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Course Content
Course Title Process Hazards Analysis(PHA) HAZOP & What If /Checklist Methods
With an Introduction to Human Errors in Petroleum Industrv
Description To give an introduction of the principals of the overall meaning of the Process Hazard Analysis (PHA) with a brief of the most commonly used methods with an introduction to the Human Errors in the field of the Petroleum Industrv
Objectives 1. Understand the role of the Process Hazards Analysis in the Petroleum Industry
2. Understand the PHA Terminologies 3. Appreciate the accompanied Hazards in the Petroleum
Industry 4. Differentiate between the Occupational Safety and The
Process Safety 5. Increase the Awareness of the participants of the main
different between the Methods 6. Concentrate on the most commonly used methods in the
petroleum Industry (HAZOP & What If! Checklist Methods)
7. Appreciate the Field of the Human Error in the Industry 8. Appreciate the Differences between the Occupational
Ergonomics and Human Factors 9. Identify the Common Error Likely Situations 10. Increase the ability of the audiences to participate
efficiently in the conducted PHA sessions. Outlines The course will be given in five successive days covering
• Introduction To Process Hazards Analysis (PHA)
• HAZOP Technique
• Introduction to Human Error
• Illustration of the Twenty Error Likely Situations with practical Examples
Audiences This course is dedicated for the personnel ofa supervision task nature those are Process and Production staff, Engineering Staff, Managerial Staff, Maintenance Engineers and Projec~/Cons"uctionsEngineers
Numbers Maximum Of10 Attendees
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• Process Variables
Process
is defined as any activity involving the use, storage, manufacture, handling or movement of highly hazardous chemicals, or combination of these activities.
Process Variables includes
1. Flow Rate
A Hazard
Hazard is defined as "An inherent c_hemical or physical characteristic having any potential to cause a significant undesired event may resulted in harm to the people, environment or properties"
Chapter-l 3
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Process Hazards Analysis
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The application of one or more analytical methods to identify and evaluate process hazards for the purpose of determining the adequacy of or need for control measures.
It is used to analyze potential causes and consequences of fires, explosions, releases of toxic or flammable chemicals, and major spills of hazardous chemicals. It focuses on equipment, instrumentation, utilities, routine and non-routine human actions, and external factors that might impact a process.
Chapter-l 4
(I )~lock Qow diagrams or simplified process flow diagrams.
(2)Process parameters limits that, when exceeded, are considered anupset condition.
(3)Qualitative estimates of the consequences of deviations that could occur if established process limits are exceeded.
• The PHA must be in place prior to process startup.
Chapter-l 5
Purpose of PHA
·PHA is a method to identify and analyze the significance of potential hazards associated with processing or handling highly hazardous chemicals.
•PHA helps employers and workers to make decisions for improving safety and reducing the consequences of undesired or unplanned releases of hazardous chemicals.
•PHA helps to create a way of thinking among all managers, employees and contractors so that they will recognize process hazards during the normal course of their work.
Chapter-l 6
probability scenarios that could cause fatalities
A process hazard is an inherent chemical or physical characteristic with the energy potential for damaging people, property, and/or the environment. The key word in this definition is potential.
In a process or system, hazards are not always obvious. Energy may be stored in many different forms, including chemical (reactivity, flammability, corrosivity, toxicity), mechanical
and thermal.
PHAs are usually directed toward the identification of very low probability scenarios that could cause fatalities, serious injuries or major economic loss.
Chapter-l 7
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PHA Direction
• PHA helps understand that unlikely events can occur..,
Since such undesired events occur only rarely, even the most experienced personnel may not have considered the possibility of their occurrence, so a PHA is needed to help them understand and appreciate that such events can occur.
PHA May be considered as an incident investigation conducted prior the incident takes place
Chapter-l 8
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• High Risk Hazards
• The first goal of a PHA is identify hazards, Having identified the hazard, the PHA team would then normally be expected to risk-rank that hazard in terms of consequence and predicted frequency
• A PHA should focus on the identification of process-related hazards, i.e., on the identification of process upsets that could create high risk hazards.
• The third goal of a PHA analysis should be to concentrate on high-risk hazards. Every hazard has associated with it a consequence (safety, environmental, economic) and likelihood or predicted frequency
Chapter-l 9
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Identifying the hazards
Steps to be taken to identify the hazards List all obvious hazards. Most processes include a number of hazards that
are already fully recognized, such as the flammability of hydrocarbon or the
inhalation toxicity of H2S.
Examine all process parameters. Parameters (e.g., pressure, temperature,
flow rate, level) that are controlled or measured in a process are good
indicators of possible process hazards. Process parameters should be
examined for all modes of operation, independent of process chemicals,
because some hazards exist that do not involve the chemicals. For example,
if a process uses high-pressure steam, then both thermal energy and
pressure-volume energy hazards exist even though steam is non-toxic, non­
flammable, and non-reactive with most materials.
Document the identified hazards. The PHA report should list identified
hazards in tabular form and/or discuss each hazard briefly in the text. Doing
both is preferred. New or previously unidentified hazards should receive
particular attention and discussion.
High Risk Hazards
It is required that, processes posing the greatest risk to workers be analyzed first.
A methodology for ranking is not specified, but any method chosen must account for
(1) the extent of the process hazards.
(2) the number of potentially affected employees.
(3) the age of the process.
(4) the operating history of the process.
Chapter-I 11
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• Purpose of Occupational safety
• Overall System Safety
The purpose of a Process Hazards Analysis is to find hazards associated with the process being analyzed.
The process safety cares about process variables and the way of interactions between the operations and maintenance personnel and the process
Occupational safety, on the other hand, is more concerned with "normal" safety topics such as lock-outltag-out, protective clothing, and safe access to equipment.
Occupational~oncentrateson subjects related to the human being suchtheir behavior and self tendency to inv~lve­ themselves in a risky situations
Occupational Safety and Process Safety are both part of overall System Safety, but they are separateand.distinct fr9D1 one another.
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• Challenge statements of "I've never seen that happen"
PHAs can be used to get team members to "think the unthinkable." This is why one of the most important roles of the PHA team leader is to get the team members to think imaginatively, and to challenge statements of the type, "I've been here fourteen years, and I've never seen that happen ...",
Chapter-l 13
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Team Formation
• Team Size
• Cross-section of disciplines
• Team members must be compatible and Interactive
PHAs must be performed by a team. Teams can vary in size and in operational background, but must have expertise in engineering and process operations. Individuals may be full-time team members or may be part of a team for only a limited time. That is, team members may be rotated according to their expertise in the part of the process being reviewed.
The team conducting a PHA must understand the method being used. In addition, one member of the team must be fully knowledgeable in the implementation of the PHA method.
The team members should represent a cross-section of disciplines and functions with experience and knowledge specific to the process being evaluated. typically including operations, engineering, maintenance, and process design. Having all the disciplines present helps ensure that all types of hazard scenarios are discussed. Furthermore, the interaction between team members helps uncover those hazards that may be created due to communication difficulties or misunderstandings between departments.
Chapter-l 14
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Recommendations I Findings
• It is not the purpose of a PHA to issue specific recommendations.
• Purpose of PHA is to find the potential of problems not to solve them
The purpose of a PHA is to identify hazards, and then to assign a risk ranking to those hazards. It is not the purpose of a PHA to issue specific recommendations.
The PHA team should be particularly careful not to become an "engineering department"; the purpose of the PHA is to find problems, not to solve them.
