Safety assessment methods

1) Job Hazard Analysis (JHA)； 2) Safety Checklist Analysis (SCL) ； 3) Preliminary Hazard Analysis (PHA) ； 4) Hazard and Operability Analysis (HAZOP) ； 5) Failure Mode and Effects Analysis (FMEA) ； 6) Fault Tree Analysis (FTA) ； 7) Event Tree Analysis (ETA) ； 8) Methods such as Job Safety Analysis (LEC).

A list of safety assessment methods is available for reference, but file upload is not supported. Go check the data area. http://bbs.hcbbs.com/viewthread.php?tid=418951&extra=page%3D1&frombbs=1 This post was last edited by *aoling on 2009-3-18 10:03]

What is popular nowadays is QRA, quantitative risk assessment, which can evaluate the probability of accidents and their consequences in plant facilities; it belongs to quantitative assessment methods

Hey, the guy on the fifth floor, could you explain the QRA analysis method in detail?

General specifications for safety standardization of hazardous chemical enterprises 5.2.1.3 Enterprises may select effective and feasible risk assessment methods for risk assessment as needed. Common evaluation methods include: 1) Job Hazard Analysis (JHA) ； 2) Safety Checklist Analysis (SCL) ； 3) Preliminary Hazard Analysis (PHA) ； 4) Hazard and Operability Analysis (HAZOP) ； 5) Failure Mode and Effects Analysis (FMEA) ； 6) Fault Tree Analysis (FTA) ； 7) Event Tree Analysis (ETA) ； 8) Methods such as Job Safety Analysis (LEC). Others: Overview of safety assessment methods: Safety assessment methods are tools used for qualitative and quantitative safety evaluations. The content of safety assessment is very extensive; depending on the purpose and targets of the safety assessment, the content and indicators vary as well. Currently, there are many safety assessment methods, and each method has its own scope of application and conditions for use. When conducting a safety assessment, an appropriate safety assessment method should be selected based on the object of the assessment and the safety assessment objectives to be achieved. Classification of safety assessment methods: The purpose of classifying safety assessment methods is to select appropriate assessment methods based on the object being assessed for safety reasons. There are many ways to classify safety assessment methods. Common ones include classification by the degree of quantification of the assessment results, classification by the reasoning process used in the assessment, classification based on the characteristics of the system under evaluation, and classification according to the objectives that safety assessment aims to achieve. Classification by the degree of quantification of evaluation results: Based on the degree of quantification of safety evaluation results, safety evaluation methods can be divided into qualitative safety evaluation methods and quantitative safety evaluation methods. Qualitative safety assessment method. Qualitative safety assessment methods primarily involve a qualitative analysis of the conditions related to the processes, equipment, facilities, environment, personnel, and management of a production system, based on experience and intuitive judgment. Qualitative safety assessment methods include safety checklists, expert on-site inquiry and observation methods, factor diagram analysis, accident initiation and development analysis, job hazard analysis (Graham-Kinnear method or LEC method), failure mode and effects analysis, and hazard operability studies. The characteristic of the qualitative safety assessment method is that it is easy to understand, convenient to master, and the assessment process is simple. Currently, qualitative safety assessment methods are widely used in the safety management of enterprises both domestically and internationally. However, qualitative safety assessment methods often rely on experience and have certain limitations. The results of safety assessments can sometimes vary considerably depending on the experience and background of the personnel involved in the assessment. At the same time, since safety assessment results cannot provide a quantified level of risk, there is a lack of comparability between the safety assessment results of different types of objects. (2) Quantitative safety assessment method. Quantitative safety assessment methods involve the use of indicators or patterns (mathematical models) derived from extensive experimental results and comprehensive statistical analyses of accident data, to conduct quantitative evaluations of various aspects of a production system such as its processes, equipment, facilities, environment, personnel, and management. The outcomes of such safety assessments are quantitative indicators, including the probability of accidents occurring, the extent of damage caused by accidents, the quantitative level of risk, as well as the relevance or importance of the factors that lead to accidents. Based on the different categories of quantitative results obtained from safety assessments, quantitative safety assessment methods can also be divided into probability risk assessment methods, injury (or damage) extent assessment methods, and hazard index assessment methods. ①Probabilistic risk assessment method. The probability risk assessment method is a safety assessment technique that, based on the accident occurrence probabilities of the fundamental causative factors, applies probability analysis methods from mathematical statistics to determine the relevance (or importance) of these fundamental causative factors, as well as the accident occurrence probability of the entire assessment system. Fault type and impact analysis, fault tree analysis, logic tree analysis, probability theory analysis, Markov model analysis, fuzzy matrix methods, statistical chart analysis, and others can all be used to calculate the accident occurrence probability of the entire assessment system by utilizing the accident occurrence probabilities of the fundamental causative factors. The n-probability risk assessment method is based on a large amount of experimental data and statistical analysis of accidents, thereby ensuring a high degree of reliability in the assessment results. ②Damage (or destruction) range evaluation method. The injury (or damage) range assessment method is a safety evaluation technique that, based on the mathematical model of an accident and by applying computational mathematics methods, determines the range of injury to personnel or the extent of damage to objects caused by the accident. The liquid leakage model, gas leakage model, adiabatic gas diffusion model, pool fire flame and radiation