Hazard risk index

To discriminate between hazards having the same hazard risk index, a risk impact determination is necessary. An impact determination consists of a review of the effect of an event economically, socially and politically. Example Release of a small amount of chemical into a stream may not cause measurable physical damage, but extreme pohtical and social damage could result.)... 

Hazard risk index 1-5 unacceptable 6-9 undesirable 10-17 acceptable with review 18-20 acceptable without review... 

Software System Hazard Analysis This type of analysis is conducted similar to a hardware system hazard analysis (SHA), analyzing software functional processing steps to determine whether they may have any particular hazardous effect on the system. The analysis utilizes a hazard-risk index to illustrate the severity of each potential failure. The main advantage to this method is in its ability to positively identify safety-critical hardware and software functions as well as consider the effect of the human element in system software operations. The results of the software SHA, which identifies single-point failures or errors within a system, can often be used to assist in the development of a software fault tree analysis or, to some degree, a system FMEA. However, as with the other various SWHA techniques briefly described above, this method is also time-consuming and costly to perform. 

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). 

The Hazard Risk index (HRI) is then determined by reading the chart and as nlng risk into one of the four levels of acceptability ... 

Equally important to assessing the probability and severity of the hazardous event is knowing what to do with that information. The hazard risk index (HRI), coupled with the risk decision criteria, indicates how the hazard should be treated. Obviously, if the hazard is catastrophic aud frequent, it must be coutrolled immediately. So, an HRI of IE, 2E, 3D, 3E, 4A, or 4B would have a lower priority for corrective action than one of lA, IB, 1C, 2A, 2B, or 3A. 

The company should first decide how accidents are to be classified—from minor to catastrophic—and then use this classification system for deciding how the investigation board will be formed. Using the Hazard Risk Index discussed in Chapter 5 is another good method. NASA (No date) uses a very good technique for accident classification. A slightly modified version is shown in Table 11.2 for your immediate use. 

Chapters 5 through 9 are the best sources for tools to identity risk in the system. Once the system is defined, developing a quick preliminary hazard list will detect the gross hazards of concern to the system. The hazard analysis further refines the hazard list and clearly recognizes which hazards are of greatest concern. Also, the Hazard Risk Index is a good qualitative tool with which to note some of the qualitative risks that are required in step 6 of the risk assessment methodology. 

Of course, the problem is the danger of quantifying information that is not easily quantifiable. When data are too ambiguous or nebulous to be of utility, you can use a pseudo-quantification approach such as the hazard risk index. Risk assessment is based on the numerical comparison between risk events. Part of the risk assessment process is to compare, contrast, and evaluate risks. This risk evaluation becomes a ranking and comparison process and uses probability differences (matched with other factors such as severity of consequences) to do it. 

Table 14.4 is very similar to the qualitative risk management (hazard risk index) in Chapter 5. Note the risk management criteria at the bottom of the table. It is very important to define when action must be taken and when it can wait. This is really just prioritizing the risk. 

Hazard Risk Index Launch Commit Criterion... 

Table 14.5 uses the hazard risk index from the previous table and develops what NASA calls a launch commit criterion. This is the actual decision of whether they wish to launch or not. 

See Hazard Risk Index (HRI) Matrix and Mishap Risk Index (MRI) for additional related information. 

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 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 ... 

Two significant questions in the RAP are how should hazard risk be characterized for acceptance judgment and what acceptance criteria should be used. The risk acceptance method selected must address the concern of complexity versus utility. If the judgment criteria method is too complex it will not be used effectively. Figure 2.65 shows three different example approaches. The Hazard Risk Index (HRI) approach provided as an example in MIL-STD-882 (or some variation) is the most commonly used approach. 

Method 3 shows a risk acceptance approach using the Hazard Risk Index (HRI) method suggested in MIL-STD-882. This method provides for a good... 

An RPN is the risk ranking index for reliability, where RPN = (probability of occurrence) x (severity ranking) x (detection ranking). This number typically appears on the reliability oriented FMECA. It should be noted that the RPN is not the same as a Hazard Risk Index which is derived from probability of occurrence and severity of a hazard. The RPN provides a risk ranking order of components for reliability improvement. 

The Software Criticality Index (SCI) refers to the index number obtained from the Software Criticality Level (SCL) matrix. It is essentially the SCL number, an index number (1 through 5) derived from the SCL matrix. This term is intended to replace the older term Software Hazard Risk Index (SHRI), primarily because the word risk in SHRI is misleading for the application. 

The UK MOD base their acceptance of hazards on a risk classification scheme, which is based on the combination of the severity, probability and time of exposure for each particular hazard. For the purposes of the accident risk classification scheme, accidents are considered single events (Table B.9). These classifications can be combined to determine a hazard risk index (HRI), which is a numerical risk factor that can be used to prioritise the need for corrective action or resolution. The HRI matrix in Table B. 10 is an example showing how the hazard severity and the hazard probability categories combine to yield the HRI. 

Table B.IO Example hazard risk index matrix ...

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