Hazard risk matrix, system safety

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. 

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. 

Several texts include hazard analysis and risk assessment decision matrices. Every matrix I found has been adopted from those included in what was originally known as Military Standard—System Safety Program Requirements, MlL-STD-882. Its most recent version is now named Standard Practice for System Safety, MIL-STD-882D, 2000. Influence of that standard will be obvious in the remainder of this chapter. 

Risk is determined by assessing its two components the severity of harm or damage resulting from a hazard-related event and the probability that the event could occur. Table 15.1 presents a sample Risk Assessment Matrix, illustrating how these two factors are combined to obtain a risk level. A review of the many published risk assessment matrices appears in chapters titled A Primer On Hazard Analysis And Risk Assessment and Risk Scoring Systems in this authors book titled Innovations In Safety Management. 

A Brief Overview of Selected System Safety Analytical Approaches Working with the Risk Assessment Matrix Preliminary Hazard Analysis Energy Flow/Barrier Analysis Failure Modes and Effects Analysis Fault Tree Analysis... 

The risk assessment code (RAC) matrix and the hazard severity and probability indices and definitions used in this study were taken from EMX-XXXX (the Facility System Safety Manual). 

In Chapter I, risk matrix has been discussed. Risk graph is similarly used to categorize risks additionally it can be used to determine SIL in process industries (especially when there many hazards to analyze). The discussions are presented naturally in a generalized way, however for each application one needs to calibrate the same. In this approach, there are four sets of parameters, viz. C, F, P, and W (see Fig. VII/1.3.4 1), each arranged as a column. All of these parameters describe the nature of the hazardous situation when safety instrumented systems fail or are not available. One parameter is chosen from each of four sets and the selected parameters are then combined to decide the safety integrity level allocated to the safety instrumented functions (Annex Dlof IS/IEC 61511 3 2003). Let an example with exposure to radioactive radiation case be analyzed. 

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... 

ANSI ZlO-2012 (Occupational health and safety Systems, 2012) defines risk as an estimate of the combination the likelihood of occurrence of a hazardous event or exposure(s), and the severity of injury or illness that may be caused by the event or exposures . In ANSI ZIO, a risk matrix is used to develop an estimate of the specific risk and is based on a combinafion of experience, industry history, science, and understanding of hazards. The risk matrix provides on what the potential severity may be in a worst case scenario based on the type of exposure. 

Risk Analysis Another group of methods used in system safety involve risk analysis. In many cases, the hazards are charted into a risk decision table or risk assessment matrix (see Figure 6.5). The severity of hazards is rated and charted on one axis of the chart. The probability of occurrence is on the other axis. Then severity-probability cells are marked for the kind of action required, such as risk reduction required, management approval, or that the operation is permissible. 

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... 

A common method employed in qualitative safety artalysis is the use of a risk matrix method (Halebsky (1989), Tummsda and Leung (1995)). The two parartreters that are considered are the occurrence likelihood of the failure event and the severity of its possible consequences. Upon identifying all the hazards within the system under consideration, each hazard is evaluated in terms of these two parameters. The severity of all the failure events could be assessed in terms of the four categories (i.e. Negligible, Marginal, Critical and Catastrophic) as shown in Table 3.1. 

All the identitied hazards within the system under study can be evaluated using this method to produce a risk ranking based on the highest priority down to the lowest priority. A variation of this qualitative risk matrix approach will be presented in Chapter 5 with its application to the safety analysis of a ship. 

Figure 8.6 Annotated Personal Risk Assessment Hazard Classification Tool, A Risk Guidance Card to Help Assess Risk of Assignments. Based on and adapted from Risk Assessment Matrix, Department of Defense Standard Practice Safety System System Safety, MIL-STD-882E(2012).

A risk assessment matrix is a useful tool to identify the level of risk and the levels of management approval required for any Risk Management Plan. There are various forms of this matrix, but they aU have a common objective to define the potential consequences or severity of the hazard versus the probability or likelihood of the hazard (Safety Management System Toolkit, 2007). 

The FAA s internal Safety Management System (ASD-lOO-SSE-1) combines the two approaches by classifying hazard severity as shown in Table 5.4 allocating consequence probability as shown in Table 5.5 and then assessing risk according to the matrix shown in Fig. 5.3. 

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