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428 413 Safety Engineering 5' Fire and Explosion Hazards and Protections 6' Toxic Substances ''

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Title: 428 413 Safety Engineering 5' Fire and Explosion Hazards and Protections 6' Toxic Substances ''


1
428 413 Safety Engineering 5. Fire and
Explosion Hazards and Protections 6. Toxic
Substances ?.??.???????
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2
References 1. D.A. Crowl, J.F. Louvar,
Chemical Process Safety Fundamentals with
Applications, Prentice Hall, 1990. 2. Dennis
P. Nolan, Handbook of Fire and Protection
Engineering Principles for Oil, Gas, Chemical,
and Related Facilities, Noyes Publication 3.
W.O.E Korver, Classifying Explosion-Prone Areas
for the Petroleum, Chemical and Related
Industries, Noyes Publication, 1995
3
Fire and Explosion Hazards and Protections
4
Burnt vehicles and debris left by hydrocarbon
vapor explosions that killed 15 workers at the BP
Texas City refinery March 23, 2005.
5
Oct. 6, 2005 Huge flames rise from the Formosa
Plastics manufacturing complex in Point Comfort.
6
Fire rages at the Marcus Oil facility on evening
of Dec. 3, 2004 following powerful tank
explosion.
7
Smoke billows from heavily damaged Formosa
Plastics plant following April 23, 2004
explosion. Photo Kevin German/The State
Journal-Register.
8
Introductions
  • Fire, explosions and environmental pollution are
    the most serious "unpredictable" life affecting
    and business losses having an impact on
    industries today.
  • Accidents
  • Most accidents can be thought of as
    non-preventable, all accidents are in fact
    preventable.

9
The main cause of accidents or failures can be
  • Ignorance
  • Economic Considerations
  • Oversight and Negligence
  • Unusual Occurrences

10
Ignorance
  • Incompetent design, construction or inspection
    occurs.
  • Supervision or maintenance occurs by personnel
    without the necessary understanding.
  • Assumption of responsibility by management
    without an adequate understanding of risks.
  • There is a lack of precedent.
  • There is a lack of sufficient preliminary
    information.
  • Failure to employ competent Loss Prevention
    professionals.

11
Economic Considerations
  • Initial engineering and construction costs for
    safety measures appear uneconomical.
  • Operation and maintenance costs are unwittingly
    reduced to below what is necessary.

12
Oversight and Negligence
  • Unethical behavior occurs.
  • Professional engineers and designers commit
    errors.
  • Contractual personnel or company supervisors
    knowingly assume NO risks.
  • Lack of proper coordination in the review of
    engineering designs.
  • Failure to conduct prudent safety reviews or
    audits.

13
Unusual Occurrences
  • Natural catastrophes - earthquakes, extreme
    weather, etc.
  • Political upheaval - terrorist activities.
  • Labor unrest, vandalism.

14
Fire and Explosion Protection Engineering Role
  • is not a stand alone discipline,
  • should be an integrated aspect of how a facility
    is designed arranged and constructed.
  • Should be integral with all members of the design
    team, be it structural, civil, electrical,
    process, etc. Risk engineer should mainly be in
    an advisory role.
  • In addition Risk Engineer must have expertise in
    hazard, safety, risk and fire protection
    principles and practices applied to the petroleum
    or other related industries.

15
Risk Management and Insurance
  • The four methods, in order of preference are
  • Risk Avoidance
  • Risk Reduction
  • Risk Insurance
  • Risk Acceptance

16
  • Senior management responsibility and
    accountability are the keys to providing
    effective fire and explosion safety measures at
    any facility or operation.

17
Fire Dynamics
  • Combustion reaction the structure of the flame
    or reaction zone.
  • 2 types of reactions
  • Premixed flame reaction oxidizer and fuel are
    mixed prior to their entry to the combustion
    zone.
  • Diffusion flame reactions oxidizer and fuel are
    mixed in the vicinity of the flame.

