7289717 Hazards and Risks Assessment Methods

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- L- LOÏCOÏC IISNARDSNARD --

EENVIRONMENTALNVIRONMENTAL HHEALTHEALTH - L- LEVELEVEL IVIVNNOVEMBER OVEMBER 19991999

HHAZARDAZARD/R /R ISK ISK AASSESSMENTSSESSMENT MMETHODSETHODS

&&

AAPPLICATIONSPPLICATIONS ININ EENVIRONMENTALNVIRONMENTAL HHEALTHEALTH & S& SAFETYAFETY PPRACTICERACTICE

CCOURSEWORK OURSEWORK 11

HHEALTHEALTH & S& SAFETYAFETY R R ISK ISK MMANAGEMENTANAGEMENT

UUNITNIT CCOO--ORDINATOR ORDINATOR ::SSHIRLEYHIRLEY FFANTIEANTIE



H!"# & R$% A%%'%%(')* M'*+,#%

Management of Health and Safety at Work

Regulations 1992

"'.$"' '(0,2'"% *, 3""2 ,* "$% %%'%%(')*%4(' "")5'(')*% *, $(0'(')* )'3'%%"2

('%"'%4 00,$)* 3,(0'*')* 0',0' )# "")5'6," 00",0"$*' $)6,"(*$,) )# *"$)$)5

FTA

CHA

Task

HAZOP

PPHA

ETA

What-if

QRA

FMECA

FMEA

???

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H!"# & R$% A%%'%%(')* M'*+,#%

Introduction

"The assessment and management of risk is fundamental in the provision of a safe

and healthy working environment. In addition to being a legal requirement in many

circumstances, risk assessment is an essential tool in the determination and

prioritisation of control measures" 1.

In order to realise this risk assessment, a lot of methods have been developed by the

risk professionals and then adopted in international regulations or standards. These

methods are most of the time easily understanding, but because of the wide variety of

them, the choice is sometimes difficult. At first sight, lots of Risk Assessment ethods

seems to be all the same, but they have all different aims and results! some methods

analyse probability of ha"ard, others search the root or immediate causes of an accident,

or try to demonstrate a failure in the system,#

This essay will try to e$plain briefly %& of these methods, and also to be a guide for

the choice of the most suitable risk assessment method in each cases.

A crucial distinction between different ha"ard'risk analysis methods is whether the

analysis starts with a component failure and tries to investigate the possible effects on

the occurrence of ha"ards (that I will call ) Type 1 Methods*, or whether they start with a

specific ha"ard an try to trace back by which sorts of component failures they may be

caused Type ! Methods*2.

% +$tract from the Risk anagement niversity ourse % - /hirley 0antie, /enior 1ecturer.2

3 ) ost of this essay is e$tract from the 4eoff 5ells6 book ) 7 a#ard Identification $%isk &ssessment 7 ! Reportto this book for further information on Risk Assessment ethods.

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H!"# & R$% A%%'%%(')* M'*+,#%

Type 1 MethodsType 1 Methods

11 F* T"'' A)2%$% -F* T"'' A)2%$% - FTAFTA

0ault Tree Analysis8 are widely used as communication aids to demonstrate system

failures and their development to manager, designers and operator. The use of fault tree

in 9ualitative analysis demonstrates the effect of system failure modes and design

changes.

This method starts with an identified ha"ard as the root of a tree and works

backwards to determine its possible causes. A cause can be defined as an A: or ;Rcombination of events, thereby revealing the combinations of component failures that

may cause the ha"ard. A 0ault Tree Analysis follow the system structure, such that the

upper levels in a fault tree correspond to the system, and the lower levels corresponds to

system components.

E7')*% G*'%

D'%$5)*$,) R'0"'%')**$,) D'%$5)*$,) R'0"'%')**$,)

T,0

&I)*'"('#$*' AND

N,"(,"

E'(')*"2OR

8 /ee e$ample of 0TA in Appendi$es

C,(0,)')*F$"'

HAZARDS

8 Investigate the possible effects on the

occurrence of haards8

- < -



H!"# & R$% A%%'%%(')* M'*+,#%

E7')* T"'' A)2%$% -E7')* T"'' A)2%$% - ETAETA

+vent Tree Analysis< can be used to analyse the probabilities of different outcomes

which have been identified during a safety study. +vent tree analysis takes at its starting

point the event that can affect the system and tracks them forward through se9uences ofinterfacing system components to determine their possible conse9uences.

