# PAL-VMEA: A Novel Method for Enhancing Decision-Making Consistency in Maintenance Management
## 6 Case Study
The favorable and unfavorable evidence results of each evaluated factor, for the given example, plotted in the USC  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & **Value** & \(\mathbf{a_{w}}\) & \(\mathbf{b_{w}}\) & \(\mathbf{H}\) & \(\mathbf{G}\) \\ \hline
**F  
Considering the obtained results for the sub-KPC's oil volume (F1 = 9) and air pressure (F2 = 9); the variability of the NF's oil leakage (F3 = 2), clogging of the oil pipeline (F4 = 3) and leakage in the air pipeline (F5 = 1); and the sensitivity of each sub-KPC to its NFs (F6 = 9, for oil leakage, F7 = 8, for oil pipeline clogging, and F8 = 10, for air pipeline leakages), presented in Table 13, the VMEA form completed for this case study is shown in Table 14.  
Table 14 presents the expected result of the proposed method, i.e., the VMEA form filled with values where epistemic uncertainty was properly worked out in order to increase the robustness of the results. The interpretation of this table is relatively simple, since the VRPN values (both for the NF and for the Sub-KPC) clearly indicate which disturbance (failure) the analyzed system is more sensitive, in the case of VRPN (NF), as well as which physical quantity (Sub-KPC) should be monitored in order to predict the occurrence of the failure in question, in the case of VRPN (Sub-KPC). These two pieces of information are essential for proper maintenance planning, especially in the Reliability-Centered Maintenance (RCM) case. In order to create a reference for the obtained results, the same experts who participated in the PAL-VMEA process evaluated the VMEA weights and, through meetings and the classic brainstorming process, arrived at the results presented in Table 15. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**System:**} & \multicolumn{2}{c}{**Subsystem:**} & \multicolumn{2}{c}{**KPC:**} \\ \multicolumn{2}{c}{**Speed Governor**} & \multicolumn{2}{c}{**Air-Oil Accumulator**} & \multicolumn{2}{c}{**Pressurize the Control Fluid**} \\ \hline \multirow{2}{*}{**Sub-KPC**} & **Weighting** & \multirow{2}{*}{**NF**} & **Size of** & **Sensitivity** & **VRPN** & **VRPN** \\  & **of Sub-KPC** & & **variation in NF** & **to NF** & **(NF)** & **(Sub-KPC)** \\ \hline \multirow{2}{*}{Oil Volume} & \multirow{2}{*}{9} & Leakage & 2 & 9 & 162 & \\ \cline{2-5}  & & Clogging & 3 & 8 & 216 & \\ \hline Air Pressure & 9 & Leakage & 1 & 10 & 90 & 90 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: VMEA form—air-oil accumulator example. Figure 7: Air-oil accumulator example Unitary Square on the Cartesian Plane (USCP). Seeking to determine a comparison between the results obtained with the PAL-VMEA method and the brainstorming process, the 66 NFs and 24 KPCs of the entire analyzed system were evaluated and the result are shown in Figure 8,b, respectively. In this case, each point represents an ordered pair formed by the result of the two processes (PAL-VMEA and brainstorming) for the same NF or KPC. The diagonal line represents the total correspondence between the results of the two methods, i.e., \(\text{NF}_{\text{brainstorm}}=\text{NF}_{\text{PAL-VMEA}}\) and \(\text{KPC}_{\text{brainstorm}}=\text{KPC}_{\text{PAL-VMEA}}\). The colors intensity in the graphs represents the distance between the results, with the yellow zone representing the region of equivalence between results, the red zone representing the region in which the results found via brainstorm are greater than PAL-VMEA results, and the green zone representing the opposite. It is noted that the results of the two methods have some correlation, which is equal to 0.757 in the case of NFs and 0.840 in the case of KPCs, but the variation between results for the same criterion is significant. In most cases, the values found with the PAL-VMEA method are greater than those obtained via the brainstorming process (which would mean a more conservative result for the former), especially in the case of KPCs.