Industry 4.0: smart test bench for shipbuilding industry

The term Industry 4.0 (I4.0) was introduced at the Hannover Messe in 2011. It has since received widespread attention from industries and governments around the world [1, 2] as it offers significant opportunities to optimise production and development through digitalisation [3]. Consequently, researchers and scholars across the world are closely monitoring the “fourth industrial revolution” [4]. The impact of I4.0 exceeds the frontiers of industrial production and can affect all industrial sectors through the establishment of smart factories [5, 6]. There are numerous approaches to the digitisation of industry depending on the level of industrialisation in a given country: in developed countries, IT is used to recover or maintain the competitiveness of industry; while in developing countries, industrialisation is linked to digitisation [7]. The enabling technologies of I4.0 can effectively contribute to the digital transformation of an organisation [8‐10] with the goal of sustainable development [11‐13]. The so-called fourth industrial revolution promises to offer digital technologies that will radically change the traditional architecture of production [14].

Digital technologies such as the Internet of Things (IoT), cloud computing, big data analytics, etc. can significantly improve the connectivity, communication, and automation in an organisation [15, 16]. In addition, by using sophisticated sensors, important information can be obtained from process data [17] to improve production [18] and the effectiveness and efficiency of the final products [19]. The principles of I4.0 can also be applied to shipyards [20].

In recent years, several studies have assessed the potential of additive manufacturing [21] in the ship building sector, as it offers several interesting opportunities including weight reduction and performance improvement.

This study evaluates the application of I4.0 at the Liberty Lines shipyard. Liberty Lines S.p.a., is a leading fast ferry operator based in Trapani (Sicily), Italy. A case study on the preliminary transformation of the Liberty Lines shipyard into a shipyard 4.0 is conducted herein. The aim of this study is to improve the performance and sustainability of the shipbuilding industry by optimising a naval propulsion system.

The preliminary implementation of I4.0 technologies is established herein through the design of an IoT platform that can support a test bench that can test and validate an innovative high-power azimuth thruster. The thruster was designed and built at a scale of 1:1. Once tested, the thruster can be installed on a high-speed craft (HSC) for passenger transport. The test bench enables both experimental and final product testing. The use of I4.0 technologies allows the interconnection of the test system with the network of the company, providing remote control and management of the test system.

The IoT platform and innovative test bench integrate the shipyard production layout with I4.0 logic. To satisfy the current market demands, Liberty Lines have the following objectives: 1) to increase the performance and efficiency of the propulsion plant; 2) to determine a path to gradually improve the green footprint of the organisation; and 3) to improve the production processes at the company level. Essentially, these objectives offer a complete digital transformation of manufacturing that not only includes the production and management of the shipyard, but also includes product design and engineering techniques [22]. Furthermore, as the experimental test data can be directly transmitted to the technical office, engineers can analyse the data in real-time and to perform an interactive design to improve the performance of the entire propulsion system or critical system components. Remote control and management are key functionalities that offer the necessary maintenance and control services, and further increase the safety of machines that operate at considerable mechanical stress (high power, high operating pressures, high temperatures, etc.) [23]. The proposed approach allows to create an innovative environment to support the interactive engineering with design and development phases that are performed in parallel rather than in series in order to reduce production time and costs. Thus, I4.0 offers numerous challenges and opportunities to industries (e.g., resource efficiency, costs, work organisation, and synchronisation between ICT—Information and Communications Technology—and people) to achieve sustainable development [24]. Increases in the efficiency and effectiveness of the propulsion system can allow shipping companies to install environmentally-friendly high-performance propulsion systems with long life-cycles on naval units, thereby reducing operating costs and increasing profitability. In addition to improving the monitoring of the propulsion system during its operation [25‐28], these factors contribute to the innovations offered by I4.0 to the shipbuilding industry (Shipping 4.0).

The torque values were measured using strain gauge rosettes (Fig. 8) and torque transducers were installed on the drive shafts. Electrical strain gauges were connected to the wireless torque transmitter, which sent the signal to the receiver installed on a workstation. This setup provides accurate and reliable torque data.

Electrical strain gauges were also installed on the test bench frame and the pod struts to compare the strain recorded during the experiment with that obtained from finite element analyses [40‐43].

Optimum lubrication of the transmission components during power transmission plays a key role in the proper functioning and long service life of the roller bearings. Essentially, lubrication creates a film that separates the two contact surfaces, preventing wear and premature fatigue failure. In addition, proper lubrication extracts heat from the internal elements, allows proper heat exchange, and ensures that the bearing works at optimum operating temperatures during its service life. Quick identification of a sudden increase in temperature can prevent bearing damage and the resulting failure of the thruster.

The cylindrical roller bearings and the single row tapered roller bearings in the thruster are thermally stabilised up to temperatures of 150 °C. Therefore, this value represents a limit beyond which the rolling elements would be damaged or the raceways would experience rapid wear, thereby compromising the operating quality of the thruster.

