static electricity - hazard and control

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<p>ChilworthSafety and Risk Management P. Ltd.</p> <p>Electrostatic Ignition Hazards Assessment &amp; Controlpresented by Alok Singh Chilworth Safety &amp; Risk Management P. Ltd.</p> <p>1Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>Electrostatic Ignition Hazards Assessment &amp; Control</p> <p>Safety and Risk Management P. Ltd.</p> <p>Course Content: - Understanding electrostatic hazards - Flammable atmospheres - Identifying static hazards - Control of static electricity - Discussion2Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>1</p> <p>Chilworth</p> <p>COURSE OBJECTIVES You will learn</p> <p>Safety and Risk Management P. Ltd.</p> <p> how electrostatic charge is generated how to recognise electrostatic hazards which cause fires and explosions how to control electrostatic charge to reduce the risk3Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>UNDERSTANDING ELECTROSTATIC HAZARDS &amp; BACKGROUND Understanding Definitions4Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>2</p> <p>Chilworth</p> <p>ELECTROSTATIC EFFECTS Electrostatic effects are everywhere: hair clothes car balloon TV, computer monitor</p> <p>Safety and Risk Management P. Ltd.</p> <p> Electrostatic effects: are commonplace are predictable can be controlled</p> <p>+ + + + + + +Email: info@chilworth.co.in</p> <p>- - 5</p> <p>Tel: Mumbai Office 022-66942350</p> <p>Delhi Office 011-26136979</p> <p>Chilworth</p> <p>STATIC ELECTRICITY Uses photocopying surface coating printing electrostatic precipitator</p> <p>Safety and Risk Management P. Ltd.</p> <p> Problems clinging dust attraction powder segregation nuisance / shock ignition (fire / explosion)</p> <p>6</p> <p>Tel: Mumbai Office 022-66942350</p> <p>Delhi Office 011-26136979</p> <p>Email: info@chilworth.co.in</p> <p>3</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>INTRODUCTION DEFINITIONSConductive: The ability to allow the flow of an electric charge; possessing a conductivity greater than 104 pS/m or a resistivity less than 108 ohm-m Antistatic/ static dissipative: Capable of dissipating a static electric charge at an acceptable rate (charge generation rate less than charge relaxation rate) Nonconductive/ Insulating: The ability to resist the flow of an electric charge (charge generation rate greater than charge relaxation rate) Electrostatic Discharge: Release of static electricity in the form of a spark, corona discharge, brush discharge, or propagating brush discharge that might be capable of causing ignition under appropriate circumtances7Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>INTRODUCTION DEFINITIONS Surface Resistivity: Describes the ability of a solid surface totransmit electric charges. Units of Surface Resistivity are Ohm/square.</p> <p>Safety and Risk Management P. Ltd.</p> <p> Volume Resistivity: Volume resistivity is defined as the resistanceof unit length of a sample of unit area. It is thus a property of the material itself, regardless of the dimensions of the sample.</p> <p>Volume Resistivity, pv= R A/dpv is the volume resistivity, R is Resistence (ohms), A is the sample area and d its length. The unit of Volume Resistivity are Ohm meters</p> <p>8Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>4</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>STATIC ELECTRICITYStatic electricity is a (stationary) surplus or deficit of electrical charge Electrostatic charge is a surface effect Two kinds of charge are known: Positive and Negative</p> <p>Unit of electrical charge is COULOMB, (C), equal to 6.24 1018 electrons</p> <p>9Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>ELECTRICAL FIELD STRENGTH</p> <p>Safety and Risk Management P. Ltd.</p> <p>Two kinds of charge are known; Positive and Negative. Under static conditions, separated like charges exert a mutual force of repulsion separated unlike charges exert a force of attraction</p> <p>The field of force associated with charge is referred to as an ELECTRIC FIELD, in units of volts per meter ( most often indicated by kV/m).10Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>5</p> <p>Chilworth</p> <p>ASSESSMENT OF STATIC HAZARDSFlammable Atmosphere</p> <p>Safety and Risk Management P. Ltd.</p> <p>Charge Generation</p> <p>Charge Accumulation</p> <p>Enough Energy</p> <p>Discharge Mechanism</p> <p>11Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>IDENTIFICATION OF ELECTROSTATIC HAZARDS</p> <p> FLAMMABLE ATMOSPHERES CHARGE GENERATION CHARGE ACCUMULATION ELECTROSTATIC DISCHARGES</p> <p>12Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>6</p> <p>Chilworth</p> <p>ASSESSMENT OF STATIC HAZARDSFlammable Atmosphere</p> <p>Safety and Risk Management P. Ltd.