Fault detection tree analysis

Risk can be analyzed in one of two basic ways inductively or deductively, that is either bottom-up or top-down. In a deductive analysis a system failure is postulated. The analyst then works backward to deduce what combinations of events could have occurred for the system failure to have taken place (a detective solving a crime is thinking deductively). Fault tree analysis (FTA), the topic discussed in this section, is deductive. An inductive analysis works in the other direction. A single failure, such as a pmnp stopping or a valve closing at the wrong time, is postulated. The... 

Fault Tree Analysis (FTA) is a well known and effective method for analyzing hardware systems 1-3. This paper describes a possible use of FTA in a software embedded system for temperature control. The analysis is first applied to the hardware and software systems but concentrates on the software section afterwards, two critical events were detected by FTA and steps were taken to overcome them. Although this work describes a specific situation it can be applied to many control systems. 

Unlike the fault tree analysis the failure mode and effects analysis detects systematically all effects - including those considered to be harmless - which can appear for all possible failure modes of a logical element and that successively for all logical elements. 

Having defined the dependability criteria within the specification, the purpose of this activity will include an investigation of the relationship between the development lifecycle (including the proof of safety invariants, refinement of the dependability criteria/perspectives and validation/verification approaches) and the dependability lifecycle which includes safety analysis (eg, the relationship between fault trees, proof of safety invariants, and static analysis tools), fault detection/protection and failure detection/containment. 

Common Warehouse Metamodel Event Tree Analysis Fault Detection System Fluid... 

In the simplest terms, a fault-tree for risk analysis requires the following information probabiUty of detection of a particular anomaly for an NDE system, repair or replacement decision for an item judged defective, probabiUty of failure of the anomaly, cost of failure, cost of inspection, and cost of repair. Implementation of a risk-based inspection system should lead to an overall improvement in the inspection costs as well as in the safety in operation for a plant, component, or a system. Unless the database is well estabUshed, however, costs may fluctuate considerably. 

This type of hazards analysis can be either deductive or inductive. A deductive (top-down) analysis is one that first defines an undesirable event, and then considers what events and chains of circumstances are needed to occur before the overall undesirable event occurs. A deductive approach is used by detectives to solve crimes. A widely used type of deductive analysis in process risk analysis is the fault tree method, described in the next chapter. 

Thus the initial fault set detected from the thermal domain tree is Qp, Q, R, and P. However, the initial fault hypothesized from the hydraulic domain analysis and. The common hydraulic fault in both these sets is Qp and it too has same qualitative state. The final fault candidate list is Qj, Pj , and P. Since single fault hypothesis is considered, Qp should be the cause of the fault. 

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