L4 PHA Student Handout

7/28/2019 L4 PHA Student Handout

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Calgary Tel 1-403-221-8077 Fax 1-403-221-8072E-mail: [email protected] Website: www.seal.ab.ca

PROCESS HAZARDS ANALYSIS

LEADERSHIP TRAINING

NPC TRAINING PROGRAM

STUDENT HANDOUT

Presented byMarcel Leal-Valias


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PROCESS HAZARD ANALYSIS

S.E.A.L. InternationalI

Table of Contents

COURSE OBJECTIVES.................................................................................................. 1

COURSE OBJECTIVES ....................................................................................................... 1OVERVIEW OF PHA ......................................................................................................... 2PHA IN ANUTSHELL........................................................................................................ 3HISTORY OF PHA............................................................................................................. 4

QUANTITATIVE & QUALITATIVE HAZARD ANALYSIS.................................... 5

QUANTITATIVE AND QUALITATIVE HAZARD ANALYSIS OVERVIEW ................................ 5PHA AND RISKANALYSIS COMPARED ............................................................................ 6

OVERVIEW OF HEALTH, SAFETY & ENVIRONMENT HAZARD

MANAGEMENT .............................................................................................................. 7

SAFETY MANAGEMENT SYSTEMS REVISITED BY HAZARDS ANALYSIS ........................... 9

ELEMENTS OF FACILITY RISK .............................................................................. 13

PROCESS ACCIDENTS ..................................................................................................... 14PROCESS RISKREDUCTION STRATEGIES........................................................................ 15HUMAN FACTORS IN FACILITY RISK.............................................................................. 15

Factors Influencing Human Performance ................................................................ 17Human Error In Accident Causation........................................................................ 18Human Error Risk Reduction Checklist at Different Levels of Interaction.............. 21

SITING ISSUES IN FACILITY RISK.................................................................................... 22ENVIRONMENTAL ISSUES IN FACILITY RISK................................................................... 23

PHA TEAMS................................................................................................................... 25

SIZE OF PHATEAM ....................................................................................................... 25WHY A TEAM APPROACH?............................................................................................. 25RESPONSIBILITY OF GROUP PARTICIPANTS IN PHAS ..................................................... 27THINKING SKILLS REQUIRED OF PARTICIPANTS IN PHAS .............................................. 27

PHA METHODOLOGIES ............................................................................................ 30

VIDEOPROCESS HAZARDS ANALYSIS......................................................................... 30GENERAL PHAPROCEDURE FLOW CHART .................................................................... 31OBJECTIVES OF A GOOD PHASTUDY ............................................................................ 32PROCESS SAFETY INFORMATION FORHAZARDS ANALYSIS............................................ 32VIDEOPROCESS SAFETY INFORMATION...................................................................... 32METHODOLOGIES OVERVIEW ........................................................................................ 35

HAZard and OPerability Analysis (HAZOP) ........................................................... 35Preliminary Hazards Analysis.................................................................................. 44Checklist Analysis ..................................................................................................... 47What-If Analysis........................................................................................................ 49What-If/Checklist Analysis........................................................................................ 51Failure Modes and Effects Analysis (FMEA)........................................................... 53


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S.E.A.L. InternationalII

Other PHA Methodologies Reserved for Specific Safety Concerns.......................... 57ADVANTAGES AND DISADVANTAGES OF PHAMETHODOLOGIES .................................. 58LIMITATIONS OF PHA.................................................................................................... 59

METHODOLOGY SELECTION CRITERIA ............................................................ 60

FACTORS TO CONSIDERWHEN SELECTING THEAPPROPRIATE PHAMETHODOLOGY.. 60Purpose of Study ....................................................................................................... 60Type of Results Required .......................................................................................... 61Type of Information Available .................................................................................. 61Time Frame for Completion of Study........................................................................ 61Development Phase of the Facility ........................................................................... 62Relative Risks Associated with Chemicals, Process and/or Facility Location......... 64PHA Team Experience Level .................................................................................... 65Operating History (Past Incidents)........................................................................... 65Resource Availability and Management/Leader Preference .................................... 65

METHODOLOGY SELECTION FLOW CHART .................................................................... 66COST BENEFIT CONSIDERATIONS................................................................................... 67

DOCUMENTATION ISSUES....................................................................................... 68

DOCUMENTATION FORDECISION MAKING .................................................................... 68DOCUMENTATION FORFUTURE REFERENCE .................................................................. 68WORKSHEET REPORT..................................................................................................... 69COMPLETED REPORTS.................................................................................................... 70

Usual Format for PHA Report.................................................................................. 71LEGAL ISSUES (DUE DILIGENCE)................................................................................ 72

PHA LEADERSHIP....................................................................................................... 73

PHAFACILITATION SKILLS ........................................................................................... 73

TEAM LEADERQUALIFICATIONS ................................................................................... 73PHALEADERSHIP RESPONSIBILITIES............................................................................. 74

Causes and Solutions for PHA Quality Problems .................................................... 77PHAGROUP DYNAMICS ................................................................................................ 78GETTING THE BEST FROM YOURTEAM ......................................................................... 80

PHA WORKSHOP (HAZOP & WHAT-IF)................................................................ 84

DEFINING SCOPE AND OBJECTIVE OF PHAS................................................................... 84ESTIMATING TIME FORPHAS AND PLANNING SCHEDULE ............................................. 87QUALITATIVE RISKRANKING MATRIX FORPHAS......................................................... 89FIRST MEETING.............................................................................................................. 93

DOCUMENTING THE PHAWORKSHEET ......................................................................... 94CREDIBILITY OF CAUSES................................................................................................ 95ACCIDENT CAUSES CATEGORIES TO BE CONSIDERED BY PHATEAM .......................... 97PHAFOLLOW-UP .......................................................................................................... 98

PHA WORKSHOP DRAWING RESOURCES .......................................................... 99

APPENDIX.................................................................................................................... 101

GLOSSARY OF PHATERMS.......................................................................................... 101


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S.E.A.L. InternationalIII

COMMON HAZOPTERMINOLOGY............................................................................... 108SIMPLIFIED CHECKLIST FORHAZARD ANALYSIS ......................................................... 110SAMPLE HAZARD CHECKLIST ...................................................................................... 114SAMPLE MATERIAL INCOMPATIBILITY INDEX.............................................................. 118LIST OF HIGHLY HAZARDOUS CHEMICALS,TOXINS AND REACTIVES .......................... 119

METHODOLOGY SELECTION AND/ORPRIORITY ORDERING WORKSHEET FORCONDUCTING PHAS .................................................................................................... 124ARTICLE....................................................................................................................... 131

Extend HAZOP to Computer Systems ................................................................ 131ARTICLE....................................................................................................................... 132

Culture................................................................................................................ 132STANDARDS ................................................................................................................. 133

Management of Process Hazards....................................................................... 133STANDARDS ................................................................................................................. 134

OSHA 29 CFR PART 1910................................................................................. 134

READING ENGINEERING DRAWINGS ................................................................ 135

TYPES OF ENGINEERING DRAWINGS USED IN PHASTUDIES ....................................... 135OVERVIEW OF READING P&IDS .................................................................................. 136

Valve Markings ....................................................................................................... 136Examples of P&ID Abbreviations........................................................................... 137

ENGINEERING DRAWING INFORMATION....................................................................... 139Function Blocks ...................................................................................................... 140Reference Symbol Sheets......................................................................................... 142General Symbols ..................................................................................................... 143Instrument/Process Line Symbols........................................................................... 147Valve Body Symbols................................................................................................ 148Self Actuated Valves................................................................................................ 150Flow Rate Symbols.................................................................................................. 152Actuator Symbols .................................................................................................... 154Typical Letter Combinations................................................................................... 155

GENERAL REFERENCES......................................................................................... 156


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S.E.A.L. International1

CCOOUURRSSEE OOBBJJEECCTTIIVVEESS

Course Objectives

The objectives for this course are:

To build an understanding of the concepts of Process Hazards Analysis (PHA)

and its role in Health, Safety and Environment management.

