Bob Lacovara, CCM, CCT-I Convergent Composites © Convergent Composites

© Convergent Composites 2011 As a result of several catastrophic dust explosion events OSHA issued a national enforcement emphasis on dust U.S. Department of Labor Occupational Safety & Health Administration 2

© Convergent Composites 2011 U.S. Department of Labor Occupational Safety & Health Administration A series of composites plants have had routine inspections where dust issues were cited or dust was a discussion item 3

© Convergent Composites 2011 The risk of a composites plant dust explosion has not changed, nor have there been any recent documented incidents. However, the regulatory emphasis elevates the technical possibility of such an incident. What are the chances? 4

© Convergent Composites 2011 Combustible Dust Policy Institute: 50% of dust explosions involved a dust collector 10% of combustible dust incidents involved ductwork Few combustible dust incidents have to do with housekeeping Most combustible particulate incidents occur inside process equipment 5

© Convergent Composites 2011 What is a dust explosion? 6

© Convergent Composites 2011 Combustible Dust New NFPA 654 Definition Definition is a combustible particulate solid that presents a fire or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations, regardless of particle size or shape is a combustible particulate solid that presents a fire or explosion hazard when suspended in air or the process-specific oxidizing medium over a range of concentrations, regardless of particle size or shape 7

© Convergent Composites 2011 Explosion: Rapid oxidation that results in a sudden increase in gas volume and temperature, accompanied by an overpressure shock wave 8

© Convergent Composites 2011 Deflagration: Propagation of a combustion zone through a fuel-oxidizer mixture at a rate less than the speed of sound and capable of producing a significant increase in pressure. 9

© Convergent Composites 2011 Defining the Terms Flash Fire: A rapidly moving, short duration flame front resulting in intense thermal radiation 10

© Convergent Composites 2011 Defining the Terms Dust Explosion: In plain English - The ignition of airborne particles resulting in an explosion or a deflagration. 11

© Convergent Composites 2011 How does a dust explosion occur? 12

© Convergent Composites 2011 Dust Hazard Basics Primary Event An occurrence where standing dust is dislodged forming a small dust cloud Sudden flush of air over a dust laden surface Mechanical vibration that dislodges dust Small localized explosion Dust Explosion Characterization 13

© Convergent Composites 2011 Dust Hazard Basics A large dust cloud is formed by the primary event Ignition source ignites dust cloud Large scale deflagration occurs Catastrophic event Secondary Event Primary Event An occurrence where standing dust is dislodged forming a small dust cloud Sudden flush of air over a dust laden surface Mechanical vibration that dislodges dust Small localized explosion Dust Explosion Characterization 14

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Event occurs that dislodges a small amount of dust 15

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Dust is exposed to an ignition source 16

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Small dust cloud ignites Small dust cloud ignites 17

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Pressure wave dislodges a large dust cloud 18

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Large dust cloud ignites 19

© Convergent Composites 2011 How Does a Dust Explosion Occur? The Safety Issue Large Scale Deflagration Occurs 20

© Convergent Composites 2011 What are the conditions required for a dust explosion? 21

© Convergent Composites 2011 Dust Explosion Fuel Oxidant(Oxygen) Ignition Source Conditions for a Fire 22

© Convergent Composites 2011 Dust Explosion Conditions for a Dust Explosion Fuel Oxidant(Oxygen) Ignition Source Mixing Ratio Confinement 23

© Convergent Composites 2011 Dust Explosion Mixing Ratio To ignite airborne dust the particle to air concentration must be between the upper and lower explosive level (This ratio is different for various types of dust) To ignite airborne dust the particle to air concentration must be between the upper and lower explosive level (This ratio is different for various types of dust) 24

© Convergent Composites 2011 Dust Explosion Explosive pressure is a function of concentration Higher concentrations are easier to ignite Explosive pressure is a function of concentration Higher concentrations are easier to ignite Effects of Dust Concentration 25

© Convergent Composites 2011 Temperature is generally not a factor Humidity may be a significant factor Hydroscopic nature of the dust High moisture content reduces potential Low humidity increases electrostatic discharge potential (ESD) Temperature is generally not a factor Humidity may be a significant factor Hydroscopic nature of the dust High moisture content reduces potential Low humidity increases electrostatic discharge potential (ESD) Effects of Air Temperature & Humidity Dust Explosion 26

© Convergent Composites 2011 Dust Explosion Hybrid Mixtures - Dust + Vapor At dust concentrations below the minimum explosive concentration, and at vapor concentrations below the LFL, a flammable hybrid mixture can occur 27

© Convergent Composites 2011 How is dust characterized in terms of hazard potential? 28

© Convergent Composites 2011 Dust Characterization Hazard Determination The lowest temperature of a hot surface which will cause a dust cloud to ignite and propagate flame Minimum Ignition Temperature (MIT) Dust Layer / Dust Cloud Expressed in 0 F 29

© Convergent Composites 2011 Dust Characterization Hazard Determination Minimum Ignition Energy (MIE) A measure of how sensitive an explosible dust is to electrical spark ignition. Gives guidance on whether ignition by electrostatic discharge or process conditions is likely to occur in practice Expressed in mJ (milijoules) 30

© Convergent Composites 2011 Dust Characterization Hazard Determination The lowest concentration of dust or powder that will ignite on contact with an ignition source and propagate a dust explosion Minimum Explosible Concentration (MEC) Expressed in g/m 3 31

