Hazid

What can go wrong and how?

Hazard Identification

1

QRA procedure

Define the potential accident scenarios

Evaluate the consequences

Estimate the impact

Estimate the risk

Evaluate the risk

Identify and prioritize potential risk reduction measures

Scenario 2Scenario 1 Scenario Scenario 3 Scenario n

Estimate the frequencies

2

HAZARD IDENTIFICATION

TECHNIQUES

3

Harmful, irritant or sensitising

Flammable

Corrosive

Oxidising

Toxic

Explosive

Dangerous for the environment

4

Hazards related to the chemical itself

5Material property data for HA

Hazard Identification Methods

Non-Scenario Based Hazard Evaluation Procedure: Safety Reviews

Checklist

Relative Ranking

Preliminary Hazard Analysis

Scenario Based Hazard Evaluation Procedure: What-If Analysis

What-If/Checklist Analysis

HAZOP Hazards & Operability study

FMEA Failure Mode & Effects Analysis

FTA Fault Tree Analysis

ETA Event Tree Analysis

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Hazard Evaluation

Each technique has strengths and weaknesses;

Performing a hazard evaluation without understanding its

motivation and without no well-defined purpose is a

waste of time and efforts.

Factors that influence the selection of a techniques

include:

Motivation for the study

Type of results needed

Type of information available

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Motivation for the study

Why do we want to do this study?

Development of new processes?

Improvement of existing process?

Extension of an existing process (change)?

Decommissioning of a process?

Satisfy a regulatory or legal requirement?

Is information needed to make risk-informed decisions

concerning a process?

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Type of Results Needed

List of hazards

List of potential incident situations

List of alternatives for reducing risk

Identification of areas needing further study

Input for a quantitative risk analysis

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Type of Information Available

Available information depends on:

Stage of life the process when the study needs to be done

E.g.: conceptual design of a process:

It is highly unlikely P&ID is already proposed:

E.g. What-If Analysis is more appropriate than HAZOP

Quality and currentness of documentation.

E.g., for an existing process, if P&IDs are not up-todate:

HAZOP can not be performed

Study may not only futile but a waste of time and resources.

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Type of Information Available to

Perform the Study

Choice of Hazard Evaluation

Techniques

Sa

fety

Rev

iew

Ch

eck

list

Pre

-HA

Wh

at-

if

Wh

at

if-

Ch

eck

list

HA

ZO

P

FM

EA

FT

A

ET

A

R&D

Conceptual Design

Pilot Plant Operation

Detailed Engineering

Construction / Start-up

Routine Operation

Expansion or Modification

Incident Investigation

Decommissioning

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Commonly Used Rarely Used or Inappropriate

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Typical Staff Effort

SAFETY REVIEWS

Non-Scenario Based Hazard Evaluation Procedure

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Purpose

Ensure that the plant and its operating and maintenance practices match the design intent and construction standards:

Keeps operating personnel alert to the process hazards;

Reviews operating procedures for necessary revisions;

Seeks to identify equipment or process changes (new hazards);

Evaluates the design basis of control systems, instrumented protective systems, and emergency relief systems;

Reviews the application of new technology to existing hazards;

Reviews the adequacy of maintenance and safety inspections.

Success strongly depends on the experience of the Team

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Types of Results

Provides qualitative descriptions of potential safety

problems and suggested corrective actions.

Report includes:

deviations from the design intentions;

deviations from authorized procedures;

lists of newly discovered safety issues.

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Resource Requirement

Process material safety properties;

Applicable codes and standards;

Previous safety studies;

Detailed plant descriptions (P&IDs and flowcharts);

Plant procedures for start-up, shutdown, normal

operation, maintenance, and emergencies;

Personnel injury reports / incident reports

Maintenance records (functional checks, PRV tests,

vessel inspections)

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3 steps of a Safety Review

Preparing for the review Assemble a detailed description of the plant (See resource

requirements)

Schedule interviews with specific individuals responsible for safe process operation

Performing the review Should start with a general orientation tour of the plant and progress

to specific inspections and interviews

Roundtable discussion

Documenting the results Report with specific recommended actions.

Justifications the recommendations

Plan for Follow up actions

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Some questions to be addressed

Is there a system for keeping important process documentation and drawings up to date?

Is the equipment in good condition?

Are the pressure reliefs or other safety devices properly installed, well-maintained, and properly identified?

Do plant records show the history of inspecting and testing the equipment and safety devices?