To provide a basic understanding of all the major hazard identification techniques

and when each should be used.

To provide an understanding of the responsibilities involved in PHA leadership.

To provide basic skills and practice in the use of the What-If and HAZOP

techniques.

To provide training in the use of software as a tool in the facilitation of PHA.


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Overview of PHA

A PHA is a systematic multidisciplinary team study. It focuses on identifying and

analysing the significance of potential process hazards and on making initial

recommendations for eliminating and/or reducing the consequences of potential

incident/accidents.

A PHA is the foundation of any Process Safety Management Program.

A PHA is interested in the potential causes, likelihood and consequences of

process incidents.

A PHA works by combining the experience, knowledge and intuitive

imaginations of expert team members with a selected analytical methodology.

A PHA provides companies with the information necessary to make operating

decisions, to help improve safety, and to manage the risk of operations.

Various hazard identification methodologies provide flexibility according to time

scope and objectives of study.

A PHA should be conducted several times during a facilitys design, construction

and operating life cycle.

Some methodologies not only identify hazards, but also operability problems.

A PHA assigns qualitative likelihood and severity ratings from which a relative

risk ranking can be estimated.

A PHA identifies high level hazards for possible further quantitative risk analysis.


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S.E.A.L. International

PHA in a Nutshell

FOUNDATION FOR PROCESS HAZARDS ANALYSIS

Historical

Experience

PHA

Methodology

Kno

and I


What can gowrong?

How likely is

it?

What are

consequen


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History of PHA

HAZOP, the first formal PHA, was developed in the UK at ICI over 30 years ago.

Other methodologies have followed as requirements for less comprehensive and

time consuming reviews have emerged.

The occurrence of major industrial accidents and the subsequent forceful safety

and environmental legislation throughout the world has led to Process Safety

Management (PSM) or Process Hazards Management becoming an industry

standard.

Companies have become increasingly aware that operating a safer facility leads to

a more profitable business and that, in the long run, safety is in the best financial

interest.

Development of sophisticated software to aid in the sometimes tedious task of

PHA has lead to its adoption throughout the process chemical industry.

PHA was legislated (1992) in the USA as part of OSHA CFR 29, Part 1910.

PHA is part of American Petroleum Institute (API) Recommended Practice 750,

1990, which stands as the recommended standard for Canadian process industries.

OSHA 29 CFR, British Standards 8800 and Norwegian regulations have become

the world standards.


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QQUUAANNTTIITTAATTIIVVEE && QQUUAALLIITTAATTIIVVEE HHAAZZAARRDD AANNAALLYYSSIISS

Quantitative and Qualitative Hazard Analysis Overview

Safety is Good Business Both qualitative and quantitative hazard analyses are important in identifying and

analysing risk.

It is a given that money properly spent on safety increases profitability through

fewer injuries and reduced lost time, and through reduced property and production

losses.

However, too much money can be spent on safety and the benefits can be

outweighed by the cost. For instance, if the predicted expenditure to remove an

identified hazard is very high, it will be necessary to statistically quantify its

probability and the scope of its consequence to decide how it can be best

minimized.

PHA is the initial predictive identification of potential hazards.

RISK ANALYSIS provides a statistically based quantitative assessment of the

probability and consequence of major hazards identified in a PHA.


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PHA and Risk Analysis Compared

PHA RISK ANALYSIS

Initial predictive identification of all

potential hazards - estimates likelihoodand severity, suggests improvements

USE ON EVERY PROJECT- at everystagefrom concept throughdecommissioning

QUALITATIVE- based on the experience,knowledge and creative thinking ofworkers involved in the process

MULTIDISCIPLINARY TEAM

Several methodologies available

What-if

What-if/Checklist HAZOP

FMEA

Preliminary Hazards Analysis

Subsequent assessment of major hazards

only statistically based probability /consequence hazard assessment

SELECTIVE- if the potential exists for acatastrophic accident or if no easy andobvious solution to identified hazard isevident

QUANTITATIVE- requires extensivestatistical data and specialized expertise very costly

ONE OR TWO SPECIALLY TRAINED

PEOPLE

Also called:

Hazan

Risk Assessment Probabilistic Risk Assessment (PRA)

Quantitative Risk Assessment (QRA)


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OOVVEERRVVIIEEWW OOFF HHEEAALLTTHH,, SSAAFFEETTYY && EENNVVIIRROONNMMEENNTT HHAAZZAARRDD

Health, Safety & Environment

Cost SavingsQuality Production

Customer Satisfaction

Process Review

ManagementCommitment

Hazard C

Hiring &Health

Monitoring

Inspections

Accident /Incidents

Hazard Assessment

Off-The-Job Safety

EmergencyPreparedness

& Response

Com

HSE SteeringCommittee

HazardousMaterials

PreventativeMaintenance


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Safety Management Systems Revisited By Hazards Analysis

Hazard identification and assessment has to be the starting point for successful HSE

management. The information gained from a PHA about potential hazards, is essential to

any HSE Management Program. Human, process, equipment, environmental and

production hazards can be identified and the information used to develop and fine-tune

all the component systems of a Safety Management Program.

Let us revisit the HSE Management System introduced in the introductory session, this

time reflecting on the pivotal role that PHA plays in each component.

