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Module 3

Module 3. Ignition Control. Terminal Objectives. Upon the successful completion of this module, participants will be able to explain the work procedures for controlling ignition. . Enabling Objectives. Identify the five elements present in a dust explosion. Identify ignition sources.

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Module 3

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  1. Module 3 Ignition Control

  2. Terminal Objectives Upon the successful completion of this module, participants will be able to explain the work procedures for controlling ignition.

  3. Enabling Objectives • Identify the five elements present in a dust explosion. • Identify ignition sources. • Discuss hot work permits and Lockout/Tagout (LOTO). • Discuss use of separator devices. • Identify classifications applicable to combustible dust contained in the National Electric Code (NEC).

  4. 5 Elements for Dust Explosion • Combustible dust in fine particles • Oxygen • Dust dispersed into air • Energy source to ignite mixture • Confinement

  5. Triangle and Pentagon

  6. Ignition Sources • Anything that delivers enough energy for ignition • Examples • Static electricity • Hot surface • Open flame or ember • Electric arcs and sparks

  7. Ignition Sources • Examples • Industrial trucks • Powder actuated tools • Smoldering nests • Heat from accidental mechanical impact

  8. Static Electricity • Electrical charging of materials • Charging through physical contact • Properly ground to prevent discharge

  9. Hot Surfaces • Any surface that exceeds min. auto-ignition temperature • Combustible dust/liquids on hot surface • Combustible liquids • Lubricants • Oils

  10. Open Flame/Glowing Ember • Eliminate all open flames or embers • Potential sources • Candles • Smoking • Flares • Matches/lighters • Furnances

  11. Electric Arcs and Sparks • Electric Arc • Continuous discharge of a current • formed when strong current jumps gap • Spark • Random, momentary discharge

  12. Industrial Trucks • Creates spark when engine engaged • Spark can occur in • Starter • Combustion • Backfire • Diesel engine • Gases sucked in/shutoff not possible

  13. Powder Actuated Tools • Provides spark when bullet is fired • Concussion from firing can shake dust loose

  14. Smoldering Nests • Collection of material in dust environment • Material can smolder • Chemical/biological reaction

  15. Accidental Mechanical Impact • Can occur in rotating equipment • Repeated impact creates hot spots • Spark can occur if material is capable • Titanium • Some aluminums

  16. Hot Work • Obtain permit PRIOR to hot work • Combustible material • If possible remove all material • Remove outside 35-foot radius • Cover with flame retardant tarps if unmovable

  17. Electrical Lockout/Tagout • Used to prevent sparks • Eliminates accidental ignition

  18. Separator Devices • Removes foreign materials capable of igniting dust • Isolation device must be installed • When using air separation air device • Install on return air lines

  19. Intrinsically Safe Devices • Equipment/wiring incapable of releasing sufficient energy to cause ignition • Examples • Pressure, flow, and level switches • Solenoid valves • thermocouples

  20. Explosion Proof Devices • Use explosion proof devices • Light fixtures • Engine switches • Pumps/motors • Sole option when IS-rated device is unavailable

  21. National Electric Code • Standard for safe installation of electrical wiring/equipment • Part of National Fire Codes • 1st published in 1897 • Updated every 3 years

  22. National Electric Code • NEC Classification-Article 500 • Class: designates type of flammable substance • Group: designates specific substances • Division: designates likelihood of flammable substances

  23. National Electric Code-Class II Dusts • Group E: combustible metal dusts • Group F: combustible carbonaceous dusts • Group G: other combustible dusts

  24. Next Module Module 4: Support Systems

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