Are pressure vessels or critical or hazardous service equipment repaired by certified welders?

For equipment that handles corrosive or erosive materials, have metallurgical inspections and metal-wall-thickness measurements been taken at frequent intervals?

Does the plant have trained inspectors available whose recommendations for repair or replacement are accepted by management?

Are safe work practices followed and permits used?

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CHECKLIST


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Purpose

Uses a written list of items or procedural steps to verify

the status of a system in order to:

Ensure that organizations are complying with standard

practices.

Provide a common basis for the review of a hazard assessment

If combined with another hazard evaluation method (What-

If/Checklist Analysis) can be used to identify Hazards

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Types of Results

Qualitative results

List of questions which receive the following answers:

yes

no

not applicable

needs more information

List of possible safety improvement alternatives for

managers to consider

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Appropriate checklist: Based on deficiencies or differences with standard design or

operating practices

Checklist prepared from prior experience

Engineering design procedures

Standard Procedures Manual

Someone to complete the checklist who has basic knowledge of the process being reviewed.

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Examples

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Examples

http://www.harsnet.net/harsmeth/HarsMeth%20text/HarsMeth%20version%202.pdf

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Examples

http://www.harsnet.net/harsmeth/HarsMeth%20text/HarsMeth%20version%202.pdf

RANKING METHODS


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Purpose

Determine the process areas that present the most significant: hazard of concern

the potential severity of consequences

the overall risk

Determine the processes that that present significant hazards and require further deeper study.

Compare several process siting, generic design, or equipment layout options, to choose the best option.

Should normally be performed early in the life of a process, before the detailed design is completed

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Ranking Methods

Numerical values that represent the relative level of

significance that the analyst gives to each hazard,

potential consequence or risk depending on the approach

used.

Ordered list of processes, equipment, operations, or

activities.

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Ressource Requirements

Basic physical and chemical data on the substances used in the process or activity.

General process diagrams and equipment layout drawings

Maximum inventories of materials

Plants process conditions

Geographic layout of material storage areas is usually needed.

Do not normally require detailed process drawing

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Dow Fire and Explosion Index

Dow Chemicals have developed this method and found it

useful.

As part of safety promotion in the process industries,

they have made it available to others;

The Dow Fire and Explosion Index (FEI) rates relative

hazards of storing, handling, processing flammable and

explosive materials

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Breaks the process down into units or sections

Methodology:

Define the material factor

Adjust this with various penalties

Then take credits for safety procedures and safety systems

Finally arrive at a number that rates the hazard

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Material factor

The material factor is a

property of the chemicals

being handled.

Compute for mixtures or

use worst value

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Penalties for general process hazards:

Exothermic reactions that might self-heat

Endothermic reactions that could react because of an external heat source such as a fire

Material handling and transfer, including pumping and connection of transfer lines

Enclosed process units preventing dispersion of escaped vapors

Limited access for emergency equipment

Poor drainage of flammable materials away from the process unit

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Penalties for

General Process

Hazards Factor

(F1)

F1General Process

Hazards Factor

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Penalties for special process hazards:

Toxic materials, which could impede fire fighting

Less than atmospheric pressure operation with a risk of outside air entering

Operation in or near the flammable limits

Dust explosion risks

Higher than atmospheric pressure

Low-temperature operation with potential embrittlement of carbon steel vessels

Quantity of flammable material

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Penalties for

Special Process

Hazards Factor

(F2)

F2

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Special Process

Hazards Factor

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1 2 3F F F Process Unit Hazards Factor (F3)

3F&EI F MF Fire and Explosion Index (F&EI)

F&EI

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Material

factor

General Process

Hazards Factor

Special Process

Hazards Factor

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F&EI index value Degree of hazard

1 60 Light

61 96 Moderate

97 127 Intermediate

128 158 Heavy

128 158 Severe

Determining the degree of hazard from the Dow F&EI

Control

Isolation

Fire protection

C2

C1

C3

Loss control credit factor

(C1 x C2 x C3)

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F&EI

Loss control

credit factor

x Base Maximum Probable

Property Damage

(Base MMPD in $)

Value of area of

exposure ($) Damage factor=(based on F&EI

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F&EI

Loss control

credit factor

x Actual Maximum Probable

Property Damage

(Actual MMPD)

Loss control

credit factor= Base MMPD (in $)

Example: new facility for handling

tanker deliveries of butadiene

Butadiene has material factor of 24

(flashpoint -105oC, poor NFPAhealth rating, high heat of combustion)

1.5 x 2.94 = 4.41

FEI = 4.41 x 24 = 106

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PRELIMINARY HAZARD

ANALYSIS


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Purpose

Evaluate hazards early in the life of a process.