Management Commitment

provides the essential information for risk management decision making

can pinpoint gaps in management and administrative controls

demonstrates management commitment to the safety of personnel boosting

employeemorale

Hazards Identification and Assessment

identifies a wide range of hazards to people, process, structures, equipment, and

the environment, e.g. chemical, biological, ergonomic, radiation, etc.

identifies actual and hidden potential hazards

allows hazards to be prioritised according to risk ranking making management

decision making easier

identifies high risk hazards requiring further quantitative analysis

can provide recommendations for mitigating consequences of accidents

highlights opportunities for improving operability

Hazard Controls

Rules & Procedures

design layout information can identify design errors and highlight opportunities

for debottlenecking and improving operability.

identifies a need for formal operating, maintenance and emergency procedures


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highlights weaknesses in existing procedures

can be adapted to perform Job Hazard Assessments and Critical Task Analyses

identifies the need for a refresher training schedule

Management of Change

identifies design or material errors of the proposed change

follows the effect of the proposed change on the rest of the process and facility

identifies where procedures are missing and need to be improved

identifies where additional training may be required

identifies the health, safety and environmental considerations of proposed changes

can provide initial recommendations for mitigating consequences of accidents

Contractor Management

identifies requirement for procedures and training

identifies potentially hazardous interaction with the operation

Training - Management & Employees

trains management and PHA participants in the hidden hazards of their workplace

highlights gaps and deficiencies in training

Communication (Record Keeping)

highlights gaps and deficiencies in communication

provides reported and stored information about hazards and gaps in Safety

Management Systems

provides recorded system for resolution of HAZOP recommendations

identifies the hazard potential of proposed changes

provides the opportunity to prove due diligence

Inspections

provides a paper trail for resolution of recommendations for hazard reduction

highlights gaps and deficiencies in HSE Management


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Hazardous Materials

identifies potential immediate and long term health concerns

identifies potential chemical interaction hazards

identifies gaps in existing precautionary procedures

can provide recommendations for mitigating consequences of accidents

Hiring & Health Monitoring

identifies areas where additional health monitoring may be required

Emergency Preparedness & Response

identifies potential types of emergencies and harm

identifies gaps and deficiencies in the Emergency Response Plan

Accident/Incident Investigation

provides a paper trail for accident/incident investigation

provides valuable past incident information for a PHA - highlights potential

hazards

HSE Steering Committee

identifies workplace hazards

identifies need for additional controls

Preventive Maintenance

identifies areas and equipment requiring regular preventive maintenance

trains maintenance personnel in the process and its potential hazards

Off The Job Safety

assists participants with general safety awareness

Process Review/Audit

provides the basis for an audit

broadly identifies the actual or potential gaps in the overall Safety Management

System

provides paper trail


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Conclusion

Proactively taking care of the safety of people, production, equipment and the

environment makes good economic sense. The way to start to take care of safety is by

identifying and assessing the actual and potential hazards in the facility and by putting a

well-planned system in place to manage them.

If you do not know what can go wrong, or how often it is likely to go wrong and what the

consequences may be, it is impossible to plan or operate a safety system effectively.

Often, time and money can be spent reacting to accidents and near misses without

really getting very far in reducing the existing and potential hazards and their associated

visible and hidden costs.


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EELLEEMMEENNTTSS OOFF FFAACCIILLIITTYY RRIISSKK

Hazard potential arises from any combination of risk elements, such as process, material,

siting, environment and human interaction, and exists at all levels throughout a facility

lifecycle.

To identify ways to eliminate or reduce the frequency and consequences of process

accidents, it is essential to understand the breadth of hazard potential in a facility. Process

hazards are always a combination of hazardous materials and the conditions under which

they are handled. However, it usually takes a sequence of events to create an accident

outcome. The important thing to remember as a PHA facilitator or participant is that each

event in the sequence presents an opportunity to avert the accident or to mitigate the

severity of its outcome. PHAs can play an important educational role in helping workers

participating in them to understand potential accident sequences in their facility and see

the significance of failure of defenses at any level.

Process accidents are rarely the result of isolated events; they are usually the result of a

sequence of failures or errors.

Initiating events are the first events in an accident sequence, the event or action that

sets off a chain reaction. Sometimes the initiating event may be the only event if there

is no built in protection against it or the event is so severe that existing protection is

overwhelmed by the event.

Propagating events are the secondary events that link an initiating event to an

accident outcome. These events are the responses that engineered safety features and

administrative controls make when the initiating event occurs. Usually these events

can be correlated to equipment failure, human error, inadequate safety defences,

inadequate administrative controls or unusual external conditions.


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Process Accidents

HAZARDOUS MATERIALS + PROCESS CONDITIONS

INITIATING EVENTS

Design ErrorsManagement System FailuresHuman ErrorsExternal Events

PROPAGATING EVENTS

Equipment FailuresSafety System FailuresIgnition SourcesManagement System FailuresHuman ErrorsExternal Contributions (e.g. theweather)

ACCIDENT OUTCOMES

EmissionsFiresExplosions

Projectiles

ACCIDENT EFFECTS

Toxic (acute & chronic)ThermalOverpressure

RadiationContamination

DAMAGE ASSESSMENTS

EmployeesSurrounding CommunityEnvironment

ProductionCompany AssetsCompany ReputationCompany Liability


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Process Risk Reduction Strategies

Risk reduction strategies are built-in defenses and appropriate responses to initiatingevents that avert an incident or mitigate the severity of outcome.

Operator Control Systems Alarms/early warning

Control system response

Manual and automatic ESD Fire/gas detection system

Operating Safety Systems Relief valves

Depressurization systems

Isolation systems High reliability trips

Back-up systems

Specially designed structures

Mitigation Systems

Dikes and drainage Flares

Fire protection systems

Explosion vents

Toxic gas absorption

Ventilation systems

Emergency Plans

Sirens/warnings Emergency procedures

Personnel safety equipment

Safe shelters

Escape and evacuation

Management

Commitment to Safety ManagementProcess Safety Information availableand up to date.

Training Systems

Operations

Contractors Procedures

Source: Adapted from Table 1.3, Guidelines for Hazard Evaluation Procedures, AIChE, New York, 1992.

Human Factors in Facility Risk

Human error is seen as the incompatibility of task demands and human emotional, mental

and physical capabilities. Human errorhas been the major cause of almost all

catastrophic accidents in the chemical process industry and has an ultimate impact on

profitability through losses and lower quality product. Human error can be reduced if the

workplace culture and the tasks within it are designed with consideration for the needs

and capabilities of those who will interact with it.


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The PHA objective, in considering human factors in facility risk, is to look at all aspects

of potential human interaction with a process to predict what could possibly happen.

When human causes are taken into account, hazards that appear unlikely on a hardware

level may significantly increase in likelihood.

SCOPE OF HUMAN ERROR

HUMAN FAILURE

ERRORS VIOLATIONS

Deliberate actions Different from those prescribed

Carries known associated risks

Ignores operational procedures

Violation errors occur because of aperception of lack of relevance, timepressure or laziness.

Competency exists

Intentions are correct

Slips occur while carryingout habitual, routine, skillbased activity automaticpilot syndrome

Incorrect intention

Inadequate knowledge

Incorrect information processing

Inadequate training

Mistakes occur because of poor attitude, incorrectassumptions or incorrect tunnel vision application ofrules.

SLIPS MISTAKES


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Source: Adapted from Fig. 2.6, Guidelines for Preventing Human Error in Process Safety, AIChE, New York, 1992

Factors Influencing Human Performance

As humans interface with processes and systems, they can be considered a liability or a

safeguard. Factors that influence performance and create liability need to be considered

when attempting to identify potential human error hazards. The following factors must

be considered when attempting to identify the potential for human error.