intensity evaluation model, fireball explosion injury model, explosion shock wave overpressure injury model, vapor cloud explosion overpressure damage model, toxic substance leakage and diffusion model, and the NT equivalent method for boiler explosion injuries all belong to the methods for evaluating the range of injury (or damage). The damage (or destruction) range evaluation method involves using mathematical models for calculations; as long as the calculation models, along with the initial and boundary values required for the calculations, are chosen appropriately, reliable evaluation results can be obtained. The evaluation result indicates the extent of injury to people or the extent of damage to objects caused by the accident; therefore, it is intuitive and reliable. This result can be used for hazard zoning, and it also makes it possible to further calculate the severity of injuries to people within the affected area, as well as the degree of damage to objects in that area and the direct economic losses incurred. However, such evaluation methods require a significant amount of computation, and computers are generally needed to carry out the calculations. In particular, it is often difficult to select appropriate initial and boundary values. Moreover, the evaluation results depend heavily on the evaluation model as well as the initial and boundary values; even slight inaccuracies or deviations in the selection of these values can lead to significant distortions in the evaluation results. Therefore, this type of evaluation method is suitable for safety assessment using system accident models and initial and boundary value comparisons. ③Hazard index evaluation method. The hazard index evaluation method for application systems utilizes an accident hazard index model; based on the basic properties and conditions of the system, as well as its materials, equipment (facilities), and processes, it employs computational approaches to gradually determine the potential losses from accidents, the equipment that can cause accidents or contribute to their escalation, the level of danger associated with accidents, and the effectiveness of safety measures. Commonly used methods for evaluating hazard indices include Dow Chemical’s fire and explosion hazard index evaluation method, the Mond fire, explosion, and toxicity index evaluation method, and the evaluation method for major sources of flammability, explosiveness, and toxicity. In the hazard index evaluation method, the complexity of the system structure resulting from the use of such indices, which makes it difficult to calculate the probability of accidents using probabilities, is resolved by dividing the system into several evaluation units. In this evaluation method, complex systems with organic connections are generally divided into several relatively independent evaluation units according to certain principles. For each evaluation unit, the potential losses resulting from accidents, the level of accident risk, and the effectiveness of safety measures are calculated step by step. Then, the evaluation results of different units are compared to identify the most dangerous equipment and conditions within the system. The evaluation index value incorporates factors related to both the likelihood of an accident occurring and its consequences, thereby overcoming the drawback of it being difficult to determine the probability of an accident and its impacts. The disadvantage of this type of evaluation method is that the safety assessment model used does not pay enough attention to the functionality of the system’s safety protection facilities. As a result, as long as the types and quantities of hazardous substances in the system are roughly the same, and the system’s process parameters and spatial layout are similar, even if the service life of the systems differs significantly and thus the actual safety levels vary greatly, the evaluation results remain largely identical. This leads to poor flexibility and sensitivity of this type of evaluation method. 2) Other classification methods for safety assessment: Based on the logical reasoning process of safety assessment, safety assessment methods can be divided into inductive reasoning assessment methods and deductive reasoning assessment methods. The n-inductive reasoning evaluation method is an evaluation approach that deduces outcomes from the causes of accidents; it starts with the most fundamental dangerous and harmful factors, gradually analyzes the direct factors that lead to the accident, and ultimately determines the possible accidents that could occur. The n-deductive reasoning evaluation method is an evaluation approach that infers causes from outcomes; that is, starting from an accident, it identifies the direct factors that led to it, then analyzes the factors related to these direct factors, and ultimately determines the most fundamental dangerous and harmful factors responsible for the accident. According to the objectives of safety assessment, safety assessment methods can be divided into accident causation factor safety assessment methods, hazard classification safety assessment methods, and accident consequence safety assessment methods. The safety assessment method for accident causation factors employs logical reasoning to derive the most fundamental hazardous and harmful factors from accidents, or to infer accidents from those fundamental hazards and harmful factors. Such methods are suitable for identifying the hazards and harmful factors in a system as well as for analyzing accidents; they generally fall under qualitative safety assessment methods. The risk grading safety assessment method is a safety assessment approach that determines the risk level of a system through qualitative or quantitative analysis. Such methods are suitable for classifying the risk levels of systems, and they can be either qualitative safety assessment methods or quantitative safety assessment methods. The safety assessment method for accident consequences can directly provide quantitative values regarding these consequences; such values may include the probability of a system failure occurring, the extent of damage caused by the accident, the losses resulting from the accident, or a quantitative measure of the system’s risk level. Furthermore, depending on the evaluation subject, safety evaluation methods can be classified into equipment (facilities or processes) failure rate evaluation methods, human error rate evaluation methods, material factor evaluation methods, system hazard evaluation methods, etc. n