</p> <p>13Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>FIRE TRIANGLEOXIDANT FUEL</p> <p>Safety and Risk Management P. Ltd.</p> <p>IGNITION SOURCE</p> <p>OXIDANT A substance which supports combustion. FUEL Solid, liquid (vapor or mist) or gas capable of being oxidized. IGNITION SOURCE An energy source capable of initiating a combustion reaction.14Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>7</p> <p>Chilworth</p> <p>CONDITIONS FOR EXPLOSIONOxidant</p> <p>Safety and Risk Management P. Ltd.</p> <p>Mixing</p> <p>Confinement</p> <p>Fuel</p> <p>Ignition source</p> <p>15Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>Information for assessing electrostatic caused fire and explosion hazards of fuels include: FLAMMABLE CHARACTERISTICS Flammable Limits (LFL and UFL) Flash Points Limiting Oxygen Concentration IGNITION SENSITIVITY Minimum Ignition Energy, MIE CONSEQUENCES OF IGNITION Maximum Explosion Pressure, Pmax Maximum Rate of Pressure rise, (dP/dt)max16Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>8</p> <p>Chilworth</p> <p>FLASH POINT DATAo</p> <p>Safety and Risk Management P. Ltd.</p> <p>M A T E R IA L</p> <p>F L A S H P O IN T C CLO SED CUP OPEN CUP 43 -9 44 16 7</p> <p>A c e tic a c id A c e to n e n -b u ta n o l M e th a n o l T o lu e n e</p> <p>40 -1 7 29 10 4</p> <p>17Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>FLAMMABILITY OF DUSTS Can only be measured Test usually based on vertical tube In UK: Group A = flammable Group B = non-flammable for T &gt; 110 C furnace test needed before a Group B can be confirmed</p> <p>Safety and Risk Management P. Ltd.</p> <p> Group B powders may burn or be thermally unstableTel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>18</p> <p>9</p> <p>Chilworth</p> <p>MIE of Some Gases &amp; VaporsMaterial Propanol Ethyl Acetate Methane Propane Ethane Methanol Acetylene Hydrogen Carbon DisulfideTel: Mumbai Office 022-66942350 Delhi Office 011-26136979</p> <p>Safety and Risk Management P. Ltd.</p> <p>MIE(mJ) 0.650 0.460 0.280 0.250 0.240 0.140 0.017 0.011 0.00919Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>MIE of Some Dust CloudsMaterial PVC Zinc Wheat Flour Polyethylene Sugar Magnesium Sulfur Aluminum Epoxy Resin ZirconiumTel: Mumbai Office 022-66942350 Delhi Office 011-26136979</p> <p>Safety and Risk Management P. Ltd.</p> <p>MIE(mJ) 1,500 200 50 30 30 20 15 10 9 520Email: info@chilworth.co.in</p> <p>10</p> <p>Chilworth</p> <p>EXPLOSION LIMITS</p> <p>Safety and Risk Management P. Ltd.</p> <p> Fuel - air mixtures are only flammable within the flammable range</p> <p>21Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>FLAMMABILITY LIMITS (vol.%)In air LEL Hydrogen Methane Propane Ethylene Carbon monoxide Toluene Methanol Ethanol IPA 4.0 5.0 2.1 2.7 12.5 1.2 6.0 3.3 2.0 UEL 75.0 15.0 9.5 36.0 74.0 7.1 36.0 19.0 12.7</p> <p>Safety and Risk Management P. Ltd.</p> <p>22Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>11</p> <p>Chilworth</p> <p>EXPLOSIBLE CONCENTRATION FOR DUST Lower explosion limit (LEL) for dusts usually 30 - 100 gm-3 visually dense cloud measured in 20 litre sphere25W 2m</p> <p>Safety and Risk Management P. Ltd.</p> <p> UEL not measurable or useful several kg m-3</p> <p>40 g/m Coal Dust</p> <p>23Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>LIMITING OXYGEN CONCENTRATION FOR GASES Varies with the materialMATERIAL</p> <p>Chilworth</p> <p>Safety and Risk Management P. Ltd.</p> <p>LOC (%) 13.5 11.0 5.0 5.0 10.0</p> <p> Can be estimated from the LEL Typically 8 - 12 vol.% If unknown, assume 5 vol.% Examples are for N2 as inert gasTel: Mumbai Office 022-66942350 Delhi Office 011-26136979</p> <p>Acetone Benzene Carbon disulphide Hydrogen Methanol</p> <p>24Email: info@chilworth.co.in</p> <p>12</p> <p>LIMITING OXYGEN CONCENTRATION FOR DUSTS Generally higher than for gases Typically 10 - 15 vol.% If unknown, assume 5 vol.% Examples are for N2 and Flue gases as inert gasMATERIAL Rye Flour Organic Pigment Methyl Cellulose Beta-naphthol Sulphur Paraformaldehyde Aluminium</p> <p>Chilworth</p> <p>Safety and Risk Management P. Ltd.</p> <p>LOC(%) 13.0 12.0 10.0 9.5 7.0 6.0 5.0</p> <p>25Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>ASSESSMENT OF STATIC HAZARDSFlammable Atmosphere</p> <p>Safety and Risk Management P. Ltd.