Chapter-l 15
PHA Assumptions
PHA team consider the following assumption.
The calculations of the process design are correct and had been reviewed (team members shouldn't make a calculations review by themselves) on the other hand team may challenge the design basis of the process itself.
•Equipments shall be considered fit for its use of intention. However team may argue about the suitability of the equipments for the abnormal conditions
•PHA team shall consider the on hand operating procedures are updated, accurate and reflects the operations practices.
·Declared policies of the organization will be considered to be enforced
Chapter-l 16
Process Hazards Analysis
Safe Operating Limits
Safe Operating Limits
Fundamental to all types of process safety work is the concept of Safe Operating Limits. The facility designers should define a safe operating envelope for all critical process variables
A Safe Operating Range that lies between the Safe Upper Limit (SUL) and Safe Lower Limit (SLL). The Normal operating value lies inside this Safe Operating Range.
Operation outside that envelope is unsafe by definition, and is therefore not permitted. The PHA team needs to know what the safe limits are in order to have definitions for the word "safe" and "deviation."
Chapter-l 17
• COMPONENTS OF RISK
Risk ~. , ·onsequence * F
2. The consequences of that hazard (safety, environmental, economic)
3. The frequency with which the hazard occurs, or is expected to occur.
The three terms are combined as shown in the Equation
Risk hazard = Consequence * Frequency
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SUBJECTIVE NATURE OF RISK
• Risk is fundamentally a subjective, and, at times, an emotional topic.
i7J- Risk hazard = Consequence * Frequency (1)
"- Equation (1) puts consequence and frequency on equal rank; it implies a linear trade-off between the two. For example, a hazard resulting in one fatality every hundred years has the same objective risk value as a hazard resulting in ten fatalities every thousand years. In both cases the fatality rate is 1 in a hundred years, or 0.01 fatalities yr-1.
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High risk hazards Vs High consequence hazards,
• PHA teams concentrate so much on high consequence hazards.
• High consequence hazards are the most emotionally affecting
-In practice, many PHA teams concentrate NOT so much on the identification of high risk hazards, BUT of high consequence hazards.
-Most PHA teams would spend more time analyzing the incident of (catastrophic vessel failure) rather than the more frequent seal failure. In other words, they are looking more for high consequence rather than high-risk hazards.
-Another reason for focusing on high consequence incidents, is that they are the ones that tend to get the most publicity, that are the most emotionally affecting
-Higher frequency incident may be fixed more easily
-Higher consequences scenarios are difficult to be imagined or visualized
Chapter-l 20
Factors affecting the public perception of risk
• The degree of control over the risk. • The familiarity of the consequence. • Willing to accept risk if there are
direct benefits • High-consequence accidents less
acceptable than more frequent, low consequence accidents.
Factors affecting the public perception of risk include:
-The degree to which a person has direct control over the risk. For example, someone who finds the presence of a chemical plant in his community unacceptable may willingly driving over speed because he feels that he has some control over the risk associated with the latter activity
-The familiarity ofthe consequence term. For example, people understand and accept the possibility of a fatality in a road accident, but may be more worried about the consequences of being exposed to unknown toxic chemicals.
-Pcople are more willing to accept risk if they are direct recipients of the benefit.
-high-consequence accidents less acceptable than more frequent, low consequence accidents.High consequence/low frequency accidents are perceived as being more serious than low consequence/high frequency accidents.
Chapter-I 21
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Modified Risk Ranking
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In general, people find rare, high-consequence accidents less acceptable than more frequent, low consequence accidents. For example, it is fact that the number of peoples die every year in the high ways accidents are more than those die in airplane crash, However the community precept the later with more panic.
The difference between the two risks is a perception rooted in emotion.
Risk hazard = Consequence n * Frequency..... (2)
Where n > 1
high consequence/low frequency accidents are perceived as being more serious than low consequence/high frequency accidents.
Chapter-l 22
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QUANTIFYING RISK
Reasons of Quantifying the Risk
-Quantification helps get around the fixation problems, as well as the general "I think I You think" difficulties that tend to occur in qualitative work.
-Quantification also helps to overcome the circulation problems
-Quantification can help the PHA leader challenge the person who has considerable experience and who may be over-confident (and incorrect) in his or her opinions.
Chapter-l 23
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Human Presence Contingency
• It is important to consider how often the human presence at the site.
The presence of humans in an area automatically raises the level of risk consequently, one of the best ways of improving safety is simply to remove people from the site of potential releases.
It is important to consider how often the human presence at the site of the analyzed system.
Chapter-l 24
• Logic Analysis
Creative Thinking
An effective PHA will encourage the team members to identify low frequency/high consequence hazards that have never been seen in the field. The team members should be encouraged to think of hazard scenanos
team members typically have trouble accepting and understanding unlikely combinations of events. To help overcome this block, the leader may choose to describe a number of real accidents that occurred elsewhere to show how "weird" they were - yet they happened.
CHECKLISTS AND STANDARDS
Typically, checklists are developed for equipment items such as pumps, pressure vessels, valves, and tanks. Checklists can also be created from standards such as regulations, codes, and company policies.
FORMAL LOGIC ANALYSIS
To clarify the logic as to how accidents may occur, and also provides a foundation for the quantification or risk.
Chapter-l 25
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• A pressure relief valve is a safeguard against high pressure
• Special procedures and training in how to handle a particular high­ hazard scenario could be regarded as safeguards.
Any device used during normal operation is not a safeguard; nor is a post-accident mitigation system.
Post-accident safety systems such as the use of firefighting equipment ( or the Emergency Response Team do not qualify as safeguards because they come into use after the event has occurred, when the plant is already in an unsafe condition.
Chapter-l 26
~ HAZARDS Of
SAFEGUARDS
• Safeguards can themselves create a hazard, although usually much less serious than the one that they are protecting against.
For example although the safety relief valve when working properly it is protected the facilities from overpressure by directing the relieved gases to the flare, the flared gases may affect the workers themselves or may impact the environment.
Chapter-l 27
Active Safeguards
~ {aSSiVe Safeguards
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-An active safeguard would be a device such as an interlock or relief valve that responds to an unsafe condition. The active safeguard need an action/actions to be performed in order to be activated, Pressure transmitter should senses the overpressure and send a signal to the logic solver to be analyzed and send the order to the tenninal valve ESD to close.
-A passive safeguard would be a device such as an overflow drain on a tank or Dike around the tank - no action is required to make it to work.
-Generally, passive safeguards offer better protection because they are more reliable.
Chapter-l 28
Operational Systems
At the lowest level, a deviation is handled by Operating systems such as normal control loops and operator intervention.
Safety Instrumented Systems (SIS) whose only purpose is to bring the plant into a safe state in the event of a serious upset. Hence, such systems are true safeguards - they take action before an unsafe condition is reached.
Mechanical safety systems such as spring loaded relief valves and rupture disks are usually the last line of defense in an out-of-control situation, and therefore should never actually be required to operate.
Chapter-I 29
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PHA TECHNIQUES 1. Hazard & Operability Method (HAZOP) 2. What-If 3. Checklist 4. What-If/Checklist 5. Failure Modes &Effects Analysis (FMEA) 6. Fault Tree Analysis 7. Other Appropriate Methods
No one of these methods is inherently any better than any of the others. They all have their place, and are often used in combination with one another.