Temperature data are influenced by the heat exchange that occurs with the air-conditioned laboratory environment during the experiment, and the heat exchange that occurs with water during actual operation. However, this study evaluates both the geometric configuration and the lubrication conditions, leading to a more functional use of the roller bearings selected to support the transmission shafts. Appropriate lubricating oil injectors (Fig. 9) that provided punctual and precise lubrication of the parts subjected to wear were used to lubricate the bearings and bevel gears of the upper gearbox. In particular, compared to splash lubrication (oil bath method), the experimental results demonstrated a reduction of approximately 15% of the dissipated power.

Figure 10 denotes the positions at which eight PT100 thermo-resistance sensors were installed to detect the instantaneous temperature during operation. Four sensors were positioned on the bearings of the upper gearbox (sensors T1, T2, T5, and T6), while the other four were installed on the cylindrical roller bearings positioned near the contra-rotating propellers (sensors T3, T4, T7, and T8).

The cylindrical roller bearings on which sensors T3, T4, T7, and T8 were installed prevent the optimal lubricant supply required on the contact points between the rolling elements and the raceways due to their proximity to the thruster propellers.

At the maximum motor power and rotation speeds of close to 1000 rpm, the possibility of optimal heat dissipation from the bearing is drastically reduced. To ensure the operational life of the bearing, more expensive supply and sealing systems are required. These supply ducts should be as short as possible, face the lubrication holes of the roller bearings directly, and provide a separate duct for each bearing.

Using the test bench to test the validity of the proposed solutions, the oil inlet ducts were redesigned. This increased the heat dissipation capacity. Several tests were conducted at various torque values using the torque-applying device. Initially, the electric motor was operated with no load, i.e., without the introduction of torque in the closed-loop circuit. Without additional torque, the power provided by the electric motor must only overcome the friction in the bearings and gear wheels. The system was kept in rotation for an initial duration of 10 min. Subsequently, torque was introduced according to the load diagram shown in Fig. 11. The figure illustrates the trend of the torque introduced into the system and the power values of the electric motor with time. The total test duration was approximately 3 h, during which the two thrusters continued to rotate under the applied load.

Figure 12 shows the temperature values recorded by the eight sensors installed on the roller bearings (Fig. 10).

As shown in Fig. 12, sensors T3 and T4 recorded non-optimal temperature values towards the end of the test due to the inadequate lubrication of the bearings. Therefore, the oil supply ducts must be redesigned to ensure adequate dissipation of the heat produced during the load test. A screenshot of the IoT platform is shown in Fig. 13. The figure shows the real-time display of the temperature data recorded by the eight sensors. Notably, the IoT platform enables the recording of data during the tests, and a comparison and analysis of the results of different tests.

Figure 14 shows the trend of the temperature values recorded by the eight sensors after repositioning the lubricating oil injectors and redesigning the oil supply ducts.

As shown in Fig. 14, considering the temperature values recorded by sensor T4 towards the end of the experimental, the redesign of the lubrication system reduces the temperature of the bearing by approximately 27%.

The preliminary implementation of I4.0 on a prototype test bench for a high-power azimuth thruster under full load conditions was studied, designed, and validated. To set up the test bench with I4.0 capabilities, IoT sensors were used to collect and record the data, and a decision-making support tool was developed. The research objects—the test bench and the azimuth thruster—were equipped with the sensors to record the data to be analysed. Subsequently, data analysis was used to evaluate the efficiency of the product and the operating process. After testing and validation, the azimuth thruster can be installed on a high-speed craft for passenger transport. In accordance with previous experimental results, the main parameters that affect the efficiency of the system—the strain of the mechanical parts, the operating pressure, and the temperature—were recorded herein.

Based on the analysis and processing of the temperature data recorded during the tests, the oil supply ducts were redesigned and the lubricating oil injectors were repositioned. This decreased the temperature of the roller bearings by approximately 27%. Moreover, compared to splash lubrication (oil bath method), the optimisation of the lubricating oil injection method in the upper gearbox reduced the power dissipation by approximately 15%. These results not only increase the life of the transmission components, but also increase the effectiveness and efficiency of the entire propulsion system. Additional advantages include a decrease in noise levels and vibrations, compactness, and reductions in weight, fuel consumption, installation, and maintenance costs. The used approach contributes to the development of an innovative environment to support the interactive engineering where the design and development phases are performed in parallel rather than in series in order to reduce production time and costs.

In conclusion, the preliminary results obtained using the IoT platform can help the company to achieve its goal of improving the performance, efficiency, and sustainability of the propulsion system. To fully exploit the potential of the IoT platform developed herein, further studies must be conducted to manage the entire production process of the naval unit and interconnect the platform with business management systems.

Future studies will focus on the realisation of a digital replica of the propulsion plant that can overcome the limits of traditional design, which requires several expensive experimental tests to validate the project.