Hazid

Hazard Identification What can go wrong and how?

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QRA procedure Define the potential accident scenarios Scenario 1

Scenario 2

Scenario 3

Estimate the frequencies

Scenario …

Scenario n

Evaluate the consequences

Estimate the impact Estimate the risk Evaluate the risk Identify and prioritize potential risk reduction measures

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HAZARD IDENTIFICATION TECHNIQUES 3

Hazards related to the chemical itself Harmful, irritant or sensitising Flammable Corrosive Oxidising Toxic Dangerous for the environment Explosive

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Material property data for HA

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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 6

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 7

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

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ETA

FTA

FMEA

HAZOP

What ifChecklist

What-if

Pre-HA

Checklist

Safety Review

Choice of Hazard Evaluation Techniques

R&D Conceptual Design Pilot Plant Operation Detailed Engineering Construction / Start-up Routine Operation

Expansion or Modification Incident Investigation

Decommissioning Commonly Used

Rarely Used or Inappropriate 12

Typical Staff Effort

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Non-Scenario Based Hazard Evaluation Procedure

SAFETY REVIEWS

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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 15

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 18

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? 19


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 (WhatIf/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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Resource Requirement • 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. 23

Examples

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Examples

http://www.harsnet.net/harsmeth/HarsMeth%20text/HarsMeth%20version%202.pdf 25

Examples

http://www.harsnet.net/harsmeth/HarsMeth%20text/HarsMeth%20version%202.pdf 26


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 28

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 • Plant’s process conditions • Geographic layout of material storage areas is usually needed.

• Do not normally require detailed process drawing 30

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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Dow Fire and Explosion Index • 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 32

Dow Fire and Explosion Index Material factor

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Dow Fire and Explosion Index The material factor is a property of the chemicals being handled. Compute for mixtures or use worst value

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Dow Fire and Explosion Index • 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 35

Dow Fire and Explosion Index Penalties for General Process Hazards Factor (F1)

F1

General Process Hazards Factor

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Dow Fire and Explosion Index • 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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Dow Fire and Explosion Index Penalties for Special Process Hazards Factor (F2)

F2

Special Process Hazards Factor 38

Dow Fire and Explosion Index

Process Unit Hazards Factor (F3)

F1  F2  F3

Fire and Explosion Index (F&EI)

F&EI  F3  MF

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Material factor General Process Hazards Factor

Special Process Hazards Factor F&EI 40

Dow Fire and Explosion Index Determining the degree of hazard from the Dow F&EI

F&EI index value

Degree of hazard

1 – 60

Light

61 – 96

Moderate

97 – 127

Intermediate

128 – 158

Heavy

128 – 158

Severe

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Control

C1

Isolation

C2

Fire protection

C3

Loss control credit factor (C1 x C2 x C3) 42

Dow Fire and Explosion Index F&EI

Loss control credit factor

Base Maximum Probable Property Damage (Base MMPD in $)

=

Value of area of exposure ($)

x

Damage factor (based on F&EI

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Dow Fire and Explosion Index F&EI


Actual Maximum Probable Property Damage (Actual MMPD)

=

Base MMPD (in $)

x


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Dow Fire and Explosion Index Example: new facility for handling tanker deliveries of butadiene Butadiene has material factor of 24 (flashpoint -105oC, poor “NFPA health rating”, high heat of combustion)

1.5 x 2.94 = 4.41 FEI = 4.41 x 24 = 106 45


PRELIMINARY HAZARD ANALYSIS 46

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. 48

Resource Requirement • • • • • • •

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

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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 51

Example

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Scenario Based Hazard Evaluation Procedure

WHAT IF ANALYSIS WHAT IF/CHECKLIST 53

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. 54

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 56

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 57

Example of "What-If"

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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). 59

Scenario Based Hazard Evaluation Procedure

HAZARD AND OPERABILITY STUDY (HAZOP) 60

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 62

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 64

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 Start

Select a process section

Select study nodes

Record and assign action items

Pick a process parameter Develop Action items

Apply guide words to process parameters

Assess acceptability based on consequences

Typical causes of deviations

Explain the design intention

Identify existing safeguards to prevent deviation

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• Selection of NODES – Major process vessels • Reactor • Storage vessel • Catch tank


Select study nodes


– 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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Select study nodes

• Choice of a process parameter – – – – – – – – –

Flow Pressure Temperature Level Composition Source Destination Duration Sequence

Pick a process parameter


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HAZOP Methodology • Choice of a Guide Words – NO, NOT, NONE – MORE, HIGHER, GREATER – LESS, LOWER Record and assign action – AS WELL AS items – PART OF Apply guide Develop Action – REVERSE words to process items parameters – OTHER THAN – etc


Start


Select study nodes





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HAZOP Methodology

Choice of a Guide word

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HAZOP Methodology • Choice of a Guide Words – NO, NOT, NONE – MORE, HIGHER, GREATER – LESS, LOWER Record and assign action – AS WELL AS items – PART OF Apply guide Develop Action – REVERSE words to process items parameters – OTHER THAN – etc




Start


Select study nodes



Parameter + Guide Word = Deviation 74

HAZOP Methodology Parameter + Guide Word = Deviation

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HAZOP Methodology Parameter + Guide Word = Deviation

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Select study nodes

Record and assign action items

Pick a process parameter Develop Action items

Apply guide words to process parameters





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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

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FAILURE MODES AND EFFECTS ANALYSIS (FMEA) 90

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 mode’s affects the system or plant: • Determines the effect (E) of the failure mode (FM) by the system’s response to the equipment failure

•  Generates recommendations for increasing equipment reliability (improving process safety) 91

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

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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

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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

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Hazid

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