Economic and Political Environment

regulatory climate

legislation

general economic conditions

Corporate Policy and Management Systems

safety culture and policies

resource allocation

Process Environment

materials handled

complexity of process

frequency of human interaction

perceived danger by workers

protective clothing and equipment

Physical Work Environment

noise

lighting

temperature

environmental conditions


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Work Control Systems

supervision

standard, emergency, maintenance and contractor procedures

level, clarity and frequency of training/instruction

quality of checks and warnings

frequency of use

Working Conditions

work hours

shift rotations

distribution of work contractor interaction

Operator Attributes

training

skill and experience

physical/intellectual capability

morale and motivation

Human Error In Accident Causation

Human error is either an active or a latent (waiting to happen) error.

Active Human Error

Active human error has an immediate and direct effect on the cause of a hazardous

situation or is the direct initiator of a chain of events, which leads to an accident.

Latent Human Error

Latent human error is different in that the consequences of the error may only become

dynamic after a period of time when the condition caused by the original error combines

with other errors or system failures to bring about unsafe conditions.

Latent human error is of the most concern for PHA teams. Most latent human errors

occur at the engineering design or at management policy level. It is at the engineering


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design level that PHA study teams must be most vigilant. For instance, inappropriate

design for valve placement or inadequate space allowed for worker movement in

attending to routine inspections and maintenance will increase the probability of active

errors.

The Flixborough disaster discussed in the video in the introductory session is an example

of latent human error. Engineering staff should have realized that the constant pressure

fluctuations within and between the reactors would have an adverse effect on the

temporary bypass pipe if it were not adequately supported.An error of this kind would

have been picked up in a well-conducted PHA of the modification.

The value of having knowledgeable and diversely experienced PHA team members

becomes particularly evident when dealing with the potential for human error during a

PHA.

WINDOW OF INCIDENT OPPORTUNITY


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Inappropriate policies at the corporate level, or incorrect or deficient implementation of

policies by management at the line level can create an error inducing environment at the

operational level. This environment at the process and physical work level leaves the

door for actions or decisions that are unsafe. If engineering and human defenses against

foreseeable hazards at any level prove inadequate, an incident will occur.

The individual who performs the action leading to an incident is usually the last straw

that breaks the system already made vulnerable by the latent errors of poor management.


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Human Error Risk Reduction Checklist at Different Levels of Interaction

MANAGEMENT

Tangible management commitment to

facility safety and training is shown.

Process safety information is keptcomplete and current.

Safety policies are clearlycommunicated to employees.

Appropriate employee participation ispart of safety management.

PROCEDURES

A task analysis has been performed.

Critical tasks have been identified.

Critical task deviations have beenanalyzed for potential hazards.

Tasks are designed for the humans whowill perform them.

Routine/non-routine and emergencyprocedures are current, appropriate,clear, concise and consistent.

Procedures provide quality checks andwarnings.

Procedures are used.

WORKING CONDITIONS

Noise, lighting and temperature are atappropriate levels.

Adequate protective clothing andequipment is provided.

Hours worked are appropriate forcomplexity of continuous taskperformance.

Shift rotation allows for optimalperformance.

DESIGN AND CONSTRUCTION

Equipment is accessible, clearlylabeled.

Materials used comply with appropriatecodes and standards.

Adequate safety measures are built intodesign.

Adequate containment of hazardouschemicals is built into design.

Buildings are designed and sited tocomply with existing guidelines andstandards for worker and equipmentprotection.

Buildings are appropriately located inrelation to hazardous materials or

processes.

TRAINING

Quality training is provided for all newemployees.

Performance is evaluated and trainingis refreshed regularly.


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Siting Issues in Facility Risk

Siting issues should be addressed in every PHA, or for a large complex facility, siting can

be the subject of its own specialised PHA. Siting includes the physical site of the

facility, the location and layout of equipment, and the location of hazardous materials,processing and storage. Siting issues are considered in relation to the people who occupy

the site for any length of time and the geographic and environmental implications.

During a PHA, the following are some of the issues that need to be considered.

Site Selection Considerations:

(Usually considered at conceptual stage of facility lifecycle.)

adjacent facilities

nearby communities

transport availability

availability of utilities (e.g. power and water)

topography and average weather conditions

environmental sensitivity

Layout Considerations:

industry and insurance guidelines and statutory regulations

process materials being handled or stored (inherent properties)

extremity of physical process conditions

location and spacing of process plant buildings and equipment to provide access

for routine operation and emergency services

location and spacing of process plant buildings and equipment to ensure safe

distances from process and storage of hazardous chemicals

buffer zones between hazardous material storage and extreme processes to reduce

potential for domino effects

building design and construction standards to withstand the intrusion of fire,

explosion and toxic effects

occupancy level of areas in proximity to process units and material storage


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Protective Mechanisms and Equipment:

containment

drainage

fire proofing

ventilation

explosion barriers

crash barriers

fire water supply

NOTE: PHA-Pro provides a comprehensive Siting Checklist in the OSHA templates

Environmental Issues in Facility Risk

PHAs are not only interested in the safety of life and production, but international

regulations and human responsibility insist that they are also interested in the safety of

the environment.

The following are some of the issues that should be considered during a PHA.

On and off-site contamination:

ground water contamination contaminated surface water run-off

soil contamination

plant life

food chain

air quality and ozone depletion

Human impacts:

Chronic and acute exposure to toxic materials through contaminated drinking water,

agricultural products and air.

allergies

eye irritation

lung damage


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genetic mutations

poisoning

Wildlife impacts:

migratory routes

critical habitats for endangered species

genetic mutations

Domestic animal impacts:

contamination of feed and water

genetic mutations

poisoning

impact on agriculture and food supply

Micro/Macro biological impacts:

ecosystems

food chain

surface and ground water

air quality

eradication of habitat or species


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PPHHAA TTEEAAMMSS

A PHA is performed by a multidisciplinary team experienced in engineering, operations

and maintenance. Other relevant experts should be included as required. At least one

member of the team should have knowledge specific to the process being evaluated and

at least one member should be knowledgeable in the PHA methodology being used and

impartial in the evaluation.

Size of PHA Team

As few as two or three and as many as seven or eight depending on the

methodology chosen and the size and complexity of the facility. Too many

participants reduce the efficiency of any PHA.

Why a Team Approach?

Advantages of team approach:

Range of expertise and experience creates a wide information pool base for

decision-making.

Representatives from different cultural groups in a facility can bring multiple

perspectives to problems and the implications of proposed actions. (See article

Culture in Appendix.)

Multidisciplinary teams provide an inclusive safety culture in which to learn

about, and understand other operating cultures.

Groups can make higher quality decisions because they have a greater combined

capacity to comprehend a problems complexities and its alternative solutions.

Groups can fill in each others blind spots and jolt each other out of rigid

thinking.

Groups can help each other see the big picture more clearly.

Groups stimulate creativity by piggy backing on each others ideas to

sometimes create an unusual solution to a routine problem.

Groups can enhance commitment of participants to carry out the groups decision.