Chapter-l 30
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• Used simply to ensure compliance with regulations
HAZOP is an abbreviated term for HAZard and OPerability study. It is a technique that identifies the potential hazards and operating issues with the design and construction of equipment and plant. The study involves the interaction of a multi-disciplinary team. The identification is carried out using a series of keywords to examine deviations and their subsequent effects on the process as a whole. Once the hazard and operability concerns are identified, appropriate actions are recommended.
Being the most systematic and thorough type of PHA, the HAZOP technique is sometimes used simply to ensure maximum compliance with regulations,
Chapter-l 31
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WHAT-IF METHOD
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The What-If method is the least structured of the creative PHA techniques. Its use requires a team composed of experienced analysts capable of identifying incident scenarios based on their experience and knowledge.
Chapter-l 32
CHECKLISTS
• Uses a set of pre-written questions to stimulate discussion and thinking.
• The list of questions should be long enough.
• Powerful in case of analyzing typical process section(s)
The Checklist Method uses a set of pre-written questions to stimulate discussion and thinking. The questions are developed prior to the PHA by experts who have conducted many PHAs and other similar analyses, and by experts in the process being reviewed.
The list of questions should be long enough to ensure that no obvious issues are overlooked.
In case of applying a pre-written checklist provided by codes, standards or recommended practice for example (API RP-14C) for a typical process section, it becomes very powerful
Chapter-l 33
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WHAT-IF I CHECKLIST
• Approach combines the two methods
The What-If/Checklist approach combines the two methods just discussed. In fact, it encourages a team to think creatively, using a Checklist to provide structure to the discussion
Chapter-l 34
• For determining the ways in which equipment items can fail
• Used primarily in the aerospace and nuclear power industries
Failure Modes and Effects Analysis (FMEA) is a technique for determining the ways in which equipment items and their internal components can fail, and what the consequences of such failures would be on the overall system reliability and safety.
Traditionally, the FMEA method has been used primarily in the aerospace and nuclear power industries, but not so much by the process industries because single equipment failures do not usually have catastrophic results.
Chapter-I 35
FAULT TREE ANALYSIS • Tree is a logic diagram that shows
the combination of events
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• Its application is for a single individual approach
A Fault Tree is a logic diagram that shows the combination of events that have to take place before an accident can occur. Fault Trees are normally used to analyze systems rather than to creatively identify hazards, although the Qualitative Fault Tree method can provide a fresh approach to hazards identification. The Fault Tree method differs from the other PHA techniques discussed to this point in that its application is often more suited for a single individual rather than a team. Teams have trouble discussing situations involving multiple contingent events
Chapter-l 36
high level of experience
• Using a checklist method
If several processes require PHAs or if an existing facility is large, and PHAs are being carried out for the first time the PHAs must be prioritized. Major Hazards Screening Analysis (sometimes referred to as a preliminary hazard analysis) may be used to determine and document the priority order for conducting PHAs. A Preliminary Hazards Analysis is used for those areas with the highest consequence (not risk) are handled first.
At a minimum, the Rule requires the prioritization to consider the potential severity of a hydrocarbon release, the number of potentially affected employees, and the operating history ofthe process, including the frequency of past hydrocarbon releases and the age of the process.
The Major Hazards Screening should be conducted by individuals with a high level of experience both in the way processes operate and in hazard identification. Generally, they will use a checklist method
Chapter-l 37
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-The hazards associated with raw materials, and final products.
-Equipment used, particularly high-speed rotating items, vessels and piping subject to corrosion, and equipment operating at high pressures and temperatures.
-Layout of equipment, and ancillary services, such as fire fighting systems.
-Operations, including procedures and training.
-Maintenance, including procedures and training
Chapter-l 38
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The selection of a PHA method depends on many factors including the size and complexity of the process and existing knowledge of the process. Has the process been in operation for a long time with little or no modification, and has extensive experience been generated with its use? Or is the process new? All PHA methods are subject to certain limitations.
Because PHAs depend on good judgment, assumptions made during a PHA must be documented, understood, and retained for future PHAs.
When a new process is being designed and constructed, it is normal for different types of PHA to be performed at each stage of the design.
some guidance is provided as to which method can be used at which stage in the process.
Chapter-l 39
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• Excellent opportunity for eliminating hazards entirely
.e What-Ifmethod is probably the best method for this phase ofthePHA
A Conceptual Design PHA provides a preliminary safety analysis at the time that the basic process or plant design is still being developed (which means that proposed changes may not cost much to implement).
A conceptual PHA provides an excellent opportunity for eliminating hazards entirely and for making fundamental changes to the process to achieve an Inherently Safer Design.
the What-If method is probably the best method for this phase of the PHA because it is good at encouraging conceptual and creative thinking.
Chapter-l 40
It -I f method works well at this stage
har- list method is also a good choice at this stage.
Once the basic process design is complete, a Preliminary Design PHA can be conducted. The available documentation will generally be limited to block flow diagrams, preliminary Process Flow Diagrams (PFDs) and Material Flow Diagrams (which also provide information on materials of construction). Once more, the What-If method works well at this stage because opportunities to make major changes in the process design remain. The What­ If/Checklist method is also a good choice at this stage.
Chapter-l 41
L DE.SIGN
• The final design PHA is usually a full,\Z()
At the conclusion of the final design, a complete set ofP&IDs will have been published. Other documentation available to the PHA team will include electrical loop drawings, MSDS, and draft operating manuals. The final design PHA is usually a full HAZOP involving many people. This approach is thorough, and should not be performed until the P&IDs are finalized. If a problem arises within the facility after it is built, it is the Final Design PHA that will be used as evidence that the company carried out a proper PHA.
Chapter-l 42
RE· e. §'.. "". \J I
• The last process safety evaluation to be carried out before the start-up
The last process safety evaluation to be carried out before the start­ up of a new or modified facility is the Pre-startup Safety Review, or PSSR. A PSSR is not a PHA instead it serves to ensure that the plant was constructed as required by the original design and that all required changes (including those stemming from the PHA) have either been implemented or meet the original design intent
Chapter-l 43
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CHAN
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• Any significant proposed change to a plant that is already running
h -I ror a brief is a good choice for the PHA.
Any significant proposed change to a plant that is already running, or whose design has been finalized, should be analyzed with a PHA as part of the Management of Change process. A What-If or a briefHAZOP is a good choice for the PHA.
Chapter-l 44
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• Mothballed J J c::>- "'(: • Turn down and the site used for
something else
Ius t..1' is preferred in the case of the plant that is being mothballed
• If the plant is to be demolished, the will used
When a plant is decommissioned, it has two possible fates. The first is that it will be simply mothballed in the hope that it can be renovated and restarted at some unspecified time in the future when economic conditions call for such action. The second possibility is that the plant will be tom down and the site used for something else. In either case, a PHA should be performed, with the What-If technique probably being the preferred method. In the case of the plant that is being mothballed
If the plant is to be demolished, the checklist will be used
Chapter-l 45
PROCESS HAZARDS ANALYSIS STRENGTHS
Process Hazards Analysis
STRENGTHS OF PHA
Time to Think
-it gives the team members time to systematically and thoroughly think through the hazards associated with the facilities for which they are responsible. Most team members are normally very busy with their day-to-day work.
