In the literature

many works on determining inspection interval by the delay time concept generally assumed that the time of inspection span and the time of failure renewal are negligible.However

in realistic cases

the above time should not be neglected for both the time itself and its effect.In order to model the effect of the possible overlapping of inspection span with failure downtime on determining the optimal inspection interval

we propose a block-based inspection model for a single component-based on delay time concept.We further compare this model with the age-based model to show the practical sense.The developed models are also demonstrated by numerical examples.