0rom the event which initiates any specific accident se9uence, normally a significant

release, the functioning and failure of safety subsystems are analysed using forward

logic. This result in a tree structure with the branches developing from left to right. 3y

assigning a probability to each branch the probabilities of every possible outcome

following the initiating event can be determined.

C,)3'0* H!"# A)2%$% -C,)3'0* H!"# A)2%$% - CHACHA

oncept =a"ard Analysis is used for the identification of ha"ard characteristics in an

attempt to identify areas which are recogni"ed as being particularly dangerous from

previous incidents in the past.

;; P"'$($)"2 P",3'%% H!"# A)2%$% -P"'$($)"2 P",3'%% H!"# A)2%$% - PPHAPPHA

A >>=A follows up the results of oncept =a"ard Analysis to provide further

information on factors such as wanted and unwanted reactions, the reduction of ha"ards

and ha"ardous characteristics on the plant, the identification of incident scenarios and

the evaluation of emissions, effluents, wastes and off-specification products.

A#7)*5'%:

Identifies the potential for ma?or ha"ards at a very early stage of pro?ect development.

>rovides basis for design and siting decisions.

=elps to ensure plant to plant and plant to environment compatibility.

0acilitates a later full ha"ard analysis.

D$%#7)*5'%:

Is not comprehensive and must be followed by a full =A@;> before construction

begins.

< /ee e$ample of +TA in Appendi$es

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H!"# & R$% A%%'%%(')* M'*+,#%

<< W+*-I6 A)2%$% -W+*-I6 A)2%$% - W+*-I6 W+*-I6

5hat-If analysis uses a creative team brainstorming 7what if7 9uestioning approach

to the e$amination of a process or operation to identify potential ha"ards and their

conse9uences. =a"ards are identified, e$isting safeguards noted, and 9ualitative severityand likelihood ratings are assigned to aid in risk management decision making.

Buestions that begin with 7what-if7 are formulated by engineering personnel

e$perienced in the process or operation.

A#7)*5'%:

Team of relevant e$perts e$tend knowledge and creativity pool.

+asy to use.

Ability to focus on specific element (i.e. human error or environmental issues*.

D$%#7)*5'%:

Buality is dependent on knowledge, thoroughness and e$perience of team.

1oose structure can let ha"ards slip through.

:oes not directly address operability problems.

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H!"# & R$% A%%'%%(')* M'*+,#%

Type 2 MethodsType 2 Methods

11 F$"' M,#' )# E66'3* A)2%$% -F$"' M,#' )# E66'3* A)2%$% - FMEAFMEA

0ailure ode and +ffect Analysis assumes that the failure modes of the system

component are known. ;n the basis of these failure modes, the causes of each failure is

then evaluated in the system. 0+A is a forward analysis method, and investigates

effects of a single component failure! it is not possible to investigate the problem caused by combinations of component failures.

0+A is a fundamental ha"ard identification and fre9uency analysis techni9ue

which analyses all the faults modes of a given e9uipment item for their effects both on

other components and the system.

A#7)*5'%:

/ystematic, component by component analysis aids thoroughness.

3eneficial at all stages of a facility6s life.

an easily be updated for plant modifications.

D$%#7)*5'%:

ot efficient for identifying combinations of e9uipment failure.

:oes not directly address siting, general safety, or environmental issues.

:oes not directly address operability problems.

an be time consuming.

C,(0,)')*F$"'

HAZARDS

8!race back by "hich sorts of component failures they may be caused 8

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H!"# & R$% A%%'%%(')* M'*+,#%

F$"' M,#'%4 E66'3*% )# C"$*$32 A)2%$% -F$"' M,#'%4 E66'3*% )# C"$*$32 A)2%$% - FMECAFMECA

0+A is an e$tended variant of 0+A, where the criticality of each effect is

recorded.

H!"# )# O0'"=$$*2 S*#$'% -H!"# )# O0'"=$$*2 S*#$'% - HAZOPHAZOP

=A@;> is the most widely used method of analysis used in the process industries. It

is recommended for use by legislators, regulators and engineering institutions. A

=A@;> study is a formal, systematic e$amination of a processing plant in order to

identify ha"ards, failures and operability problems, and assess the conse9uences from

such maloperation.

