A development of the quantitative life span assessment model for the railroad signaling equipment

초록

The lifespan of the railroad signaling installation composed by electronic parts is expressed in terms of mean time to failure(MTTF) or mean time between failure(MTBF). Generally a failure is defined as a failure of intended function, and failure rate in component unit is estimated. In order to quantitatively estimate the reliability related with a failure of intended function on the railway signaling equipment, a prediction of failure rates in component unit has been performed by the state modeling for equipment structures(series, parallel, redundancy, hybrid etc), which is based on the relevant standards such as MIL-HDBK-217FN2, IEC 62380 and RIAC 271Plus etc. Being as these quantified failure rate are estimated only in case of ideal failure in component unit, so it differs from a failure rate under operating conditions in which effects of interaction between parts and environmental factors are unintendedly missing. Therefore, the relevant standards of reliability and safety for the railway signaling equipment(for example, IEC 62278) recommend to confirm if a predicted failure rates satisfies with a targeted object. And quantitative demonstration methods such as the Failure Reporting Analysis and Corrective Action System(FRACAS) or the Data Reporting Analysis and Corrective Action System(DRACAS) are commonly used to verify a predicted failure rates. However, to ensure accuracy of these predicted failure rates through the failure reporting analysis, it need to collect the trial-operational informations from many test products installed in the site. So, there are many difficulties in the demonstration of predicted failure rates for the railway signal equipment which the test products are is not sufficient and takes a long times for trail-test. In this study, the accelerated testing on temperature stress having an effect on failure of electronic parts will be proposed as a demonstration methods for prediction of failure rate ahead of installing equipment according to the MIL-HDBK-217FN2. And a reliability assessment model based on RIAC’s failure patterns for electronic parts will be developed to estimate a change of reliability through a prediction of failure occurring in operation.