1 introduction to hazard and risk

8/13/2019 1 Introduction to Hazard and Risk

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INTRODUCTIONTO HAZARD

AND RISK


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BHOPAL,INDIA


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NIGERIA


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OUTCOMEO Differentiate safety and healthO Type of hazardO Major hazard in chemical industryO Past industrial accident


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Safety vs healthSafety Health

A state of environment A state of the individual

Typically injured related (not only) Typically disease related (but notonly)

Does not include positive health Includes positive health External Internal

Occupational safety the protection of peoplefrom physical injury

Occupational health the protection of thebodies and minds of people from illness


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Engineers professional ethicsFundamental principles

Engineers shall uphold and advance theintegrity, honor and dignity of engineeringprofession by :- using knowledge & skill for enhancement ofhuman welfare.- honest and impartial and serving withfidelity to public, employers, clients.- striving to increase competence andprestige of engineering profession.


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FUNDAMENTAL CANONS:

O Engineers shall hold paramount the safety, health and welfare ofthe public and shall strive to comply with the principles ofsustainable development in the performance of their professionalduties.

O Engineers shall perform services only in areas of their competence.O Engineers shall issue public statements only in an objective and

truthful manner.O Engineers shall act in professional matters for each employer or

client as faithful agents or trustees, and shall avoid conflicts ofinterest.

O Engineers shall build their professional reputation on the merit oftheir services and shall not compete unfairly with others.

O Engineers shall act in such a manner as to uphold and enhance thehonor, integrity, and dignity of the engineering profession and shallact with zero-tolerance for bribery, fraud, and corruption.

O Engineers shall continue their professional developmentthroughout their careers, and shall provide opportunities for theprofessional development of those engineers under theirsupervision.


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Economics of safetyO Lives, injuries, damages to plant and

equipmentO Loss productionO Increased costs

O Insurance, medical, rehabilitation,training and retraining

O Lowering of workplace moraleO Substantial loss of market shareO Profitability


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Accident pyramid


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HAZARD

CATEGORIES


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Unsafe act A violation of an acceptable safe procedure whichcould permit the occurrence of an accident

A hazardous physical condition or circumstances

which could directly permit the occurrence of anaccident.This could be the result of an unsafe act by

someone

Unsafe Condition


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Example of unsafe act:

Operating without authorityFailure to warn or secureOperating at improper speed

Making safety devices inoperableUsing defective equipmentUsing equipment improperlyFailure to use PPEImproper loading, placementServicing equipment in motion


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Example of unsafe condition:

Inadequate guards or protection

Defective tools, equipment

Congestion, bad housekeeping

Inadequate warning systemFire and explosion hazards

Hazardous atmospheric condition

Excessive noiseInadequate illumination or ventilation


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IDENTIFY UNSAFE ACTS AND CONDITIONS; AND POSSIBLETYPES OF ACCIDENT


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HAZARD

CATEGORIES


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Categories of hazardsO Chemical

O ThermodynamicsO Electrical & electromagnetO HealthO ExternalO MechanicalO Biological


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examplesO Chemical hazards

O AcidityO Alkalinity

O CorrosivityO ExplosivenessO FlammabilityO ToxicityO AsphyxiationO Compressed or

liquified gasO DustO Oxidizers

O Thermodynamicshazards

O High pressureO VacuumO Heat transferO High temperatureO Low temperatureO Fluid jets


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examplesO Electrical &

electromagnet

hazardsO High voltageO RadiationO Static electricityO

Electrical currentO Poor insulation

O Health hazardsO NoiseO PollutionO VibrationO Radioactivity

O Temperature extremes


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Major Hazards in

Process Industries


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Toxic Release

xplosion

Fire


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TOXIC RELEASE


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Hazard from Toxic SubstancesO

Effects that are IrreversibleO Carcinogen-cause cancerO Mutagen-cause chromosome (gene) damageO Teratogen- cause birth defects

O Effects that may or may not be irreversibleO Dermatotoxic affects skinO Hemotoxic affects bloodO Hepatotoxic- affects liver

O Nephrotoxic affects kidneysO Neutotoxic affects nervous systemO Pulmonotoxic- affects lungs


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FIRE


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FireJet Fire

Flash FirePool Fire


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Jet fires

O A jet fire is the combustion of material emergingwith significant momentum from an orifice, from asource under pressure , e/g. a flammable liquid orgas is ignited after its release from a pressurized,

punctured vessel or pipe.O The pressure release generates a long flame

which is stable under most conditions.O The duration of a jet fire is determined by the

release rate and the capacity of the source .


