safety management

• Hazard


  Anything, any source, any situation with the potential to cause damage to equipment or properties, delay to operations or work schedules, bodily injury, ill-health, death
• Process Hazards Classification


  • Chemical
  • Physical
  • Biological
  • Mechanical
  • Electrical
  • Ergonomic
• Chemical hazards


  Any chemical sources that can cause fire, explosion, or others such as toxic/harmful effect to health when exposed to it
• Fire


  • An exothermic chemical reaction /combustion with energy released in the form of heat and light
• Fire Triangle


  • Fuel, an oxidizer and an ignition source are needed to start or to sustain a fire. If any of the three components is eliminated, there will be no fire.
• Fire Tetrahedron


  • Fuel, an oxidizer, an ignition source, and a chemical chain reaction are needed to start a fire. If any of the 4 components is eliminated, then there will be no fire.
• Ignition sources


  • sparks
  • heat
  • flames
  • static electricity
• Static electricity

  Static electricity charges can be created whenever two surfaces with different conductivity contact and separate. The build-up of electric charges on a surface will eventually "discharge", sparking off and giving us an electrostatic shock.
• Bonding & Grounding

  Bonding is physically connecting two objects together with a copper wire. Grounding is to connect an object to earth with a copper wire & a grounding rod. Bonding & grounding reduces the voltage of the entire system to ground level or zero voltage, eliminating the potential for electrostatic sparks.
• Fire-fighting


  1. Removing fuel

  2. Reducing oxygen

  3. Removing heat

  4. Interrupting chemical chain reaction
• Portable fire extinguishers

  first line defence to stop fire before it gets out of hand, provides an escape route through a large fire, contains a fire until help comes, must be trained to use it, maintained regularly, inspected monthly and replaced according to manufacturer's recommendation
• Fire Classification by the SCDF

  • Class A: Fires involving ordinary combustible materials like wood, paper, etc can be extinguish by all extinguish reagent
  • Class B: Fires involving flammable liquids, solvents, oils, paints, thinner & liquefiable solids can be extinguish by all extinguish reagent
  • Class C: Fires involving flammable gases no effective extinguish reagent, isolate flammable gas where possible
  • Class D: Fires involving combustible metals no effective extinguish reagent
  • Class F: Fires involving cooking media in cooking appliances no effective extinguish reagent
• Extinguishing Agents

  • Water for class A
  • Foam for class A and B
  • Inert gases for class A and B
  • Multipurpose dry chemical for class A and B
• Explosion

  Uncontrolled combustion producing a rapid increase in temperature & pressure, rapid release of energy over a small time & generating a pressure wave of finite amplitude traveling away from the source, leading to rupturing of vessel or system causing the products of the rapid combustion to be released uncontrollably
• Differences between Fire & Explosion

  • Fire: Combustion occurs at surface, slow release of heat energy, no pressure wave generated

  Explosion: Combustion of entire fuel, rapid release of heat energy, pressure wave generated due to rapid volume expansion
• Vapour Cloud Explosion (VCE)


  The most dangerous and destructive explosions in the chemical process industry, caused by ignition of a vapour cloud of flammable material
• How a vapour cloud explosion VCE occurs

  1. Sudden release of large amounts of fuel (rupture of pipe, uncontrolled exothermic reatcion evaporating large quantity of organic material)
  2. Formation of large vapour cloud in its flammable range (no wind , vapour cloud able to mix with air)
  3. Delayed ignition resulting in a vapour cloud explosion
• Boiling-Liquid Expanding-Vapor Explosions (BLEVE)


  A special type of accident that can release large quantities of materials, occurs when a pressurised vessel containing a liquid above its boiling point ruptures in a fire and releases pressurized liquid rapidly into the fire, leading to rapid combustion, pressure wave, fire ball, vessel fragments & burning liquid droplets
• Dust Explosions

  Rapid combustion of fine solid particles, occurs when fine particles are dispersed in air and ignited, many solid materials become flammable when reduced to fine powder
• Dust explosion prevention & mitigation

  Smooth surfaces, eliminate places where solids accumulate, frequent monitoring & cleaning of dryer, vacuum up spilled powder instead of sweeping, deflagration venting to control release of explosion energy

