work permits go beyond welding and cutting

Static grounding systems verified to work and inspected routinely?

Hot spot checks with InfraRed camera – ie, hot equipment insulation breakdown

Document initial findings and routine integrity checks

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Hot Work Procedures Cover?Hot Work Procedures Cover?

In addition to Welding, Brazing, Torch Cuts

Grinding?g Mechanical Sparks? Static Electricity? Mechanical Friction? Grounding &

bonding portable equipment?

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Hot Work Procedures Cover Hot Work Procedures Cover Static Grounding?Static Grounding?

Ducts grounded?

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Dust drum bonded to dust collector? – Courtesy Stuart R. Browne Manufacturing Co.

Equipment grounded?Courtesy Milrail Co.

Hot Spot Monitoring Hot Spot Monitoring –– Look for Look for High Temperature SurfacesHigh Temperature Surfaces

Hot process equipment: heaters, dryers, extruders, steam pipes, electrical equipment.

Direct ignition of

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Direct ignition of explosion dust cloud

Ignition of dust layer that then ignites dust cloud (higher temps possible)

©Sierra Pacific Infrared Thermography

Infra-Red Imaging Cameras Reveal “Hot Spots”

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Explosion Protection Equipment to Explosion Protection Equipment to Include in Maintenance ProceduresInclude in Maintenance Procedures Protection Systems

Process controls and interlocks Static Grounding Hazardous Classification Electrical Classified fork trucks Explosion Venting Explosion Prevention Explosion Isolation

Dust collection systems Vacuum cleaning equipment

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Sustaining Explosion Protection Results Sustaining Explosion Protection Results ––Maintenance (NFPA 654) Maintenance (NFPA 654) -- RetroactiveRetroactive

Personnel training Hazard recognition Dust collection system Explosion protection Initial & annual refresher training

Testing (verify system performance as per design) New system Annually by owner After system modification

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Inspection or monitoring Written plan and checklists (very specific

requirements NFPA 68, NFPA 69) Typically monthly checks

Sustaining Explosion Protection Results Sustaining Explosion Protection Results ––Maintenance (NFPA 654) Maintenance (NFPA 654) -- RetroactiveRetroactive

Report unusual changes Retain records for 2 years

Maintenance Written plan Routinely remove dust accumulations Maintain collectors & fans as per manufacturer

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Sustaining Explosion Protection Results Sustaining Explosion Protection Results ––Management of Change (NFPA 654)Management of Change (NFPA 654)

Management of Change Procedures Technical Basis for proposed change Safety and health implications Permanent or temporary change

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p y g Modifications to operating and maintenance

procedures Employee training requirements Authorization requirements Retroactive requirement

Checklist for Combustible Dust Issues?

Hazard CommunicationsHazard Communications Combustible dust hazards are:

Understood by operators Addressed in plant safe work practices Managed by equipment maintenance

M d b d l li Managed by procedural compliance Managed by appropriate personal protective

equipment Managed by correct Management of Change

OSHA Guidance Document on Combustible Dust Hazard Communications

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Combustible Dust Combustible Dust Hazard CommunicationHazard Communication

IntroductionOSHA’s Hazard Communication StandardStandardIdentifying and Controlling the Potential for Dust ExplosionsMSDS PreparationProduct LabelsTraining & InformationReferencesOSHA AssistanceRegional Offices

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Possible Safe Work PracticesPossible Safe Work Practices

Clean up procedures Bonding and grounding procedures

Preventing static ignition (if low MIE) Preventing static ignition (if low MIE) Equipment operation to prevent dusting Emergency procedures Change Management procedures Other?

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Flame Resistant Clothing?Flame Resistant Clothing?

Workplace hazard assessment to determine if flammable materials are present in quantities that will generate a flash fire and endanger a person

If dust hazard cannot be eliminated, NFPA 2113 recommends appropriate Flame Resistant Clothing

No regulatory hazard assessment yet Train operators on care and cleaning

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Flame Resistant FabricsFlame Resistant Fabrics((Minimize burns from flash fires)Minimize burns from flash fires)

Everyday wearing apparel will ignite and burn

Polyester will burn melt and drip Polyester will burn, melt and drip

Flame resistant protective apparel is designed to self extinguish almost immediately.

Advancing the Science of Safety www.tecgenfr.com

60

80

100

urv

ival 25% Body Burn

50% Body Burn

Chances of Survival from Burn InjuryChances of Survival from Burn Injury(Can’t protect against explosion)(Can’t protect against explosion)

0

20

40

Age Range, Years

% S

u

75% Body Burn

Source American Burn Association(1991 - 1993 Study)

Goal: minimize burn injury level

20‐29 30‐39 40‐49 50‐59

Advancing the Science of Safety www.tecgenfr.com

FRC Example: TECGEN® FRC Example: TECGEN® Note: Undergarments of the wrong Note: Undergarments of the wrong material can melt, causing burnsmaterial can melt, causing burns

TECGEN XTREME® TECGEN® baselayer TECGEN® balaclavas

TECGEN® gloves

TECGEN® welding sleeves

Emergency ResponseEmergency Response

Dust fires and explosions have different problems to address Evacuation routes & assembly areas Evacuation routes & assembly areas Fire fighting techniques

Mist versus hard spray Class D Extinguishers for metal dusts

Document the issues and train personnel

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Incident InvestigationIncident Investigation

Gather data and share information within the organization on

Use the data to track trends and make improvementsmake improvements

No OSHA reporting requirements yet

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Incidents: History of Fires, Explosions?Incidents: History of Fires, Explosions?

ExplosionsExplosions(overpressure )(overpressure )

DeflagrationsDeflagrations

Is there a dust explosions triangle like the “Safety Triangle”?

Fatalities

Lost Work Day

203B OSHA Comb. Dust Update 50

Deflagrations Deflagrations (large flash fires)(large flash fires)

Dust firesDust fires(small fires)(small fires)

Near MissesNear Misses(minor puffs, pops, flames) (minor puffs, pops, flames)

Lost Work Day

Recordable

Near misses

History of Fires, Explosions?Attitude towards past incidents?

Hide or ignore Fear of legal or regulatory action Employees fear management action Familiarity bug – “just a part of doing y g j p g

business in my industry – no big problem”

Investigate to eliminate root cause Incidents are warning of unsafe conditions Use the data to reduce risk of employee

injury and business interruption Trends in my industry or similar processes

203B OSHA Comb. Dust Update 51

SummarySummary

Procedures need to be integrated with protective equipment Coordinate protective functions

Prevent operator error from ignorance Prevent operator error from ignorance

These procedures mentioned in either OSHA CD NEP or NFPA

OSHA Regulations will emphasis procedures more than equipment – get ready with procedures that make sense now

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