Hazard, Hazid, Hazan and Hazop – part of Safety and Risk Management
Hazard, Hazid, Hazan and Hazop – part of Safety and Risk Management
Hazard, Hazid (hazard identification), Hazan (hazard analysis), and Hazop (hazard and operability studies) are important safety and risk management techniques in the steel industry (Fig 1).
Fig 1 Safety and risk management techniques
Hazard is defined as ‘a condition, an event, or a circumstance that can lead to or contribute to an unplanned or undesirable event’. Hazard is a potential cause to generate a disaster. It has got the potential to cause (i) serious harm to the individual or the environment, (ii) harm, the severity of which depends on the extent and frequency of exposure to the hazard, and (iii) harm that does not usually occur, or is not usually detectable until a significant time (years) after exposure to the known hazard. Any activity, procedure, plant, process, substance, situation or other circumstance that has the potential to cause harm constitutes a hazard.
Hazards are logically classified in the same way as the disaster events are classified. Since a hazard exists because it may result into a disaster, it is usually viewed as natural based, human systems based, or conflict based. Not every hazard results into a disaster, but every disaster is the result of a hazardous condition, whether or not that condition was recognized in advance of the event.
Hazards are normally not identical, not uniform, not exclusive, and not transposable. They are not uniform in their range of occurrence, impacts, or timelines. They have got non identical pattern of development. Hence each hazard is to be understood in the context of its time and place. One hazard generally does not substitute for another, at least at the higher level of classification. Since hazards are not the same, each hazard is to be examined to determine its characteristics in the context of the time and place in which it is likely to impact the organization.
For the characterization of hazards, the following are the key indicators in terms of the situation.
- Magnitude and intensity ranges
- Time and season
- Timeline of development
- Place and extent of impact area
- Possibility of its prediction
- Related hazards
- Cascading effects
The outcomes of the above key indicators helps in estimating the relative hazard any event poses. The more severe the magnitude of the event or the intensity of impact, the higher is the hazard. Events which can occur at any time of day throughout the year pose a different type of hazard than those that are seasonal or that commonly occur during only part of the day. The individual event in a restricted season may be of catastrophic intensity. The longer the event duration the greater the hazard. It is necessary to consider both the impact and the recovery periods, which may be prolonged for weeks, months, or years. The shorter the timeline for development of the event the higher the hazard.
The wider the area the disaster impacts may cover, the greater the hazard the event poses. The presence of critical facilities in the probable impact zone increases the hazard. This includes facilities necessary for the coordination of disaster response or the operation of emergency teams.
The more often events happen the greater the hazard because of cumulative effects. This is not universally so. In some cases relatively minor events may release energy that may lead to catastrophic failures. Events that are difficult to predict, create a higher hazard because of the lack of reliable signals that protective measures are necessary. Also events that trigger other events or that cause cascading effects are higher in their hazard potential than events that do not typically do so.
Hazard identification or Hazid
Hazid stand for hazard Identification. Steel industry, which is a high risk industry, often requires that all hazards with the potential to cause a major accident are identified.
Hazid is a high level hazard identification technique which is commonly applied on an area by area basis to hazardous installations. Hazid study is the systematic method of identifying hazards to prevent and reduce any adverse impact that could cause injury to personnel, damage or loss of property, environment and production, or become a liability. It is a component of the risk assessment and risk management. It is being used to determine the adverse effects of exposure to hazards and to plan necessary actions to mitigate such risks.
Hazid is one of the best known methodologies to identify potential hazards because it provides a structured approach to identify hazards, potential undesirable consequences, and evaluate the severity and likelihood of what is identified. Hazid involves machine or equipment designers, management and end users, and ensures a full identification of hazards and safeguard procedures in a workplace.
There are the following two possible purposes in identifying hazards.
- To obtain a list of hazards for subsequent evaluation using other risk assessment techniques. This is sometimes known as ‘failure case selection’.
- To perform a qualitative evaluation of the significance of the hazards and the measures for reducing the risks from them. This is sometimes known as ‘hazard assessment’.
Through Hazid, management identifies, in consultation with employees, contractors (as far as is practicable) and safety personnel the following.
- All reasonably foreseeable hazards at the plant that may cause a major accident
- The kinds of major accidents that may occur at the plant, the likelihood of a major accident occurring and the likely consequences of a major accident.
Hazid process is to be an ongoing to ensure existing hazards are known, and new hazards are recognized before they are introduced due to the following.
