Risk matrices frequency matrix

Some companies are now using Risk-Based Inspections (RBI), especially for the costly preparation efforts for internal inspections. RBI is a method that is gaining credibility and popularity. Organizations calculate a proposed inspection frequency by considering the consequences of failure (as described previously) and the likelihood of failure based on the anticipated internal corrosion rates. The method employs a risk matrix. 

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. 

Typical example of risk matrix are defined by the popular safety codes MIL-STD-882D (DOD 2000) and lEC 61508 (CEI 2002). The frequency is categorized into 5 categories (6 in IEC61508) and severity of the consequences into 4 categories. This is the basis to constitute a plane matrix of 20 (24 in IEC61508) cells, with an associated risk level. 

A rating of a risk from lowest to highest or vice versa. A rating is usually derived from a risk matrix assessing the risk from frequency or probability (high to low) against its consequences (minor to severe), whereby the function of the two provide a relative ranking of the risk compared to other risks, and the result will indicate the level of action that is required to resolve the risk. See also Risk Matrix. 

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. 

Table 21.2 Risk matrix for the assessment of audit frequency of distributors. Darker shades reflect higher priority...

The pharmacist puts the combination of the qualities in a risk matrix system and connects the scores to the frequency of assessing the distributors (Table 21.2). 

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. 

Here, risk levels also can be defined as discussed previously, but in the reverse manner. Here, the top left part of the matrix is the highest risk area, whereas the bottom right part is lowest risk. There is no upper and lower limit. Too much increase/ decrease of in the categories of risk frequency or consequence, has no practical value really. So, in practice, these are restricted to 3 x3 or 5 x5 matrix, which need not be a square matrix as is evident from the above (6x4). Table 1/3.3.2-6 is an example of 4x4 semi-quantitative risk matrix. 

Comprehensive identification of hazards requires brainstorming method. It shall consider 3 Ps person, plant, and procedure. All hazards must be specifically identified for which frequency and consequence in a risk matrix (as discussed in Clause 3.0) should be considered. For better understanding, see Fig. 1/4.3.5-1. 

The column headings in bold are essential. However, in some cases, either a guide word or parameter is put as a subheading just above the table, as shown in Fig. IV/1.3.1-1A and B. It is always better to include the safeguard column in tabular format. Also all entries should be numbered for proper understanding as well as tefetencing. To facilitate risk matrix formation for risk ranking, frequency of occurrence, severity, etc., other columns may be added. 

From these two data categories a criticality matrix as detailed in Chapter I (in the name of risk matrix) is formed. In many cases, both probability of occurrences and severity categories are numbered in the scale of 1—10 and a criticality matrix can be formed for the same purpose. As these are already covered in Chapter I they are not repeated here. Analysts need to understand that these are for reference only. Analysts use their judgment of failure mode frequency for each specific application. The analyst should tailor the analysis to focus on significant components or subassemblies where failures will result in undesirable system-level effects. Based on these judgments, analysts develop risk categories for the specific application. 

As outlined on pages 26 and 27 of the 2008 U.S. Department of Education s Guide to School Vulnerability Assessments, a risk matrix is one way a school can determine change priorities. As displayed in Table 1.4, schools can determine which hazards should be higher or lower priority based on frequency, magnitude, warning, severity, and overall risk priority. 

The calculated value of f is then compared with a target frequency. The target frequency may be derived from detailed risk tolerance criteria, or may take the form of a risk matrix. This comparison allows decisions to be made on whether further risk reduction is required and what performance any further risk reduction needs to achieve, including the SIL, if the additional protection layer is a SIS. 

Risk matrices provide a framework for an explicit examination of the frequency and consequences of hazards. The method may be used to rank the hazards in order of significance, screen out insignificant ones, or evaluate the need for risk reduction of each hazard. A risk matrix separates the dimensions of probability (POP) and consequence (COF) into typically three to six categories (A to E in Fig. 12.9). 

Risk matrices may use quantitative definitions of the frequency and consequence categories or some numerical indices of frequency and consequence (e.g., one to five) before adding the frequency and consequence pairs to rank the risks of each hazard or each box on the risk matrix. The strengths of the risk matrix approach are [10]... 

Frequency of occupational accidents. The frequency of occupational accidents must not be higher than for comparable platforms in operation. Norskoil also uses a risk matrix similar to the one shown in Table 22.4 in determining the acceptability of occupational accidents. 

The Risk matrix helps evaluate if a risk given by an estimated probability of occurrence (frequency) and a classification of the damage (consequence) is acceptable or not Fig. 1 shows an example for a risk matrix. 

Estimate risk consequence and frequency p. Hazards list or risk matrix... 

Table 5.1 shows the risk matrix table that presents in a tabular format, a risk level related to the frequency and severity of a hazard. RRN ranges from 1 (least frequent and least severe consequence) to 10 (most frequent and most severe consequence). 

The calculation makes use of the fact that both the frequency and severity bands of the risk matrix are approximately logarithmic (e.g. a risk level of 6 is treated as 10 ) (MSC (1997b)). Using 7 as a base then ... 

Once the hazards are identified with respect to each of above accident categories, compartments and operational phases, it is essential that they are screened so that they can be properly evaluated and the trivial ones to be excluded from further investigation. The Risk Matrix Approach (Loughran et al. (2002), MSA (1993), Wang et al. 1999)) can be used to combine frequency and severity rankings for the estimation of RRN values. 

So what Risk assessment (i.e. assess frequency relative to the consequence) Risk matrix... 

In this particular risk ranking matrix, the risk level is not inversely equal, i.e. C4 PI do not carry the same risk as P4 Cl. Generally it is considered the risk is higher when the consequences are more severe rather than when frequency is greater). 

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