Chapter-l 47
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Cross-Discipline Thinking
•An effective PHA brings together people with different skills and backgrounds, thus leading to fruitful cross-disciplinary thinking. The presence of persons from multiple disciplines is particularly helpful at flushing out potentially hazardous assumptions
Chapter-l 48
Process Training
•PHAs provide an excellent training forum for those who are unfamiliar with the process being analyzed. These people obtain an excellent overall picture of the process
Chapter-l 49
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Information
•During the course of a PHA, the team will almost certainly find problems with some of the Process Safety Information ­ particularly the availability of Safe Upper and Lower Limits.
Chapter-I 50
LIMITATIONS OF PHA
False Confidence
•Management sometimes has trouble understanding that the team no matter how well qualified will not identify all hazards.
Chapter-l 52
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Safeguards
-Safeguards can be another source of false confidence. It is highly unlikely that a highly hazardous situation has never been considered at all; hence, safeguards such as relief valves and interlocks will already be in place.
Chapter-l 53
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LIMITATIONS OF PHA
Team Quality and Composition
-The quality of any PHA depends entirely on the composition of the team, and on the capabilities of the team members.
Chapter-l 54
Sophisticated Use Of Language
·PHAs use complex language constructs. A statement such as, "If the valve could leak, a vapor cloud would form, and so we should reduce the pressure" is far from easy to understand for those whose first language is not English. No doubt all languages could come up with similar examples.
Chapter-l 55
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•PHA reports can be very difficult to read and understand
Chapter-l 56
Chapter-l 57
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LIMITATIONS OF PHA
\fi Abstraction
-The focus on high consequence/low probability accident scenarios can give the impression that PHAs are abstract and irrelevant.
Chapter-l 58
Boredom
·Process Hazards Analyses are frequently long-winded and boring. It is difficult for anyone to maintain concentration and enthusiasm when the meetings drag on for days
Chapter-l 59
LIMITATIONS OF PHA
Equipment Orientation
•Most PHA teams are composed of persons who have a technical background. As such, they tend to view the plant in terms of equipment rather than people or management systems.
Chapter-l 60
CONCLUSIONS
Process Hazards Analyses have become an integral part of the way in which most companies in the process industries do business.
A wide range of PHA techniques is available, but all are team efforts in which a combination of plant knowledge and creative thinking helps everyone understand what hazards exist on the facility.
Chapter-l 61
hat If
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th
What-if analysis involves the examination of possible deviations from the design, construction, modification, or operating intent of a process. It can be used to examine virtually any aspect of facility design or operation. Because it is so flexible, it can be performed at any stage in the life of a process using whatever process information and knowledge is available. ~.- . i .-1. c- t-"{) -~ -~~
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Team Approach:
The what-if analysis is a creative, brainstorming examination of a process or operation conducted by a group of experienced individuals able to ask questions concerns about undesired events.
What-ifSessions should be conducted with a team who represents different disciplines ofthe system
Loosely Structured
What-If method is the least structured creative method ofPAH it is depend on the brain storming of the team members and the successfulness of the event is highly dependent on their ability of different up set scenarios creation and questions formulation.
It is requires a highly qualified and knowledgeable about the process members
Chapter-2 3
~~ EGYPTIAN TRAINING SERVICES ~ J9#~c:Jl.5.tA<»=:.l
Hazards Identifications
Questions together with the answers will comprehensively identify the hazards and...
potential hazards.
Imaginatively generate a series of questions
What-If team would be encouraged to generate a series of questions within the pre-identified scope of the process hazards review with their own perspective. Through the questioning process, an experienced group of individuals identify possible accident events
Develop answerers of the raised questions.
Team that created from different disciplines will develop answers of the formulated questions.
Questions together with the answers will comprehensively identify the hazards and potential hazards, their consequences, and existing safety levels, then suggest alternatives for risk reduction. The potential accidents identified are neither ranked nor given quantitative implications
Chapter-2 4
Team should be fanned by multi-disciplined represents different departments (Operation. Maintenance, Engineering, HSE...etc) that will leads to
1. Ensure that each discipline is represented
2. Each discipline brings different perspectives and different responsibilities to the review.
Chapter-2 5
What-If / Check List Method J.'I\; C-..w.J~1 <...:lk.~ Qu=.,.J1£Jrfi EGYPTIAN TRAINING. SEFlVICES Jg.;l+JJe~ LJl6",.. (M~!
Performing the Analysis
process description by operations staff who have the process knowledge.
• Potential safetv issues to be 01
identified
The scope of the study should be agreed upon by the team members.
The analysis meetings should begin with a basic explanation of the process by operations staff who have overall facility and process knowledge.
The meetings then revolve around potential safety issues identified by the analysts.
Chapter-2 6
• Questions may Address any abnormal conditions
• The team proceeds from the beginning to the end of the process
• SCRIBE recorded the analysis '"
details
The questions may address any abnormal condition related to the facility, not just component failures or process variations. The questions are formulated based on PHA team member experience and applied to existing drawings and process descriptions. The team generally proceeds from the beginning of the process to its end, Or dividing the process into functional systems. Or begin with the introduction of feed material and follow the flow until the end of the process.
The questions, and eventually the answers (including hazards, consequences, engineered safety levels, and possible solutions to important issues), are recorded by the team member designated as "scribe," so that they can be viewed by all team members.
During the process, any new what-if questions that become apparent are added.
Chapter-2 7
heck List
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ethod • Easy to use and can be applied @
any stages of process
• Effective to identify common '"
hazards
The checklist analysis method is versatile, easy to use and can be applied at any stage in the life of a process.
It is primarily used to indicate compliance with standards and practices. It is also effective way to identify common and recognized hazards.
A traditional checklist analysis uses a list of specific items to identify known types of hazards, design deficiencies, and potential accident scenarios associated with common process equipment and operations.
Checklists are most often used to evaluate a specific design with which a company or industry has a significant amount of expenence.
Chapter-2 8
What-If / Check List Method
Check List 11 d
• Uses a set of pre-written questions to stimulate discussion and thinking.
• The list of questions should be Comprehensive
The Checklist Method uses a set of pre-written list of questions or items to stimulate discussion and thinking and to verify the status of the system..
Checklists may vary widely in level of detail, depending on the process being analyzed.
The questions are developed prior to the PHA by experts who have conducted many PHAs and other similar analyses, and by experts in the process being reviewed.
The list of questions should be long enough to ensure that no obvious issues are overlooked.
Check list may not caught all the potential hazards of the system to be analyzed.
In case of applying a pre-written checklist provided by codes, standards or recommended practice for example (API RP-14C) for a typical process section, it becomes powerful
Chapter-2 9
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• process design not comply with standard are discovered through responses to the questions
• To be applied conscientiously to identify problems that require attention.
A checklist is developed so that aspects of process design or operation that do not comply with standard industrial practices are discovered through responses to the questions in the list.
A detailed checklist can be as extensive as necessary to satisfy the specific situation, but it should be applied conscientiously in order to identify problems that require further attention.
Detailed checklists for particular processes should be augmented by generic checklists to help assure thoroughness. Generic checklists are often combined with other methods to evaluate hazardous situations.
Chapter-2
Perforlni 2 the i\nalvsis ~Y ~
• May applied by less experienced engineers/Staff
• Team members to compare the process equipment and operations to the checklist items
After a checklist is prepared, it can be applied by less experienced engineers if necessary.
Team members should walkthrough and visually inspect the process areas to compare the process equipment and operations to the checklist items.
Chapter-2 11
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• The analysts respond to checklist based on observations, process documentation, interviews, and personal perceptions.
