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FPST 1213

FPST 1213 . Flammable Liquids. Definitions. Difference between a liquid and a gas? NFPA 30 provides an arbitrary distinction for our purposes: at 100 °F, vapor pressure  40 psia is a liquid > 40 psia is a gas. Flammable vs. Inflammable.

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FPST 1213

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  1. FPST 1213 Flammable Liquids

  2. Definitions • Difference between a liquid and a gas? • NFPA 30 provides an arbitrary distinction for our purposes: at 100°F, vapor pressure •  40 psia is a liquid • > 40 psia is a gas

  3. Flammable vs. Inflammable • Inflammable is the correct term, however the “in” in inflammable has lead to confusion, some think it means “not” • Flammable has been adopted to prevent confusion

  4. Flash Point (page 8-90) • Ignition occurs at ignition source but does not propagate away from the source • The lowest temperature at which the Vapor Pressure of the liquid is just sufficient to produce a flammable mixture at the LFL • Fire Point is where the liquid first burns continuously

  5. Flashpoint Tests • Conducted using a closed cup tester • Or an Open Cup tester

  6. Flammable vs. Combustible • NFPA • Flammable Liquids – Flash point less than 100°F • Combustible Liquids – Flash points at or above 100°F • DOT • Flammable: less than or equal to 141°F • Combustible: >141°F

  7. Ignition Temperature • Autoignition Temperature • The temperature to which a closed (or nearly closed) container must be heated so that the liquid will spontaneously ignite and burn

  8. Ignition Temperature and Molecular Weight • As MW the Ignition Temperature

  9. Flammable Range • Lower Flammable Limit (LFL or LEL) • Minimum concentration of vapor to air below which propagation of a flame will not occur in the presence of an ignition source. (Too Lean) • Upper Flammable Limit (UFL or UEL) • Maximum vapor to air concentration above which propagation of a flame will not occur in the presence of an ignition source. (Too Rich)

  10. Vapor Density • The weight pure unit volume of a pure gas or vapor. Reported relative to air as a vapor density ratio • Analogous to Specific Gravity • Vapor Density Ratio= MW/29 • VDR>1 heavier than air

  11. Vapor Pressure • Liquid in a closed container • Vapor-Air mixture above liquid • Acetone at 100°F has a VP=7.6 psia • Tabulated • Petroleum products based on Reid Method • Compare to Air (14.7 psia) • Concentration= 7.6/14.7=52%

  12. Vapor Pressure • Mixture of liquids complex • Depends on: • Miscible • Partly miscible • Or immiscible – can treat as separate

  13. Specific Gravity • The weight per unit volume of a liquid compared to water. • Specific Gravity= Densityliquid/Densitywater • SG<1 lighter than water (floats) • SG>1 heavier

  14. Boiling Point • The temperature at which the equilibrium vapor pressure of a liquid equals the total pressure on the surface • Acetone if heated in 1 atm until VP=14.7, then its concentration is 100% and it is at its boiling point

  15. Storage & Handling • Properly designed containers that are liquid tight and from which release of vapors is carefully controlled.

  16. Safety Containers • Avoid danger of leaking • Minimize likelihood of: • Spillage • Vapor release • Container Rupture if exposed to fire conditions

  17. Tanks & Drums • Tanks • Above ground • Underground • Inside buildings

  18. Liquids expand when heated • Must have air/vapor space to prevent overflow/spill/rupture • BLEVE for LPG • Vapor Space may be in flammable range • Gasoline usually “too rich”. BUT if in the –10 to -50°F range could be flammable

  19. Expansion of Flammable Liquids • Heated volume = (Original volume)*(1+T) Example: Heat 1,000 gallons of Acetone 40°F 1,000(1+.00085*40)=1032

  20. Venting • Tanks must be vented and fitted with flame arresters IAW NFPA 30 and API 2000 • Emergency Vents (Rupture disks)

  21. Cleaning and Maintenance • Purging • Water • Steam • Air • Inert Gas

  22. Aerosols

  23. Precautions & Safeguards • Isolate the Hazard • Confine Liquid & Vapors • Ventilate • Explosion Venting

  24. Precautions & Safeguards (2) • Eliminate Ignition Sources • Mechanical Sparks • Electric Arcs/Sparks • Electrostatic Ignition • Open Flame • Housekeeping • Spill Control

  25. Education • Need to Know • Right to Know • MSDS

  26. Calculating Vapor Volume Ft3= 8.33 x specific gravity of liquid (H2O=1) .075 x vapor density of vapor (air=1)

  27. Metric

  28. Example Page 8-92 • Acetone SG=.792 VD = 2

  29. Dilution below LEL • LEL Acetone = 2.6% by vol. • >97.4% air is too lean • 97.4/2.6 = 37.4 • 44 cu.ft x 37.4 = 1645 cu. Ft.

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