1 Combustible Dust Procedures Combustible Dust Procedures 1 Gary Q. Johnson, P.E. Gary Q. Johnson, P.E. Workplace Exposure Solutions Workplace Exposure Solutions NC NC-IVC IVC – Raleigh, NC Raleigh, NC April 30, 2010 April 30, 2010 Agenda - Procedures Housekeeping Ignition Source Control Hazard Communication Training Administrative Procedures 2 Personal Protective Equipment Equipment Maintenance Management of Change Emergency Procedures & Incident Reporting Copyright Gary Q. Johnson 2010 Back to the Dust Explosion Pentagon: Back to the Dust Explosion Pentagon: Multiple Strategies to Reduce Cleanup Risk Multiple Strategies to Reduce Cleanup Risk Heat or ignition source: prevent static electricity, prevent static electricity, sparks sparks Confinement of dust cloud: building & equipment building & equipment designed to safely contain or designed to safely contain or vent vent Dispersion of dust particles: prevent dust prevent dust layer getting airborne layer getting airborne – clean up method? clean up method? 3 Oxidizer (oxygen in air): reduce O reduce O 2 with inert gas (asphyxiation with inert gas (asphyxiation hazard?) hazard?) Combustible dust (fuel): prevent accumulation prevent accumulation – housekeeping housekeeping •Chemical Engineer Chemical Engineer – Ohio State Univ. Ohio State Univ. •Professional Engineer Professional Engineer – Ohio Ohio •Industries: Industries: pharma pharma, 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, training tree resins, printing, wood products, training How We Got Here Page 4 •7+ yrs Consultant 7+ yrs Consultant – Dust Collection Systems, Dust Collection Systems, Combustible Dust Combustible Dust •27 yrs Procter & Gamble 27 yrs Procter & Gamble – HSE Exposure HSE Exposure Control Control 5 years US Navy 5 years US Navy – nuclear submarines nuclear submarines •ACGIH Ventilation Committee (past) ACGIH Ventilation Committee (past) •Intl.Soc.Pharm.Engrs Intl.Soc.Pharm.Engrs – Baseline Guides Baseline Guides Imperial Sugar Imperial Sugar – Dust accumulations Dust accumulations were fuel for building wide deflagrations were fuel for building wide deflagrations 5 Dust Cloud Density > MEC Dust Cloud Density > MEC 6 Pneumatic conveying system leak like dust cloud from compressed air blow down – cannot see 3-4 feet thru cloud
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Agenda - Procedures Housekeeping Ignition Source Control Hazard Communication Training
Administrative Procedures
2
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
••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
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
2
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
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?
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?
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
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
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
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?