• If the process do not match features on the checklist, the analysts note the deficiency.
The analysts respond to the checklist items based on observations from their visual inspections, process documentation, interviews with operating personnel, and personal perceptions.
If the process attributes or operating characteristics do not match the specific desired features on the
checklist, the analysts note the deficiency.
Chapter-2 12
EGYPTIAN TRAINING SERVICES J9.;41IB~L..J~""a;.~
• First Level Questions Pressure \/es
• Second Level Separa rs • Third Levels Low Pressure Separators
Most Familiar way to organize the check lists is to categorize them into a brake done levels for example to classify the into primary equipments then to categorize a secondary equipment as sub sets or secondary level and so on
For Example First Category
13
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Limitations of Chec List
• When derived from handbooks or similar sources, many entries in a checklist may not be.,
applicable
• process hazards may be so unusual
When derived from handbooks or similar sources, many entries in a checklist may not be applicable to the process being studied.
In other cases, process hazards may be so unusual they are not in standard checklists. Thus, it may be difficult to assure that all hazards have been analyzed.
I,
hat If I heck Lis ethod
The what-if/checklist analysis method combines the creative, brainstorming features of the what-if analysis with the systematic features of the checklist analysis. The PHA team uses the what-if analysis method to brainstorm the types of accidents that can occur within a process. Then the team uses one or more checklists to help fill in any gaps. The what-if analysis encourages the PHA team to consider potential accident events and consequences that are beyond the experience of the authors of a good checklist and, thus, are not covered on the checklist. Conversely, the checklist provides a systematic nature to the what-if analysis.
Normally, a what-if/checklist analysis is used to examine the potential consequences of accident scenarios at a more general level than some of the more detailed PHA methods. It can be used for any type of process at virtually any stage in its life cycle. However, this method is generally used to analyze the more common hazards that exist in a process.
Chapter-2 15
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heck List bination
Combining What-If method with Check List Methods leads To
-Comprehensive coverage of a broad ranges of hazards and potential hazards.
-Consensus by a wide range of disciplines on the revealed recommended track to the safe operation of hazardous materials.
-A report to be reader friendly and easy to understand
Chapter-2 16
• Node-By-Node Approach
Node-By-Node Approach
Is the most commonly used approach whereas the process is broken down to sections to be separately analyzed and it is preferred to be in a sequential manner.
Equipment and Functions Approach
This approach is not commonly used in petroleum industry and it is similar to FMEA
Chapter-2 17
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oncerned Items
Component Failure
Component Failure.
Concerning scenarios of failure of the process component under certain condition that may cause a lose of containment.
• What-If a Specific component Failure occurred under certain conditions.
What-If the Pressure Vessel ruptured
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Abnormal Process variables
Abnormal Process Variables.
Concerning about the process variables being abnormal outside the safe operating limits.
• What-If the process variable becomes abnormal
What if the pressure increased
Chapter-2 19
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oncemed Items
Human Performance
Human Performance.
Concerning with the human performance as an element of the overall process and his interactions with the process
• What -If the Human Performance performed incorrectly.
• What-If the operator open wrong valve inadvertently
(
External Influence (Events / Conditions)
Concerning with the external conditions or events that can badly affect the normal operations mode of the process
• What-If an External conditions occurred affected the normal operations mode.
What-If an External Fire occurs
Chapter-2 21
~e~(.....I'i.6""'a..=l
• Answers for internal use
• Answers for PHA sessions
Answers For Internal use
For the internal use purposes the answers of the questions shall considered the existing safe guards installed against the upset either administrative or the devices safeguards.
Answers for PHA Purposes
For the purpose of PHA the answers of the questions will give no credibility in the first place for the safe guards (Or consider they are not exist) then identify the risks and eventually taking the credibility of the existing safe guards
Chapter-2 22
What-If / Check List Method C41J<:llJ1 <....:iLon=...! C:1u=<>J1 EGYPTIAN TRAINING SEFlVlCES
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Intension
Intention
What is the design intention of the process and how is the expected normal process operation.
Chapter-2 23
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Questions
Questions
Questions that are usually (but not mandatory) begin with What-If that are challenging the design intentions and imaginatively assuming process upset
Chapter-2 24
Chapter-2 25
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hat If TerlTlinology
Safe Guards
Safe Guards.
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hat if Terminolog.y
Findings Recommendations
Findings & Recommendations
Enlisting of the overall findings with a suggestions for procedural or design change or further engineering studies to be required
Chapter-2 27
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uestions Formutatio
• Brain Storming
Brain Storming
The objective of the What-If is to encourage the team to think imaginatively in order to generate a series of questions those are relevant to the overall scope of the hazards analysis.
Challenging Design Intentions.
Team should fell free of challenging the design intention of the ( process and the design basis.
Chapter-2 28
• Questions NOT answers
-Each question should be recorder in a complete sentences to let the member who raised it the it is captured correctly.
-Questions should be (AS POSSIBLE) captured due to the node sequences. This will help to insert any additional questions in the review stage
-There is no such thing called a dumb question. This well lead to encourage the team member to participate effectively
-Questions only to be raise. No answers required the time being
Chapter-2 29
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\~--_~-. • Que.stipns Acauis~tion ~tc\c\s) (')\0, I'''Jy~~ij'v1 Pr(j~~/t'/;,r 0'--'-(' ~-- = • Questions to be answered
• While time for thinking
• Not limited with What If
-Questions about the design basis or equipments capabilities may be answered in time but not the what if questions.
-Team may be allowed to take a while oftime to think of and prepare the brainstorming questions.
-The analysts are encouraged to voice any potential safety concern in terms of questions that begin with "what-if." However, any process safety concern can be voiced, even if it is not phrased as a question. For example:
I wonder what would happen if .
Questions may started with How, What, When, How likely ... etc not limited to What If.
Chapter-2
brainstorming session
• To stimulate the missing questions
-The check list shouldn't be in the hands of team members prior the end of brainstorming. It will affect their ability of thinking imaginatively.
-Check lists should be used to stimulate questions that may had missed by group interaction
Chapter-2 31
EGVPTIAN TRAINING SERVICES Jg.;J+Ij~L....1.~"'~=~
Blocked-in Pump
If a centrifugal pump is blocked in while it is still running, the liquid trapped within the pump will heat up due to the energy that is being added by the rotating impeller. Sometimes the rise in temperature will cause the pump seal to leak thus dissipating the pressure at the pump without creating a major hazard.
Chapter-2 33
What-If / Check List Method )/c e..w!:>lJ1 c....:;k.~ C1uc=J1 ~ EGYPTIAN TRAINING SEFWICES
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External Fire "High Temperature"
\
"High Flow"
The team should list all control valves that are currently in the manual operating mode. For each valve, the team should then ask the following questions:
1. Why is the valve in manual?
2. What would happen if it were switched to automatic?
3. Is the valve part of a safety shutdown system?
The last question is the key. The operators may say that, if there is an emergency, they will be sure to move the valve to its fail-safe position. However, humans are unreliable during an emergency, whereas instruments can be trusted not to panic or run away. Nor will instruments come to work with an "attitude" or suffering from a "bad day."
cnapter-z 35
\ ~~ EGYPTIAN TRAINING SERVICES
What-If / Check List Method
Special reverse flow scenarios involving check valve failures have already been discussed. In general, when a reverse flow can create a high hazard scenario, a check valve is installed. For example, it is normal to install a check valve on the discharge of a centrifugal pump so as to prevent liquid from flowing backwards through the pump should it stop working.
