Hazid

Hazard Identification What can go wrong and how?

1

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

2

HAZARD IDENTIFICATION TECHNIQUES 3

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

4

Material property data for HA

5

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?

8

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

9

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.

10

Type of Information Available to Perform the Study

11

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

13

Non-Scenario Based Hazard Evaluation Procedure

SAFETY REVIEWS

14

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.

16

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)

17

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

Non-Scenario Based Hazard Evaluation Procedure

CHECKLIST

20

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

21

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

22

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

24

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

Non-Scenario Based Hazard Evaluation Procedure

RANKING METHODS

27

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.

29

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

31

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

33

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

34

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

36

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

37

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

39

Dow Fire and Explosion Index

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

41

Dow Fire and Explosion Index

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

43

Dow Fire and Explosion Index F&EI

Loss control credit factor

Actual Maximum Probable Property Damage (Actual MMPD)

=

Base MMPD (in $)

x

Loss control credit factor

44

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

Non-Scenario Based Hazard Evaluation Procedure

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.

47

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

49

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 51

Example

52

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).

55

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"

58

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

61

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

63

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

65

Scribe Attributes • • • • • •

Attention to detail Responsive Good listener Good typing skills Good spelling/grammar skills Process/technical knowledge

66

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

67

HAZOP Methodology Start

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

Select a process section

Select study nodes

Explain the design intention

– 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

68

HAZOP Methodology

69

HAZOP Methodology

70

HAZOP Methodology Start

Select a process section

Select study nodes

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

Flow Pressure Temperature Level Composition Source Destination Duration Sequence

Pick a process parameter

Explain the design intention

71

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

Assess acceptability based on consequences

Start

Select a process section

Select study nodes

Pick a process parameter

Explain the design intention

Typical causes of deviations

Identify existing safeguards to prevent deviation

72

HAZOP Methodology

Choice of a Guide word

73

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

Assess acceptability based on consequences

Typical causes of deviations

Identify existing safeguards to prevent deviation

Start

Select a process section

Select study nodes

Pick a process parameter

Explain the design intention

Parameter + Guide Word = Deviation 74

HAZOP Methodology Parameter + Guide Word = Deviation

75

HAZOP Methodology Parameter + Guide Word = Deviation

76

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

77

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

78

HAZOP Example

79

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

92

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

93

Type of Results

94

Type of Results

95

Type of Results

96

SUMMARY

97

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.

98

Outcomes of HazID Techniques

99

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.

100

References

101