- Prior to modification of any facility
- Prior to change in the method of work or workforce
- Before and during abnormal operations, troubleshooting
- Plant condition monitoring, early warning signals, employee feedback from routine participation in work, and after an incident.
Hazid is a transparent process and is critical to the safety of the plant, equipment, and operating personnel. The benefits of Hazid studies include the following.
- It is a flexible method which is applicable to any type of installation
- It reveals hazards at an early stage before they happen
- It leverages the experience of operating personnel as part of the team
- It identifies hazards, cause and consequences as well as preventive measures
- Hazards are recorded and managed to be avoided, mitigated or highlighted
- It establishes screening criteria for hazards
- Non critical hazards are documented to demonstrate that the events in question could be safely ignored
Hazard analysis or Hazan
Hazan is a hazard analysis and is a term used in safety engineering for the logical, systematic examination of an item, process, condition, facility, or system to identify and analyze the source, causes, and consequences of potential or real unexpected events which can occur. A hazard analysis considers system state (e.g. operating environment) as well as failures or malfunctions. Hazan is the identification of undesired events that lead to the materialization of a hazard, the analysis of the mechanisms by which these undesired events could occur, and, usually, the estimation of the consequences. Every hazard analysis consists of the following three steps.
- Estimating how often the incident will occur.
- Estimating the consequences for the employees, the process, the plant, the public and the environments.
- Comparing the results of first two steps with a target or criterion to decide whether or not action to reduce the probability of occurrence or to minimize the consequences is desirable, or whether the hazard can be ignored, at least for the time being.
Hazan is therefore the essential prerequisite for the complete risk assessment process which includes (i) analysis of the hazards, (ii) assessment of the risks which the hazards present, and (iii) determination of ameliorating measures, if any, required to be taken.
Hazan is the first step in the process used for the assessment of the risk. The result of a hazard analysis is the identification of different type of hazards. A hazard is a potential condition which either exists or not exists (probability is 1 or 0). It may in single existence or in combination with other hazards (sometimes called events) and conditions become an actual functional failure or accident (mishap). The way this exactly happens in one particular sequence is called a scenario. This scenario has a probability (between 1 and 0) of occurrence. Often a system has many potential failure scenarios. It also is assigned a classification, based on the worst case severity of the end condition. Risk is the combination of probability and severity. Preliminary risk levels can be provided in the hazard analysis. The main goal of hazan is to provide the best selection of means of controlling or eliminating the risk.
Tab 1 provides safety related severity definitions generally used in hazards analysis
|Tab 1 Safety related severity definitions|
|Catastrophic||Results in multiple fatalities and/or loss of the system|
|Hazardous||Reduces the capability of the system or the operator ability to cope with adverse conditions to the extent that there would be:|
|(i) Large reduction in safety margin or functional capability|
|(ii) Operators physical distress/excessive workload such that operators cannot be relied upon to perform required tasks accurately or completely|
|(iii) Serious or fatal injury to the work men|
|(iv) Fatal injury to personnel and/or general public|
|Major||Reduces the capability of the system or the operators to cope with adverse operating conditions to the extent that there would be:|
|(i) Significant reduction in safety margin or functional capability|
|(ii) Significant increase in operator workload|
|(iii) Conditions impairing operator efficiency or creating significant discomfort|
|(iv) Physical distress to workmen including injuries|
|(v) Major occupational illness and/or major environmental damage, and/or major property damage|
|Minor||Does not significantly reduce system safety. Actions required by operators are well within their capabilities. Include:|
|(i) Slight reduction in safety margin or functional capabilities|
|(ii) Slight increase in workload|
|(iii) Some physical discomfort to the operators|
|(iv) Minor occupational illness and/or minor environmental damage, and/or minor property damage|
|No safety effect||Has no effect on safety|
Tab 2 gives typical likelihood of occurrence of an event for the hazard analysis
|Tab 2 Likelihood of the occurrence of an event|
|Probable||Qualitative – Anticipated to occur one or more times during the entire system/operational life of an equipment|
|Quantitative – Probability of occurrence per operational hour is greater than 0.00001|
|Remote||Qualitative – Unlikely to occur to each item during its total life. May occur several times in the life of an entire system or group of equipment.|
|Quantitative – Probability of occurrence per operational hour is less than 0.00001, but greater than 0.0000001|
|Extremely Remote||Qualitative – Not anticipated to occur to each item during its total life. May occur a few times in the life of an entire system or group of equipment.|
|Quantitative: Probability of occurrence per operational hour is less than 0.0000001, but greater than 0.000000001|
|Extremely Improbable||Qualitative – So unlikely that it is not anticipated to occur during the entire operational life of an entire system or group of equipment|
|Quantitative – Probability of occurrence per operational hour is less than 0.000000001|
Some of the terms used in the hazan and their definition are given below.
