Main window of the RAM Commander's Fault Tree Analysis Module
Fault Tree Analysis Module Features
• Handy methods for diagram printing and simple Copy & Paste transfer to other applications
• Easy to use Events Library
• Generation of Minimal Cut Sets (MCS)
• Calculation of Unavailability Q(t), Mean Unavailability Q
• Calculation of Importance and Sensitivity
• Calculation of Frequency W(t) and Intensity L(t)
• Calculation of Unreliability F(t) and Number of Failures E(0,t)
• Generation and calculation of Binary Decision Diagram (BDD)
• TRUE/FALSE event status visual propagation
• MCS visual presentation on a fault tree
• Set of required reports - FTA diagram, MCS, events library etc.
• Link between FTA and the product tree
• Link between FTA and FMECA modules
• Integration with Safety analysis module
• Automatically build Fault trees from FMECA, FMEA and RBD
• Data import from RiskSpectrum, Aralia SimTree, CAFTA and Isograph FaultTree+
Fault Tree Analysis is one of the most widely used methods in system reliability and failure probability analysis. A fault tree is a graphical representation of a logical structure depicting undesired events ("failures") and their causes. You create the logical structure by using gates and represent undesired incidents by using basic events. Reliability parameters are assigned to each basic event. Widely used in system reliability studies, fault tree analysis offers the ability to focus on an event of importance, such as a highly critical safety issue, and work to minimize its occurrence or consequence. The probability of a top-level event can then be determined by applying appropriate mathematical techniques. The resulting fault tree diagram is a graphical representation of the chain of events in your system or process, built using events and logical gate configurations.
FTA Basic Event data
Two types of analysis can be conducted using Fault Tree Analysis Software:
• Qualitative Analysis: performed by means of Minimal Cut Sets (MCS) building
• Quantitative Analysis: calculating the Absolute probabilities, i.e. the probabilities of system failures
Example of FTA Unavailability and MCS Analysis report
After Unavailability calculation and MCS analysis, Importance and Sensitivity Analysis may be performed. Results of Importance analysis help select those fault tree events, which contribute most to the system's unavailability. Sensitivity analysis helps choose those events, for which a relatively small change will lead to a relatively large system unavailability changes. Calculated values are Fussell-Vesely importance (FV Imp), Risk Decrease Factor (RDF), Fractional Contribution (FC), Risk Increase Factor (RIF) and Sensitivity Value for each Basic or Undeveloped Event.
Example of FTA Importance and Sensitivity Analysis report
Fault Tree Analysis is acknowledged as a key tool for increasing safety. It is unique and indispensable in analyzing risks and determining various combinations of hardware and software failures together with human errors that could result in a specified risk or system failure. Fault tree analysis is useful both in designing new products/services and in identifying problems of the existing products/services. In the quality planning process, the analysis can be used to optimize process features and goals and to design for critical factors and human errors. As a part of process improvement, it can be used to help identify root causes of each trouble and to design remedies and countermeasures.
FTA is used by other RAM Commander modules - the Safety Assessment Software Module (compatible with aviation safety requirements, SAE ARP4761 and other standards) and MMEL (Master Minimum Equipment List analysis for aviation industry).