The Hazard Risk Matrix

TABLE 2.3 Example of a Hazard Risk Assessment Matrix—Values Can Be Assigned Based Upon Oi anization Preferences 

Risk Assessment Matrix Ij HAZARD SEVERITY CATEGORIES )  

FREQUENCY OF OCCURRENCE (PROBABILITY) U Catastrophic n Critical m Marginal IV Negligible 

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Table 2.3 shows the hazard risk matrix, which incorporates the elements of the hazard severity table and the hazard probability table to provide an effective tool for approximating acceptable and unacceptable levels or degrees of risk. By establishing an alphanumeric weighting system for risk occurrence in each severity category and level of probability, one can further classify and assess risk by degree of acceptance. Obviously, from a systems standpoint, use of such a matrix facilitates the risk assessment process. 

The more complex the system or process to be evaluated, the more essential is the need for a HAZOP study. The HAZOP study is conducted in much the same way as the what-if analysis, usually by the same review team. There are minor differences, however, in terminology and approach. In the HAZOP study, certain guidewords are normally used to aid the review team and help identify specific areas where deviations from design intent can occur. Guidewords can include pressure, flow, level, temperature, and power. HAZOP also attempts to identify the severity of the outcome if such deviations from the norm occur as well as the probability or likelihood of occurrence. The hazard risk matrix established and explained in Chapter 2 (Table 2.3) can be used for this purpose since it provides both severity and probability rankings for a given hazardous situation. 

Use of a variety of system safety concepts and tools, such as the order of precedence for hazard reduction, the hazard severity and probability tables, and the hazard risk matrix, will assist the analyst in determining the appropriate risk assessment code to assign to a particular hazard risk. The RAC will prioritize for management the specific level of risk associated with a specific, identified hazard concern. 

Alternatives to the standard risk matrix are possible, but they tend to be application specific and so must be constructed for each new system. For many systems, the use of severity alone is often adequate to categorize the hazards in trade studies. Two examples of other alternatives are presented here, one created for augmented air traffic control technology and the other created and used in the early architectural trade study of NASA s Project Constellation, the program to return to the moon and later go on to Mars. The reader is encouraged to come up with their own... 

All findings from these hazards analyses were ranked using the < client > risk matrix system (see Attachment). The reports for each process analyzed summarize the methodology by which the hazards analysis was conducted and set forth the findings of the... 

Using the hazard assessment matrix, what is the level of risk for the following activities ... 

The implementation of the actions defined in step 6 needs to be monitored and followed by a new cycle of risk review whereby a number of products may have moved in the hazard/ exposure matrix from the black area into the gray or white area. This repetitive process will m e information that is more pertinent available, focusing attention on specific areas and therefore helping to reduce further the risk related to the transport of chemicals. It is expected that this process will result in a decrease in the number of logistics accidents, which could be used as one objective yardstick to measure the improvements achieved. 

Provides an Overview of Risk Tolerance as Related to Identified Hazard and Associated Risk. Source Risk Management System Guidance Pack, The Residual Risk Matrix, 2011 System Safety Process... 

The Hazard Risk Index (HRI) matrix is a risk management tool used by system safety for hazard/mishap risk assessment. The HRI matrix establishes the relative level of potential mishap risk presented by an individual hazard. By comparing the calculated qualitative severity and likelihood values for a hazard against the predefined criteria in the HRI matrix, a level of risk is... 

The relative risk index (or HRI) is derived from the matrix cell resulting from the intersection of the likelihood and severity axes that represent a particular hazard. The HRI matrix maps hazard severity on one axis and hazard likelihood on the other axis. Once a hazard s severity and likelihood are determined, they are mapped to a particular HRI matrix cell, which yields the hazard index and the relative risk for that hazard. The hazard risk level establishes who can accept the risk by authority level. 

The MRI is an index number indicating qualitatively the relative risk of a hazard. It is derived from the MRI matrix by identifying the matrix cell resulting from the intersection of the hazard likelihood and hazard severity values. The MRI number establishes the safety significance of a hazard and who can accept the risk for the hazard. It should be noted that hazard risk and mishap risk are the same entity, just viewed from two different perspectives. Therefore, the MRI and the Hazard Risk Index (HRI) are essentially identical tools ... 

This chapter presented a disruption risk assessment method for managing the supply disruptions in a global supply chain. The assessment can help practitioners to quantify risks in their supply chains based on hazards, vulnerability, and risk management practices. The disruption risk scores of suppliers facilities and transportation links can lead a company to proactively manage its suppliers. They then can use the disruption risk matrix to visualize the relative risk of all idenfified hazards. We presented a case study of a global distribution company to illustrate the application of this framework in assessing disruption risks for facilities and transportation links. This framework can be used to develop a company disruption risk profile, which in turn can be used to identify the critical network components that are prone to disruptions and to prioritize the risk mitigation activities. 