Although check valves certainly improve the operational integrity of a system, it is questionable if they can be regarded as true safeguards due to their tendency to stick in the open position ­ particularly if solids are present in the fluid.
Chapter-2 36
What-If / Check List Method t rrk ~<:>:LII <..JL;,<:>..:::>J~l ~ EGYPTIAN TRAINING SERV.ICES
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Fail Safe Positions "High/Low Flow"
All control valves have a f':lil positi~n. In the event of a power failure and/or loss of instrument air, the valve's spring operator will cause the valve to fail open, fully closed, or remain in its current position.
A useful task for the PHA team is to check the fail position of each control valve
Chapter-2 37
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Relief systems (relief valves, rupture disks, relief headers, knock­ out tanks, blow-down pots, at»d flare headers) usually represent the facility's last line of defense. If these systems are
required to work, and they do not work, then a very serious accident could ensue.
The design philosophy behind such systems is that the high pressure material in a vessel has a straight shot to atmosphere, with no intervening valves or restrictions. (A flare does not put restrictions in the relief line; it merely forces the materials to exit through a flame.) Therefore, the PHA team should carefully consider all possibilities for plugging of these systems
Chapter-2
Block Valves below Relief Valves
Many companies permit a block valve to be placed beneath each relief valve. This allows them to block in the relief valve, remove it for testing and service, and reinstall it, without having to shut down the process. The hazard associated with this practice is obvious: if a high pressure situation develops while the block valve is closed, the vessel could over-pressure, and rupture. For this reason, other companies prohibit the use of block valves below relief valves altogether.
If it necessary to work on relief valves routinely, protection can be provided by installing two or more relief valves at each location. That way, one relief valve can be blocked in, while the others provide protection
Chapter-2 39
What-If / Check List Method C4LJ<:llJ1 c....:i1o<:>=:.J 6u=c>J1 EGYPTIAN TRAINING SERVICES
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Pressure in Relief Headers "High Pressure"
Although a process flow sheet will indicate that a relief valve opens at a certain pressure, it is important to realize that actually it is differential pressure that opens the valve. Therefore, if the set point for a relief valve is say, 50 psig, and the pressure in the
relief header is 10 psig, then the relief valve will open when the absolute pressure in the vessel it is protecting is 60 psig. Such a scenario could occur if a plant-wide upset has caused multiple vessels to discharge into the relief header at the same time - the amount of material in the header may be so great that its pressure rises. To get around this difficulty, some relief valves are designed to overcome this problem by opening at a specified absolute pressure. The PHA team should check which approach is being used in the facility that is being analyzed
Chapter-2 40
Underground Piping "Loss of Containment"
Underground piping can be hazardous for two reasons. First, because it is underground, it is possible that not much is known about the condition of the piping: "out of sight, out of mind." The first indication of a problem may be contamination of the ground water or some other polluting event.
The second difficulty with underground piping is that it may be subject to external corrosion, particularly if cathodic protection systems are not in place.
Chapter-2 41
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Applicable for Process and Non-Process
(
Suitable for several stages of design
Because it is so flexible, it can be performed at any stage in the life of a process using whatever process information and knowledge is available.
Chapter-2 43
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Easy to be learned & Applied
It is easy to be learned and it can be used to examine virtually any aspect of facility design or operation.
Chapter-2 44
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Can Focus on a specific concerns
Chapter-2 46
Chapter·2 47
Limitations
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Highly Dependent of the quality of the team members and the
comprehension of the Check List
Chapter-2 48
Chapter-2 49
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regulations
Chapter-2 51
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•Team Approach • Systematically Structured
The HAZOP study was developed to identify hazards in process plants and to identify operability problems that, although not hazardous, could compromise a plant's productivity.
Team Approach:
Like What-if method, HAZap should be conducted with a team who represents different disciplines of the system
Systematically Structured
In contrary with the What-If method HAZap The HAzap study should be performed in a deliberate, systematic manner during study the process sections to reduce the possibility of omissions and to stimulate the imaginative scenarios and identify potentials of process upset or malfunctions that badly impact the Environmental, Safety and productivity Issues
Within a study node, all deviations associated with a given process parameter should be analyzed before the next process parameter is considered. All of the deviations for a given study node should be analyzed before the team proceeds to the next node.
Chapter-3
• Concentrates on how the design cope abnormal conditions
The best time to conduct a HAZOP is when the pipe and instrumental diagrams (P&ID) are available because it is possible to change the design without major cost. The HAZOP study concentrates on how the design will cope with abnormal conditions
Chapter-3 3
EGYPTIAN TRAINING SERVICES ~IBi.b.Q W~;Ma;o.~
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If 25~ -Nod~/Section
Node is any section of the.. process in which a process parameters change occurs
Node
Node (Sometimes called PrQ..cess Section) is identified as any section or piece of the process that inside it the process parameters or variables are substantially changes.
For Examples
Tank has its own varying level.
Separator pressure and level may vary.
Temperature is an important variable that considered in Heat Exchanger
Chapter-3
Purpose & Function
The team should be concerned about the purpose of every process section and identifies the specific vessels, equipments piping segments and instrumentation to be included in the HAZOP study
Chapter-3 5
~~ EGYPTIAN TRAINING SERV.ICES ~ J~IS~~p,a;;.~
Node Selection
atecrials Volume/Stock
Materials Volume
HAZOP team is usually concerns about the trapped volume or the stock materials holed by the vessels, tank and equipment
Chapter-3 6
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Node Selection
Materials Composition
The compositionlPhase of the materials handled within different section of the process is also an item for example gas outlet of production separator, oil outlet and water outlet.
Chapter-3 7
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Node Selection
Stud bjectie.s
Study objectives
Study objectives should be clearly identified prior conducting the analysis session to help the team in the node selection for example does the HAZOP is made for a novel process, Existing facilities also the complexity and scale of the facilities to be analyzed for example" Management of change for small modification or introducing a new major equipment of applying a new technology.
Chapter-3 8
Isolation Points
Reliable isolation points between the nodes is an important item to be considered.
Chapter-3 9
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Major Eguipments/Component
It is strongly suggested to consider every major component to be a study node for example production separator, Main injection pumps, inlet scrubber, Storage tanks, Generators .....and so forth
Chapter-3 10
5 ctions On
One line section between each major sections
At least one line section (Study Node) between each major Section of the process is suggested for example Separator and charge pump are connected at least with one node also inlet scrubber and GIL module should be connected with at least one study node.
Chapter-3 11
HAZards & OPerability (HAZOP) <-w=..ll Cik,=::..J Qu=.:.J1 EGYPTIAN TRAINING SERVICES
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One line section between each major section
At least one line section (Study Node) between each major Section of the process is suggested for example Separator and charge pump are connected at least with one node also inlet scrubber and GIL module should be connected with at least one study node.
Chapter-3 12
S ctio for Eac Split
Additional line section for each flow split (unique function or destination)
The main branches from common major sections (Headers) those have a unique function or distention may be a study node.
Chapter-3 13
isperception
HAZOP & PHA are the Same.
• Most of the people thought that HAZOP & PHA are the same. It is not true, HAZOP is just only a subset of PHA.
PHA is an approach, while HAZOP is a technique or Methodology
Chapter-3 14
H Z P ispercepuon
HAZOP Creates New Knowledge.
