## 3 Experimental Testing of Coating by Oil Dispersion  
The solution parameters were based on \(6\) m long steel pipe coating requirements. Compared to the investigation of the technological feasibility of the problem, selected pipes with a d = 15, 25 and 35 mm diameter were chosen. Wall thickness in the case of modal analysis, mathematical modeling and experiments did not play any role in our findings. The material of the test and experimentally verified tubes was selected from polyethylene (PE) foam, available under the trade name \"Mirelon\" (Figure 13), originally intended for insulation of water pipes for hot and cold water. This material was chosen for its consistency in mass across the entire cross section, for easier handling, price, and for the possibility of mechanical examination of the inner surface by touching it with a normal knife. Figure 12: The course of the surface density of the oil film depending on the vertical change in the direction of the input velocity vector. Figure 13: “Mirelon” or “Tubolit” is a brand of polyethylene (PE) foam that has been used as a suitable substitute for steel pipes when measuring an oil coating produced from injected dispersion oil fraction. Adhesiveness of oil particles to the PE pipeline during the flow of the multiphase compound was numerically dealt with by application of the [PERSON] et al. [21] model, considering the wall lubrication coefficient (formula 4), whereas the results of numerical calculation of the application of the values Cw1 = -0.01 and Cw2 = 0.05 showed good match with the experiment results. The oil adhesiveness itself showed no dependence on the type of the pipe material. The standard deviation of the weight of one meter of dry Mirelon with a 15 mm inner diameter is 0.082 g, the standard deviation for 25 mm is 0.18 g, and the standard deviation for 35 mm is 0.63 g. If steel pipes were to be used, it would have been very difficult to measure the oil layer inside the steel pipe as the certified scales with the required carrying capacity are not sufficiently precise and sensitive. The ratio between the weight of the pipe and the weight of the oil film is far more favorable for weighing a material such as \"Mirelon\". For example, the dry weight of a 1 m long Mirelon tube with a 25 mm width and a wall thickness of 5 mm weighs approximately 11.5 g, the weight of a steel tube (EN 10 210-2 standard) of 25.3 mm diameter and a wall thickness of 0.8 mm (thinner is not normally produced) weighs approximately 515 g. The dry tube was weighed first, followed by weighing when wet. In percentage points, the differences thus obtained, i.e., between the dry and the wet tube, would have been too small. The measurement of the oil film itself would not have been possible. Precise experimental measurements are given in previous works by [PERSON] [23; 24]. The chemical substance called \"Anticorrid DFV 2001\" is accurately described in detail in the manufacturer's document described by [PERSON] [16]. Selected essential oil parameters of \"Anticorrid DFV 2001\" used in the experimental measurement are listed on the product card:  
- vapor pressure: 1 mbar, at the temperature of 20 \({}^{\circ}\)C;
- density: 830 kg/m\({}^{3}\), at the temperature of 25 \({}^{\circ}\)C, in compliance with DIN 51 757 standard;
- kinematic viscosity: 4.6 mm\({}^{2}\)/s, at the temperature of 20 \({}^{\circ}\)C, in compliance with DIN 51 562 standard. Material used for measurement (Mirelon 15--the inner diameter of the pipe was 15 mm):  
- \"Mirelon 15\" with a length of 2 m--adhered by a sticky tape to a 6 m tight section;
- \"Mirelon 25\" with a length of 2 m--adhered by a sticky tape to a 6 m tight section;
- \"Mirelon 35\" with a length of 2 m--adhered by a sticky tape to a 6 m tight section. The original Mirelon tubes are 2 m long. Prior to the application, three pieces were joined together into a single tube of 6 m. The connection was made using a high quality adhesive tape, so that oil leakage from the joint was not possible.