Minimum Ignition Energy (MIE)

1 16W070 83rdStreet Burr Ridge, Illinois 60527(877) Fauske1 or (630) 323-8750 Fax: (630) 986-5481 E-mail: Ignition Energy (MIE) Assessment of Dust Explosion Hazards Practical Facts to ConsiderPresented by:Ashok Ghose Dastidar, PhD MBA,Vice President, Dust & Flammability Testing and Consulting ServicesAshok Ghose Dastidar Chemistry Dalhousie University MBA Saint Mary s University Master of Applied Science Technical University of Nova Scotia Chemical Engineering Dalhousie University 24 years research in the field of dust & gas/vapor explosions Safety Consulting Engineers, Inc. 2001-2007 Fauske & Associates, LLC 2007- Memberships AIChE, ASTM, NFPA Editorial Advisory Board of Powder/Bulk Solids and Journal of Loss Prevention in the Process Industries Chairperson of the ASTM E27 Committee NFPA Technical Committee 654, 655, 91, 61, 664, & 4842 Fundamentals of Dust ExplosionsDust Fires & Explosions4 Like all fires, a dust fire occurs when fuel (the combustible dust) is exposed to heat (an Ignition source) in the presence of oxygen (air)Removing any oneof these elements of the classic fire triangle eliminates the possibility of a fireDust Fires & Explosions(continued)5 Dust explosions require the presence of two additional elements dust dispersion and confinementSuspended dust burns more rapidly and confinement allows for pressure buildup.

2 Removal of either the suspension or the confinement elements prevents an explosion, although a fire may still occurHazard IdentificationScreening TestsIs My Material Combustible? Two main testsDetermination of Combustibility UN Test ( ) Test Method for Readily Combustible Solids Identifies if the material presents a fire hazardDetermination of Explosibility ASTM E1226 Go/No Go Methodology ASTM E1515 Minimum Explosible Concentration7 Characterize the Explosion Potentialof a Material Explosion severity violence of the explosionKSt Dust deflagration indexPmax Maximum explosion overpressure(dP/dt)max Maximum rate of pressure rise Ignition sensitivity ease of ignitionMIE Minimum Ignition energyMEC Minimum explosible concentrationMIT Minimum Ignition TemperatureLIT Layer Ignition TemperatureLOC Limiting Oxygen Concentration8 Minimum Ignition EnergyIdentification ofElectrostatic Hazards10 Metal PlantPersonnelNon-ConductorsBulk LiquidLiquid MistMetal PlantPersonnelNon-ConductorsBulk PowderDust CloudLiquid SystemPowder SystemCharge GenerationCharge AccumulationSystematic Approach to Electrostatic Hazard AssessmentIncendivity of DischargeSensitivity of Flammable AtmosphereMinimum Ignition Energy (MIE)

3 ASTM E2019 Predicts the ease and likelihood of Ignition of a dispersed dust cloud MIE of a flammable dust is the Minimum spark Energy needed to ignite an ideal concentration under lab conditionsA capacitive discharge spark is used for this testTest can be run with or without inductanceCompared to typical ES Ignition sources11 Spark Discharge from a Capacitor12 =12 ( 12 22)Where: WSTORED= capacitor stored Ignition Energy , JoulesC= capacitance of the discharge circuit capacitor, FaradsV1= voltage to which the capacitor is charged, VoltsV2= voltage on the capacitor after discharge, VoltsK hner MIKE 3 now T V13 Minimum Ignition Energy Test14 Statistically Interpolated MIE -Es15 =10 2 2 2 1 + 2+1I[E2] = number of tests with Ignition at the Energy E2.(NI+I)[E2] = total number of tests at the Energy (mJ)Dust Loading in chamber(mg)Probability300600900120015003 0 NIIIINI3 of 510 NININI0 of 3 =10 30 3 30 105+1=17 90 msDelay Time161mJ < MIE < 3 mJEs = msDelay Time171mJ < MIE < 3 mJEs = mJ150 msDelay Time181mJ < MIE < 3 mJEs = Times Reported191mJ < MIE < 3 mJEs = Ignition Energy (MIE) ASTM E2019(continued) Examples: sugar (powdered) 30 mJ, paper dust 20-60 mJ, aluminum 50 mJ, magnesium 40 mJ20 MIE (mJ)Recommended Precautionper BS 5958500 Low sensitivity to Ignition ; ground plant belowthis level100 Considergrounding personnel below this level25 The majority of Ignition incidents occur below this level10 High sensitivityto Ignition .

4 Consider restrictions on the use of high resistivity non-conductors below this level1 Extremely sensitiveto Ignition at this level. Handling operations should be such that they minimize the possibility of suspending the powder in air.; dissipate or discourage charge operationsWith or Without Inductance21 Fine Chemical 27 m meanWith inductance Es = 4 mJFine Chemical 27 m meanWithout inductance Es = 8 mJParticle Size Influence22 Fine Chemical 34 m meanWith inductance Es = 7 mJFine Chemical 34 m meanWithout inductance Es = 12 mJParticle Size Influence23 Fine Chemical 16 m meanWith inductance Es = mJFine Chemical 16 m meanWithout inductance Es = mJMIE at Elevated Temperatures24 =10 +( ) ( (25 )+ )Reduced Oxygen MIEK hner Mike 3 NiacinCaRo15 Tested without inductance Different lines for different configurations25 Chaudhari and MashugaJournal of Loss Prevention in the Process Industries 48 (2017)

5 145-150 Reduced Oxygen MIECTL MIE Unit11010010001000010121416182022 Minimum Ignition Energy [mJ]Oxygen Concentration [ ]Non IgnitionIgnition26 NiacinCaRo17 Tested with inductanceClosing Extension of the standard methodTemperatureOxygen levelPressure?27 Minimum Ignition Energy (MIE)Is not an intrinsic material propertySample specific Size distribution Morphology Moisture Run with or without inductanceElectronic SparkStatic Electric SparkE