Safety Lectures Handouts

7/29/2019 Safety Lectures Handouts

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P. Lettieri

Safety, Hazards and Risks


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P. Lettieri

History

Safety and Loss Prevention

Hazards & Risk Analysis

Properties of Materials

Flammable

Chemical - Toxicity

Control of Chemical Reactions

Content


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Objectives

Why do we study safety and loss prevention ?

Why is it that in the final examination for this course,the question on safety is compulsory?

Why does the IChemE make safety the only area in

which corporate members MUST have training andexperience ?

The history of accidents will answer these questions!


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Safety

HealthEnvironment

Duration of exposure (time)

Intensityofex

posure

sustainabledevelopment

Safety and Sustainable Development


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Historical Aspects of Safety

1750BC: Code of Laws of Hammurabi

Deuteronomy Chapter 22 verse 8

1785: Count Morozzo

1921: Oppau

1966: Aberfan 1974: Flixborough

1976: Seveso

1984: Bhopal Mexico City

1988: Piper Alpha


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Early Health & Safety LawIf a builder build a house and do not

make its construction firm, and the housewhich he has built collapse and causedeath of the owner of the house, thatbuilder shall be put to death

Hammurabi Law 229 (circa 1750 BC)


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1974: Flixborough

4 5 6


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Reactor4

Reactor6

originalconnections and

flexible bellows

temporary pipe

with dog-leg


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1988: Piper Alpha


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Accident Pyramid

?000Critical situations

Unsafe habits

Near-misses

Property Damage300

Minor Injury

Medical treatment30

Disabling injury

Lost time accident1


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Cost of Top 10 Accidents in UKsince 1974 (1996 costs M)

Company, Location Date CostTexaco/Gulf, Pembroke 1994 100MBP Oil, Grangemouth 1987 100MLaporte Chemicals, Warrington 1984 43M

National Freight, Sheffield 1984 37MBASF, Wilton, Teeside 1995 20MJ Kelman Transport, Renfrew 1977 20MAmoco, Milford Haven 1983 18M

RA Lister, Dursley, Glos 1983 16MMorganite Ceramic Fibres, Merseyside 1984 10MShell, Ellesmere Port 1990 10M

Source: IChemE Loss Prevention Bulletin, No 140, April 1998


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Cost of Top 10 Accidents Worldwidesince 1974 (1996 costs $M)

LocationDate CostPasadena, Texas 1989 $1,456M

La Mede, France 1992 $458MPampa, Texas 1987 $396M

Antwerp, Belgium 1989 $356MThessaloniki, Greece 1986 $300MNorco, Louisiana 1988 $293MSweeny, Texas 1991 $264M

Romeoville, Illinois 1984 $241MPort Neal, Iowa 1984 $182MSodegaura, Japan 1992 $172M

Source: IChemE Loss Prevention Bulletin, No 140, April 1998


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What causes an Accident?

Deficient Procedures or documentation

Lack of knowledge or training

Failure to follow procedures

Deficient planning or scheduling

Miscommunication

Deficient supervision Policy problems


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Prime Responsibilities for Accidents

(1981-83)

Senior management %Local management %

Workers %

Management and Workers %

Others %

No one %TOTAL 100%


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Fatalities Reported to HSE

0

200

400

600

800

1000

1200

1400

1960 1970 1980 1990 2000

H&SWA1974

PiperAlpha


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LOSS PREVENTION Code of Hammurabi

Health and MoralsAct of 1802

Factories Act 1844 Health and Safety

at Work Act 1974


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Health and Safety at Work Act 1974

Duties of the employers:-

Employers must safeguard so far as is reasonably practicable,

the health, safety and welfare of the people who work for them

Duties of the employees:-

Employees have a duty to take reasonable care to avoid injury to

themselves or to others by their work activities

Duties of manufacturers and suppliers:-

Designers, manufacturers, importers or suppliers of articles or

substances for use at work must ensure that, so far as

reasonably practical, they will be safe when used


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Establishing a

Safe System Of Work

It is managements duty to:

Define the safe system of work

Train people in that safe system

Observe that they are working in thismethod


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LOSS PREVENTION


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Loss Prevention

Definition:- A systematic approach to

preventing accidents or minimisingtheir effects

Prevent the unwanted event fromhappening


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Recent Approaches to Safety

1950s 1960s 1970s 1980s 1990s 2000s

Design standards

Plant inspections

Human factors

Performance indicators

TechnicalSafety

SafetyAudits

Management

SystemsCulture

?

