# Reliability and Risk Centered Maintenance: A Novel Method for Supporting Maintenance Management
## 4 Case Study  
To demonstrate an application of the proposed RRCM method, a Brazilian hydroelectric power plant with four generating units and an installed capacity of approximately 200 MW was considered. Three items from one of the generating units were selected: 2.1. water intake gates, 2.2. water intake grids, and 6.7. turbine guide bearing. As they are systems of different complexities, their selection contributed to demonstrating the  
Figure 8: Guidelines for verifying the applicability, technical feasibility, and effectiveness of a maintenance task. application and results of the RRCM for different FMRLs. A total of 17 potential failure modes were analyzed. Figure 9 presents the developed hierarchical functional tree of the generating unit with the items that were analyzed highlighted in gray. As presented in the Maintenance Plan Definition and Implementation process, the first five steps are related to the item study and are similar to those applied in a traditional RCM analysis: 1. select the item; 2. define its functions; 3. define the functional failures for each function; 4. define their functional failure effects; and 5. define the failure modes for each functional failure. The results of these five steps for the selected items are presented in Table 2.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  
These fundamental five steps are followed by the classification of the risk of each failure mode according to the five possible Failure Mode Risk Level (FMRL) categories: very high, high, medium, low, and very low. As the RRCM does not indicate or restrict how the analysis to categorize each FMRL should be performed, it allows for the utilization of supporting tools that are better suited to the characteristics and context of each system being analyzed. In this case study, a risk matrix was chosen to be used and each FMRL is obtained from the relationship between the Functional Failure Impact (FFI) and the Failure Mode Probability (FMP) given by the risk matrix presented in Figure 10. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Item** & **Functions** & **Functional Failures** & **Functional Failure** & **Failure Modes** \\ \hline \multirow{4}{*}{2.2. Water intake} & Protect the water intake components and turbine Water intake to flow & Do not protect systems from debris carried by the river & Loss of protection of the intake components and turbine & Deformed or ruptured water intake grids \\ \cline{2-5}  & & Do not allow the water intake from water does not flow through the turbine & Water intake grids are completely clogged \\ \cline{2-5}  & & Allow water intake when the generating unit is in operation & Allow a lower intake water flow is lower than rated & Turbine water flow is partially clogged \\ \cline{2-5}  & & & Excessive clearance in the bearing housing \\ \cline{2-5}  & & & Insufficient lubrication \\ \cline{2-5}  & & & & Inadequate viscosity of oil \\ \cline{2-5}  & & Do not restrict the radial displacement of the turbine shaft & Excessive shaft vibration & Overheated lubricating oil \\ \cline{2-5}  & & & & Oil \\ \cline{2-5}  & & & & Damaged bearing components \\ \cline{2-5}  & & & & \\ \hline \multirow{2}{*}{Ensure the hydrogneator shaft alignment} & Do not ensure the proper hydrogneator shaft alignment & Excessive shaft vibration & Improper bearing elements positioning \\ \hline \multirow{2}{*}{Prevent oil leakage} & Do not prevent oil leakage & Oil leakage to the plant’s facilities and the river & Cracks in the bearing housing \\ \cline{2-5}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._  
Figure 10: Risk matrix for FMRL classification. The FFI value is obtained from Equation (1), in which the Environmental Impact (EnI), the Personnel and Facilities Impact (PFI), and the Power Generation and Availability Impact (PGAI) of the functional failure are considered.