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ABSTRACT
Protection systems are designed so that they can prevent disasters when critical events (demands) occur. These systems are usually inactive and their functionality is only noticeable during a demand or through inspections. Furthermore, the level of deterioration of the system can worsen due to the actions of external events (shocks), which can accelerate the process of its natural wear. Thus, in order to ensure the readiness of such systems, we modeled a hybrid inspection and replacement policy for safety brakes subject to shocks. The policy considers additional inspections beyond the scheduled inspections subject to misclassification. The system is replaced when any inspection indicates that it has failed, either immediately after the Mth inspection, or immediately after the Kth met demand, or immediately after an unmet demand – whichever comes first. Our model is motivated by a real case of a safety brake in a steel mill. We compared this policy with two other classical policies and saw that it has significant cost-saving potential in relation to both. The results indicate how important inspections are for systems with hidden failures and show when the observation of shocks should be prioritized over inspection actions.
Acknowledgements
This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. The work of Augusto Rodrigues has been supported by FACEPE (Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco). The work of Cristiano Cavalcante and Alexandre Alberti has been supported by the CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico).
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data statement
The data presented in this article were calculated using code written in python. This code calculates the cost-rate using the expressions presented in the paper. A demonstrator of the code can be accessed here: https://augustojsrodrigues-kmt-analytical-code-yxz40z.streamlit.app/. With this code, the reader can verify the results presented and explore new cases.
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Notes on contributors
Augusto José da Silva Rodrigues
Augusto José da Silva Rodrigues received his B.Sc. degree (2018) and his M.Sc. degree (2020) in Industrial Engineering from Federal University of Campina Grande (UFCG, Brazil) and Federal University of Pernambuco (UFPE, Brazil), respectively. He is currently a Ph.D student in Industrial Engineering at UFPE. Also, he is a Member of RANDOM (Research Group on Risk and Decision Analysis in Operations and Maintenance) at UFPE, and a Member of the Institute of Mathematics and Its Applications (IMA, U.K.). His current interests include applied operational research, focused on maintenance and reliability modelling.
Flávia Ataide da Motta
Flávia Ataide da Motta received her B.Sc. degree (2003) and her M.Sc. degree (2012) in Mechanical Engineering from University of Pernambuco (UPE) and from Federal University of Pernambuco (UFPE), respectively. She is Engineer at UFPE where she is doing her Ph.D. Her research interests include maintenance modelling, safety risk assessment and heat transfer.
Cristiano Alexandre Virginio Cavalcante
Cristiano Alexandre Virginio Cavalcante is a full professor at Federal University of Pernambuco (UFPE), Brazil. He received his B.Sc. degree in Mechanical Engineering from UFPE, in 2001, and M.Sc. and Ph.D. degrees in Industrial Engineering from UFPE in 2003 and 2005, respectively. He also held two Post-Doctorates, at UFPE (2006) and at University of Salford, England (2008). Dr. Cavalcante has been the recipient of a research fellowship from the Brazil National Research Council (CNPq) since 2009. Also, he is the leader of RANDOM (Research Group on Risk and Decision Analysis in Operations and Maintenance) at UFPE, Fellow of the Institute of Mathematics and Its Applications (IMA, U.K.) and a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE). He has authored or coauthored more than 60 scientific papers in peer-reviewed journals on topics related to: operational research, maintenance modeling, risk, reliability, safety, warehouse management, warranty, and MCDM/A (multicriteria decision making and aid).
Alexandre Ramalho Alberti
Alexandre Ramalho Alberti is an Assistant Professor in the Department of Industrial Engineering at Federal University of Pernambuco (UFPE), Brazil. Also, he is a Member of RANDOM (Research Group on Risk and Decision Analysis in Operations and Maintenance) at UFPE. He received his B.Sc. degree in Mechanical Engineering from Federal University of Santa Catarina (UFSC), Brazil, in 2014, and M.Sc. and Ph.D. degrees in Industrial Engineering from UFPE in 2018 and 2020, respectively. His research interests focus on applied operational research.