Mishap risk assessment

Element 3—risk assessment. For each identified hazard, the mishap severity and probability or frequency are estabhshed. A mishap risk assessment matrix is used... 

In 882E, Appendix A provides Guidance For Implementation Of A System Safety Effort, It runs 43 pages long. It is good reading. Item A.4.1.2.1.3 speaks of Mishap risk assessment matrix and scaling as follows ... 

To emphasize It is not necessary to adopt a complicated and costly risk assessment system when the situations at hand can be resolved with a qualitative (subjective) and simpler system. Item A.7 in Appendix A, Example Mishap Risk Assessment Matrices, is truly educational. In several places in this book, readers are advised to develop risk assessment matrices suitable to the hazards and risks with which they deal and to keep them simple. That idea is supported in A.7, where it is said that ... 

Mishap risk assessment matrices should be tailored to each system or class of systems based on the expected range of severity of potential mishaps and the range of probability or frequency of these mishaps. 

A CSI is essentially the same as an SCI except that systems required to identify CSIs have additional statutory and regulatory requirements that the contractor must meet in supplying those CSIs to the government. For systems required to have a CSI list, HA and mishap risk assessment is used to develop that list. The determining factor in CSIs is the consequence of failure, not the probability that the failure or consequence would occur. CSIs include items determined to be life-limited, fracture critical, fatigue-sensitive, and so on. Unsafe conditions relate to hazard severity categories I and II of MIL-STD-882. A CSI is also identified as a part, subassembly, assembly, subsystem, installation equipment, or support equipment for a system that contains a characteristic, failure mode, malfunction, or absence of which could result in a Class A or Class B accident as defined by DoDINST 6055.7. 

For systems required to have a CSI list, HA and mishap risk assessment is used to develop that list. A CSI is essentially the same as an SCI except that... 

DI-SAFT-81300A, Mishap Risk Assessment Report. 

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 HRI matrix also goes by other names however, regardless of the name used, the matrices are essentially the same entity because hazard risk is the same entity as mishap risk. Some of the alternate names include Risk Hazard Index (RHI) matrix, MRI matrix, and Mishap Risk Assessment Matrix (MRAM). 

Mishap risk assessment (before and after DSFs are implemented)... 

An SCN is a proposed change to the specifications of the already solidified and controlled design. SCNs are part of the CM process and the CCB. The SSP should review each and every proposed and actual SCN for safety impact. Each SCN must be evaluated to determine the potential effect on safety-critical components or subsystems HAs and mishap risk assessments may be... 

MIL-STD 882D (para A.4.4.3.2.3) provides the matrix in Table B.15 for mishap risk assessment. 

Risk iuialysis of accidents serves a dual purpose. It estimates tlie probability tliat iui accident will occur and also assesses the severity of the consequences of an accident. Consequences may include dmnage to tlie surrounding enviromnent, financial loss, injury to life and/or deatli. This Part of the book (Part IV) is primarily concerned witli tlie metliods used to identify liazards and causes and consequences of accidents. Issues dealing witli healtli risks have been explored in die previous Part (III). Risk assessment of accidents provides an effective way to help ensure eidier diat a mishap will not occur or reduces the likelihood of an accident. The result of die risk assessment also allows concerned parties to take precautions to prevent an accident before it happens. 

Preliminary Hazard List Description. The incorporation of this information into a PHL entry is shown as Table I. This entry describes the nature of the hazardous event (column 1), why or how the hazard may result in a mishap (column 2), the effects on operating personnel, equipment, and the facility (column 3), the risk assessment code assigned to the uncontrolled hazard (column 4) and any comments the originator may have (column 5). 

By using a matrix to quantify and prioritize the risks the intrinsic subjective nature of risk assessment is not reduced, but a consistent framework for evaluating risk is provided. Although different matrices may be used for various applications, any risk assessment tool should include the elements of hazard severity and mishap probability. The risk level defined in the matrix represents the degree of risk associated with a hazard by considering these two elements. 

In order to produce believable RACs or any other quantitative risk assessment, reliable, valid data are required. Even though considerable data exist, they are not necessarily available or in the correct format. Improvements can be made in the sharing of lessons learned, mishap information, reliability data, and the other information needed to support the system safety effort. A well-organized effort to identify and catalog existing databases and to develop plans for the systematic collection and dissemination of new data would benefit the entire safety community. 

Require an assessment of mishap risk be presented as part of any program evaluation or review, and as a part of all decisionmaking milestones. 

Risk Assessment 1 2A (see Tables 2.1—2.3). Because the severity of such an occurrence is categorized as critical (i.e., severe injury, occupational illness, or system damage) and, because of the proposed system design, the probability of a mishap of this nature is categorized as frequent (i.e., likely to occur frequently), the risk assessment matrix assigns this risk a classification of 2A, which, according to Table 2.3, is an unacceptable level of risk. 

Risk Assessment 2 2B (see Tables 2.1-2.3). Liquid contact with parts is assessed as a critical occurrence, since the potential damage to the parts would most likely render them unusable. The likelihood of such a mishap is considered highly probable, based on the proposed system design. The risk assessment matrix (Table 2.3) indicates that a risk classification of 2B is unacceptable. Therefore, the system safety precedence tells us that such risk should be approached with the intention of elimination, or possible reduction to an acceptable level. 

Risk Assessment 3 2C (see Tables 2.1—2.3). Because the probability of the abovementioned mishap has been assessed as occasional (i.e., likely to occur sometime in the life of an item) and the severity of the mishap outcome can be categorized as critical, the risk classification from Table 2.3 indicates that such a mishap is assessed as 2C. This level of risk, although not totally unacceptable, by definition, is still undesirable and must therefore be reduced or eliminated through design controls. 

Risk Assessment 6 2C (see Tables 2.1-2.3). Obviously, critical mishaps such as those described above might possibly occur during the life cycle of this system ( occasional ). The risk assessment matrix indicates that such risk is undesirable and must, if at all possible, be controlled or reduced to acceptable levels or eliminated totally. 

Risk the probabihtyofoccurrence and the severity of a mishap. There are six probabihty levels Frequent, Probable, Occasional, Remote, Improbable, and EUminated. There are four severity levels Catastrophic, Critical, Marginal, and Neghgible. The levels form a risk assessment matrix, shown in Figure 36-1. 

Five examples of risk assessment matrices follow. First, an adaptation is shown in Table 7 of the Mishap risk categories and mishap acceptance levels as in the working draft of MIL-STD-882E, the Department of Defense Standard Practice For System Safety. A comment in Appendix A of 882E is pertinent here A mishap assessment matrix allows classification by mishap severity and mishap probability and assists in managing the decision-making to achieve the necessary risk elimination or reduction to an acceptable level. ... 

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