basing reaction on outcome severity vs risk probability

On failure, ECLSS subsystems are generally exposed to imperfect repairs, which imply that the repair actions bring the subsystems to a state that is in between the new state and the state prior to failure. Moreover, the systems are interrelated with each other for proper functionability of entire subsystem. The ECLSS of an OSS is a critical system, which includes several complex subsystems, such as atmosphere management, water management, food production, waste management and crew safety. Maintenance of complex system like OSS ECLSS is a challenging task for the modern day maintenance engineers, as high skills and expertise are required to accomplish these tasks proficiently. The case study of environmental control and life support system (ECLSS) of orbital space station's (OSS) is selected as an example to illustrate the presented methodology. Garima Sharma, Rajiv Nandan Rai, in Safety and Reliability Modeling and its Applications, 2021 9.5 Case study 1 Nonetheless, every possible step should be taken to eliminate class A and B failure modes, or at least to reduce their probability of occurrence, by making appropriate design changes. The area of the matrix labeled “approximate desirable design region” indicates a low probability of failures with class A and B severity effects and anywhere from a low to high probability of class C and D failures that can be tolerated. This matrix can help set priorities for addressing potential failures and developing appropriate corrective measures. The criticality matrix represents the combined factors of the severity of the potential failure's effects and the probability that the failure will occur. The criticality matrix presented in Figure 4-1 provides a mechanism for comparing the probability and severity of failure modes. The failure may result in death or system loss. The failure will lead to mission loss and may also cause severe injury, major property damage, or major system damage. The failure will lead to delay or loss of availability or mission degradation and may also cause minor injury, minor property damage, or minor system damage. The failure will lead to unscheduled maintenance or repair but will not be serious enough to result in injury, property damage, or system damage. The qualitative approach, used when failure rate data are not available, groups occurrence probabilities for individual item failures together into levels that establish qualitative failure probabilities.ĭetailed Description of the Classification The military standard method consists of distinct qualitative and quantitative approaches. The Department of Defense, in Procedures for Performing a Failure Mode, Effects, and Criticality Analysis set forward a technique for ranking potential failure modes that is often used in the defense, aerospace, and nuclear power generation industries. The scales and categories used may, of course, vary from one organization to another. When the scales used range from 1 to 10, the value of an RPN will be between 1 and 1,000.

SR is the ranking of severity of effects.ĭR is the ranking of probability of detection.įailure modes with a high RPN are more critical and given a higher priority than ones with a lower RPN. Where OR is the ranking of probability of occurrence.

Basing reaction on outcome severity vs risk probability