PurposeThis study presents a reliability-based and sustainability-informed maintenance optimization model for telecommunications equipment. It considers several risk attributes associated with sustainability dimensions (i.e. social, economic and environmental aspects).Design/methodology/approachMany companies have developed long-term strategies to promote higher resource utilization, which has led to a paradigm shift in the role of maintenance. In parallel, reliability has been recognized as a fundamental factor in characterizing the optimal blend of maintenance strategies for a given system. It is essential for accurate failure prediction, which contributes toward more efficient use of all resources.FindingsThe corresponding subattributes are identified based on expert opinions and then incorporated into the proposed model. Subsequently, using the multiobjective particle swarm optimization (MOPSO), the proposed sustainability risks together with the maintenance costs are optimized, and the proper blend of maintenance strategies is identified.Originality/valueEffective management of all human and natural resources, which are particularly emphasized by the concept of sustainability, has attracted much attention in recent years. However, contributions that effectively apply this concept in maintenance problems are very few and very few studies have attempted to quantify sustainability.
PurposeOnline spiral pipe manufacturing is one of the most common processes for producing water and gas transmission pipes. Weld quality and pipe circumstances are the most important qualitative characteristics of these pipes determining the overall cost of production. The purpose of this paper is describing how to implement Six Sigma on the production of spiral welded pipes with a real case study.Design/methodology/approachFirst, the capability of the pipe production process has been performed by using the defects per million opportunities to allow for comparison and analysis of the project effectiveness. Then, the variation pattern of this index, after an improvement project, has been investigated. Finally, Taguchi's loss functions are used to evaluate the effectiveness of these projects.FindingsThe results represent a significant improvement in the production process and a reduction in production costs regarding both weld quality and pipe circumstances. Due to the successful implementation of Six Sigma project in welding and pipe quality improvement, the Define, Measure, Analyze, Improve and Control (DMAIC) method can be used effectively in defining weld and pipe quality.Originality/valueIn this proposed work, for the first time, research on the implementation of Six Sigma in the pipeline and welding industries on two online spiral production machines has been investigated. The DMAIC method has been used for the first time to improve the dimensional quality and weld quality of spiral pipes.
In recent years, an increased focus has been given to replacing high Global Warming Potential (GWP) refrigerants with relatively low GWP alternatives. Energy efficiency, carbon reduction and HFC phase-down will push the heat pump market towards natural refrigerants. Propane (R-290) is a type of hydrocarbon refrigerant with zero ozone depletion potential and very low GWP (< 4). R-290 is a pure refrigerant and has excellent thermodynamic properties. The research presented in this project is a study of the refrigerant side of an ASHP to analyze the thermodynamic performance of the propane refrigerant under different operating conditions. For this purpose, a test rig was designed and constructed in a single packaged air source heat pump unit. In addition, the air side of the tested heat pump was designed for energy recovery in cooling and heating modes. The compactness of the system and installation of air dampers allows its placement for coupling to the building renewable air sources, such as a building integrated photovoltaic/thermal (BIPV/T) system.
In recent years, an increased focus has been given to replacing high Global Warming Potential (GWP) refrigerants with relatively low GWP alternatives. Energy efficiency, carbon reduction and HFC phase-down will push the heat pump market towards natural refrigerants. Propane (R-290) is a type of hydrocarbon refrigerant with zero ozone depletion potential and very low GWP (< 4). R-290 is a pure refrigerant and has excellent thermodynamic properties. The research presented in this project is a study of the refrigerant side of an ASHP to analyze the thermodynamic performance of the propane refrigerant under different operating conditions. For this purpose, a test rig was designed and constructed in a single packaged air source heat pump unit. In addition, the air side of the tested heat pump was designed for energy recovery in cooling and heating modes. The compactness of the system and installation of air dampers allows its placement for coupling to the building renewable air sources, such as a building integrated photovoltaic/thermal (BIPV/T) system.
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