Application of Accelerated Failure Time Models in Reliability Analysis Considering Dynamic Environmental Conditions

Historical reliability data are commonly used forreliability analysis of production plants. For this purpose,several handbooks and databases are developed in oiland gas industry, where reliability data of similar oil andgas equipment units are collected. The use of such datawithout considering the aging effects of components dueto varying environmental conditions leads to unreliableresults. Developing physics-based models to describeequipment failure rate, as a function of the elements ofthe operating environment through reliability tests, if notimpossible, can be costly and time-consuming. In thisstudy, the concept of accelerated failure time models isadapted to propose an approach, where historicalreliability data are analysed while the aging impact ofdynamic environmental conditions on the degradation ofcomponents is accounted for. That is, the effects ofenvironmental conditions are included as multiplicativefactors reducing component failure times. The underlyingassumption of this study is that environmental conditionsdo not change component failure mechanisms.Additionally, this study assumes that correctivemaintenance activities remove all the degradation fromcomponents so that historical failure times can beconsidered independent and identical. The results of thisstudy illustrate that the reliability performance ofcomponents under varying environmental conditionsdiffers considerably from those exposed to normalconditions.

Keywords:

Environmental conditions , reliability analysis , accelerated failure time model , stress level