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Disadvantages of team approach:

Time Pressure

Groups can feel the pressure of time and rush through a discussion so it is

necessary to avoid using arbitrary deadlines; assess the demands of the task

realistically before estimating the deadline.

Social Pressure

Groups can feel pressure to conform to group norms (e.g. participants will

frequently accept the first feasible solution that seems acceptable to the majority

of members while other, perhaps superior, solutions go unexamined).

Groups can succumb to groupthink and minimise critical testing of ideas

because of a fear that conflict will create disharmony (often happens in close knit

groups such as facility co-workers).

Ego Pressures

Group pressure sometimes can lead to ego defensive strategies that are counter-

productive to group efficiency.

Domination of discussion by one individual can inhibit challenges to the ideas of

the talker and the presentation of alternative points of view.

Apprehension by participants perceiving themselves as having lower status than

others in the group can lead to acquiescence to the ideas of members seen as

having higher status.

A competitive environment destroys group effectiveness when members allow

individual goals of winning the argument to take priority over the shared goal of

solving the problem.

Egocentric communication within a group does not listen to the ideas of others so

decisions are often made according to whoever pushes their own point of view the

hardest.


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It is the responsibility of both participants in PHAs and the leaders of PHA teams to

recognize the negative potential within the group and work towards creating group

cohesion and efficiency.

Responsibility of Group Participants in PHAs

Be on time - commit to schedule and study goals.

Remain focused.

Respect the ideas of others.

Actively participate.

Critically evaluate ideas not the person who presented the idea.

Contribute all relevant information and ideas.

Be prepared for some degree of conflict.

Think in the long term as well as the here and now.

Be prepared to find out if you do not know.

Think laterally, keep an open mind. Think, out of the box.

Note: PHA leadership responsibilities will be addressed in detail in a later section.

Thinking Skills Required of Participants in PHAs

Creative Thinking Skills

Creative thinking requires that you deviate from the routine or common ways of

doing things to find unique solutions to problems.

Creative thinking listens to intuition and hunches and explores them for their

potential.

Creative thinking is able to adapt to different thinking modes and combine the

thinking outcomes


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Thinking Modes

Teams work best when a number of different personality/information processing

styles make up the group and a conscious effort is made by team members to

adopt different thinking modes.

objective thinking just the facts (interested in concrete details)

intuitive thinking (listen to your gut feeling)

worst case thinking (What is the worst thing that could happen?)

best possible scenario of what is practical and beneficial

forward thinking of alternatives, solutions and linking of old and new

Big picture thinking that organises and controls the detailed thinking

process

Critical Thinking Skills

Effective decision-making requires critical testing of assumptions, ideas and

arguments.

Critical thinking explores as many bases as possible for acceptance or rejection of

an idea by asking questions that test the relevance of assumptions and inferences

and finds holes in the logic of arguments.

E.g. It is assumed and inferred by the P&ID being studied that product will

normally flow from point A to B safely and without interruption to operation. To

test this assumption it is questioned:

Could there be no flow?

How could it occur?

What would be the consequences of no flow?

Would the consequences be hazardous or would it prevent efficient operation?

What are the solutions?

Warning:

To protect the egos of those who offer ideas, the group should consider an idea a

separate entity that belongs to no one once it enters the group discussion.


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Exercise:

To test your creative and out of the box critical thinking skills, mount the jockey on the

horse.

After completing exercise, think how the kind of thinking you applied to the task could

also be adapted to identifying hazards and finding solutions to hazardous situations.


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PPHHAA MMEETTHHOODDOOLLOOGGIIEESS

Video Process Hazards Analysis

In this video, you will see an overview of PHA and the most often used techniques. Use

the remainder of the space to make any notes.

NOTES:


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General PHA Procedure Flow Chart

Define Node or System

Hazard Identification - Various Methodologies

Accident Likelihood

Estimation

Accident Severity

Estimation

Risk Ranking

Recommendation

Accept risk Modify system

Operate System

Possible Hazard Consequences

Identify Existing Safeguards


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Objectives of a Good PHA Study

To identify hazards, not to necessarily provide solutions to hazards.

To provide the greatest possible confidence that all of the potential hazards are

identified while taking up the minimum resources needed to get the job done.

To provide a qualitative estimate of the likelihood and the severity of potential

accidents.

To qualitatively evaluate the consequences of failed engineering and

administrative controls.

To provide management with a concrete and easy to use basis for making risk

management decisions.

To identify ways in which operability might be improved.

To provide information which can be useful in improving future designs.

To provide objective documented evidence of a thorough well conducted study

for audit and insurance purposes.

PHAs are only as effective as the action taken to implement the recommendations

made during the study.

Process Safety Information for Hazards Analysis

The quality of any PHA depends directly on the quality and quantity of information

available to the study team. Differing amounts of information will be available at

different facility lifecycle stages and will, therefore, affect the PHA methodology chosen.

For a satisfactory PHA, easily accessible information is required, at the least, about the

hazards and characteristics of the chemicals used, about the process technology and how

it works, and about the equipment used in the process.

Video Process Safety Information

In this video, you will learn about some of process information required for a PHA and

how to gather it in a time effective manner. Use the remainder of the space to make any

notes.


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NOTES:


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The video pointed out the need for hazardous material information and for information

about the technology of the process under review. The following gives a comprehensive

list of necessary and ideal process safety information for a PHA.

As a minimum the following information should be available for any PHA:

Material Safety Data Sheets (MSDS) for all hazardous, toxic or explosive

chemicals

process flowsheets and material balance information with a range of operating

pressures

temperatures, flows, levels and compositions

safe upper and lower limits for pressures, temperatures and flows

overview of the process and a process description

Mechanical Flow Diagrams (MFD)

shutdown key or emergency shutdown system logic diagrams

operating and maintenance procedures

list of safety critical components

Emergency Response Plans (ERPs)

If possible also try to access the following information:

plot plans and equipment layouts Piping and Instrument Diagrams (P&IDs)

electrical single line diagrams and area classification drawings

flare, vent and relief system design basis

relief valve specification sheets and design capacities

building ventilation design basis

flare and gas detection design basis

equipment failure history logs and failure analysis

fire system design basis, i.e., extinguishers, firewater, dikes, protective coatings

and firewalls

process equipment specification sheets or fabrication drawings and applicable

piping, electrical or foundation design specifications


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Methodologies Overview

HAZard and OPerability Analysis (HAZOP)

HAZOP is the most comprehensive PHA at all stages of facility life, from detailed design

through construction and routine operation. It identifies operability problems as well as

hazards to personnel, the public, company property and the environment.In a HAZOP study, the process under review is first broken down into nodes, which are

logical and manageable segments that have a definable design intent. Each node is

studied in detail by applying each of the relevant guidewords to design parameters to

identify potential cause and consequence of hazards and operability problems. Equipment

failure, human error, engineering and administrative controls, and external events are all

considered as potential causes of hazards. Using a Risk Ranking Matrix, severity and

likelihood rankings are estimated and a numerical risk ranking is assigned to each

identified hazard.

Requires considerable amounts of process and safety information.

