# The Use of Augmented Reality for the Management of Equipment Ageing with a Virtual Sensor
[PERSON] and [PERSON] [21] described the recent spread of AR technologies and stated that these are not yet ready for industrial implementation in some areas, whereas they are in other sectors. The most common applications of AR concern training for the management of operations [22; 23; 24] and assisting in the routine maintenance of industrial equipment by following visual instructions and interactive guides superimposed on the real equipment for a more effective workflow, even with remote assistance [25; 26; 27; 28; 29]. [PERSON] et al. [30] described how AR, combined with instant messaging and image recognition technologies, could greatly assist chemical plant inspections to solve the problems associated with low efficiency and poor standardisation. The use of AR in the inspection sector appears as one of the most important in the industrial context, where AR represents a promising technique for improving the transfer of information from the digital to the operator in a smart and non-intrusive way [31; 32]. Depending on the industrial sector and the scope, inspections could typically involve controls to be performed on products [33; 34] or equipment; in the first case, it concerns the detection of design discrepancies, while in the second one, it is used to intercept possible causes of malfunction. The execution of this activity is therefore essential in the manufacturing process, especially where many factors, such as the complexity of the products and the inability of the operator to comply with certain assembly sequences,can potentially lead to mistakes or design changes. The control of the equipment for maintenance purposes or due to malfunctions is important for the production continuity and safety purposes, especially in the chemical industry due to the reasons discussed above. A critical aspect related to the inspections concerns the annotation and formalisation of detected errors and design changes, and the subsequent sharing of the information with the technical office; these activities require a high mental workload [35]. In the context of major accident hazard industries, it is possible to find applications of AR for the following scopes:  
* to overcome the limit of using paper-based checklists during on-site inspections. The use of AR technologies makes the inspection more efficient and advanced than the conventional approaches [36; 37];
* to help operators in performing tasks and operations by means of man-machine interaction through the addition of information to the real work environment [32; 34; 38; 39] (such as live video streams, pictures, or instructions);
* to support education for managers and employees with computer-generated 3D environments [40; 41] and train in hazardous materials handling by means of simulations [38]. Therefore, the literature shows that currently, this technology is not mature enough to perform inspections aimed at verifying the integrity of equipment and visualising the deterioration level. As part of a recently concluded research project [42], a virtual sensor has been developed to elaborate and visualise information relating to the deterioration of critical equipment; it also produces prognostic estimates of the corrosion rate, the critical pit probability, the evolution of the material corrosion, and the residual useful life (RUL) of the equipment. The virtual sensor supports on-field inspections by visualising the information in AR via a mobile device display, such as a smartphone or a tablet or via wearable device (e.g., smart glasses). During the first phase of the development of this virtual sensor, greater importance has been given to the optimisation of the processes for the implementation of the mathematical models that use several different types of input data. In this manuscript, the investigation of the human-machine interaction (HMI) in using this device is presented; this work resulted in a user-friendly interface, which improved the usability of the software, making it accessible even to personnel that are not experts in advanced technologies.