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O Flame length increase directly with flow

rate.O Crosswinds affect flame length.O An increase in crosswind velocity

causes the flame to bend over quicklyand be convected by the wind.

O The flame length increases withcrosswind velocity.

O A jet flame is similar to a Bunsen burnerflame


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Jet Fire


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POOL FIREO A pool fire is the combustion of flammablevapor evaporating from a layer of liquid at thebase of the fire.

O It occurs on ignition of an accumulation ofliquid as a pool on the ground or on water orother liquid.

O A steadily burning fire is rapidly achieved asthe vapor to sustain the fire is provided by the

evaporation of the liquid by heat from theflames.


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Pool Fire


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Flash Fire/Vapor Cloud FireO

Occurs when a vapour cloud forms from a leakand is ignited, but without creation of significantoverpressure.

O Released a flammable vapour from a processequipment or pipe followed by ignition

O If the ignition is prompt, the cloud may bemodest in size, but if the cloud has time tospread over an appreciable part of the site and isthan ignited, a major vapour cloud fire mayresult.

O It is a quick and short phenomenon which can beaccompanied by mechanical effects (blast).


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Flash Fire


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Explosion


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Types of Explosion

O Vapor Cloud ExplosionO BLEVEO Dust Explosion

V Cl d E l i


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Vapor Cloud ExplosionO The most dangerous and destructive explosions in

the chemical process industries

O When flammable vapour is released to theatmosphere, it will form a cloud suspended in theair, filling the atmosphere to a height limited by itsdensity.

O If it is ignited at some early stages, flash fire will beformed.

O However if ignition is delayed and triggered withinthe explosive limit, it will generate more devastatingeffect known as the VCE.

Phillips Pasadena USA


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Phillips Pasadena, USA

23rd Oct. 1989 23 Deaths 130 Injuries Vapour Cloud explosion Loss US$ 500 Millions


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BLEVE

B L E VOI

LING

IQ

UID

XP

ANDING

XP

LOSION

S

EAP

OR

BLEVE is a consequence of holding a pressurizedflammable liquids above its boiling point.

C f BLEVE


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Causes of BLEVEO A BLEVE can be defined as a major failure of

container at a moment in time when the containedliquid is at a temperature well above itsatmospheric pressure boiling point.

O The most common type of BLEVE occurs when apressure vessel that is partially filled with liquid isexposed to a fire.


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O Second type of BLEVE is that which occursmechanically damage tanks.

O In some cases, the damage done to a pressurized tankof liquefied gas in a transportation accident has beensufficient to cause an immediate catastrophic failure ofthe tank.

O In other cases, the damage to the tanks appeared to beminor, but the stresses imposed on the mechanicallydamaged areas were sufficient to cause the tank to failcatastrophically at a later time.

O In this instances, BLEVEs can occur with out thepresence of a fire and might or might not followed byfireball.


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O A third type of BLEVE can occur if a pressurevessel is allowed to become completely filledwith liquid.

O As the temperature rises, the pressure reliefcapacity is insufficient to keep the internalpressure from exceeding the strength of thetank.

O This type of BLEVE can occur with out thepresence of a fire and might or might not be

followed by a fireball.


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BLEVE


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O Materials that may form combustible dust

include metals (such as aluminium andmagnesium), wood, coal, plastics, biosolids, sugar, paper, soap, dried blood,and certain textiles.

O In many accidents, employers andemployees were unaware that a hazardeven existed.


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