Reliability, availability and maintainability analysis of the conveyor system in mechanized tunneling

Abstract Evaluation of reliability, maintainability and availability (RAM) plays an important role in performance estimation of tunneling systems. Reliability predictions, maintenance planning, reliability assessment, failure detection and risk evaluation are necessary for tunneling machines. The RAM analyses of tunneling equipments have been widely investigated in recent years. The aim of this study is to RAM analysis of the material hauling system in an earth pressure balance tunnel boring machine (EPB-TBM). For this purpose, failures and repairs data from main conveyor system of Tabriz Metro Line 2 in Iran were collected. Performing trend and serial correlation tests showed that the data are independent and identically distributed (iid) and therefore the statistical techniques can be used for modeling. To carry out the analysis, the main conveyor system was divided into three sub-systems including conveyors 1, 2 and 3, which are located on the TBM machine, inside the tunnel and station. Analysis results indicated that reliability of conveyor subsystems 1, 2 and 3 after 267, 58 and 300 h reaches to zero, respectively. Moreover, availability results showed that all subsystems are available for more than 89 percent of the time. To improve system reliability, preventive maintenance is required for each subsystem. Based on the obtained results, reliability-based preventive maintenance time intervals for 80 percent of reliability level for subsystem 1, 2 and 3 are 43, 3 and 6 h, respectively.