Optimal periodic and random inspections with first, last and overtime policies

Abstract

It has been assumed for a standby unit that periodic inspection is performed more easily to detect failures, but such a strict periodic mode would be impractical if the unit is executing some procedures without stops. From the above viewpoint, this paper first optimises a random inspection policy in accordance with random procedure times, compares it with periodic inspection and computes a modified checking cost for random inspection to determine the case where such a random inspection would be adopted. Second, this paper proposes three new inspection models in which inspections with deterministic policies are scheduled strategically while their performances need to be limited by completion times of operation procedures. These policies are called inspection first, inspection last and inspection overtime. The total expected inspection and downtime costs of each model until failure detection are obtained, and optimal policies which minimise them are derived analytically. Furthermore, the three inspection policies are compared with periodic inspection, inspection first and last are compared with each other, and a modified checking cost for inspection overtime is discussed when the policy would be better than periodic inspection.

Maintenance Overtime Policy with Cumulative Damage

“…The maintenance models that the unit is replaced at a random operating time are studied (Nakagawa, 2014;Chen et al, 2010a;Chen et al, 2010b). Maintenance overtime policies where the unit is replaced at the first time of a completion time of works over planned time have been discussed (Nakagawa and Zhao, 2015;Zhao and Nakagawa, 2013;Zhao et al, 2014). In the model, the unit is not replaced while it is working, because it has much loss cost to stop its work.…”

Periodic and sequential inspection policies with mission failure probabilities

“…Recent works on periodic inspections were studied extensively: Optimal periodic inspection intervals for geodistributed infrastructure systems subject to hidden failures were computed 5 . Inspections with periodic and random policies have been modeled by considering triggering approaches of first, last, and overtime 6 . Planned periodic inspections and unplanned opportunistic inspections were considered into maintenance and inventory policies to find the hidden failures of the units in a k ‐out‐of‐ n system 7 .…”

“…5 Inspections with periodic and random policies have been modeled by considering triggering approaches of first, last, and overtime. 6 Planned periodic inspections and unplanned opportunistic inspections were considered into maintenance and inventory policies to find the hidden failures of the units in a 𝑘-out-of-𝑛 system. 7 A redundancy allocation problem for cold-standby systems with degrading components was studied when periodic inspection and preventive maintenance are performed on the cold-standby components.…”

Which Replacement Is Better at Working Cycles or Number of Failures

“…Nakagawa and Zhao considered about first and last policies for replacement and inspections when the policies are triggered by two factors. [14]- [16]. Replacement first means that the unit is replaced preventively at time of events such as operating time, number of repairs, working cycles, cumulative damage, etc, whichever occurs first, and replacement last means that the unit is replaced preventively at the above events, whichever occurs last.…”