© Convergent Composites 2011 Dust Layer Thickness 1 mm thick - Potential for 10g/m 3 concentration European standards test “smoldering” temperature 5 mm and 50 mm thick dust layers Thicker deposits require lower allowable surface temperature 1 mm thick - Potential for 10g/m 3 concentration European standards test “smoldering” temperature 5 mm and 50 mm thick dust layers Thicker deposits require lower allowable surface temperature Dust Characterization 32

© Convergent Composites 2011 Dust Characterization OSHA Guidelines: In the absence of definitive test data OSHA will seek compliance for an acceptable limit of 1/32 in. (0.79 mm) Previous OSHA Determination Determination 33

© Convergent Composites 2011 Dust Characterization NFPA Use of Separation (6.2.3) Allowable dust thickness is determined with an engineering evaluation designed to determine separation distances based on the properties of materials handled, type of operation, accumulations, building design and surrounding exposures New NFPA 654 Standard Standard National Fire Protection Association 34

© Convergent Composites 2011 Ceiling or Overhead Beam Concentrated Dust Source 1 ft. 2 ft. 3 ft. 4 ft. 5 ft. Dust Bulk Density = g/cc Thickness = 0.125” Thickness = 0.125” Area = 1 ft 2 Area = 1 ft 2 1,786 g/m 3 66 g/m 3 28 g/m 3 14 g/m g/m 3 Uniform Downward Hemispherical Diffusion Model 35

© Convergent Composites 2011 Uniform Downward Linear Diffusion Model Dust Bulk Density = g/cc Thickness = 0.125” Thickness = 0.125” Area = 500 ft 2 Area = 500 ft 2 2 ft. 1 ft. 3 ft. 4 ft. 5 ft. 187 g/m 3 93 g/m 3 62 g/m 3 46 g/m 3 37 g/m 3 Overhead Beams 36

© Convergent Composites 2011 Diffusion Models Spreadsheet 37

© Convergent Composites

© Convergent Composites 2011 Dust Explosion Prevention General Principles 1.Reduce amount of dust (fuel) available 2.Avoid flammable atmospheres 3.Eliminate/control ignition sources 4.Provision against consequences of ignition 39

© Convergent Composites 2011 Dust Explosion Prevention Reduce Dust Generation Make Less Dust Improve product design to eliminate cutting/grinding Improve cutting/grinding process Use wet trimming/water jet cutting Improve QC - Less re-work 40

© Convergent Composites 2011 Dust Explosion Prevention Contain Dust Making Operations Dust Capture Point capture at tool - Hoods, guards, or suction devices Confine cutting-grinding-sanding to specific Confine cutting-grinding-sanding to specific dust making areas dust making areas Operate in grinding booths/areas Operate in grinding booths/areas Segregate from general process Segregate from general process 41

© Convergent Composites 2011 Dust Explosion Prevention Maintain Dust Collection Systems Routinely clean duct work and plenums Eliminating residual dust build-up reduces fire hazard Eliminating residual dust build-up increases system efficiency 42

© Convergent Composites 2011 Dust Explosion Prevention Verify Grounding Continuity of Flexible Hoses Reduces static charge in system Electrical Ground 43

© Convergent Composites 2011 Dust Explosion Prevention Properly Ground Bags and Collection Equipment Electrical Ground 44

© Convergent Composites 2011 Dust Explosion Prevention Isolate Dust Collection Equipment From Personnel & Process Best practice includes reducing in-plant exposure to potential hazards hazards 45

© Convergent Composites 2011 Dust Explosion Prevention Housekeeping Periodically clean: Beams, rafters, girts Beams, rafters, girts Dropped ceilings Dropped ceilings Storage areas Storage areas Behind partial panel walls Behind partial panel walls Interior roof surfaces - booths/offices Interior roof surfaces - booths/offices Areas where dust may accumulate Areas where dust may accumulate 46

© Convergent Composites 2011 Dust Explosion Prevention Requires implementation of a planned inspection process to determine dust accumulation rates and determine housekeeping frequency Revision of 654 Revision of New NFPA 654 Requirement Requirement

© Convergent Composites 2011 Dust Explosion Prevention Establishes a Hierarchy of Cleaning Methods Vacuum cleaning Vacuum cleaning Sweeping Sweeping Water wash down Water wash down Compressed air blow down Compressed air blow down (only after other methods & with (only after other methods & with protected electrical equipment) protected electrical equipment) Revision of New NFPA 654 Requirement Requirement

© Convergent Composites 2011 Dust Explosion Prevention Codes & Standards Reference OSHA PSM regulation PSM regulation General Duty Clause 5(a)(1) General Duty Clause 5(a)(1) 1910 Subpart S - Electrical installations 1910 Subpart S - Electrical installations – Ventilation requirements – Ventilation requirements HazComm HazComm 49

© Convergent Composites 2011 Dust Explosion Prevention National Fire Protection Association General - NFPA 654 General - NFPA 654 Facility Design Codes Facility Design Codes NFPA NFPA Life Safety Codes Life Safety Codes NFPA 101 NFPA 101 Building Codes – IBC Building Codes – IBC NFPA 5000 NFPA 5000 Codes & Standards Reference 50

Contact: Bob Lacovara, CCM, CCT-I Convergent Composites 51 © Convergent Composites 2010 All rights reserved