</p> <p>Charge Generation</p> <p>26Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>13</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>CONTACT CHARGINGWhen two materials make and then break contact, the contacting surfaces acquire a net charge, with one becoming negative and the other positive In practice, electrostatic charging is due to multiple frictional contact/rubbing between surfaces</p> <p>++++++++++++</p> <p>------------</p> <p>++++++++++++ +</p> <p>- -- - - - - - - - - - -</p> <p>27Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>CONTACT CHARGING</p> <p>A factor affecting electrostatic charging is the type of contact two materials make, i.e. friction, force and velocity of contact In liquids electrostatic charging depends on the presence of ions in the liquid. Ions of one polarity could be absorbed at the interface and they then attract ions of opposite polarity which form a diffuse layer of charge in the liquid, close to the surface. When the liquid is moved to the interface, it carries away some of this diffuse layer and a net charge is developed on the liquid, provided it is sufficiently nonconductive to prevent recombination28Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>14</p> <p>ChilworthSafety and Risk Management P. Ltd.</p> <p>CONTACT CHARGING EXAMPLESPOWDER HANDLING Sieving Pouring Mixing Grinding Pneumatic Transfer LIQUID HANDLING Liquid transfer through pipes Agitation of two phase mixtures, Settling of two phase mixture, Tel: Mumbai Filtration Office 022-66942350 Delhi Office 011-26136979</p> <p>29Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>ASSESSMENT OF STATIC HAZARDSFlammable Atmosphere</p> <p>Safety and Risk Management P. Ltd.</p> <p>Charge Generation</p> <p>Charge Accumulation</p> <p>30Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>15</p> <p>Chilworth</p> <p>ELECTROSTATIC CHARGE ACCUMULATION - EXAMPLES</p> <p>Safety and Risk Management P. Ltd.</p> <p>ConductorsTel: Mumbai Office 022-66942350 Delhi Office 011-26136979</p> <p>Insulators31Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>ELECTROSTATIC CHARGE ACCUMULATIONElectrostatic charge can accumulate on: Isolated Metal Plant Personnel - Personnel can attain potentials of 10 to 50kV - Maximum discharge energy = 100 mJ</p> <p>Safety and Risk Management P. Ltd.</p> <p>MIE - Gases</p> <p>MIE Dusts Non-conductive Material (Surface Resistivity &gt; 1011 Ohm/Square) - Accumulation of static charge - Insulation of conductive items - Charge retention on liquids &amp; powder in non-conducting containers 32Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>16</p> <p>Chilworth</p> <p>ELECTROSTATIC CHARGE ACCUMULATIONElectrostatic charge can accumulate on:</p> <p>Safety and Risk Management P. Ltd.</p> <p>Bulk Liquids - Liquid conductivity &gt; 100 pS/m, No or LITTLE static charge generation Liquid Mist Powder Dust CloudIf water vapor is present in air, it absorbs onto surfaces and forms a slightly conducting surface layer. The extent to which the water absorbs and the increase in conductivity depends on the nature of the surface and the humidity of 022-66942350 Delhi Office Tel: Mumbai Officethe atmosphere. 011-26136979 Email: info@chilworth.co.in</p> <p>33</p> <p>Chilworth</p> <p>LIQUID CONDUCTIVITYConductivity of Some typical LiquidsRef. Plant/Operations Progress (Vol. 11, No. 2)</p> <p>Safety and Risk Management P. Ltd.</p> <p>LIQUID Acetone n Butyl Alcohol Ethyl Acetate Methyl Alcohol Gasoline (leaded) Isopropyl Ether Toluene Gasoline (unleaded) XyleneTel: Mumbai Office 022-66942350</p> <p>CONDUCTIVITY COMMENT (pS/m) 6 106 2 107 104 107 2.9 4.4 Conductive Conductive Conductive Conductive Semi-conductive Semi-conductive Non-conductive Non-conductive Non-conductive34</p> <p>100 500 MIE</p> <p>Safety and Risk Management P. Ltd.</p> <p>37Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>SPARK DISCHARGE - EXAMPLES Between earth and isolated metal drum (nylon wheels on trolley) isolated person (insulating footwear) isolated pipe section (insulating gaskets) isolated conducting liquid (in plastic drum)Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Safety and Risk Management P. Ltd.</p> <p>38</p> <p>19</p> <p>Chilworth</p> <p>BRUSH DISCHARGE - EXAMPLES Caused by</p> <p>Safety and Risk Management P. Ltd.</p> <p> charged insulating bulk container charged insulating liquid charged dust cloud charged thunder cloud39Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>PROPAGATING BRUSH DISCHARGEOrigin high charging situations on high resistivity materials insulator with metal close by Energy not established &gt; 1 Joule (1000 mJ) Incendivity vapour gases dusts mists?Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Safety and Risk Management P. Ltd.</p> <p>40</p> <p>20</p> <p>Chilworth</p> <p>PROPAGATING BRUSH DISCHARGE - EXAMPLES High charging level on thin, highly insulating material: pneumatic conveying though coated metal duct internally coated cyclone insulating bulk container high speed conveyor belt</p> <p>Safety and Risk Management P. Ltd.</p> <p>41Tel: Mumbai Office 022-66942350 Delhi Office 011-26136979 Email: info@chilworth.co.in</p> <p>Chilworth</p> <p>CONE (BULKING) DISCHARGEOrigin highly charged powder in bulk Energy up to ~25 mJ for fine powders higher energies for granular materials Incendi...</p>