The combination of the hazard severity and the hazard probability defines the hazard risk classes. These classes are listed in Table 4 with different levels of tolerability Class A forms the intolerable area of the risk matrix, Class B and C the tolerable area and class D means acceptable risk. 

The preparation of a matrix and the subsequent evaluation of the hazards identified can lead to a qualitative judgment of process risk and to the identification of available pathways to reduce that risk. Software is available to assist in making and maintaining interactionlike matrices. One example is a database shell called CHEMPAT (AIChE, 1995). When CHEMPAT is customized by the user, a compatibility chart is produced based on user-supplied chemical information. 

Hazard assessment is a consequence analysis for a range of potential hazardous chemical releases, including the history of such releases at the facility. The releases must include the worst-case scenario and the more likely but significant accident release scenarios. A risk matrix can be used to characterize the worst-case and more likely scenarios. 

Vapor-phase monitoring to meet the 3X specification will most likely not be sufficient to verify agent destruction in the solid materials from the bulk sites because these materials could contain either strongly adsorbed agent or occluded agent that could be released in the future. Because of the unique analytical interferences resulting from the composition of particular waste streams, the measurement methods will have to be specific to each waste stream, and each method will have to be validated for the specific waste matrix. Criteria for determining the detection limit for each method should be based on the hazard and risk evaluations for that waste stream. 

Using the consequence and likelihood categories, risk matrix, and risk evaluation criteria, the team reviewed three release scenarios (small, medium, and large) for the segments identified for each of the chemical movements. The result of the semi-quantitative risk estimation for this facility s hazardous material transportation operation is detailed in Table 4.12. From this results table, the following are determined ... 

Having determined consequence and frequency values to do with a particular hazard, the overall risk is determined using a third matrix such as that given in Table 1.13, which shows four levels of risk. 

Quantification, particularly the use of the Pareto Principle (see Chapter 15), helps get around many of the I think/you think discussions that can arise during a hazards analysis. Yet most analyses are not quantified beyond use of a simple risk matrix such as that shown in Chapter 1. 

What is the risk associated with the hazard just identified (evaluated from a risk matrix such as Table 5.2) ... 

Once the hazards have been identified, and their causes, consequences, and frequencies discussed, the team should risk rank each identified hazard scenario. If a risk matrix is used then the estimated risk values for the two scenarios are B and C, respectively. 

Determine the consequence and likelihood of the hazard scenario. This evaluation should include an examination of safety, environmental, and economic losses (including the requirements associated with safety and environmental regulations). Based on an assessment of the overall risk associated with the identified hazard, decide if additional safeguards or Layers of Protection/lndependent Protection Layers (IPL) are required. The criterion for acceptable risk could be single numerical value, or it could be determined through use of a risk matrix. 

First, the importance of learning lessons from past process safety incidents is highlighted in Section 3.2. The subsequent section presents preliminary hazard review procedure, risk matrix, what-if method, plot plan and layout review, pressure relief system review and fire safety design aspects. Section 3.4 presents PHA techniques and procedures hazards and operability analysis (HAZOP), failure modes and effects analysis (FMEA), instrumented protective system (IPS) design, fault trees, event trees, layer of protection analysis (LOPA) and finally SIS life eyele. The importanee of revision of PSI is highlighted in Seetion 3.5. 

Earlier in this chapter, reference was made to a speaker who reviewed the hazard analysis and risk assessment methods used in his company, which relied on typical risk assessment and decision-making matrices, to achieve acceptable risk levels. Use of such matrices is a method some organizations apply to arrive at acceptable risk levels. Table 15.1 is an example of such a risk assessment matrix. Using the results from Table 15.1, levels of remedial action or risk acceptance for individual risk categories can be established, as in Table 15.2. 

As with all materials that have been recently developed, the health risks associated with SiC whiskers are not well known however, because their sizes and shapes are similar to that of asbestos, therefore they are considered hazardous. Airborne dispersion and subsequent inhalation are the most serious health hazards. However, with proper worl lace handling requirements and procedures, large quantities of SiC whiskers can be safely processed. No release of whiskers has been observed from dense ceramic matrix composites during fracture or wear processes. Material Safety Data Sheets (MSDS) are packaged with all products containing loose whiskers and the directions in the data sheets should be followed. At the present time, the American Society for Testing of Materials (ASTM) has developed procedures and handling practice standards for SiC whiskers [14]. 

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