Development of an acceleration model for subsea pressure

Accelerated Life Testing (ALT) is an effective method of demonstrating and improving product reliability in applications where the products are expected to perform for a long period of time. ALT accelerates a given failure mode by testing at amplified stress level(s) in excess of operational limits. Statistical analysis (parameter estimation) is then performed on the data, based on an acceleration model to make life predictions at use level. The acceleration model thus forms the basis of accelerated life testing methodology. Well established accelerated models such as the Arrhenius model and the Inverse Power Law (IPL) model exist for key stresses such as temperature and voltage. But there are other stresses, failure mechanisms and special cases where there is no clear model of choice. One such scenario is the case where viscoelastic strain due to subsea pressure is the dominant failure mechanism. This paper presents the steps followed in the development of an acceleration model for subsea pressure. Although a final model has not been developed, the data obtained through a series of tests leads to an acceleration model that follows an exponential functional form. The life predictions based on the model also incorporate the use of field data. The test results were based on an accelerated life test performed over a period of one year and also includes several short term progressive stress tests. Further research on the development of the model includes independent testing to verify the true nature of acceleration of life through subsea pressure.