Modified-opportunistic inspection and the case of remote, groundwater well-heads

We develop a model of a maintenance policy in which inspections are partly opportunistic and partly scheduled. Opportunities for inspection occur at random, and the system is inspected at such an opportunity only if the system is aged at least S. Further, once the system reaches age T, an emergency inspection is performed. The purpose of inspection is to determine whether the system is in the defective state, which acts as a warning stage prior to failure. The policy represents a reality in which flexible inspections prioritise production or missions or convenience, subject to statutory or safety regulations. The model is a generalization of the delay time model. Inspection of pumps at groundwater well-heads, which are geographically remote, motivates the model. Main-tenance interventions at other nearby installations are opportunities. Policy outcomes (cost-rate, mean time between operational failures) are studied numerically for a range of values of the parameters of the model. The model is useful for practice because it quantifies the benefit and disbenefit of flexibility in the inspection policy. We show that in some circumstances making better use of opportunities can simultaneously reduce cost and increase reliability.

Automated summary

This study presents a maintenance policy model that combines opportunistic and scheduled inspections. The inspections are randomly determined, with the system only being checked if it has reached a certain age. In addition, emergency inspections are carried out once the system reaches a specific age. The model considers the flexibility of inspections based on production, missions, and convenience, while still adhering to statutory and safety regulations. The model's outcomes were analyzed numerically to assess the cost-rate and mean time between operational failures for different parameter values. The model proves useful in quantifying the advantages and disadvantages of flexible inspection policies and demonstrates that better utilization of inspection opportunities can lead to cost reduction and increased reliability.