A =A@;> study generates a list of identified problems, usually with some

suggestions for improvement of the system, and can be used for )

probabilistic safety assessment

design changes

development of operating instructions and procedures for use in training

9uality control and management standards

This method, in order to investigate the effects of deviations from normal operating

conditions during each phase of a system6s operation, use a series of guide words)

/ignificant release of material

0ailure to recover situation

:angerous disturbance of plant

Inade9uate emergency control

=a"ardous deviation

0ailure to control situation (on alarm*

>rocess deviation

Inade9uate normal control

Immediate causes of incident

A#7)*5'%:

ost systematic and comprehensive of methodologies.

an be used in con?unction with =uman +rror analysis.

>rovides greatest safety assurance.

D$%#7)*5'%:

an be time consuming and costly.

an be tedious if not well facilitated.

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H!"# & R$% A%%'%%(')* M'*+,#%

;; >)*$6$'# R$% A%%'%%(')* ->)*$6$'# R$% A%%'%%(')* - >RA>RA

Buantified Risk Assessment is widely used as a techni9ue to aid management

decision and defined by the ;A5+ organisation as) 7The identification of causes

of possible accidents followed by a technical analysis to determine the likelihood ofoccurrence and potential conse9uences of those accidents leading to a numerical

estimate of an appropriate measure of risk, together with the value ?udgements made

with regard to a significance of estimated level of risk7.

The steps of the method are )

=a"ard Identification

0re9uency +stimation

onse9uence Analysis

Risk +valuation

/ensitivity Analysis

The elements of the procedure are used both to generate information and as an aid to

decision-making.

<< T% A)2%$% -T% A)2%$% - T% T%

Task analysis has been developed as a systematic method for analysing a task into its

goals, operations and plans.

Task analysis is a process of sorting out what people might do or actually do when

carrying out operations. The analysis must answer to 9uestions such as )

5hat actions do the operators carry out F

=ow do operator respond to different cues in their environment F

5hat errors might be made an deviations caused in plant operations F

=ow might any error be recovered from, or any deviation be controlled F

=ow do operators plan their actions F

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H!"# & R$% A%%'%%(')* M'*+,#%

Conclusion

Risk assessment is the scientific process of asking how risky something is. It is a

process of collecting and analysing scientific data 7to describe the form, dimension, and

characteristics of risk 7. A lot of Risk Assessment ethods e$ist, but their is no good or

bad methods. Risk assessment can take different approaches depending on the purpose

and scope of the available information or data used in an assessment. :epending of

what you want to obtain by a risk assessment, you will need to use a specific method.

Risk assessment is re9uired by law, but is firstly a very good tool to prevent in?uries,

accidents on people or properties.

0or better outcomes, or in case of doubt in the choice of the method, different ones

should be used. The results of these methods would compare after to look for the more

relevant.

W,"# C,)* : 15281528

:orothy >atton, e$ecutive director of the +nvironmental >rotection Agency (+>A*

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H!"# & R$% A%%'%%(')* M'*+,#%

Internet References

S6'*2-C"$*$3 S2%*'( :http)''www.informatik.uni-bremen.de'Gagbs'lehre'safety%'riskanalysis.html

>)*$**$7' R$% A%%'%%(')* - ABS G",0 I)3? R$% & R'$=$$*2 D$7$%$,) :http)''www. abs-?bfa.com'9ra.html

H'*+ )# S6'*2 R'5*$,) - # short guide @H'*+ & S6'*2 E'3*$7' W'= S$*' :http)''www.open.gov.uk'hse'pubns'hsc%8.htm

F$7' %*'0% *, R$% A%%'%%(')* @H'*+ & S6'*2 E'3*$7' W'= S$*' :http)''www.open.gov.uk'hse'pubns'indg2%E.htm

A G$#' *, R$% A%%'%%(')* R'.$"'(')*% - $ommon provisions in health and safety la"@H'*+ & S6'*2 E'3*$7' W'= S$*' :http)''www.open.gov.uk'hse'pubns'indg%C8.htm

