## 5 Analysis and Discussion
### Failure Modes, Effects, and Criticality Analysis  
Ref. [10] highlighted that it is possible to carry out a FMECA only on the direct causes, as illustrated in their study of the Hurricane Katrina disaster. The basic FMECA template proposed by ref. [10] was also adopted in this study (Tables 1-4) to summarize the effects (symptoms), cause of failure, and how the failure could be prevented or mitigated. It also includes the likelihood of occurrence, severity, difficulty of detection scores, and the calculated Risk Priority Numbers (RPNs). \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Keyword** & **Likelihood Description** & **Frequency** & **Score** \\ \hline \multirow{2}{*}{Rare} & Very unlikely to occur during the & \multirow{2}{*}{\textgreater{}50 years} & \multirow{2}{*}{1} \\  & lifetime of the operation & & \\ \hline \multirow{2}{*}{Unlikely} & Unlikely to occur during the & \multirow{2}{*}{Typically occurs} & \multirow{2}{*}{2} \\  & lifetime of the operation & & within 10–50 years & \\ \hline \multirow{2}{*}{Possible} & May occur during the lifetime of & \multirow{2}{*}{Typically occurs} & \multirow{2}{*}{3} \\  & the operation & & within 1–10 years & \\ \hline \multirow{2}{*}{Likely} & May occur frequently during the & \multirow{2}{*}{Typically occurs once} & \multirow{2}{*}{4} \\  & lifetime of an operation/project & & \\ \hline \multirow{2}{*}{Frequent} & Recurring during the lifetime of an & \multirow{2}{*}{Occurs more than twice a year} & \multirow{2}{*}{5} \\  & operation & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: RPN word model for FMECA of direct causes of the PGM LHD fire HPI in terms of probability of occurrence (O). \begin{table}
\begin{tabular}{l l l} \hline \hline
**Keyword** & **Severity Description** & **Score** \\ \hline Minor & Repair cost only & 1 \\ \hline Medium & Minor property damage & 2 \\ \hline \multirow{2}{*}{Serious} & Significant property and minor & 3 \\  & economy damage & 4 \\ \hline \multirow{2}{*}{Major} & Major property and significant & \multirow{2}{*}{4} \\  & economy damage & 4 \\ \hline \multirow{2}{*}{Catastrophic} & Loss of life, major property and & \\  & economy damage & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RPN word model for FMECA of direct causes of the PGM LHD fire HPI in terms of severity (S). The RPN is calculated as follows:  
**RPN = Probability of occurrence of failure (O) \(\times\) Severity (S) \(\times\) Difficulty of detection (D)**  
There is no standard for RPN as this varies from one organisation to another. However, one good source for scoring RPN in FMECA can be found in FMEA Studio ([[https://www.iqasystem.com/news/risk-priority-number/](https://www.iqasystem.com/news/risk-priority-number/)]([https://www.iqasystem.com/news/risk-priority-number/](https://www.iqasystem.com/news/risk-priority-number/))) (accessed on 5 January 2025). The word models with the criteria used to rate the scores of the incident are provided in Tables 1-3 below. Based on the FMECA in this study, it is important to note that all failure modes were assigned a severity score of 4, which related to the TOP event. According to ref. [10], the FMECA can be used to anticipate failures and prevent reoccurrence or mitigate the severity of occurrence. Ref. [10] further highlighted that if  
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Item** & **Component and Mode of Failure** & **Effect, i.e., Symptoms** & **Cause of Failure** & **O** & **S** & **D** & **RPN** & **How Can Failure be Eliminated or Mitigated? ** \\ \hline \multirow{4}{*}{**1**} & Electric cables for add-on systems & \multirow{4}{*}{Cable short-circuit for additional systems.} & Breakdown in cable insulation; there was no consultation of OEM on designs and routing of cables for additional systems. & \multirow{4}{*}{2} & \multirow{4}{*}{4} & \multirow{4}{*}{3} & \multirow{4}{*}{**24**} & 1. Approval of designs for add-on systems by OEM 2.