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Introduction to HAZOP

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Overview

�Learning goals – Understand why a HAZOP should be

carried out

– Determine where and when a HAZOP

will be suitable and also limitation for

use

– Become aware of alternative methods

�Topics– History of HAZOP

– Why HAZOP?

– HAZOP and Risk Management

– Project phases

– Other Hazard Identification

techniques

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History of HAZOP (1)

� Process industry had poor record in 1950s–60s

� Designs previously based on Codes of Practice, Design Reviews and Checklists

� BUT:

– Sophisticated technology

– Larger and more hazardous plants

– Commissioning “blow-outs"

� In early 1960s ICI wanted a better Design Review process

– Hazard reviews were unstructured and discipline oriented

– Aim was to substantially improve safety and operability

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History of HAZOP (2)

� In early 1960s ICI asked Method Study group to make a recommendation, who:

– concluded design for normal operation was usually good

– suggested a team was needed to address deviations from normal

– introduced a set of guidewords to identify possible deviations

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Benefits of HAZOP study

Slide 5

Criteria With HAZOP Without HAZOP

No. of major mods to plant 0 2-3

No. of minor mods to plant 3 10-15

Time from start-up to designflowsheet rate

1 year 3 years

8 years experience of ICI Mond Division in UK

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Why carry out a HAZOP study?

� As an aid to design of safe plant

� As a step in the overall procedure of safe plant design

� As a training aid

� As an aid to design of operable plant

� As a cost saving exercise

� As an aid to preparation of operating manuals

� As a rigorous, systematic check of the design, for safety, operability and

conformity to codes, etc.

� To demonstrate to management, authorities and the public that all possible has

been done to avoid hazards

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What do authorities require?

� The VN Safety Management Regulation has been developed by PVN (with

assistance from DNV & PSAN) and approved by prime minister of VN, so all O&G

operators are required to follow this

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What happens if we don’t?

� Non-compliance!

� More accidents?

� Late modifications?

� Operability problems?

� Frustration?

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What are the Objectives of the study?

� What is the point of holding the study?

– To improve a process

– Requirement of some authority

– Identify hazards

– Quantify risks

– Information transfer

� The objective of the study will shape:

– The scope

– External & internal parameters to be taken into

account

– Battery limits

– Who should attend

– When and where to hold the study

– Duration of the study

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HAZOP and Risk Management

� HAZOP

– is a detailed, structured hazard and operability

problem identification process1 …

– carried out by a team …

– to identify potential deviations from the design

intent,

– examine their possible causes, and

– assess their consequences.

� HAZOP

– forms part of the RISK MANAGEMENT toolkit2

– is one of the most powerful techniques for process

hazard identification

– often gives us the tools to manage (“treat”) the risk

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References1 IEC 61882:20012 ISO 31000:2009

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What is Risk?

Slide 11

RISK

harm

accident

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Risk Assessment

Slide 12

RISK

CALCULATION

harm

accident

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Major Accident

Hazard

Protective‘Barriers’

Weaknessesor ‘Holes’

� Barriers may be physical engineered containment

or behavioral controls dependent on people

� Holes can be latent/incipient, or actively opened

by people

Fortunately, most hazards don’t cause a disaster…

� Hazards are contained by

multiple protective barriers

� Barriers may have weaknesses

or ‘holes’

� When holes align hazard energy

is released, resulting in the

potential for harm

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Strategic concepts

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� In order to reduce the potential for future major incidents and losses, three layers of protection are to be considered:

– plant – engineering hardware, control systems, and layouts to eliminate, control and mitigate potential hazards to people, and improve productivity

– processes – management systems to identify, control and mitigate risks, and drive continuous operational improvement

– people – capability of our people in terms of leadership skills, relevant knowledge and experience, and the organizational culture they create

– In layers of protection, ‘hard barriers’ are more reliable than ‘soft barriers’, but all rely on people

Hazard

‘hard’ barriers‘hard’ barriers‘hard’ barriers‘hard’ barriers ‘soft’ barriers‘soft’ barriers‘soft’ barriers‘soft’ barriershazard hazard hazard hazard

reductionreductionreductionreduction

physical controls

procedures generic systems

people’s behaviours

Accident or Loss

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Strategic concepts and the role of HAZOP

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� Unless we IDENTIFY our hazards we cannot manage the risk

� Unless we put in place sufficient BARRIERS we cannot manage the risk

- “Barriers may be physical engineered containment or behavioral controls dependent on people”

� HAZOP is a vital early step in achieving these

hazardhazardhazardhazard

‘hard’ barriers‘hard’ barriers‘hard’ barriers‘hard’ barriers ‘soft’ barriers‘soft’ barriers‘soft’ barriers‘soft’ barriershazard hazard hazard hazard

reductionreductionreductionreduction

physical controls

procedures generic systems

people’s behaviours

“Traditional”HAZOP

ProceduralHAZOP

ManagementSystems

Accident or Loss

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“Defence in Depth” Philosophy

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Major Accident

Hazard

Elimination of hazards by design

Prevention at source, e.g. equipment design, material selection

Detection , e.g. Fire & Gas Detection

Mitigation , e.g. ESD/EDP, Fixed Fire Protection

Emergency Response means

Maintenance & Inspection

Procedural controls

Emergency Response Plan

Training & Competence

Learning from incidents“HARD” BARRIERS

“SOFT” BARRIERS

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Bow Tie Diagram

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Consequence1 E

FF

EC

TS

Consequence2

Cause1

Cause2

TOPEVENT

HAZARD

Barrier Decay Mechanism

Barrier Decay Mechanism

Barriers to eliminate & prevent causes of

hazardous event

Barriers to controlconsequences &

effects

Barriers Decay Mechanism Controls

Barriers Decay Mechanism Controls

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Hazard Identification techniques

� HAZID – used early in project identify

and evaluate hazards

� “What-If?”/SWIFT – Creative brain-

storming using questions to develop

scenarios for undesirable events

� FME(C)A – a systematic analysis of a

system to identify potential failure

modes and their affects

� Checklist – traditionally to ensure

compliance with standard practices,

namely do’s and don'ts, and to reveal

most common hazards

� SJA – Safe Job Analysis, used to

identify hazards and risk reducing

measures for a particular work task or

activity

� Bow tie analysis – a fault tree leading

to a hazard, in turn leading to outcomes.

This is more a visualization tool and

means of examining causes,

consequences and barriers.

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HAZOPs in Project Phases

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Project life cycle

Benefits

• Identifies major threat & risk contributors

• Can provide input for fine tuning & improvement

• Good for comparing competing alternatives

• Identifies safety measures in design

• Provides input for procedure development

• Identifies potential threats/requirements from regulators

• Identifies potential threats associated with deviations from plans & procedures

• Key input to MOC• Identifies threats and

quantifies risk

• Identifies threats and quantifies risk

Risks Lack of detail leads to general findings

Strategy, Feasibility & Concept Selection

Design & Developme

nt

Construction

Installation &

Commission

Operation & Life

ExtensionDecommissio

n

Increasing level of focus in specific areas

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HAZOP � � � � �

Bow tie � � � �

HAZID � � � � �

FME(C)A � �

Checklist � � � �

What-If � �

SJA � � �

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Hazard identification techniques in project phases

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Project life cycle

Strategy, Feasibility & Concept Selection

Design & Developme

nt

Construction

Installation &

Commission

Operation & Life

ExtensionDecommissio

n

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Reference documents

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