## 2 Description of the Equipment, Facilities, and Data Collection  
A multistage (4-stages) hydrogen compressor is used to compress the gas from 0.034 MPa to 27.95 MPa, cooling the hydrogen after each stage to prevent its temperature from reaching above 423 K. According to [61], the present level of preventive maintenance corresponds to level 3, as there exists a monitoring and alarm system that alerts operators in the event of any anomalies, in addition to the mandatory preventive maintenance every three months. The objective is to implement Industry 4.0 technologies with the aim of enhancing maintenance up to level 4 and reducing the over maintenance through the utilization of real-time data monitoring based on predictive techniques. The acquisition of knowledge involves the training of a neural network that employs self-attention mechanisms to identify the hyperparameter configuration that most effectively aligns with the type of data generated by sensors. Due to the enormous volume of real-time sensor data generated in facility operations, a highly specialized distribution control system is implemented in order to enable efficient analysis and decision-making. Figure 2 illustrates how data are collected through the asset's sensors and connected via Ethernet to the control racks, which then send the signal to the unique database, which then shares the data through the OPC-UA server for subsequent processing by users. No data can be managed or stored either on the cloud or external servers due to the organization's current security policy, thus the raw sensor data are transmitted directly to clients, who process the monitoring in real-time through a SCADA system and adjust variable values as required to prevent out-of-range operating situations. Two separate wirings comprise the sensors: one monitors endogenous variables, while the other monitors exogenous ones. The variables are grouped based on the connection in Table 1. The variable to be predicted is \"H\({}_{2}\) post intercooling pressure\" or simply outlet pressure. The hydrogen pressure is performed by an absolute pressure stainless steel transmitter designed for explosion environments. This device features a piezoresistive metallic diaphragm and can operates over 30 MPa with a PROFIBUS--PA compatible analog output (4-20 mA). The current measurement device is a three-phase connection and 0-400 A measurement range with PROFIBUS-PA compatibility. The equipment produces data points every minute, with the output pressure nominally set at 27.95 MPa and controlled within limits of 25.99 and 29.91 MPa. With the objective of stabilizing the process and improving the predicting capacities of the neural network, it is necessary for operation to occur on a fifteen-minute basis and it is imperative to adjust the control limits to align with the new average values. This makes it easier to predict the next few hours of operation, as opposed to predicting the equipment's behavior over the next few minutes. By applying the central limit theorem, the new limits for the average out pressure have been established at 27.44 and 28.45 MPa utilizing the expression \(\sigma=(29.91-25.99)/(6\sqrt{15})\) to estimate the new standard deviation. Thus, the new limits control will be set at \(\pm 3\) \(\sigma\). \begin{table}
\begin{tabular}{c c} \hline \hline
**Exogenous Variables** & **Endogenous Variables** \\ \hline Fresh H\({}_{2}\) flow (500 Nm\({}^{3}\)/h) & H\({}_{2}\) outlet pressure; Stages 1–4 \\ Cooling flow (Nm\({}^{3}\)/h), undefined & (0.39/1.97/8.29/28.4 MPa) \\ \hline H\({}_{2}\) inlet temperature (318 K) & H\({}_{2}\) temperature; Stages 1–4 \\  & (418/398/403/403 K) \\ \hline  & Compression ratio; Stages 1–4. \\  & (11.5/5.0/4.2/3.5 Dimensionless) \\ \hline  & H\({}_{2}\) post intercooling pressure (27.95 MPa) \\ \hline  & H\({}_{2}\) post intercooling temperature (373 K) \\ \hline  & rpm (min\({}^{-1}\)); undefined \\  & Compressor consumption (300 A) \\ \hline \hline \end{tabular}
\end{table}