Bibliography

H!"# I#')*$6$3*$,) & R$% A%%'%%(')*4 G',66 W'%4 199<

(Institution of hemical +ngineers - I/3 & E2 8 <*

M," H!"#% & *+'$" M)5'(')*4 G',66 W'%4 199(Institution of hemical +ngineers - I/3 & E2 8C 2*

BS ;;; - 0"* : 199Risk management. 4uide to risk analysis of technological systems ( I+ C&8&&-8-)%*

Other Sources

R$% M)5'(')* U)$7'"%$*2 C,"%'4 S+$"'2 F)*$'4 S')$," L'3*"'"4 U)$7'"%$*2 ,6G"'')$3+

' Introduction to (ualitative %isk &ssessment in ) Management , th of ;ctober %

' a#ard Identification, %2th of ;ctober %

FTA U)$7'"%$*2 C,"%'4 Y7'% D*$*4 S')$," L'3*"'"4 U)$7'"%$*2 ,6 B,"#'4D'0"*(')* E)7$",)(')* H'*+ )# S6'*24 F")3'

- %% -

http://www.informatik.uni-bremen.de/~agbs/lehre/safety1/riskanalysis.html

http://www.lawrights.co.uk/


http://www.open.gov.uk/hse/pubns/hsc13.htm

http://www.open.gov.uk/hse/pubns/indg218.htm


http://www.informatik.uni-bremen.de/~agbs/lehre/safety1/riskanalysis.html


http://www.open.gov.uk/hse/pubns/hsc13.htm





H!"# & R$% A%%'%%(')* M'*+,#%

Appendixes

D'6$)$*$,)%

H!"#/R$% A%%'%%(')* M'*+,#% )# *+'$" %'(+$tract from Ma*or a#ards and their Management , 4eoff 5ells*

R$% A%%'%%(')* T'3+)$.'%(+$tract from the %isk Management +niversity ourse, /hirley 0antie*

F* T"'' A)2%$% - E(0'(+$tract from the -T& +niversity ourse, Hves :utuit*

E(0' ,6 E7')* T"'' ,6 5% "''%'

(+$tract from Ma*or a#ards and their Management , 4eoff 5ells*

R,' )# %' ,6 >)*$6$'# R$% A%%'%%(')*(+$tract from the %isk Management +niversity ourse, /hirley 0antie*

F"*+'" I)6,"(*$,)

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H!"# & R$% A%%'%%(')* M'*+,#%

DefinitionsDefinitions

H!"#

7 & physical situation with a potential for human in*ury, damage to property, damage

to the environment or a combination of these7.

R$%

7The likelihood of a specified undesired event with a specified period or in

specialised circumstances7.

R$% A%%'%%(')*7The act of *udging the significance of the risk and prioritise the different risks7.

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H!"# & R$% A%%'%%(')* M'*+,#%

Hazard/isk Assess"ent Methods and their #seHazard/isk Assess"ent Methods and their #se

CHA PPHA HAZOP FMEA FTA ETA T% >RA W+* - I6

Root auses

Immediate

auses

ontrol of

situation

Release of

material

Release

mitigation

:amage and

harm

:eviations from

good practice

=a"ard

identification

Incident

scenarios

1ikelihood of

event se9uencesRelative

Buantitativ

e

Buantitativ

eBuantitative

Buantitativ

e

agnitude of

conse9uencesRelative

Buantitativ

e

Risk assessment >rioriti"e onte$tBuantitativ

e

CHA - oncept =a"ard Analysis

>rimaryPPHA - >reliminary >rocess =a"ard Analysis /econd

HAZOP - =a"ard and ;perability studies

FMEA - 0ailure ode and +ffect Analysis

FTA - 0ault Tree Analysis

ETA - +vent Tree Analysis

T% - Task Analysis

>RA - Buantified Risk Assessment

W+*-I6 - 5hat-If Analysis

- %< -



H!"# & R$% A%%'%%(')* M'*+,#%

isk Assess"ent Te$hni%#esisk Assess"ent Te$hni%#es

DEFINE SYSTEM3oundaries, aims, information

IDENTIFY HAZARDS

ANALYSEEFFECTS/CONSE>UENCES

In?ury severity, e9uipment damage,

fire'e$plosion,#

ESTIMATE OVERALL RISK (0re9uency* $ (onse9uences*

REECT/ACCEPT RISK

ompare )odes of practice, e$isting situation,

targets'criteria

ontinuing

=a"ards

echanical, non-

mechanical

=a"ards as a Result

of 0ailures m'c

components, safety

system,

management

system

MODIFYSYSTEMTechnical,

procedural

NO CHANGEmonitor

heck list

/afety inspection/afety auditsAccident /tatistics+$perience

=a"ard Indices=A@;>0+ATask Analysis

+TA

odelling

umerical :ata

(probability or fre9uency*)