  
• Chemical Hazards - Other Harm

  • Toxicity (e.g. hydrogen cyanide)
  • Corrosivity (e.g. hypochlorite solution)
  • Ability to self-polymerise (e.g. butadienes)
  • Shock sensitivity (e.g. nitroglycerines)
  • Thermal instability (e.g. ruthenium)
  • Pyrophoricity (e.g. Iron sulphide)
• Manufacture of Polymers

  A lot of heat can be released during polymerisation, polymerisation can also occur quickly, the quick heat release can vaporise the monomer or other flammables resulting in an explosive vapour cloud, the build-up of flammable gases can "explode" the reaction vessel
• Corrosivity


  • Corrosives damages bodily tissues in contact/exposed to it
• Ability to self-polymerise


  • Uncontrolled polymerisation
• Shock sensitivity


  • Detonation of solid & liquid explosive or explosive mixture when shocked
• Thermal instability


  • Thermal explosion due to bulk self-heating or runaway reaction with heat
• Pyrophoricity


  • Fire upon atmospheric contact
• Manufacture of Polymers


  1. A lot of heat can be released during polymerisation

  2. Polymerisation can also occur quickly

  3. The quick heat release can vaporise the monomer or other flammables resulting in an explosive vapour cloud

  4. The build-up of flammable gases can "explode" the reaction vessel

  5. During production, heat release is controlled by slowly adding the reactants & by cooling of the reactor
• Safety Data Sheet (SDS)

  Identifies the hazards of the chemical & the appropriate warning info
• Flammable liquids


  • Category 1: Extremely flammable liquid and vapour
  • Category 2: Highly flammable liquid and vapour
  • Category 3: Flammable liquid and vapour
  • Category 4: Combustible liquid
• GHS Hazard Category - 95% Ethanol

  • Flammable liquid: Category 2
  • Acute toxicity (oral, dermal, inhalation): Category 3
• Safe chemical handling

  • Chemical inventory - keep the minimum amount & dispose of expired chemicals
  • Chemicals should be separated & stored according to hazard groups
  • Store corrosive chemicals below eye level
  • Secondary containment for concentrated acids or bases; toxic chemicals
  • All containers labelled with full chemical names & appropriate hazard warning info.
  • Provide eyewashes & safety showers
  • Wear appropriate PPE
  • Use proper ventilation when handling hazardous vapours

  
• Physical hazards


  • Noise
  • Radiation
  • High pressure or vacuum
  • Heat
  • Vibration
• Biological Hazards


  • Viruses
  • Bacteria
  • Fungi
  • Parasitic worms transmitted via insects, animals & certain plants
• Mechanical Hazards

  • Entanglement hazard
  • Cutting hazard
  • Crushing hazard
• Basic checklist for machine safety

  • Risk assessment conducted on handling equipment/machinery?
  • Safe Work Procedure (SWP) developed for operating the machine?
  • Appropriate personal protective equipment worn?
  • Worker adequately trained & competent in operating the machine?
  • Worker familiar with the emergency response procedure?
  • Machine safety devices functioning properly? (e.g. machine guards, interlocking door)
• Intrinsically safe electrical devices limit the amount of electrical & thermal energy to a level that is incapable of causing an ignition
• Major contributors of electrical hazards

  • Damaged tools & equipment including exposed electrical parts/worn out cables
  • Inadequate wiring & overloaded circuits
  • Improper grounding
  • Operating electrical equipment in wet conditions
• Effects of current on the human body

  • 1 mA: Slight tingling sensation
  • 2 - 9 mA: Small shock
  • 10 – 24 mA: Muscles can contract and causes one to 'freeze'. Burns apparent at the point of contact
  • 25 -74 mA: Respiratory muscles paralyzed, burns at entry and exit
  • 75 – 300 mA: Ventricular fibrillation. Shock usually fatal
  • 300 mA: Death. Survivals will have severe burns to skins, limbs & internal organs. May require amputations of limbs
• Electrical Safety


  • Use only electrical instruments, appliances & tools that are safety approved (PSB or PUB approved stickers)
  • Check all power cords for signs of damage, rectify loose fitting & connections. Replace damaged ones
  • Never handle electrical appliances, machinery or equipment with damp or wet hands
  • Always connect the electrical/electronic circuit to the power supply last. This is to ensure that everything is okay before powering up the circuit