Accidentrate


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Safety Management

Plan Organise

Control Monitor

Review


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Policy Supporting Human Resource Development

Minimising Financial Losses

Recognising that accidents and ill health result fromfailings in management control

Recoginsing that the development of a culturesupportive of H&S is necessary to achieve adequatecontrol over risks

Ensuring a systematic approach to the identification

of risks and allocation of resources to control them Supporting quality initiatives aimed at continuous

improvement


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Loss Prevention and TotalQuality Management

Commitment to the customer, the employee and

the community by the senior management team Commitment to the importance of human factors,

covering the job, the individual and the

organisation Commitment to prevention of loss whether it is ofproduct, of people or of customers

Commitment to continuous improvement of theproduct as well as the work situation

Commitment to setting standards and measuringthe performance of individuals or groups againststandards

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Organising for Loss

Prevention

Operation Plan

Safety Improvement Plans are

developed Meetings are attended

Decisions made are implemented

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Human Factors Human Error

Slips / Lapses of Attention

Mistaken Actions Wrong Perceptions

Violations

Operator Response Routine operator action

Operator intervention in an emergency Operator hears alarm

Operator recognises what the alarm means

Operator decides what action is required

Operator performs the action

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Controlling for Loss

PreventionStandards Measure Compliance

Evaluate

Measurement

Results

Workcompleted

satisfactorily

Plan for LossPrevention

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ReviewingPerformance

Organising

Planning andImplementing

Measuring

Performance

Policy

Auditing

key elements of a safety

management system

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. ett e

Legislation

Old-StyleLegislation Prescriptive

Detailed rules andregulations

What must be done

Do it anyway

New-Style Legislation Based on likelihood of harmdone

Framework rules with

guidelines How it must be managed

Identify anything that causesharm and likelihood of itoccurring first,rank them and prioritise actionsaccordingly

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Safety Culture

demonstrate commitment to safety and thus generate high levels ofmotivation and concern for health and safety throughout theorganisation

adopt good communications between all levels of the workforce andthus provide a bridge across the management hierarchy boundaries

accept that the promotion of safety culture is a long-term strategywhich requires sustained effort and interest

adopt a formal health and safety policy, supported by adequate codesof practice and safety standards

balance safety and production or service goals and stress that health

and safety is equal to other business objectives evaluate safety systems to provide information feedback with a view

to developing ideas for continuous improvement

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HAZARD and RISK HAZARD

Anything that can cause harm A physical situation with a potential for human

injury, damage to property, damage to theenvironment or some combination of these

RISK

The likelihood that someone will be harmed by thehazard

The likelihood of a specified undesired eventoccurring within a specified period

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Safe Systems of Work we have to identify the hazard

we evaluate the risk

we establish a control system to

minimise the risk

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Risk Assessment each job may be broken down into tasks

the potential for causing lossdetermined

the method of working detailed.

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IdentifyHazards

EstimateRisks

Control &Review

AssessTolerability

ManagementIntervention

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Fatal, Serious,

Minor

A measure of the ConsequenceSEVERITY

Explosion of gas

cloud

An outcome resulting from an

accident

CONSEQUENCE

Pipeline dug up by

excavator

An unplanned, uncontrolled event

giving rise to death injury,ill-health, damage or loss

ACCIDENT

Operating Pressure

too high

A situation with the potential to

cause death, injury, damage,losses or liabilities

HAZARD

Defective WeldsDeviation from the normal design

intent or operating standard

FAILURE

ExampleDefinitionTerm

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Assessment of a risk involves the rating of two factors

which affect the risk

1. the severity of the hazard

2. the likelihood of an occurrence of

harm from the hazard

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>110-2-110-4-10-210-6-10-4


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= RiskFrequency Consequence

How likely is itthat the hazardwill cause an

accident?