There should also be major quantitative safety assessment methods: the Dow Chemical Fire and Explosion Index assessment method, and the ICI Mond method； Classification of the hazard level in chemical plants.

A safety assessment method is a tool for analyzing and evaluating the hazard factors and harmful factors of a system, as well as the degree of risk and harm they pose. To date, dozens of different evaluation methods for characteristics, scope of application, and operating conditions have been developed, which can be classified into qualitative safety evaluation and quantitative safety evaluation based on their properties. (1) Qualitative safety assessment: Qualitative safety assessment is a type of method that relies on experience, knowledge, observation of things, and an understanding of the laws of development and change to conduct scientific analysis and judgment. By using such methods, it is possible to identify the dangerous and harmful factors present in a system; based on these factors, technical, managerial, and educational countermeasures can be devised to control them and achieve system safety. Commonly used methods at present include analysis and evaluation techniques such as the \"Safety Checklist (SCL)\", \"Fault Tree Analysis (FTA)\\", \"Event Tree Analysis (ETA)\\", \"Hazard Assessment Methods\\", \"Preliminary Hazard Analysis (PHA)\\", \"Failure Mode and Effects Analysis (FMEA)\\", \"Hazard and Operability Study (HAZOP)\\", \"What-If Analysis\\", and \"Human Error (HE) Analysis\“. (2) Quantitative safety assessment: Quantitative safety assessment is a type of method that relies on statistical data, test data, and information from similar systems; it uses relevant standards and scientific methods to develop mathematical models in order to conduct a quantitative evaluation. There are mainly the following two types: ① Based on reliability and safety, it first identifies potential hazards within the system, determines their loss rates as well as the types of harmful factors and the extent of their impact, and then compares these findings with the relevant established standards for quantification. Common methods include: “Fault Tree Analysis (FTA)”, “Event Tree Analysis (ETA)”, “Fuzzy Mathematics Comprehensive Evaluation Method”, “Analytic Hierarchy Process”, “Graham-Kinnear Method”, “Inherent Hazard Assessment Method for Machinery Plants”, “Cause-Effect (CC) Analysis Method”, and others. ②A risk grading method based on comprehensive evaluation using material coefficients is adopted. Common methods include Dow Chemical Co.’s “Fire and Explosion Hazard Index Evaluation Method,” ICI/Mond’s “ICI/Mond Fire, Explosion, and Toxicity Index Method” from the Imperial Chemical Industries in the UK, the “Six-Stage Method” proposed by Japan’s Ministry of Labor, and the “Unit Hazard Index Rapid Sorting Method,” among others. There are various methods for safety assessment, which have been described in detail earlier. Depending on the perspective and purpose of the assessment, different safety assessment methods can be chosen. Some may start from traditional management and experience when conducting evaluations, and thus develop safety checklist methods ； Some propose system safety engineering methods from the perspective of system security ； Some are evaluation methods proposed based on the characteristics of production and the conditions of the location; such methods can often reflect those characteristics. Regardless of the safety assessment method used, it is often only applicable in certain situations and to certain subjects, and thus has certain limitations. Therefore, combining several methods in safety assessment can yield relatively satisfactory results. 　　Currently, there are various comprehensive safety assessment methods both domestically and internationally. Some of the more representative ones include Japan’s Ministry of Labor’s “six-stage safety assessment” method, DuPont’s “three-stage safety assessment” method which involves “safety checklists – failure mode and effects analysis – fault trees and event trees”, as well as China’s three-stage safety assessment method for phosgene, which consists of “safety checklists – hazard index evaluation – system safety assessment methods”. This post was last edited by wanmh on 2009-3-19 16:22]

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