Applied during the conceptual design or R&D phase of a

process plant and can be very useful when making site

selection decisions.

Used as a design review tool before a process P&ID is

developed.

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Types of Results

Qualitative description of the hazards related to a process design.

Qualitative ranking of hazardous situations:

Based on the significance of the causes and effects of the incident: Hazard Category I Negligible

Hazard Category II Marginal

Hazard Category III Critical

Hazard Category IV Catastrophic

Can be used to prioritize recommendations for reducing or eliminating hazards in subsequent phases of the life cycle of the process.

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Available plant design criteria

Written description of the conceptual design

Equipment specifications

Material specifications

Basic chemicals, reactions, and process parameters

Major types of equipment

Other sources of information:

hazard studies of similar facilities

operating experience from similar facilities

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Some factors to be considered

Hazardous plant equipment and materials e.g., fuels, highly reactive chemicals, toxic substances, explosives,

high pressure systems, and other energy storage systems

Safety-related interfaces between plant equipment items and materials

Material interactions, fire/explosion initiation and propagation, and instrumented protective systems

Environmental factors that may influence the plant equipment and materials

earthquake, vibration, flooding, extreme temperatures, electrostatic discharge, and humidity

50

Some factors to be considered

Operating, testing, maintenance, and emergency procedures

human error importance, operator functions to be accomplished, equipment layout/accessibility, and personnel safety protection

Facility support storage, testing equipment, training, and utilities

Safety-related equipment mitigating systems, redundancy, fire suppression, and personal

protective equipment

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Example

WHAT IF ANALYSIS

WHAT IF/CHECKLIST

Scenario Based Hazard Evaluation Procedure

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Purpose

Unstructured method to identify hazards, hazardous situations, or specific hazard leading to a hazardous situation from a What If Question Not concerned with how failures occur

Identify possible their consequences

Identify existing safeguards

Suggests alternatives for risk reduction if possible

Powerful method for a very experienced team. Otherwise elements may be missed.

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Type of Results

Answers to a list of questions about the process (tabular

listing).

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Resource Requirements

Chemical data, process descriptions, drawings, and operating procedures.

Very flexible method that can be used at any stage of the life cycle of a process;

Available information depends on the life cycle phase

Can be used even with limited process information and knowledge;

Preliminary questions should be developed to start of the discussion

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Example of "What-If"

Question: What if the raw material is the wrong concentration?

Answer: If the concentration of the acid could be doubled, the reaction

could not be controlled and a rapid exotherm would result.

Recommendation: Install emergency shut-down device

Install emergency relief system

or take special precautions when loading the raw material Place a valve on the line just before the reactor, that way the inlet flow

can be controlled

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Example of "What-If"

What If/Checklist

Hybrid method combines the advantages of both methods What-If and Checklist

Advantages Checklist part of the method: Built from experience of people

Avoid missing known hazards

Gives a systematic nature to the analysis

Advantages What-If Analysis part of the method : Allows creativity and brainstorming beyond the experience of the assessing

team

This technique is very effective and popular

Often used as a first hazard evaluation on a process (precursor for more detailed studies).

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HAZARD AND OPERABILITY

STUDY (HAZOP)

Scenario Based Hazard Evaluation Procedure

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Objectives

Identify Hazards

Identify Operability Problems

HAZOPs Use Multi-Disciplinary Team Approach

Guide word based

Structured and Systematic

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Strengths

Creative approach for identifying hazards, particularly those involving reactive chemicals

Exhaustively examines the potential consequences of process upsets or failure to follow procedures

Systematically identifies engineering and administrative safeguards and the consequences of safeguard failures