If an accidentoccurs, how

severe are the

consequences?

x

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FARs: Fatal Accident Rates

number of deaths per 1000 workforceduring a working lifetime 105 hours

70

62

8

4

2

FAR

Rock Climbing

Helicopter travel

Car Travel

Rail Travel

Staying at home

Other Activities

4000Steel Erectors

500Offshore Oil and Gas

30Coal Mining

4UK Industry

(factory work)

1Chemical

FARIndustry

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41/90

Risk per 109 km traveled in UK, 1986-90

104.0Motor cycle riders

70.0Pedestrians

50.0Pedal cyclists

4.4Car drivers and passengers

1.1Rail passengers

0.2UK scheduled airlinepassengers

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1 Direct Costs

Indirect Costs Management Time Compensation Claims Increased Insurance Costs

Business Interruption Loss of Good Will

TheCostIceberg

8 - 36

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ALARP

ALARPLevel


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ALARPAs Low As

ReasonablyPossible

ALARPAs Low As

ReasonablyPossibleTolerability

Intolerable Level

Tolerable ifALARP

Risk is undertakenonly if a benefit isdesired

Broadly Acceptable

Risk cannot be justified on any grounds

TolerableOnly if risk reduction is impracticable or if itscost is grossly disproportionate to theimprovement gained

TolerableIf cost of reduction would be

disproportionate to the improvement gained

Negligible Risk

Level

of Risk

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ALARP

ALARP


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ALARPAs Low As

ReasonablyPossible

ALARPAs Low As

ReasonablyPossible

Intolerable Level

Tolerable ifALARP

Broadly Acceptable

Risk Reduction regardless of cost

Relevant Good Practice

plus

Risk Reduction Measures

plus

Gross Disproportionation

Relevant GoodPractice

TECHNOLOGY

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45/90

Objectives

To identify the hazards

To decide on the likelihood or damage To determine action to be taken to

control adequately To comply with Health & SafetyLegislation

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Managing Risk

Paint section off-site in acontrolled environment ifpossible

Brush apply at site

Ensure good ventilation area

Use respirator and protectiveclothing

CONTROLMEASURES

Exposure to solventRISK

Solvent base paint system(no alternative for particular

application)

HAZARD

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Identification of Hazards

HAZard and OPerability Study - HAZOP

Fault Tree Analysis - FTA

Safety Analysis Function Evaluation -

SAFE Charts Check Lists / What if Analysis

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Ri k A t


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Risk Assessment

1. Look for the hazards

2. Decide who might beharmed, and how

3. Evaluate the risks andimplement control measureswhere necessary

4. Record you findings5. Review your assessment

and revise it if necessary

www.hse.gov.uk

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FAULT TREE ANALYSIS

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Fault Tree Analysis

LOGIC symbols

OR gate

AND gate

EVENT symbols

Basic Event

Combination Event

Fault Event - not required

to be developed further

Technique to find a sequence of faults

and causes leading to a hazardousevent

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Flat

Tyre onWay toUCL

Miss start ofLecture

DriverHits Bike with

Door

Collision

Damage toBike

Bikestolen

Minor CollisionDamage to Bike

RideBike toUCL

PotentialCalamity

CannotAvoid Car

Driver cutsoff cyclist

DriverDoes Not See

Bike

CarEncountered

RideBike toUCL

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QUENCHTANK

REACTOR

Inlet L2

L1

V2

T1

T2

L3

Outlet

V1

M

V2 open button

V1 close button

Temperature

Alarm

DAMAGE TOREACTOR DUETO HIGH

TEMPERATURE

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Th P bl


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The Problem An unstable exothermic reaction is being carried out in a

reactor protected against a runaway reaction with a quenchsystem as shown in Figure.

Two independent sensors T1 and T2 continuously monitor thereaction temperature.

The quench tank outlet valve V2 opens automatically when T1

detects a certain increase in temperature.

T2 activates an alarm in the control room independently to alert theoperator to a possible loss of control of the reaction.

When the alarm sounds the operator should press a button to closevalve V1 to stop the reactor feed.

When the operator hears the alarm he is also instructed to press thebutton that opens the quench tank outlet valve in the event thatsensor T1 fails to operate.