18
Reactions
  • Oxidation reaction is the chemical combination of
    oxygen with any substance.
  • The substance is oxidized.
  • Rust is an example of oxidized iron. In this
    case, the chemical reaction is very slow.
  • The very rapid oxidation of a substance is called
    combustion, or fire with simultaneous evolution
    of radiation energy, usually heat and light.

19
Combustions
  • Combustion theories
  • the fire triangle,
  • the tetrahedron of fire, and
  • the life cycle of fire.

20
The Fire Triangle
  • There are three things necessary to have a fire
    fuel, oxygen (or an oxidizer), and heat (or
    energy).

21
Fuel
  • Anything that will burn.
  • Fuels may be categorized into the following
    classes
  • 1. Elements (which include the metals,
    and some non-metals such as carbon, sulphur, and
    phosphorus)
  • 2. Hydrocarbons
  • 3. Carbohydrates (including mixtures that
    are made up partially of cellulose, like wood and
    paper)
  • 4. Many covalently bonded gases
    (including carbon monoxide, ammonia, and hydrogen
    cyanide)
  • 5. All other organic compounds.

22
Hydrocarbon
  • Hydrocarbon must first be in a vapor condition
    before combustion processes can occur.
  • Liquids however must have significant vapor
    emissions in order for flammable concentrations
    to be present for combustion processes to occur.
  • Gases by their nature are immediately ignitable
    and can produce a fast burning flame front that
    generates into an explosive force in confined
    areas.

23
Oxidizer
  • Oxygen is the most common oxidizing agent
  • Most firefighters consider only oxygen, since the
    greatest source of oxygen is the atmosphere.

24
Energy
  • All forms capable of providing the source of
    energy needed to start the combustion process.
  • The energy can be generated chemically by the
    combustion of some other fuel, or it can be
    generated by some other exothermic chemical
    reaction.
  • Energy may also be generated by mechanical
    action
  • Static electricity is created whenever molecules
    move over and past other molecules.
  • A third method of generation of energy is
    electrical. This method may manifest itself as
    heat, as produced in an electrical heater, as
    arcing in an electrical motor or in a "short"
    circuit, or as the tremendous amount of energy
    released as lightning.
  • The fourth method of generation of energy is
    nuclear.

25
Energy
  • Once the energy - in many cases, heat - is
    generated, it must be transmitted to the fuel
    (the "touching" of the fuel and energy legs).
  • This process is accomplished in three ways
  • Conduction the transfer of heat through a
    medium, such as a pan on a stove's heating
    element),
  • Convection the transfer of heat with a medium,
    such as the heated air in a hot-air furnace), and
  • Radiation the transfer of heat which is not
    dependent on any medium.

26
Oxidation
  • A law of nature, that when fuel, oxidizers, and
    energy are brought together in the proper
    amounts, a fire will occur.
  • If the three are brought together slowly, and
    over a long period of time, the oxidation will
    occur slowly, as in the rusting of iron.
  • If the three are of a particular combination, the
    resulting oxidation reaction might even be an
    explosion.
  • Whatever form the final release of energy takes,
    the thing that cannot be changed is that the
    chemical reaction will occur.

27
The Tetrahedron Theory
Diffusional continuous re-ignition
automatically obtained at flame temperature
levels. Fuel is in form of vapor and/or gas.
28
The Tetrahedron Theory
  • This theory encompasses the three concepts in the
    fire triangle theory but adds a fourth "side" to
    the triangle, making it a pyramid, or
    tetrahedron.
  • The fourth side is called the "chain reaction of
    burning".

29
The Life Cycle Theory
  • The input heat, which is defined as the amount of
    heat required to produce the evolution of vapors
    from the solid or liquid. The input heat will
    also be the ignition source and must be high
    enough to reach the ignition temperature of the
    fuel
  • The fuel part the fuel must be in the proper
    form to bum
  • The fourth part of the theory is proportioning,
    or the occurrence of intermolecular collisions
    between oxygen and the hydrocarbon molecule (the
    "touching" together of the oxidizer leg and the
    fuel leg of the fire triangle).