Uses systematic, structured examination augmented by creative team thinking.

Encourages interaction of team members with diverse backgrounds and

knowledge.

Looks at equipment, instrumentation, utilities, human action (routine and non-

routine), building and equipment siting, procedures, and external factors to reveal

hazardous situations.

Ranks identified risks for severity and likelihood (for sample Risk Ranking

Matrix see page 91).

Can be made applicable to almost any industry, process or system.

Can be used effectively to perform job task analyses and procedures.

Makes note of existing safeguards and evaluates them for sufficiency.

Ensures each recommendation is thoroughly explored because of the diverse team

member agendas.

Can be limited by the assumption the process will be operated as it was designed

to operate.


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People Requirements:

leader experienced in the technique.

up to eight (maximum) team members with specific knowledge about some aspect

of the process being reviewed (too many can slow study and reduce quality).

example team members:

chemical, electrical, mechanical engineering specialists

safety specialist

environmental specialist

toxicologist

vendor representative

maintenance personnel and operators

Objectives of HAZOP Analysis:

to determine if process deviation can lead to undesirable consequences.

to identify operability problems as well as hazards to personnel, the public,

company property and the environment.

to identify where more research into cause and consequence need to be

conducted.

to recommend changes or improvements to design or operation.

Approximate Time Required for HAZOP:

Depending on the size and complexity of process or modification preparation

can take from 1 - 4 days (leader) analysis, from 1 day to several weeks

documentation, 2 days.


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Select Drawings for Review

Explain Process Involved

Select Node for Review

Explain Intent of Node

Select a Parameter

Apply Guidewords/Develop Deviations

Identify Causes

Assign Cause Categories (if desired)

Identify Possible Consequences

Estimate Severity and Likelihood (Risk Ranking)

Identify Existing Safeguards

Make Initial Recommendations

Are Other Guidewords Applicable?

Are Other Parameters Applicable?

Drawing Complete

No

No

Yes

Yes

STEPSINHAZOPANALYSIS

Any Other Nodes?

Yes


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Sample Guideword Meanings

GUIDEWORDS

NO/NONE

MEANINGS

The negation of design intentions/Intention is not achieved

MORE/HIGHERQuantitative increase (above design intent) or morecomponents in the system than design intent

Usually in reference to measurable physical properties suchas flow, and temperature or extra phase, impurities, etc.

LESS/LOWQuantitative decrease (below design intent) or fewercomponents in the system than design intent

Usually in reference to measurable physical properties suchas flow and temperature

AS WELL ASQualitative increase

Something in addition to design intent is achieved

PART OF

Composition of system different from what it should be

Only part of design intent is achieved - something ismissing

REVERSE/MISDIRECTEDLogical opposite of design intent

Usually in reference to actions such as flow or chemicalreaction

OTHER THAN including

SOONER/LATER

Alternative mode (What else can happen)

Substitution of something other than design intention


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Sample Guidewords and Parameters for Creating Deviations from Design Intent for

HAZOP Studies

DEVIATION. GUIDEWORD. PARAMETER

As well as.......................................................As well asLess ................................................................LessMore...............................................................MoreNo...................................................................NoOther than.......................................................Other thanReverse...........................................................ReverseSooner/Later...................................................Sooner/LaterHigh Agitation/Recirculation.........................High........................................AgitationLow Agitation/Recirculation .........................Low ........................................Agitation

No/Less Component Separation ....................Less.Component Separation

Contaminants Enter Compressor ...................As well as...............................CompositionContaminants .................................................As well as...............................CompositionContamination................................................As well as...............................CompositionHigh Concentration of Impurities ..................As well as...............................CompositionHigh Contaminants ........................................As well as...............................Composition

No/Less Cooling ............................................Less ........................................CoolMore/Excess Cooling.....................................More.......................................Cool

Casing Rupture...............................................Other than...............................FlowHigh Flow ......................................................High........................................Flow

Leak................................................................As well as...............................FlowLeakage..........................................................As well as...............................FlowLow Flow.......................................................Low ........................................FlowLow/No Flow.................................................Low/No ..................................FlowMore/High Flow.............................................More.......................................FlowNo/Low Flow.................................................Low/No ..................................FlowReactor Rupture .............................................Other than...............................FlowReverse/Misdirected Flow .............................Reverse/Misdirected ..............FlowRupture...........................................................Other than...............................FlowShell Leak ......................................................As well as...............................FlowShell Rupture .................................................Other than...............................FlowTube Rupture .................................................Other than...............................FlowTube Leak ......................................................As well as...............................Flow


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More/Excess Heating.....................................More.......................................HeatMore Fire/Explosion Risk..............................More.......................................HeatNo/Less Heating.............................................Less ........................................Heat

Loss of Instrumentation/Control....................No.Instrumentation/ControlHigh Interface Level ......................................High.Interface LevelHigh/Excess Interface Level..........................High.Interface LevelLow Interface Level .......................................Low ........................................InterfaceLow/Reduced Interface Level........................Low ........................................Interface

High/Excess Level .........................................High........................................LevelHigh Bottoms Level.......................................High........................................LevelHigh Level .....................................................High........................................LevelLess/Reduced Level .......................................Less ........................................LevelLow Bottoms Level........................................Low ........................................Level

Low Level ......................................................Low ........................................LevelLow Tray Level..............................................Low ........................................Level

More Load on Structures ...............................MoreLoad on StructuresMore Load on Flare System...........................More.......................................Load to Flare

Maintenance Hazards.....................................Other than...............................Maintenance

Cavitation.......................................................As well as...............................PerformanceColumn Flooding ...........................................Part of.....................................PerformanceLoss of Performance ......................................Other than...............................Performance

High Pressure.................................................High........................................PressureHigh Discharge Pressure................................High........................................PressureHigh Suction Pressure....................................High........................................PressureLess/Low Pressure .........................................Low ........................................PressureLow Suction Pressure ....................................Low ........................................PressureLow Pressure..................................................Low ........................................PressureLow Pressure..................................................Low ........................................PressureMore/High Pressure .......................................More .......................................Pressure

High Reaction Rate........................................More.......................................ReactionLow Reaction Rate.........................................Less ........................................Reaction

Start-up/Shutdown Hazards ...........................Other than...Start-up/ShutdownHigh Temperature ..........................................High........................................TemperatureHigh Discharge Temperature.........................High........................................Temperature


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Less/Low Temperature ..................................Low ........................................TemperatureLow Temperature...........................................Low ........................................TemperatureMore/High Temperature ................................High........................................Temperature


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Preliminary Hazards Analysis

Preliminary Hazards Analysis identifies potential hazards at the conceptual stage of a

design when they can be corrected with minimal cost and disruption.

General focus is on the hazardous materials to be handled, the layout, operating

environment, and major process areas of the facility.

Hazards can be identified while it is still possible to make cost effective changes.

For each definable area of the process, potential hazards are identified, possible

causes and worst case consequences are listed and suggestions are made to correct

the problem.

Not considered a comprehensive study because little information on design details

or procedures is available.

