The development of ecological awareness followed by stringent laws on the protection of natural resources and workers direct the manufacturing industry at the development and implementation of alternative methods for cooling and/or lubrication in the machining of metals. The paper investigates the feasibility of using a vortex tube for cooling when turning martensitic stainless steel. Experimental research was conducted to understand the effects of vortex tube cooling on the corrosion resistance of the machined surface and on production costs. It has been determined that the vortex tube cooling has no significant influence on the corrosion resistance and that the tool costs have the most significant influence on the unit production cost. In conclusion, compared to the conventional emulsion cooling in metal cutting, the vortex tube cooling offers a cost-effective solution to the sustainable turning of martensitic stainless steel.

Maintenance of process plants such as refinery plants requires implementation of good maintenance practices due to the presence of high complexity. With regard to the aspect of refinery plants maintenance, the most significant undertaking is the turnaround (TAR) carried out through a project task with a long duration of planning and a very short duration of realisation period, which makes it one of the most complex maintenance projects in general. Such maintenance is based on multidisciplinarity that must be implemented through a quality management system at all levels of maintenance management. This paper will define and test factors in turnaround refinery project management process, which also represent the quality factors inherent to the turnaround refinery project. Research findings point to the importance of evaluating leadership, team, policy and strategy in the turnaround refinery project management process.

For the purpose of contributing to sustainable machining, the aim was to investigate the turning of martensitic stainless steel X20Cr13 under alternative cooling and lubrication techniques. The minimum quantity lubrication technique in combination with the vortex tube cooling, as the determined optimal cooling method using the Taguchi-based entropy weighted grey relational analysis (compared to emulsion and minimum quantity lubrication technique) in previous research when turning martensitic stainless steel X20Cr13, were applied in this research in accordance with the Box–Behnken design. The aim is to investigate, when applying the optimal cooling condition (minimum quantity lubrication + vortex) with the Box–Behnken design, which parameters have a significant influence on reducing the surface roughness parameters Ra and Rz and also on the tool life (T). The cutting speed (vc = 260, 290 and 320 m/min), feed rate (f = 0.3, 0.35 and 0.4 mm/rev) and depth of cut (ap = 1, 1.5 and 2 mm) were selected as cutting parameters. An exponential model for Ra, Rz and T was obtained. According to the ANOVA results, it can be seen that only the feed rate had a significant influence on Ra and Rz. For tool life, according to the ANOVA results, it can be seen that all three parameters (cutting speed, feed rate and depth of cut) have significant influence on the tool life (T). Experimental results were compared with the results of the exponential mathematical model and presented in diagrams. A new nozzle was designed for this research to allow micro-droplets from the MQL unit and chilled compressed air from the vortex tube to be connected in one stream (single-channel system) before entering the cutting zone, thus allowing for simultaneous lubrication and cooling. For the used vortex tube system with an air flow of 708 L/min and the inlet air pressure of 0.69 MPa, a temperature drop of −29 °C can be achieved in regard to the inlet air temperature of 21 °C. Therefore, the minimum quantity lubrication technique with vortex tube cooling can be recommended for turning of martensitic stainless steel X20Cr13.

A modern production strategy faces the increasing challenges of practicing green production without sacrificing machining performance. Thus, this paper compares emulsion cooling, minimum quantity lubrication without and with a Ranque-Hilsch vortex tube when turning martensitic stainless steel X20Cr13. Experimental tests were organized corresponding to Taguchi orthogonal array L 27 (3 4 ). The Taguchi based entropy weighted grey relational analysis was exploited to acquire the optimum combination of cutting speed, feed, depth of cut and cooling method that concurrently minimize surface roughness and tool life while maximizing material removal rate. The combination of minimum quantity lubrication with Ranque-Hilsch vortex tube confirmed to be the best cooling method. Hence, the use of classic metalworking fluids when turning martensitic stainless steels can be excluded, which is important for reducing environmental pollution and hence for machining sustainability.

Maintenance of process plants requires application of good maintenance practice due to a great level of complexity. From a plant maintenance point of view, the most significant activity is turnaround, an activity carried out through project task with long planning process period and very short execution period, which makes it one of the most complex projects of maintenance in general. It is exactly this kind of maintenance that is based on multidisciplinarity which has to be implemented through the system of quality management on all levels of maintenance management. This paper defines the most significant factors determining the process of turnaround projects quality management and its efficiency. Such relation is observed through moderating influence of complexity on process management efficiency in the turnaround project. The empirical research was conducted based on the survey of turnaround project participants in five refineries in Croatia, Italy, Slovakia and Hungary. For exploring the influence of research variables testing of the target relation is carried out by applying logistical regression. Research results confirm the significance of complexity as variable that significantly contributes to the project performance through the moderating influence on success of the project, as well as the influence of an efficient management on a plant turnaround project key results. Beside theoretical indications, practical implications that arise from this research study mainly refers to management process of the industrial plant maintenance project.