Reliability concepts applied to earth pressure balance tunnel boring machine

Widespread application of earth pressure balance tunnel boring machine (EPB-TBMs), especially in urban arias, requires improving performance of these machines. Effective reliability analysis could enable managers to study failures and downtimes of these machines and improve the TBMs performance. In present study reliability analysis of EPB-TBM is discussed and as a case study, reliability analysis of electrical system of the EBP-TBM in Tabriz metro in Iran is performed. For this aim, failure data were collected during about 26 months of machine operation. Statistical tests including trend and serial correlation tests indicated that the data are independent and identically distributed (iid), consequently the renewal process was used for modeling. The data analysis also revealed that the time between failures (TBFs) data confirm the Lognormal (3P) distribution. Reliability analysis showed that there is an 80.1% chance that the electrical system of present EPB-TBM be operational for 15 h without any failure. The reliability-based maintenance intervals for 90%, 80%, 70% and 50% reliability level are 8.78, 15.61, 22.61 and 39.8 h respectively. The results indicated that checking and servicing of the electrical system of NFM EPB-TBM before 15.61h operation can result in a reliable operation.

Keywords:

EPB-TBM , Electrical system , TBFs , Reliability analysis