• Some people thought that HAZOP is a mean of creating a new field knowledge, HAZOP is not, it is a technique or methodology of applying the knowledge to identify the potential hazards.
HAZOP is not providing a new technical knowledge to be learned.
Chapter-3 15
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HAZOP Replaces the Engineering Design.
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• HAZOP is not an alternative to be used instead of engineering -\ <::> C'-J . design review phase, Engineering phase should be performed prior HAZOP conduction
Engineering Design review is one of the HAZOP requirements.
t
HAZards & OPerability (HAZOP)
HAZ P rsoerceoticn
HAZOP Provides Solution.
• It is not an Objective of HAZOP to provide a detailed solution, HAZOP is only suggest a general recommendations
HAZOP members shouldn't involved into the roles of Engineering departments.
Chapter-3 17
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isperception
Management.
• HAZOP recommendations are not a mandatory obligations on the managements to be executed, HAZOP does not make the decisions for the managements
HAZOP is one of the items provided to the management to help them to take the right decisions
Chapter-3 18
HAZOP Members to Answer Questions.
• The objective ofHAZOP members participation is not to answering on demand the questions about their area of concern.
HAZOP members should be active and highly motivated to participate and succeeded the event.
Chapter-3 19
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HAZOP is an AUDIT
Most of the people thought that the HAZOP is an audit. It is not, HAZOP is merely a process hazards review
HAZOP shouldn't considered as an AUDIT.
Chapter-3 20
• Some of the discipline participants dealing with the potential hazards identified within his area of concern is some sort of criticism.
HAZOP is not Implying to Criticizes.
Chapter-3 21
P Terminology
YM!jf1 Intension
Intention
What is the original design intention of the process to be working within or the purpose of a certam activity expected to be performed.
The basic concept behind HAZOP studies is that processes work well when operating under design conditions. When deviations from the process design conditions occur, operability problems and accidents can occur.
Chapter-3 22
Guide Wards
Guide Words
The HAZOP study method uses guide words to assist the analysis team in considering the causes and consequences of deviations. These guide words are Simple listed words applied at specific points or sections in a process and are combined with specific process parameters to identify potential deviations from intended operation.
Chapter-3 23
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Deviations
Deviations
Departure from the original design intensions or the expected performance of an activity (s] ---
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Causes
Causes
How the deviation might occurs (the reason of process upset being appeared)
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Consequences Negative impact of the deviation on the process safety
Chapter-3 26
Safe Guards.
Engineering and / or administrative controllers that mitigate the risk by reducing the frequency of the causes or severity of the consequences.
Chapter-3 27
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HAZOP Terminology
Findings & Recommendations
Enlisting of the overall findings with a suggestions for procedural or design change or further engineering studies to be required
Chapter-3 28
uantitative Ir.creare .r:
Quantitative increase referred to outside upper system tolerance
More of any relevant physical parameter than there should be, such as more flow (rate, quantity), more pressure, higher temperature, or higher viscosity.
Chapter-3 29
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uantitativ Decrease (~~
Quantitative decrease referred to outside lower system tolerance
Opposite to More "Less of any relevant physical parameter than there should be, such as more flow (rate, quantity), more pressure, higher temperature, or higher viscosity".
Chapter-3 30
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No forward flow when there should be.
Sequential process step omitted.
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More things present than should be (extra phases, impurities).
Transfer from more than one source or to more than one destination.
Chapter-3 32
Qualitative Decrease referred to expected received quality
System composition different from what it should be (in multi­ component stream).
Chapter-3 33
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Reverse flow, Vacuum.
Chapter-3 34
Complete substitution or misdirection other than.
What may happen other than normal continuous operation (start­ up, normal shutdown, emergency shutdown, maintenance, testing, sampling).
Transfer from wrong source or to wrong destination.
Chapter-3 35
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Guide Words Approach
HAZOP Guide words approach
Applying the applicable guide words on process variable will systematically generate most of the upset scenarios regarding this variable. Repeating this for all the process variables well generate a compressive matrix including an upset scenario in every single cell
Chapter-3 36
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the guide word combined with the process parameter results in the deviation
Considering the deviation, the study team agrees on its possible causes (e.g., operator error causes block in pump), the consequences of the deviation (e.g., line rupture due to high pressure), and the safety levels or safe guards which prevent the cause from leading to the consequence (e.g., pressure relief valve on pump discharge line).
The consequence specified presupposes the failure of active protection systems (e.g., relief valves, process trip signals). If the causes and consequences are significant, and the safety levels are inadequate, the team may recommend a follow-up action.
Chapter-3 37
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enerai Deviations '~J (L01~
Start Up - Shut Down - Maintenance Cf'~~) Df-"vt\v.)y
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Leak - Rupture - Loss of Containment
Those general deviations are some how an indication that the facilities sitting issues are addressed
Start Up - Shut Down - Maintenance/Testing
Looking for the above general deviations helps to ensure that the human factors issues are addressed
In General most of the experts considering that Loss of Containment is considered as an ultimate deviation. and consequently tends to consider High Pressure & High Level to be the most critical deviations
Chapter-3 38
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Igorithms
2. Define Design Intentions
3. Select Process Variable C0f~5)'n-L _ \ E...---~ -\l'~~ _ ~_,)"i.-") 4. Apply a Guide Word to the selected variable to form a deviation
5, Assess the Consequences of the Deviat~on (A~Sluming. NJ~~~J \~ y5 \~ l.. GUARDS) y...~ H \~ "-!FllA.-
6. Identify the possible causes of the deviation and the likelihood
7. Involve the existing safeguards ofthe system against the deviation with an appropriate credibility
8. Based on the Consequences, causes likelihood and safeguards credibility Risk to be assessed
9. Recommendations or Actions to be taken (If Any)
1a.Repeat with anotherGuideword '* ~- ,-_._--~.,_._._--.
Chapter-3 39
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1. Is there a quantified~ of the deviation (Safe Upper & Lower Limits)?
2. What are the cause of the deviation?
3. How will be the declaration of the upset event (Deviation)?
4. What are the Consequences (The Worst)?
5. Is there any safe guards in place? (
6. What is the expected frequency of the deviation (With/Without safe Guards)
7. What is the risk associated.
8. Is there any Recommendations.
Chapter-3 40
Quantitative Definition
If missing, HAZOP team may generate an approximate values based on an engineering efforts or empirical values based on past experience of operations/Maintenance experts derived from their years of experience
Chapter-3 41
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Causes External Node interactions
Most of the events and their causes will be associated with the node itself. For example, a leak from a pump may be caused by a seal leak at that pump. However, the team should always be looking for causes from other areas of the plant. For example, if a new corrosive chemical is inadvertently introduced into the system at another location, that chemical could cause the seal to leak. Similarly, the signals to many interlock and alarm devices come from other nodes.
Chapter-3 42
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Declaration of the Upset
It is often assumed that, if an incident takes place, the operators and other affected personnel will receive information from the instrument system to tell them what is going on. This is not always the case; the team should check that sufficient instrumentation is in place and should assure that the operator is always available to be informed and respond to it, particularly ifhe has concern with more than one work place.
chapter-a 43
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Consequences
The team must decide if human presence is assumed, particularly in an area in which people are not normally present.
Human presence should be weighted considerably
Chapter-3 44
Safe Guards
The HAZOP team should know whether it is allowed to take credit for the presence of safeguards when determining the risk associated with a hazard.