30
The Life Cycle Theory
  • The fifth step is mixing that is, the ratio of
    fuel to oxygen must be right before ignition can
    occur (flammable range).
  • The sixth step is ignition continuity, which is
    provided by the heat being radiated from the
    flame back to the surface of the fuel

31
The Life Cycle Theory
32
Products of Combustion
  • Heat and combustible gases (inviscible) e.g.
  • Carbon dioxide CO2
  • Carbon monoxide CO
  • Sulfur dioxide SO2
  • Acrolein CH2CHCHO
  • Hydrochloric acid HCl
  • Hydrofluoric acid HF
  • Hydrogen cyanide HCN
  • Oxides of Nitrogen NOx
  • Flame and smoke

33
Heat Released From Combustion
  • Depend on the type of fuel, a specific amount of
    heat is released which called heat of combustion.
  • In ideal combustion of 0.45 kg (1 lb) of methane,
    approximately 25,157 kJ (23,850 Btu) are
    released.
  • The temperature of the combustion products is
    normally taken to be 1200 oC, which is a typical
    hydrocarbon fire temperature.

34
Heat Released From Combustion
  • Heat flux is considered the more appropriate
    measure by which to examine the radiation effects
    from a fire.
  • A radiant heat flux of 4.7 kW/m2 will cause pain
    on exposed skin, a flux density of 12.6 kW/m2 or
    more may cause secondary fires and,
  • A flux density of 37.8 kW/m2 will cause major
    damage to a process plant and storage tanks.

35
Fires
  • Jet Fire
  • Most fires involving gas will be associated with
    a high pressure and labeled as "jet" fires.
  • A jet fire is a pressurized stream of combustible
    gas or atomized liquid that is burning. If such a
    release is ignited soon after it occurs, (i.e.,
    within 2 -3 minutes), the result is an intense
    jet flame.
  • This jet fire stabilizes to a point that is close
    to the source of release, until the release is
    stopped.
  • A jet fire is usually a very localized, but very
    destructive to anything close to it.

36
Fires
  • Pool Fire
  • Once a pool of liquid is ignited, gas evaporates
    rapidly from the pool as it is heated by the
    radiation and convective heat of the flame.
  • Pool fires have some of the characteristics of a
    vertical jet fire, but their convective heating
    will be much less.

37
Fires
  • Flash Fire
  • If a combustible gas release is not ignited
    immediately, a vapor plume will form. This will
    drift and be dispersed by the ambient winds or
    natural ventilation. If the gas is ignited at
    this point, but does not explode, it will result
    in a flash fire, in which the entire gas cloud
    burns very rapidly.
  • It is unlikely to cause any fatalities, but will
    damage steel structures.

38
Explosions
  • A detonation is a shock reaction where the
    flames travel at supersonic speeds (i.e., faster
    than sound).
  • Deflagrations are where the flames are traveling
    at subsonic speeds.
  • The explosion occur in pressurized gas and air
    systems (i.e., process vessels and piping). It is
    generally recognized that vapor cloud explosions
    have flames that travel at subsonic speeds.

39
Explosions (Detonations)
  • Detonations can occur in solids and liquids but
    are particularly frequent in petroleum facilities
    in mixtures of hydrocarbon vapors with air or
    oxygen.
  • Detonations will develop more rapidly at initial
    pressures above ambient atmospheric pressure. If
    the initial pressure is high the detonation
    pressure will be more severe and destructive.
  • Detonations produce much higher pressures than
    the ordinary explosion. In most cases a process
    vessel or piping systems will be unable to
    contain detonation pressure.
  • The only safe procedure is to avoid process
    system detonations is to preventing the formation
    of flammable vapor and air mixtures within
    vessels and piping systems.