Gives all participants a thorough understanding of the system

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HAZOP Team Composition

Team Leader generally with HAZOP experience

5-7 team members optimum, depending on scope of

effort

Scribe

Consultants

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HAZOP Team Composition

Example of Technical Members for new design Design Engineer

Process Engineer

Commissioning Manager

Instrument Design Engineer

Chemist

Example of Technical Members for Existing design Plant Superintendent

Process Supervisor

Maintenance Engineer

Instrument Engineer

Technical Engineer

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Team Leader Attributes

Patience

Stamina

Organized

Quick thinking

Friendly and cooperative

Able to focus simultaneously on multiple items

Able to read people

Imaginative

Seeks consensus

Respected by team

Diplomatic

Ability to keep meeting on

track

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Scribe Attributes

Attention to detail

Responsive

Good listener

Good typing skills

Good spelling/grammar skills

Process/technical knowledge

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HAZOP Methodology

Record and assign action

items

Apply guide words to process

parameters

Typical causes of deviations

Identify existing safeguards to

prevent deviation

Assess acceptability

based on consequences

Develop Action items

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Start

Select a process section

Explain the design

intention

Select study nodes

Pick a process

parameter

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HAZOP Methodology

Start


Explain the design

intention

Select study nodes

Selection of NODES Major process vessels

Reactor

Storage vessel

Catch tank

Major process lines connected to process vessels Inlet line for feed A

Inlet line for feed B

Discharge line

Pumps and compressors

Heat exchangers

Etc

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HAZOP Methodology

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HAZOP Methodology

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HAZOP Methodology

Start


Explain the design

intention

Select study nodes

Pick a process

parameter

Choice of a process parameter

Flow

Pressure

Temperature

Level

Composition

Source

Destination

Duration

Sequence

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HAZOP Methodology

Start


Explain the design

intention

Select study nodes

Pick a process

parameter


items


parameters



prevent deviation




Choice of a Guide Words

NO, NOT, NONE

MORE, HIGHER, GREATER

LESS, LOWER

AS WELL AS

PART OF

REVERSE

OTHER THAN

etc

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HAZOP Methodology

Choice of a

Guide word

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HAZOP Methodology

Start


Explain the design

intention

Select study nodes

Pick a process

parameter


items


parameters



prevent deviation




Choice of a Guide Words

NO, NOT, NONE

MORE, HIGHER, GREATER

LESS, LOWER

AS WELL AS

PART OF

REVERSE

OTHER THAN

etc

Parameter + Guide

Word = Deviation

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HAZOP Methodology

Parameter + Guide Word = Deviation

Parameter + Guide Word = Deviation

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HAZOP Methodology

HAZOP Methodology


items


parameters



prevent deviation




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Start


Explain the design

intention

Select study nodes

Pick a process

parameter

HAZOP Methodology

Example on a particular node

Parameter: Flow

Guide Word: No

Deviation No + Flow

Cause Supply pipe ruptured upstream

Consequences Release of material with possible toxic effects and/or fire and explosion

Recommendation Install pressure sensor

Mechanical integrity program

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HAZOP Example

FAILURE MODES AND

EFFECTS ANALYSIS (FMEA)

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Purpose

Failure Modes and Effects Analysis (FMEA) identifies :

How single equipment can fail (or be improperly operated) open, closed, on, off, leaks, etc

E.g. for pump: Fails to stop when required, Stops when required to run, Seal leak/rupture, Pump casing leak/rupture

How each failure modes affects the system or plant: Determines the effect (E) of the failure mode (FM) by the systems

response to the equipment failure

Generates recommendations for increasing equipment reliability (improving process safety)

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Type of Results

FMEA generates a qualitative, systematic reference list

of equipment, failure modes and effects.

A worst-case estimate of consequences resulting from

single failures is included.

But:

Rarely investigates damage or injury that could arise

Not useful for identifying combinations of failures

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Resource Requirements

System or plant equipment list or P&ID

Knowledge of equipment function and failure modes

Knowledge of system and responses to equipment

failures

Staff requirements will vary with the size and

complexity of equipment

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Type of Results

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Type of Results

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Type of Results

SUMMARY

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Typical outcomes of HazID

Techniques

Lists of identified hazards, perceived problems, or

potential incident scenarios;

Descriptions of the significance of these problems or

incidents (e.g., risk posed by each scenario);

Recommendations for:

Reducing or eliminating the hazards;

Coming into compliance with codes or standards;

Reducing the risks associated with the incident scenarios.

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Outcomes of HazID Techniques

How to prioritize actions

Most hazard evaluations result in lists of recommendations for reducing the risks.

One could examine the potential causes and effects of an incident (providing this is given by the technique)

How to rank these recommendation; Suggestions:

Identification of any situation that violates a regulations, standards;

Analysts understanding of the risk posed by the potential incidents;

Analysts perception of the risk reduction gained by implementing a specific recommendation;

Risk reduction gained by implementing a specific recommendation in comparison to the resources required to implement it.

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References

Hazid

Documents

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