Usually followed later by a more comprehensive analysis.


Can be performed by as few as two people with process safety backgrounds.

Because analysts are required to use their own judgment, experienced leaders and

participants are preferable to ensure an exhaustive and detailed analysis.

Objectives of Preliminary Hazards Analysis:

to provide information required to make fundamental decisions about facility

siting, unit operations and special design considerations.

to identify areas where more research is required to ensure a safe, effective

process and design.

to provide an opportunity to incorporate recommendations into design.

to prioritise hazards in existing facilities when more extensive techniques are not

available.

Approximate Time Required for Preliminary Hazards Analysis:

Depending on the size and complexity of process, preparation can take from .5 -

3 days (leader only) analysis, from 1 - 6 days documentation, from 1 - 4 days.


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Recommended Process Safety Information:

plant design criteria

plant equipment specifications

material specifications

proposed facility layout if available

Steps in Preliminary Hazards Analysis:

1. Leader reviews all available material prior to first meeting to develop list of

possible hazards and checklist questions about location, environment and weather,

process materials, emergency equipment, etc.

2. Meeting: Leader suggests a potential hazard (e.g. toxic release) and follows the

process from beginning of flow to end, prompting with questions and encouraging

the team to question and think creatively about all possibilities.

3. Causes for the hazard are identified and documented.

4. Consequences are estimated and documented.

5. Severity and likelihood factors are estimated and risk ranking assigned.

6. Suggestions are made for improvements and documented.

7. Leader suggests next hazard and the process repeats itself.


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Checklist Analysis

A detailed list of questions, written from knowledge and experience is used to assess the

acceptability or status of the process, system or operation compared to standard design

and operating practices.

Checklist Analysis is an experience-based methodology and its value is dependent

on the quality of the checklist.

Operating systems are defined and lists of questions are generated about standard

design and operating practices for each system.

Checklist questions need to be developed by a multidisciplinary team with

experience in the process being studied.

Checklists are best tailored specifically for an individual company or plant and

built upon over time.

Questions usually require Yes, No or Requires more information answers.

Can be used at any time in the facility lifecycle to evaluate materials, equipment

and procedures, but is especially effective combined with a pre-start-up safety

review if a previous hazards analysis has been conducted at the detailed design

stage.

Can be as detailed as required for the purpose.

Can be combined with What-If Analysis for comprehensive evaluation of hazards. Can be used as an investigative tool to identify hazards and an audit tool to verify

designs and installations.

Is not an aid to identification of unknown hazards.

Does not identify operability problems well.


Requires a leader who is knowledgeable in the process and experienced in start-up

and construction.

Requires people experienced in the system/process as it is being studied.

Does not require same team members at all times. Experts come and go as

required.


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Objectives of Checklist Analysis:

to verify compliance with design, codes and regulations at startup.

to help control management of change.

to aid in a comparative review of process not yet built.

to act as an aid in training people inexperienced in a process.

Approximate Time Required for Checklist Analysis:

Depending on the size and complexity of process, preparation can take from .5 -

3 days (experienced engineers and maintenance/operations personnel to generate

checklist questions) analysis, from .5 - 5 days documentation, from .5 - 4 days.

Checklists

Checklists generated from experience, standards and codes and industry

guidelines and any other authoritative references such as engineering and

construction drawings, equipment specifications and previous hazards analysis

study findings.

Checklists can be developed by a number of people with experience in specific

parts of the process or plant. (Sample Checklist can be found in Appendix.)

Steps in Checklist Analysis:1. Acquire or develop appropriate checklists.

2. Expert team members tour the subject process with leader and compare

equipment and operation to checklist items.

3. Deficiencies are noted.

The Checklist process can be performed on a not yet built facility in a meeting room with

the team members reviewing the process drawings, completing the Checklist and

documenting their discussion of the deficiencies.


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What-If Analysis

What-If Analysis uses a creative team brainstorming what if questioning approach to

the examination of a process or operation to identify potential hazards and their

consequences. Users should be experienced and creative thinkers.

Questions that begin with what-if are formulated by engineering personnel experienced

in the process or operation and subdivided into specific categories of interest.

For example:

What if the raw material being introduced is the wrong concentration?

What if the operator forgot to manually close the valve?

Questions can also focus on specific consequences such as process safety,

operating procedures, human error or environmental safety. Does not easily

generate operability information.

Questions are applied to existing P&IDs and process descriptions.

Questions are usually added as the analysis progresses.

Hazards are identified, existing safeguards noted and qualitative severity and

likelihood ratings are assigned to aid in risk management decision-making.

Loose structure necessitates experienced team. Can only provide high level of assurance with very knowledgeable, experienced

and creative team.

Often used at design concept stage and to analyse proposed changes to a facility.


Leader experienced in the What-If Technique and five or six participants

knowledgeable and experienced in the subject process.

Objectives:

to aid in identification of possible deviations from design, construction,

modification or operating intent.

to identify hazards and suggest risk reduction methods.


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Approximate Time Required for What-If Analysis:

Depending on the stage of project development and the size and complexity of

process or modification, preparation can take from .5 - 3 days (leader) analysis,

from .5 - 6 days documentation, from .5 - 3 days

Steps in a What-If Analysis:

1. Provide relevant information to selected team members in sufficient time before

the study for their input in developing What if questions.

2. Leader divides process into logical systems and subsystems.

3. Scope and objectives of study are explained.

4. Existing safety precautions and equipment are described.

5. Team reviews information to generate more questions related to the systems of

the process.

6. List of questions is made.

7. Systems and subsystems are analysed from the beginning of the process to the end

by applying the relevant what if questions.

8. Potential hazards are identified and consequences estimated and documented.

9. Severity and likelihood factors are given and a risk ranking assigned and

documented.

10. Recommendations for improvement are made and documented.

In some cases, responsibility for follow-up on the recommendations is assigned to

individual parties or departments and documented.


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What-If/Checklist Analysis

What-if/Checklist Analysis combines the creative brainstorming features of the What-If

Analysis with the systematic features of the Checklist Analysis to provide a

comprehensive method of identifying hazards.

Creative questioning augments the systematic experienced based checklist to

provide a more complete study.

Checklists are generally structured to focus on general sources of hazards and

accidents.

Study can begin with a checklist to which what-if questions are applied to

round out gaps in the list.

Alternatively, study can begin with a brainstormed identification of hazards

followed by the structure of a checklist.

Can be used successfully at any stage in facility lifecycle.

Requires a team experienced in the process under review.

Usually provides a less detailed review than the more structured analyses such as

HAZOP.

Can be structured to provide detailed analysis but this can be time consuming

unless checklists and questions can be used from previous studies.

Objectives of What-If/Checklist Analysis:

to identify and evaluate the most common hazards in a process.

to provide a qualitative evaluation of the consequences of accident outcomes.

to evaluate the adequacy of existing safeguards.

Approximate Time Required for What-If/Checklist Analysis:

Depending on the stage of project development and the size and complexity of

process or modification, preparation can take from .5 - 3 days (leader) analysis,from .5 - 6 days documentation, from .5 - 3 days.