40
Vapor Cloud Explosions
  • The ignition of combustible gas or vapor
    releases in the open atmosphere.
  • It will only occur if there is sufficient
    congestion or in some cases turbulence of the
    open air is occurring,
  • Vapor cloud explosions are high-speed, but have
    subsonic combustion resulting in a deflagration
    not a detonation.
  • Four conditions have to be achieved
  • There has to a significant release of flammable
    material.
  • The flammable material has to be sufficiently
    mixed with the surrounding air.
  • There has to be an ignition source.
  • There has to be sufficient confinement,
    congestion, or turbulence in the released area.

41
Smoke and Combustion
  • Fatalities causes mainly from smoke and gas
    inhalation.
  • Smoke lt 1 mm.
  • The narcotic gases i.e. CO, HCN, CO2 are the main
    danger and cause incapacitation by an attack on
    the nervous system.
  • Low level of O2 in brain
  • Psychological disorder i.e. impaired judgment
    ands concentration, confused, panic and
    incapacitate personnel.

42
Smoke and Combustion
  • SO2 suffocating by blocking transport of O2 in
    the blood.
  • CO hemoglobin causes death.
  • CO has an affinity 300 times that of O2.
  • CO in blood 70-80 causes death.

43
Smoke and Combustion
  • HCN Hydrocyanic gas
  • They render the O2 unavailable to the tissues,
    and cause death through asphyxia.
  • Inhaling 180 ppm of HCN lead to unconsciousness.
    Fatal effect would be caused by CO poisoning
    after victim unconscious.
  • Hot gas Inhaling will cause tissue damage.
  • Psychological the sight and causes panic and
    disorientation.

44
Hazards Considerations
  • Ease of ignition
  • Source of ignition available
  • Spill potential
  • Fire exposure
  • Container provided
  • Flammable range
  • Health exposure

45
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48
Flammable and Combustible Liquid Hazards
  • Definitions
  • Flash point
  • Fire point
  • Limits of flammability
  • Auto-ignition temperature
  • Flammability
  • Combustibility

49
The MainCharacteristics of Combustible Materials
  • Lower Flammable (Explosive) Limit (LFL or
    LEL)/Upper Flammable Limit (UFL or UEL).
  • This is the range of flammability for
    a mixture of vapor or gas in air at normal
    conditions.
  • Material Range Difference
  • Hydrogen 4.0 to 75.6 71.6
  • Ethane 3.0 to 15.5 12.5
  • Methane 5.0 to 15.0 10.0

50
The MainCharacteristics of Combustible Materials
  • Flash Point
  • The lowest temperature of a flammable liquid at
    which it gives off sufficient vapor to form an
    ignitable mixture with the air near the surface
    of the liquid or within the vessel used.
  • Material Flash Point
  • Hydrogen Gas
  • Butane -60 oC (-76 oF)
  • Hexane -22 oC (-7 oF)

51
The MainCharacteristics of Combustible Materials
  • Autoignition Temperature (AIT)
  • The minimum temperature at to which a substance
    in air must be heated to initiate or cause self
    sustaining combustion independent of the heating
    source.
  • Material AIT
  • Heptane 204 oC (399 oF)
  • Hexane 225 oC (437 oF)
  • Butane 287 oC (550 oF)

52
The MainCharacteristics of Combustible Materials
  • Vapor Density
  • The relative density of the pure vapor or gas
    when compared to air.
  • Vapor Pressure
  • This is the property of a substance to vaporize.
  • Flammable
  • Combustible
  • Heat of Combustion

53
Purpose of the Dow Fire and Explosion Index
  • To serve as a guide to the selection of fire
    protection methods.
  • To help evaluate the overall risk from fire
    explosion (FEI).
  • To better understand the potential risks.

54
NFPA Standard and Basic Classifications of
Flammable Liquids
  • Class 1 a closed-cup flashpoint below 100 oF at
    a vapor pressure lt 40 psi.
  • Class 2 a closed-cup flashpoint at or above 100
    oF but below 140 oF.
  • Class 3 a closed-cup flashpoint at or above 140
    oF.