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Damage to Reactor due toHigh Temperature

Valve V1 Remains open

T1 fails to initiate V2

Valve V2 does not open

No Flow in L1

QuenchTank Empty

V2 Failsto Open

Valve V2 not Initiated

Operator fails to initiate V2

T1 Failsto detect

Temp riseOperator

fails to obeyalarm andOpen V2

Alarm fails to Alert Operator

AlarmFailsOff

T2 Failsto detect

Temp rise

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FLAMMABLE PROPERTIES


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FLAMMABLE PROPERTIES

All threeelements must

be present atthe same timeto have a fire.

Fuel

He

atOx

ygen

Take any ofthese away, and

you will not havea fire or the firewill be

extinguished.

The Fire Triangle

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Flash Point Temperature at which the material will just catch fire atatmospheric pressure if a source of ignition is applied.

Temperature at which the vapour pressure of the materialequals the lower flammable limit.

CTypical Values:-

-38gasoline

43 to 88diesel

13n-octane

-22n-hexane

very lowmethane

extremely lowhydrogen

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Flammable Limits Lower Flammable Limitis that concentration inair of a flammable material below which combustionwill not propagate. (lower explosion limit)

Upper Flammable Limitis that concentration inair of a flammable material above which combustionwill not propagate.

13.0 17.03.8 - 6.5natural gas

9.552propane

14.05.3methane754hydrogen

Upper LimitLower LimitVapour

Volume % Vapour in AirTypical values:-

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Variation of Flammability Characteristics


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Variation of Flammability Characteristics

with Change of Temperature

Concent

ration

Temperature

Flash point

Flammability

range

Autoignition

temperature

Upperflammablelimit

Lowerflammablelimit

Autoignition

Boiling point

Vapourpressure

curve

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Autoignition Temperature The minimum temperature at which that

material will initiate and sustain in air acombustion process without the provision of asource of ignition.

476pentane 7.65v/v%

257diesel oil

456

502

548(C)

gasoline

pentane 3.75v/v%

pentane 1.5v/v%Typical values:-

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Sources of Ignition


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Sources of Ignition Mechanical

Friction Missiles

Electrical Electrical Current Electrostatic

Lightning Stray Currents Radio frequency

Thermal Hot surfaces Self-heating

Flames Engines

Chemical

Peroxides Polymerisation Spontaneous Reactions with other

substances Thermite reaction Unstable substances Decomposition

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Types of Fire and Deflagration Pool Fire

occurs when liquid is spilt

onto a surface and thevapour ignites

Jet Fire occurs when a vessel or

pipe under pressure

leaks from a small holecausing a jet of liquid orvapour to be emitted andwhich ignites

Fire Ball

a fire burning sufficientlyrapidly for the burningmass to rise into the airas a cloud or ball

Unconfined VapourCloud Explosion

An explosion in the openair of vapour which is notconfined by walls,vessels or otherequipment.

BLEVE Boiling Liquid ExpandingVapour Explosion

Occurs when a vesselcontaining a liquid at a

temperature above itsatmospheric boiling pointruptures and ignites.

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Water: reducesh i


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Fire relief valve:set to operatebefore weakenedwalls rupture

Remote operateddepressurising valve:reduces pressure invessel

heat input

Sloping ground:

prevents liquid collecting

Insulatedsupports

Detector

Insulation:reduces heat input

Boiling liquidBoiling liquid

absorbs heat,absorbs heat,

keeps wallskeeps walls coolcool

No liquid to absorbNo liquid to absorb

heat, walls mayheat, walls may

overheat and failoverheat and fail

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Dust Explosions A dust explosion is very similar to a gas or

vapour cloud explosion, i.e. when a volume ofa flammable mixture is ignited, resulting in arapid pressure increase and fire movingthrough the cloud.

A dust explosion occurs when a combustiblematerial is dispersed in the air forming aflammable cloud and a flame propagatesthrough it.