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Failure Modes and Effects Analysis (FMEA)

FMEA is not strictly speaking a hazard identification technique, but it provides an

important source of hazard information because it documents and describes all the ways

in which individual pieces of equipment can fail and the effects of such failure on a

facility.

Can be used at all stages of a facilitys life and can be easily updated for plant

modifications.

Requires knowledge of equipment function and failure modes as well as facility

function and its potential response to equipment failure.

Requires consistent format and procedure to help ensure efficient study.

Can be conducted at component or system level.

Each equipment item within a defined system is evaluated for its failure modes.

Identifies and describes all possible ways in which equipment fails (failure

modes) e.g. On/off, open/closed, etc.

Identifies only single failure modes that cause or contribute to an accident (e.g.

individual failure is considered an independent occurrence).

Not effective in identifying the combinations of equipment failures that result in

an accident.

Investigates and documents each failure modes effect on facility safety. System level hazards can be analysed by focusing on the individual pieces of

equipment that make up the system while keeping in mind the overall effect on

the subject system.


requires leader experienced in the technique.

can be conducted with as few as two or three team members with knowledge of

equipment function and potential failure modes as well as facility function and its

potential response to equipment failure.

Objectives of FMEA:

to provide a list of equipment and their potential failure modes.

to describe how equipment fails.


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to evaluate the effects of equipment failure on other parts of the process or system

in a facility.

to make recommendations for improving equipment reliability.

Approximate Time Required for FMEA:

Depending on the number of equipment items and the complexity of process or

modification, preparation can take from .5 - 3 days (leader), analysis, from 1

day - several weeks documentation, from 2 - 8 days

Steps in an FMEA:

1. Establish the physical and operating boundaries of the study.

2. Identify and describe each equipment component.

3. Beginning at the beginning of a system boundary, evaluate the equipment items in

the order that they appear on the process flow diagram.

4. List and evaluate all failure modes for each component before proceeding to the

next.

5. For each failure mode, describe the immediate and surrounding effects and the

anticipated effects on other equipment and overall system using a worst-case

scenario assuming safeguards do not work. Document findings.

6. Estimate a qualitative rating of likelihood and severity, and by combining these

ratings, provide a qualitative risk ranking. Document findings.

7. Describe the existing safeguards or procedures that can mitigate the consequences

of equipment failure. Document findings.

8. List recommendations for corrective actions for further evaluation. Document

findings.


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Other PHA Methodologies Reserved for Specific Safety Concerns

The following PHAs are hazard evaluation techniques rather than hazard identification

techniques and are generally quantitative in nature, time consuming and require special

expertise and statistical data.

Fault and Event Tree Analyses and Cause/Consequence Analysis

Both provide graphical representations of accident root causes and sets of failures that

could result in an accident.

Quantitative Risk Analysis (QRA) (Hazan) (Risk Assessment)

See page 5.


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Advantages and Disadvantages of PHA Methodologies

ADVANTAGES DISADVANTAGES

PRELIMINARY

HAZARDSANALYSIS

Identifies the potential for majorhazards at a very early stage of projectdevelopment.

Provides basis for design and sitingdecisions.

Helps to ensure plant to plant and plantto environment compatibility.

Facilitates a later full hazard analysis.

Is not comprehensive and must befollowed by a full HAZOP beforeconstruction begins.

CHECKLIST Easy to use, relatively quick.

Quick way to verify compliance withcodes and regulations.

Limited by authors experience andknowledge.

Does not identify new or unknownhazards.

Does not directly address operabilityproblems.

WHAT-IF Team of relevant experts extendknowledge and creativity pool.

Easy to use.

Ability to focus on specific element(e.g. human error or environmentalissues).

Quality dependent on knowledge,thoroughness and experience of team.

Loose structure can let hazards slipthrough.


WHAT-IF/

CHECKLIST

Combines creative brainstorming withstructured checklist.

Flexible level of detail.

Quality dependent on knowledge,thoroughness and experience of team.


FMEA Systematic, component by componentanalysis aids thoroughness.

Beneficial at all stages of a facilityslife.

Can easily be updated for plantmodifications.

Not efficient for identifyingcombinations of equipment failure.

Does not directly address siting issues,general safety and environmentalissues.


Can be time consuming.

HAZOP Most systematic and comprehensive ofmethodologies.

Can be used in conjunction with HumanError analysis.

Only PHA to address both safety andenvironmental hazards and operabilityproblems.

Provides greatest safety assurance.

Can be time consuming and costly.

Can be tedious if not well facilitated.


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Limitations of PHA

Like any analysis, PHAs are subject to limitations. Users must understand and respect

these limitations when participating in or leading PHAs or when using the results of a

study to reduce risk. Can never guarantee that all hazards, causes and consequences have been

identified.

Are only effective if it can safely be assumed that the facility is operated in the

manner intended by the designers and in accordance with good practice.

Are only relevant to the time conducted. Even minor changes may significantly

impact facility safety.

Are subjective and only as good as the collective knowledge, creativity and

experience of the team.

Can only be effective and comprehensive if the information available is complete,

accurate and up to date.

May overlook hazards related to material quality and workmanship.

Are only effective if action is taken to implement the recommendations made

during the study.


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MMEETTHHOODDOOLLOOGGYY SSEELLEECCTTIIOONN CCRRIITTEERRIIAA

The range of PHA methodologies affords flexibility of study objective. There is not

always any one best methodology for a specific process or operation. Regardless of

methodology, the effectiveness of any study is greatly enhanced if the team is

knowledgeable and experienced and is lead by a person also knowledgeable and

experienced in the technique being used.

The following criteria for methodology selection will provide a basis for making initial

decisions, but only experience will provide the knowledge and confidence to make the

right choice for the defined purpose.

NOTE:

A danger exists that a less appropriate methodology may be chosen to save time or

because of inadequate financial or people resources. Under funded, understaffed or

rushed studies are not destined for success.

Factors to Consider When Selecting THE Appropriate PHA Methodology

Purpose of StudyThe purpose of the study is the most important factor in selecting an appropriate

methodology. The reason for the study must be clearly defined by management.

For Example:

Is the study part of policy for all new facilities?

Are the study results to be used for risk reduction planning in an existing facility?

Is the study required for regulatory compliance or insurance purposes?


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Type of Results Required

Knowing how the results will be utilised or could be utilised will help determine which

methodology to use.

For Example: simple list of identified hazards or accident scenarios for emergency planning

purposes

prioritized estimations of likelihood and severity for future quantitative risk

analysis purposes

recommendations to reduce hazards and minimize operability problems for risk

reduction planning

legal and regulatory compliance

Type of Information Available

Information needs to be of good quality and current. Using unsuitable or out of date

information is a waste of time and can, in fact add to the hazardous situation at a facility

by providing a false sense of security or incorrect risk management information.

More information becomes available in the evolution of a facility, from concept to

normal operation. Therefore, studies performed at the early stages of a design, of

necessity, must be more simp

Documents

L4 PHA Student Handout