55
NFPA Vapor Pressure vs Vapor Travelling
Distances
  • Liquid Flash Pt. Liquid VP (atm)
    Vapor Travelling
  • Class (?F) Temp (?F) Distances
  • I 50 200 0.45
    Large
  • II 100 200 0.12
    Small
  • III 140 200 0.048
    Minimal

56
NFPA Molecular Weight vs Vapor Travelling
Distances
  • Liquid Flash Pt. Liquid VP (atm) MW
    Vapor Travelling
  • Class (?F) Temp (?F)
    Distances
  • I 50 200 0.45
    Minimal Large
  • II 100 200 0.45
    Small Small
  • III 140 200 0.45
    Large Minimal

57
Dust Explosion
  • An explosion results when the dust cloud has a
    concentration above the LEL.
  • The explosion intensity depends on the rate of
    pressure rise.
  • Dust explosion is the simplest way of eliminating
    the an explosion hazard such as an automatically
    operated water spraying system that keeps solid
    fuel constantly wet.

58
Mechanism of Fire Extinguishment
  • Four majors requirements for a combustion
    reaction
  • Sufficient oxidizer
  • Fuel vapor
  • Heat input (ignition source)
  • Continuous chain reaction
  • These 4 elements also become the mechanisms for
    extinguishing a fire.

59
Extinguishment by Cooling
  • Water is the most effective means of removing
    heat from ordinary combustible materials such as
    wood, paper, cardboard,
  • Reducing and ultimately stopping the rate of
    release of combustible vapors and gases.

60
Extinguishment by Oxygen Dilution
  • The term dilution can only be applied to the
    gaseous state.
  • The necessary degree of O2 dilution varies
    greatly with the particular fuel.
  • The O2 requirements for flaming is 16 and
    smoldering is 5.
  • Carbon dioxide is used in the total flooding of
    closed or semi-closed spaces.

61
Extinguishment by Fuel Removal
  • Removing the fuel or indirectly shutting off the
    fuel vapors to combustion in the flaming mode by
    simply covering the fuel.
  • The use of surfactant foams is a typical example.
  • The cooling of a fuel surface essentially results
    in the removal of fuel vapor.

62
Extinguishment by Chemical Flame Inhibition
  • Can be applied in the flaming mode only.
  • This method is partially understood and is the
    subject of major continuing research.
  • This method is the extreme rapidity and the high
    relative efficiency with which flames can be
    extinguished.

63
Extinguishment by Chemical Flame Inhibition
(contd.)
  • Combustion is a chain reaction process. Active H
    interact with O2 molecule to produce active OH
    and O species.
  • These active species are formed as products as
    well as consumed as reactants and can be called
    chain carriers.
  • Extinguishment by flame inhibitors is possible
    only when the active species are not allowed to
    fulfill their role in sustaining the flame.

64
Extinguishment by Chemical Flame Inhibition
(contd.)
  • Inhibitors
  • Gaseous and liquid halogenated hydrocarbons
    wherein the effectiveness increase as higher
    order halogens are used.
  • Bromotrifluoromethane CBrF3 Halon 1301
  • Bromochlorodifluoromethane CBrClF2 Halon 1211
  • Dibromotetrafluoroethane CBrF2CBrF2 Halon 2402

65
Extinguishment by Chemical Flame Inhibition
(contd.)
  • Inhibitors
  • Alkali metals, salts wherein the cationic portion
    is Na, K, and the anionic portion is either
    bicarbornate, carbamate, or halide.
  • Sodium bicarbornate regular dry chemical
  • Potassium bicarbornate purple X
  • Potassium carbarmate Monnex
  • Potassium chloride Super K

66
Extinguishment by Chemical Flame Inhibition
(contd.)
  • Inhibitors
  • Ammonium salts, the most prominent of which is
    mono-ammonium phosphate wherein the cationic
    ammonium radical (NH4) and the ionic phosphate
    radical (H2PO4) are formed with the latter
    absorbing an H active radical.

67
Design Objectives in the Chemical Plants
  • A major emphasis of all systems in plants is
    defense in depth.
  • Fire safety requires fire prevention and fire
    protection to be implemented by both engineering
    design and administrative control.

