ENCH 363 Process Safety

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ENCH 363Process Safety

• Peter Gostomski

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Outline

• Review 1st Pro material
• Key definitions
• Physics/chemistry of hazards
• Risk Reduction techniques
• Procedural, active, passive, inherent
• Inherent safety design options
• Minimise, substitute, simplify, attenuate
• Health Safety legislation
• RMA, HSE, HASNO

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1st Pro material

• Flixborough, UK (1974) chemical plant, vapour
  cloud explosion, 28 dead, 36 injured
• Seveso, Italy (1976) herbicide plant, runaway
  reaction, chemical release, 447 injured, long
  term health problems, 50,000,000
• Bhopal, India (1984) - pesticide plant, chemical
  release, 2,500 dead, 200,000 injured,
  250,000,000
• Chernobyl, USSR (1986) nuclear reactor, 31
  dead, 237 injured, long term health problems,
  3,000,000,000.
• Basle, Switzerland (1986) chemical warehouse
  fire, 0 dead, 0 injured, environmental damage.
• Piper Alpha, UK (1988) - offshore oil/gas
  platform, 167 dead, 20 injured,
  1,470,000,000

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Flixborough, UK (1974) cyclohexane
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Flixborough, UK (1974) cyclohexane
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Piper Alpha (1988)
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Phillips 66, Pasadena, TX 1989 (isobutane leak)
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Phillips 66, Pasadena, TX 1989 (isobutane leak)
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Concept Sciences (1999) - KOH NH2OH (5 dead)
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Ammonium nitrate explosion, Toulouse, France
(2001)
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Ammonium nitrate explosion, Toulouse, France
(2001)
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Power Outage N.A. (2003)

• power overload caused supply to fail
• chain reaction caused power loss in eastern US
  and Canada.
• 50 million without power
• Responsibility? Costs?

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Safety Goals

• Prevent
• Death/injury to workers
• Death/injury to the general public
• Damage to the facility
• Damage to surrounding property
• Damage to the environment

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Key Definitions

• Hazard physical situation that can damage
• Risk likelihood of hazard occurring
• Risk

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Physics chemistry of hazards

• Most gases denser than air (mix slowly)
• Flammable vapors travel along ground to spark
  source
• Displace air leading to suffocation
• Vapour pressure - pressure of gas in a two phase
  system
• Flammable liquid exceeds LFL?
• Cavitation in a pump?
• Condensing steam collapse a tank?
• Antoine equation

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Fire

• Gas burns ? liquid/solids must vaporise first
• Sparks easy to come by

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Fire

• Lower flammability limit (LFL)
• Gas concentration high enough to burn in air
• Safe levels
• Mixtures have unique LFL
• Flash point temperature (FP)
• Autoignition temperature (AIT)
• LFLTol , FPTol , AITTol

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Oxygen content (suffocation)
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Static electricity

• Static charge present in many places in process
  plant
• Motors, light switches, organic liquids
• Human body
• Grounding important
• Feel shock ?

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Vacuum

• Large storage tanks easily damaged by vacuum
• Failure ?P 4 H2O, 0.15 psi, 1 kPa
• Causes

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Dust

• Dusts of most combustible solids are an explosion
  hazard
• Sufficiently small particle size
• Sufficient concentration dispersed in air
• Ignition source
• Secondary explosions often exceed initial
  explosion
• Design options