# Case Study of Expected Loss Failure Mode and Effect Analysis Model Based on Maintenance Data
## 4 Discussion  
The conventional FMEA model classes the risk of cause failure as occurrence (\(O\)), severity (\(S\)), and detection (\(D\)), quantities them with 1-10 point scales, and then derivatives a risk priority number (\(RPN\)) with multiplying them. \(RPN\) is used as a rank of risk among several causes, but it does not mean the amount of the risk. However, \(LOSS\) calculated in our EL-FMEA model means the actual cost that the system operator is most interested in. Therefore, the operator can check the magnitude of the risk and the priority of risk of a cause from the \(LOSS\). In our model, occurrence (\(O\)) corresponds to the probability of a cause failure, detection (\(D\)) to the probability of a cause detection, and severity (\(S\)) to the cost of the cause. We created dummy data that can be collected on-site to verify the model's usefulness (See Tables A1 and A2). The system we envision consists of Item 01 to 08. Item 01 to 04 are equipped with sensors, so only the sensor maintenance (SM) occurs. However, items 05 to 08 are not equipped with sensors, so regular maintenance (RM) and corrective maintenance (CM) occur simultaneously. From the maintenance table, we could derive the cause failure rates of Item 05 to 08 and the system failure rates, uptime, and downtime caused by Item 05 to 08. From the detection and failure rate of the already secured items 05 to 08, we derived alternative coefficients to determine whether the sensor is installed in items 05 to 08. In our example, the alternative coefficients of items 05 to 07 are smaller than 0.8, and the coefficient of Item 08 is 1.147. Therefore, it is considered economical to install sensors on items 05 to 07 and not in Item 08. Collecting maintenance record data in the industrial fields has recently become very convenient due to various innovative technologies. The EL-FMEA model is applicable to the risk management of systems and processes in manufacturing and service industries. First, in the manufacturing industry, maintenance records are generally collected for quality control, but it is often not guaranteed whether indicators such as failure rate and expected loss (probability) can be calculated based on the collected data. Therefore, a data collection method and procedure that can be quantitatively analyzed in this study are presented through the EL-FMEA model. Even in the service industry, it is known that service failures, customer complaints, and complaint handling time are collected to manage the service process. Similarly, if the EL-FMEA model is applied, it will be possible to calculate the service failure rate, expected loss, and alternative decision coefficient. We believe that applying the EL-FMEA model to the industrial field has the following advantages: (i) The EL-FMEA model is also fully applicable as a commonly used data processing tool (e.g., MS-Excel). (ii) The risk due to failure can be intuitively evaluated \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**State** & **Maintenance** & **Item** & \(\pi_{\text{sens}}\) & \(L\) & \(L_{\text{sens}}\) & \(m\) &
\begin{tabular}{c} **Sensor** \\ **Installation** \\ \end{tabular} \\ \hline \multirow{4}{*}{As is} & Regular & Item05 & - & \$638 & - & - & - \\  & and & Item06 & - & \$550 & - & - & - \\  & Corrective & Item07 & - & \$611 & - & - & - \\  & Maintenance & Item08 & - & \$170 & - & - & - \\ \hline \multirow{4}{*}{To be} & \multirow{4}{*}{Sensor} & Item05 & \$ 500 & - & \$415 & 0.650 & Yes \\  & & Item06 & \$400 & - & \$344 & 0.626 & Yes \\ \cline{1-1}  & Maintenance & Item07 & \$450 & - & \$405 & 0.663 & Yes \\ \cline{1-1}  & & Item08 & \$300 & - & \$195 & 1.147 & Withhold \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Expected loss after installation of detection sensor: Expected loss calculation when the detection sensors are installed on Item 5 to 8.  
through the expected loss (economic aspect). That is, an acceptable cost of loss can be set to suit the situation; (iii) The expected profit can be calculated before the risk of failure is eliminated.