68
Fire Prevention by Design
  • Can be achieved by removing fuel, removing
    ignition sources, or removing oxidizing agents
    (air).
  • 3 controls
  • Control of fuel,
  • Control of ignition sources, and
  • Control of oxidizing agent.

69
Fire Prevention by Design
  • Combustible Materials
  • It should be clear that control of combustibles
    should be a primary design criteria for plants.
    This control can be engineered by
  • Locating necessary combustible remote from the
    potential ignition sources,
  • containing combustibles in suitable enclosures
    to prevent exposure to ignition sources, and
  • selecting non-combustibles as substitutes for
    combustibles.
  • Location, containment, material
    selection/substitution.

70
Fire Prevention by Design
  • Typical design practices to prevent vapor cloud
    explosions
  • All hydrocarbon areas should be provided with
    maximum ventilation capability.
  • Enclosed spaces are avoided.
  • Installation of walls and roofs are used only
    where necessary (including firewalls).
  • Generally hydrocarbon floors areas are open
    grated construction when elevated, unless solid
    floors are provided where there is a need for
    spill protection or a fire or explosion barrier,
    otherwise ventillation requirements will prevail.

71
Fire Prevention by Design
  • Area congestion should be kept to a minimum.
  • Vessels should be orientated to allow maximum
    ventilation or explosion venting.
  • Bulky equipment should not block air circulation
    or dispersion capacity.
  • Release or exposure of flammable vapors to the
    atmosphere should be avoided.
  • Waste HC gases should be routed to the flare or
    return to the process.
  • Sampling techniques should use a closed system.
  • Process equipment liquid drains should use a
    sealed drainage system.
  • Open drain ports should be avoided and separate
    sewage and an oily water drain systems should be
    provided.
  • Surface drainage should be provided to remove
    spills immediately and effective from the process
    area.

72
Fire Prevention by Design
  • Gas detection is provided, particularly to areas
    handling low flash point materials with a
    negative or neutral buoyancy.
  • Air or oxygen is eliminated from the interior of
    process system i.e. vessels, piping and tanks.
  • Protective devices are located outside hazardous
    areas or behind protective barriers.
  • Semi or permanently occupied buildings required
    in or adjacent process areas are constructed to
    withstand expected explosion overpressure.

73
Fire Prevention by Design Vapor
  • Dispersion enhancements water sprays.
  • Large updraft air cooler fans.
  • Location optimization based on prevailing winds.
  • Supplemental ventilation systems.
  • Damage limiting construction.
  • Pre-installed or engineered features into the
    design of the facility or equipment.
  • Fireproofing.

74
Fire Prevention by Design
  • Building Materials
  • Interior finishes
  • Thermal insulator
  • Structural materials
  • Process and Equipment Materials
  • Cable insulation
  • Lubrication fluids
  • Cooling and insulating fluids
  • Solvents
  • Ion exchange

75
Fire Prevention by Design
  • Ignition Sources
  • Potential sources of heat energy
  • Electrical Energy can be converted to heat of
    ignition in a variety of ways.
  • The flow of current through a material produces
    heat by either resistance or inductance.
  • Making or breaking of an electrical circuit such
    as a short circuit or a switch can cause arcing.
  • Frequently these two forms work together for
    example, resistance heating can cause a softening
    of wire insulation and lead to a short circuit
    and fire.

76
Fire Prevention by Design
  • Potential sources of heat energy (contd.)
  • Static electricity is generated by the contact
    and separation of materials (sometimes referred
    to as frictional electricity). Energy can be
    converted to heat of ignition in a variety of
    ways.
  • Machines belts or the flow of flammable liquids.
  • Lightning.
  • Heated equipment
  • Hot piping e.g. steam lines,
  • Space heaters,
  • Open flame.

