The paper attempts to model the imperfect repair with the concept of arithmetic reduction of age (ARA) and also sequentially incorporates the effect of imperfect corrective and preventive maintenance. Four virtual age processes are devised to describe the various after repair restoration patterns as well as different restoration degrees for both CM and PM. The GRP maximum likelihood estimators (MLE) are derived and then used for parameter estimation. The expected number of failures for the proposed approaches are estimated using Monte Carlo simulation. Two different repair effectiveness indices for CM and PM are estimated for all the four approaches to provide a better insight of the maintenance processes. The residual life is predicted using residual mean time to failure based on virtual age at each repair point. The paper concludes with comparative analysis to get adequate insights into the goodness of fit for the proposed models. © RAMS Consultants.