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Dust Explosions The dust must be combustible

The dust must be capable of becomingairborne

The dust must have a size distributioncapable of flame propagation

The dust concentration must be within theexplosive range

An ignition source must be present

The atmosphere must contain sufficientoxygen to support and sustain combustion

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Material Safety Check List Flash Point

Flammability Range Autoignition Temp

Composition

Stability & Reactivity

Toxicity

Corrosion Heat of Combustion

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Material Safety Data Sheet1. Composition/ Information

on ingredients

2. Chemical Product

3. Hazards Identification

4. First Aid

5. Fire Fighting Measures

6. Accidental ReleaseMeasures

7. Handling and Storage8. Exposure Controls/

Personnel Protection

9. Physical and ChemicalProperties

10. Stability and Reactivity

11. Toxicological Information

12. Ecological Information

13. Disposal Consideration

14. Transport Information

15. Regulatory Information

MSDS Example: cyclohexane

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Chemical PropertiesChemical hazards

Asphyxiant Narcotic

Toxic

Irritant

Sensitising

Corrosive

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Chemical Properties Asphyxiant

Asphyxia is caused by the lack of oxygen reaching theblood and hence the brain.

Narcotic

When the oxygen has been displaced by hydrocarbonvapour, the physiological effect may be complicatedsince the effects of asphyxia may be combined withthe effects of narcotic, irritant and/or toxic vapour.

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Definition of terms Toxicity Acutely toxic- have an immediate effect on a person

Chronically toxic -have an effect after prolongedexposure to small quantities.

Very Toxic

A substance which if it is inhaled or ingested or itpenetrates the skin may involve extremely seriousacute or chronic health risks and even death.

Toxic

A substance which if it is inhaled or ingested or itpenetrates the skin may involve serious acute orchronic health risks and even death.

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Definition of terms


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Irritant A non-corrosive substance which, through immediate,

prolonged or repeated contact with the skin or mucousmembrane, can cause inflammation.

Sensitiser Substances or agents which on firstexposure may or

may not cause local skin effects.

Initiates a defensive-type mechanism within the bodywhich is triggered to produce reactions on second orsubsequent exposure.

Corrosive A substance which on contact with living tissues

destroy them. Burning and/or blistering, i.e. direct chemical contact

areas as in the nose and throat and on the skin.

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Definition of terms Carcinogenic

A substance which if it is inhaled or ingested or if it

penetrates the skin may induce cancer in man orincrease its incidence.

Teratogenic

A substance which if it is inhaled or ingested or itpenetrates the skin may involve a risk of subsequentnon-hereditablebirth defects in offspring.

Mutagenic

A substance which if it is inhaled or ingested or itpenetrates the skin may involve a risk of hereditablegenetic defects.

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LD50

Absorbed byinhalation

in ratmg litre-1

Absorbedpercutaneously in rat

or rabbitmg kg-1

Absorbed

orally in ratmg kg-1 (4 hrs)

2 - 20400 2000200 - 2000Harmful

0.5 250 40025 200Toxic

0.55025Very Toxic

Median Lethal Concentration(LD50)

Category

LD50: Lethal dose for 50% fatality (usually on rats) within specifiedtime period - often 14 days.

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Occupational Exposure Limits: OELs


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Skin0.0470.02624-83-9Methyl isocyanate

35601500178075067-64-1Acetone

205--108-24-7Acetic Anhydride

3715251064-19-7Acetic Acid

Notes

mg m-3ppmmg m-3ppm

CAS NoSubstanceShort term limit

15 minLong term limit

8 hrs

maximum concentrations in air averaged over a particular time periodLong term limit- used for substances producing chronic effectsShort term limit- for substances producing acute effects

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USA: Threshold Limit Values: TLVs


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TLV

refers to airborne concentrations

TLV-TWA Time Waited Average

8 hour working day for 40 hours per week repeatedlyexposed without adverse effect.

TLV-STEL

Short Term Exposure Limit

for 15 minutes max. with no more than 4 excursions

during an 8 hour day without adverse effect.

TLV-Ceiling

The concentration which must not be exceeded.

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COSHHControl

OfSubstances

Hazardous toHealth

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To comply with COSHH:1. Assess the risks

2. Decide what precautions are needed .

3. Prevent or adequately control exposure.

4. Ensure that control measures are used and maintained.

5. Monitor the exposure6. Carry out appropriate health surveillance

7. Prepare plans and procedures to deal with accidents,

incidents and emergencies8. Ensure employees are properly informed, trained and

supervised.