77
Fire Prevention by Design
  • Potential sources of heat energy (contd.)
  • Mechanical Heat Energy
  • Frictions Heat, sparks
  • Heat of compression
  • Chemical Heat Energy
  • Spontaneous heating
  • Heat of decomposition
  • Heat of solution
  • Heat of reaction
  • Human

78
Fire Prevention by Design
  • Oxidizing agents
  • The most case is O2.
  • This is accomplished by inerting process
    equipment, tanks, or rooms where applicable.

79
Fire Protection by Design
  • Focuses on managing the impact of a fire.
  • The most case is O2.
  • It is unlikely that all fire can be prevented.
  • The objectives are
  • Control of fire with building design,
  • Control of fire with fire protection systems and
    equipment.

80
Fire Protection by Design
  • Control of fire with building design.
  • It is a very effective way to manage the impact
    of fire.
  • Passive protection building design encompass
    plant layout to separate hazards from important
    areas, compartment to limit the spread of fire,
    and various fire barriers or fire retardants to
    reduce the growth or spread of fire.

81
Fire Protection by Design
  • Control of fire with fire protection systems and
    equipment.
  • Active protection to detect and suppress fire
    before un-acceptable damage has occurred.

82
Administrative Control of Fire Hazards
  • Fire safety requires
  • Active protection to detect and suppress fire
    before un-acceptable damage has occurred.
  • Purpose of administrative control
  • Training
  • Fire prevention
  • Maintain effective program

83
Method of Administrative Control
  • Procedural
  • Operating,
  • Maintenance,
  • Procurement, and
  • Design/construction
  • Permit systems
  • Hazardous work permit
  • Control of materials
  • Technical specifications

84
Enforcement of Administrative Control
  • Coordination (authority and responsibility)
  • Training
  • Inspection
  • Audits

85
Maintaining Program Integrity
  • Design review
  • Contractor supervision
  • Authority for enforcement
  • Inspection/test of fire protection equipments
  • Control of fire protection system impairments
  • Outage approval
  • Records to assure reinstatement
  • Additional safeguard

86
Hazard Control
  • Eliminate or replace liquid
  • Confine vapors maintaining the vapor outside of
    the flammable range
  • Control of ignition sources
  • Control environment (air or temperature)
  • Containers and fire barriers
  • Fire suppression

87
Employers and the self-employed must
  • Carry out a risk assessment of any work
    activities involving dangerous substances
  • Provide technical and organizational measures to
    eliminate or reduce as far as is reasonably
    practicable the identified risks
  • Provide equipment and procedures to deal with
    accident and emergencies
  • Provide information and training to employees
  • Classify places where explosive atmospheres may
    occur into zones, and mark the zones where
    necessary.

88
Industries affected
  • Storage of petrol.
  • Use of flammable gases, such as acetylene, for
    welding
  • Handling and storage of waste dusts in a range of
    manufacturing industries   
  • Handling and storage of flammable wastes
    including fuel oils
  • Hot work on tanks or drums that have contained
    flammable material
  • Work activities that could release naturally
    occurring methane
  • Dusts produced in the mining of coal
  • Use of flammable solvents in pathology and school
    laboratories
  • Storage/display of flammable goods, such as
    paints, in the retail sector
  • Filling, storage and handling of aerosols with
    flammable propellants, such as LPG
  • Transport of flammable liquids in containers
    around the workplace
  • Deliveries from road tankers, such as petrol or
    bulk powders
  • Chemical manufacture, processing and warehousing
  • Petrochemical industry - onshore and offshore 

89
Industries affected
  • Fired heaters
  • Pumps handling hydrocarbon materials
  • Reactors
  • Compressors
  • Large hydrocarbon inventory vessels, columns, and
    drums

90
Safety Measures
  • To ensure that the safety risks from dangerous
    substances are either eliminated or reduced to as
    far as is reasonably practicable.
  • Where it is not reasonably practicable to
    eliminate risks, employers are required to take,
    so far as is reasonably practicable, measures to
    control risks and measures to mitigate the
    detrimental effects of a fire or explosion or
    similar event.