Chapter-3 45
Predicted Frequency
In petroleum industry, majority of PHA teams are qualitatively assess the likelihood, If an incident has a reasonably high likelihood, experienced team members can probably recall such incidents, or near misses, thus providing a foundation for estimating event frequency. These empirical observations can be invaluable.
Chapter-3 46
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Associated Risk
It is important that all team members have a working knowledge of the risk ranking system being used.
Chapter-3 47
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Findings Recommendations
On a long HAZOP, the team may find that certain Findings are repeating themselves. For example, it may be that all centrifugal pumps of a certain type have an unusually high rate of seal failure. In such cases the team should develop generic findings and recommendations.
Chapter-3 48
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The term "Loss of Containment" given that the ultimate purpose of a process safety program is to make sure that hazardous materials remain confined in the pipes, tanks, and vessels that they are intended to be in, it could be argued that all deviation guidewords are to do with "Loss of Containment," and so there is no need to handle this term separately.
Chapter-3 50
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Reference Previous Nodes
Frequently, a HAZOP discussion is basically a repetition of what was already said in an earlier, upstream node. In these cases a simple reference to the previous discussion is all that is needed. There is no need to repeat the discussion.
Chapter-3 51
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High Flow
Generally, High Flow - in and of itself- is not a hazardous situation. Indeed, in most plants where high production rates are desired High Flow is good because it implies increased production and revenues. Although high flow can occasionally create hazards, such as erosion of pipe walls, its main effect is through other guideword combinations, such as the creation of High Level or the overloading of pump motors.
Chapter-3 52
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REVERSE Flow
Reverse Flow can create high-risk scenarios because it can lead to the mixing of totally incompatible chemicals. The attributes of Reverse Flow are usually a pressure reversal (in which a normally low pressure section has a higher pressure than a high pressure section to which it is connected, and failure of a check valve, or other non-return device).
Experienced operators often have trouble visualizing the concept of "reverse flow." They can visualize "high" and "low" flow because they have probably witnessed these, but reverse flow may be totally outside their experience. Hence the team leader should allow people plenty of time to think when discussing "reverse flow."
Chapter-3 53
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High Pressure
,
High Temperature
When discussing High Temperature, the team should keep in mind two important points. The first is that, as temperatures go up, so the metal walls of vessels will weaken, thus reducing the MAWP. A very high temperature, such as would occur in a runaway reaction, could lead to vessel failure at quite low
Chapter-3 55
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The importance of High Level has already been noted since it leads directly to a tank overflowing. With many tanks, two problems occur regarding High Level. The first is that there is often no clear guidance as to the Safe Upper Limit. Sometimes operations supervision will want to run a tank up to almost 100%, even though the chance of a spill becomes high. The HAZOP team can help develop a safe value for High Level. (
The second issue regarding High Level is that many tanks are not all that well instrumented, and may lack any kind of automatic alarm or interlock capability. Therefore, the HAZOP team may find itself recommending a significant instrument upgrade.
Chapter-3 56
High pressure; stagnant lines, line/instrument tapping blockages, filter blockages.
Chapter-3 57
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Chapter-3 58
Utilities contamination/overpressure, reverse rotation, NRV failure, vessel overfill.
Chapter-3 59
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Examples of Potential Problems of
lsdirected Flow
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High Temperature
Chapter-3 61
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Examples of Potential Problems of
Low Temperature
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Examples of Potential Problems of
High/Lo\v Level
Vessel overfill, high static head. Line routing, dead legs, liquid accumulation, cavitations, gas blow by.
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Compositions Change
Chapter-3 65
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Localized failure, choked valves, straight tees, unbalanced flows.
Chapter-3 66
Deposition Problems
Chapter-3 67
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Service Failure
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aintenance Problems
Chapter-3 69
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Start Up/Shut Down
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Chemicals ore/Less
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Impact External' Internal
Pig operations, hydrate plug, loose internals.
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Hammering Problems
hydraulic surge.
Chapter-3 73
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Examples of Potential Problems of ore Vibrations
Fatigue failures. thermal failures, critical speed, movement.
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Examples of Potential Problems of
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Human Factors
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P Problems O~f~
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Lay outlAccess
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Health Concern
Chapter-3 79
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Examples of Potential Problems of
eather Problems
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Environmental Problern
Chapter-3 81
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HAZards & OPerability (HAZOP)
Sequence Step mitted
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Examples of Potential Problems of
Sequence Step Too Shot/Long
Chapter-3 86
Sequence Step T Late/Early
Insufficient or excessive delay before moving on to the next step or following completion of previous step.
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Examples of Potential Problems of
Sequence Step In Wrorlg OrderlAction
Step done out of sequence.
An incorrect action substituted for the correct action.
Another action completed as well as the action intended.
Chapter-3 88
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Any other simultaneous activity which may impact on the overall safety of the operations.
Chapter-3 89
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Human Perrorman Petroieunl tndust
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•After many years of improvements in technical safety methods and process design, many organizations have found that, Human error is probably the major contributor to loss of life, injury to personnel and property damage in the oil industries.
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•A Thirty Year Review of Property Damage Losses in the Hydrocarbon Chemical Industries show that human errors (defined as errors made on-site that have directly given rise to the losses) account for the second highest cause.
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Human Performance in Petroleum Industry .
agers Attitu H man E
• Common Attitude
• Appreciated Attitude
e toward
-Most of the managers believe that the only effective way to reduce the human errors is to blame, punish or even exclude the individual(s) who seems (guilty) from the work place.
-Rather than simply blaming the individual, good mangers attempt to identify the root causes of the error in the work location and implement appropriate corrective actions whereas statistics indicate that careless or unfit workers responsible for only a small portion of the human errors occurred at the facility. Skilled, useful, productive, well-meaning employees commit most mistakes.
Chapter-4 Prepared By/Ibrahim Anas 5
Human Performance in Petroleum Industry
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"\lhat is the Human Error
• Systems Acceptability of Errors
• Practical Definition ofHuman Error
-. Every task that must be performed by a human is an opportunity for error. No two people (nor even one individual) will perform the same task in exactly the same way twice. Only when some limit of acceptability is exceeded is a variation considered a human error.
• Not all errors are harmful, some cause no problems, and some may actually benefit mankind.
•A practical definition of human error is "any human action (or Inaction) that exceeds the tolerances defined by the system with which the human interacts".
Chapter-4 Prepared By/Ibrahim Anas 6
Human Performance in Petroleum Industry
Error Recove
of Human to prevent an accidents
While the Human Error might trigger an accident, Error Recovery is the contribution of Human to detecting and intervening in order to prevent an accident
Error Recovery deals with the positive human contribution in safety related issues for example, through the detection of a gas by an individual on an offshore installation
Chapter-4 Prepared By/Ibrahim Anas 7
Human Performance in Petroleum Industry
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Limits of Human Performan
-Unfortunately, the limits on human performance are difficult to be defined until someone has exceeded them at least once under circumstances that resulted in an actual problem
Chapter-4 Prepared By/Ibrahim Anas 8
Human Performance in Petroleum Industry
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External Feed Back
Human interactions with a system can be simply modeled as five distinct functions.
First, the system hardware or another human in the system provide some external input. The input may be a flashing, ringing alarm.
Second, we then become actively aware of the input by discriminating it from other inputs that sensed a