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What is a substance hazardous


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to health under COSHH? Substances or mixtures of substances classified

as dangerous to health under the Chemicals(Hazard Information and Packaging for Supply)Regulations 2002 (CHIP).

Substances with occupational exposure limits Biological agents

Any kind of dust

Any other substance which creates a risk tohealth

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Material Safety Data Sheet1. Composition/ Information

on ingredients

2. Chemical Product

3. Hazards Identification

4. First Aid

5. Fire Fighting Measures

6. Accidental ReleaseMeasures

7. Handling and Storage

8. Exposure Controls/Personnel Protection

9. Physical and ChemicalProperties

10. Stability and Reactivity

11. Toxicological Information

12. Ecological Information

13. Disposal Consideration

14. Transport Information

15. Regulatory Information

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Safety Symbols


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Sa ety Sy bo s

(Highly) Flammable

Dangerous When Wet

Harmful

Biohazard

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Sources of information


80/90

UK: Heath andSafety Executive www.hse.gov.uk

source of safety data

source of guidance

e.g. OELs

publications on

specific hazards arsenic, asbestos

USA: EnvironmentalProtection Agency www.epa.gov

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RUNAWAY EXOTHERMIC


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REACTIONS A chemical reaction invariably involves an energy

change Heat is either absorbed or released

If heat is given out the reaction is said to be exothermic

An exothermic reaction can lead to thermal runaway,which begins when the heat produced by the reactionexceeds the heat removed

The surplus heat raises the temperature of the reactionmass, which causes the rate of reaction to increase

This in turn accelerates the rate of heat production

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RUNAWAY EXOTHERMIC


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REACTIONS

Rates of

Heat

Generation&

Heat

Transfer

Temperature

heatgeneration

heattransfer

runaway

stablecriticaltemperature

Q = UAT

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Causes for Runaway Reactions


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y

In batch and continuous operations

Mixing wrong materials

Contanimation

Decomposition particulalrly becaused ofover-heating

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The Essential Features for Planning


84/90

a Batch Chemical Reaction correct charging of materials

reactor cooling agitation

control

temperature

pressure

training

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Correct Charging of Materials


85/90

materials used must be charged in the correctamounts and in the correct order

problems:-

wrong material being added

wrong amounts of material being added includingthe catalyst

wrong order of charging may materially affect thereaction

wrong temperature used for the charging period

wrong rate of charging

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Reactor Cooling


86/90

heat generated by the reaction must beremoved by the cooling system chosen

problems: -

The wrong temperature for the reaction is used sothat the rate of heat generation is greater than thecooling capacity. The critical temperature hasbeen exceeded

The cooling capacity of the system is unable to

cope with increased rate of heat generationThe failure of the cooling system

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Agitation


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maintains all materials in close contact withone another and assists in temperaturecontrol

problems: -

failure of agitation by power failure or agitatorfailure causing solids to settle and loss of coolingcapacity.

agitator causing vortex and temperature probe

coming out of liquid. failure to restart agitator after sampling etc.

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Temperature and Pressure Control


88/90

Temperature

control throughout thereaction is crucial

problems: -

wrong temperature due to

probe not covered or tooshort

wrong temperature due tocontrol misaligned or

other instrument faultswrong strategy of reaction

control

Pressure

pressure in the reactoris a result of thetemperature changeand/or the release of

gases. problems: -

the rate of pressure riseis greater than that which

can be catered for by theventing system

vent design inadequate

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Training


89/90

one of the most important areas but onewhich the design engineer can influence byensuring the design philosophy is containedin the procedures for operating the plant

problems: -

operators are not properly trained

operating instructions do no not reflect the designintent

the combination of factors for the reaction involvedand simple failures of safety back-up systemscontributed to the severity of incidents

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Literature


90/90

IChemE: Guide to Chemical Reaction Hazards

IChemE: Relief Systems Handbook

IChemE: provides also a list of consultants,experts active in this field

Safety Lectures Handouts

Documents