91
Safety Measures
  • Elimination is the best solution and involves
    replacing a dangerous substance with a substance
    or process that totally eliminates the risk.  In
    practice this is difficult to achieve and it is
    more likely that it will be possible to replace
    the dangerous substance with one that is less
    hazardous (e.g. by replacing a low flashpoint
    solvent with a high flashpoint one) or to design
    the process so that it is less dangerous for
    example, by reducing quantities of substances in
    the process, this is known as process
    intensification. 
  • However care must be taken whilst carrying out
    these steps so as to ensure that no other new
    safety or health risks are created or increased.

92
Control Measures
  • Reduce the quantity of dangerous substances to a
    minimum
  • Avoid or minimize releases
  • Control releases at source
  • Prevent the formation of an explosive atmosphere
  • Collect, contain and remove any releases to a
    safe place (e.g. by ventilation)
  • Avoid ignition sources
  • Avoid adverse conditions (e.g. exceeding the
    limits of temperature or control settings) that
    could lead to danger
  • Keep incompatible substances apart

93
Mitigation
  • Reducing the numbers of employees exposed
  • Providing plant which is explosion resistant
  • Providing explosion suppression or explosion
    relief equipment
  • Taking measures to control or minimise the spread
    of fires or explosions
  • Providing suitable Personal Protective Equipment
    (PPE)

94
Reduction of Risks
  • Design, construction and maintenance of the
    workplace (e.g. fire-resistance, explosion
    relief)
  • Design, assembly, construction, installation,
    provision, use and maintenance of suitable work
    processes, including all relevant plant,
    equipment, control and protection systems
  • The application of appropriate systems of work
    including written instructions, permits to work
    and other procedural systems of organising work

95
Places where Explosive Atmospheres can occur
  • areas where hazardous explosive atmospheres may
    occur are classified into zones based on their
    likelihood and persistence
  • areas classified into zones are protected from
    sources of ignition by selecting equipment and
    protective systems meeting the requirements of
    the Equipment and Protective Systems Intended for
    Use in Potentially Explosive Atmospheres
    Regulations

96
Places where Explosive Atmospheres can occur
  • where necessary, areas classified into zones are
    marked with a specified "EX" sign at their points
    of entry
  • where employees work in zones areas they are
    provided with appropriate clothing that does not
    create a risk of an electrostatic discharge
    igniting the explosive atmosphere
  • before coming into operation for the first time,
    areas where explosive atmospheres may be present
    are confirmed as being safe (verified) by a
    person (or organisation) competent in the field
    of explosion protection. The person carrying out
    the verification must be competent to consider
    the particular risks at the workplace and the
    adequacy of control and other measures put in
    place.

97
Arrangements to deal with accidents, incidents
and emergencies
  • Suitable warning (including visual and audible
    alarms) and communication systems
  • Escape facilities if required by the risk
    assessment
  • Emergency procedures to be followed in the event
    of an emergency
  • Equipment and clothing for essential personnel
    dealing with the incident
  • Practice drills
  • Making information on the emergency procedures
    available to employees
  • Contacting the emergency services to advise them
    that information on emergency procedures is
    available (and providing them with any
    information they consider necessary)

98
Information instruction and training
  • Employers are required to provide employees and
    other people at the workplace who might be at
    risk with suitable information, instruction and
    training on precautions and actions they need to
    take to safeguard themselves and others,
    including
  • Names of the substances in use and risks they
    present
  • Access to any relevant safety data sheet
  • Details of legislation that applies to the
    hazardous properties of those substances
  • The significant findings of the risk assessment
  • The significant findings of the risk assessment.

99
Determination of the presence of dangerous
substances
  • You will need to carry out the following two
    steps -
  • Check whether the substances have been classified
    under the Chemicals (Hazard Information and
    Packaging for Supply) Regulations as explosive,
    oxidising, extremely flammable, highly flammable
    or flammable
  • Assess the physical and chemical properties of
    the substance or preparation and the
    circumstances of the work involving those
    substances to see if that can create a safety
    risk to persons from an energetic event.
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