Hazard risk matrix

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. 

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. 

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 ... 

While it is relatively easy to identify hazards at system conception, performing a hazard or risk assessment before a design is available is more problematic. At best, only a very rough estimate is possible. Risk is usually defined as a combination of severity and likelihood. Because these two different qualities (severity and likelihood) cannot be combined mathematically, they are commonly qualitatively combined using a risk matrix. Figure 10.4 shows a fairly standard form for such a matrix. 

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... 

In practice, therefore, a risk matrix does not provide as much guidance as may be anticipated. An alternative approach is to group hazards as follows. 

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... 

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. 

Based on any unacceptable and unmitigated risk identified during hazard analysis, further risk assessment and risk mitigation techniques need to be applied. LORA and conceptual SIS designs based on Risk Matrix can be employed if a qualitative to semi-quantitative method is preferred. Fault tree and event tree analyses with a robust LOPA can be applied if a quantitative method is essential... 

Table 14.6 is a Hazard/Risk Assessment Matrix that also includes suggested action levels. It is an adaptation of one of two examples... 

Class " Energy Hazard Risk Assessment Matrix s... 

Roland and Moriarty (1990) show how to develop a Hazard Assessment Matrix to determine a Hazard Risk Index using frequency of occurrence and hazard category (see figure 9-3). 

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

The two rankings of each chemical can be put into a hazard/exposure matrix as shown in Fig. 6.1. This offers a simple and practical way for prioritizing and grouping the review of the risks posed by the transport of chemicals. 

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. 

The result of an SLRA is a list of potential hazardous events that could occur at that facility, aU ranked using a risk matrix (made up of frequency and consequence components), based on the experience and knowledge of the analysts undertaking the assessment. The ranking process involves assigning each hazardous event to an appropriate frequency and consequence elass. 

Each hazardous event, once categorized, can then be represented on a risk matrix shown in Fig. 10.6, and prioritized with respect to the urgency of risk control measures that should be implemented to reduce the risk from that particular type of event. A commonly used set of definitions for each risk category on this matrix is given in Table 10.3. 

For prioritising actions both hazards (microbial contamination and faulty composition) were related to the frequency of administration. The top 10 of both frequency lists are taken into the risk assessment. The risk matrix puts the frequency of administration against the risk of contamination or the risk of faulty composition respectively (= Tables 21.4 and 21.5). These matrixes visualise which products have to be improved first. Risk reduction can be achieved by decreasing the number of steps, for example by pharmacy preparation of premixed preparations or prefilled syringes. 

A risk categorisation model combines hazard categories with exposure categories for the identification of those situations that require most attention to be improved. The risk matrix model which have been developed with the hazard and exposure categorisation given in Sects. 26.3.5 and 26.5.3 will be given as an example. It applies to inhalation risks of small scale pharmacy preparation. This approach is similar to those by the INRS [27] and COSSH [28]. 

As an example the following best practice may be formulated for a country such as the Netherlands. The categorisation model given in this chapter (see Sect. 26.3.5) applies the REACH approach to the hazard classification of any substance. Sufficient investigations on the exposure at working with up to 100 g of substance in situations with different ventilation options, led to the use of the risk matrix of Sect. 26.7.3 in practice, as basis for an interactive tool (called RiFaS) resembling ART, see Table 26.10 for an example of a RiFaS working place advice. 

This approach pre-supposes that it is possible to determine independently for each hazard whether the risk is tolerable or not. This may be applicable when the safety target is ALARP, but not so when it is GALE. The risk matrix approach also overlooks the issue that, if there are many hazards that fall into a particular risk class, this should be regarded as less tolerable than if there is only a single hazard in that class. 

For each hazard, there is potentially a wide range of accident severities. This is difficult to represent properly by traditional risk matrix methods. 

Definition of hazard, risk discussions on likelihood, consequence risk — register, matrix, ranking. Consequence ranking, preliminary hazard analysis tolerance point—ALARP refreshing on mathematics, fault tolerance, plant ageing, and basic functional safety fail safe operations in plants. 

Requirement PHA, identification of human/process error existing additional protection factors for PHA hazard identification and consequence risk analysis, estimate from risk matrix presentation of result systematic selection of various processes. 

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