Reliability Technology=uman Reliability

Analysis0TA

ost-benefit Analysis

Tolerability of Risk 0atal Accident RateIndustry average

Target'riteria

odifications

aintenancehanges

+ /tandardsRegulations

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H!"# & R$% A%%'%%(')* M'*+,#%

Fa#&t Tree Ana&'sis - E(a")&eFa#&t Tree Ana&'sis - E(a")&e

= ) =igh 1evel /ensor

T= ) Jery =igh 1evel/ensor

The risk is the ,7'"6,$)5 ,6 *+' *) . ormally, the water 9uantity reduce according to the consumption and increase according to the

source.

If the consumption stop, the level increase until the = /ensor stop automatically the source

(in closing the 0loodgate %*.

If it6s failing, the T= /ensor stop automatically the source (in closing the 0loodgate 2*, and

warn the ;perator.

In case of failure of the 0loodgate 2, the ;perator should close manually the 0loodgate 8.

The 0loodgates % K 2 are the same, so they have the same characteristics and same parameters of

probability. It6s the same for the = K T= /ensors.

- %C -



H!"# & R$% A%%'%%(')* M'*+,#%

and

Over flowing of the tank

No stop of thesupply

Floodgate 3 nonopened

and

No stop by thefloodgate 1

No stop by thefoodgate 2

Floodgate 3 no turnedon by the operator

No flow

or

or or

Floodgate1 no turnedon

Floodgate2 no turnedon

Floodgate 1

Failure of the NHsensor

or

Operator deficiency

Failure of the NTHsensor

Failure of the NTHsensor

Floodgate 2

Floodgate 3

Sensor

uto!aticfloodgate

Sensor Operator

Sensor

uto!aticfloodgate

"anualfloodgate

- %D -



H!"# & R$% A%%'%%(')* M'*+,#%

E(a")&e of E*ent Tree for a +as re&easeE(a")&e of E*ent Tree for a +as re&ease

L"5' 5% "''%' I(('#$*' $5)$*$,)=2 0",3'%% 6('

D'2'# $5)$*$,) =2)2 %,"3'

E0,%$,) ),* 6%+6$"'

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0L &.&&%'y

Hes (&.E*

Hes (&.%*

Hes (&.*

o (&.2*

o (&.*

o (&.*

Torch 0ire 0L &.&&E'y

J+ 0L &.&&&&%'y

0lash'Torch fire 0L &.&&&&%'y

:ispersion 0L &.&&&%E'y

- %E -



H!"# & R$% A%%'%%(')* M'*+,#%

o&e and #se of a ,#antified isk Assess"ento&e and #se of a ,#antified isk Assess"ent

I#')*$62 0",='(

D'6$)' %3,0' ,6 )2%$%

S')%$*$7$*2 )2%$%

E7*' "$% '7'% 5$)%* 3"$*'"$

E7*' *+' "$% 6",( +!"#%

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E%*$(*' 6"'.')3$'% )#

3,)%'.')3'% ,6 +!"#%

M,#$6$2 *+' %2%*'( *, "'#3' "$%

>RA #'3$%$,)

F$) #'3$%$,)

I(0'(')* *+' #'3$%$,)

I#')*$62 %3')"$,%

R$% 3"$*'"$

O*+'" 63*,"%

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H!"# & R$% A%%'%%(')* M'*+,#%

F#rther nfor"ationF#rther nfor"ation

M)5'(')* ,6 +'*+ )# %6'*2 * ," (Approved ode of >ractice 12% - I/3 & D%DC &<%2 E*

E%%')*$% ,6 +'*+ )# %6'*2 * ," - "# '#$*$,) - 199;(I/3 & D%DC &D%C M*

F$7' %*'0% *, "$% %%'%%(')*(I:(4*%C8(1*, free*

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7289717 Hazards and Risks Assessment Methods

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