- Hazard rate – The rate (occasions/year) at which hazards occur.
- Protective system – A device installed to prevent the hazard occurring.
- Test interval – The time interval between the testing of a protective system, and its replacement if necessary.
- Demand rate – The rate (occasions/year) at which a protective system is called to act.
- Failure rate – The rate (occasions/year) at which a protective system develops faults (fail-danger/fail-safe).
Hazard and operability study or Hazop
A hazard and operability (Hazop) study is a design review technique used for hazard identification, and for the identification of design deficiencies which may give rise to operability problems. It is a structured and systematic examination of a planned or existing process or operation in order to identify and evaluate problems that may represent risks to personnel or equipment, or prevent efficient operation. Hazop is most commonly applied to systems which transfer or process hazardous substances, or activities where the operations involved can be hazardous and the consequences of failure to control hazards may be significant in terms of damage to life, the environment or property. A hazop study is carried out using a structured approach by an experienced multi-discipline team, facilitated by a hazop leader. The hazop technique is qualitative, and aims to stimulate the imagination of participants to identify potential hazards and operability problems. The relevant international standard calls for team members to display ‘intuition and good judgment’ and for the meetings to be held in ‘a climate of positive thinking and frank discussion’. The hazop technique was initially developed to analyze chemical process systems and mining operation process but has later been extended to other types of systems and also to complex operations such as steel plant operation and to use software to record the deviation and consequence.
Hazop is a structured and systematic technique for system examination and risk management. In particular, Hazop is often used as a technique for identifying potential hazards in a system and identifying operability problems likely to lead to nonconforming products. Hazop is based on a theory that assumes risk events are caused by deviations from design or operating intentions. Identification of such deviations is facilitated by using sets of ‘guide words’ as a systematic list of deviation perspectives. This approach is a unique feature of the Hazop methodology that helps stimulate the imagination of team members when exploring potential deviations.
As a risk assessment tool, Hazop is often described as the following.
- A brainstorming technique.
- A qualitative risk assessment tool.
- An inductive risk assessment tool, meaning that it is a ‘bottom-up’ risk identification approach, where success relies on the ability of subject matter experts to predict deviations based on past experiences and general subject matter expertise.
The objectives of the hazop studies are the following.
- Identify hazards and operability issues associated with the design.
- Identify deviations from design intent, deviation causes, consequences, and safeguards.
- Provide an action list with due dates and identify appropriate person/discipline to progress the action to close out harm. However, risk assessment teams may choose to rate these factors in order to further quantify and prioritize risks if needed.
Hazop is best suited for assessing hazards in facilities, equipment, and processes and is capable of assessing systems from multiple perspectives which include the following.
- Design – This includes (i) assessment of system design capability to meet user specifications and safety standards, and (ii) identification of the weaknesses in systems.
- Physical and operational environments – It includes assessment of the environment to ensure system is appropriately situated, supported, serviced, contained, etc.
- Operational and procedural controls – These includes (i) assessing engineered controls (ex: automation), sequences of operations, procedural controls (ex: human interactions) etc., and (ii) assessing different operational modes such as start-up, standby, normal operation, steady and unsteady states, normal shutdown, emergency shutdown, etc.
Advantages of Hazop technique are as follows.
- Helpful when confronting hazards that are difficult to quantify
- Hazards rooted in human performance and behaviors
- Hazards that are difficult to detect, analyze, isolate, count, predict, etc.
- Methodology doesn’t force any one to explicitly rate or measure deviation probability of occurrence, severity of impact, or ability to detect
- Built-in brainstorming methodology
- Systematic and comprehensive methodology
- More simple and intuitive than other commonly used risk management tools
Disadvantages of Hazop technique are as follows.
- No means to assess hazards involving interactions between different parts of a system or process
- No risk ranking or prioritization capability
- Teams may optionally build-in such capability as required
- No means to assess effectiveness of existing or proposed controls (safeguards)
- May need to interface Hazop with other risk management tools