Airless Spray Quality Control Tests

High-pressure airless spraying is widely used recently and a modern method which can form inner coating in the oil and gas pipelines to prevent them from corrosion and reduce resistance. At present, the main research of high-pressure airless spraying is focused on designing variety of efficient spray devices while there is few studies on the formation mechanism of the spray and the quality control of coating. Besides, the guidance is desired for choosing actual processing parameters. In order to solve these problems, the quality control of high-pressure airless spraying is researched in this thesis. The main work of this thesis is summarized as following:1) The development of high-pressure airless spray is introduced in Chapter One, in which the processes of the paint flow, the jet atomization and the secondary atomization are introduced. On the basis of former studies, the mathematical model of high-pressure airless spray is derived, and the main factors are analyzed on the atomization characteristics of paint.2) The simulation is carried out on the process parameters of spraying on the distribution, the axial velocity of particles and the velocity of continuous phase with FLUENT. Simulation results show that the spatial distribution of particles is uniform and symmetric, and the size of particles decreases significantly where the axial velocity of particles and the velocity of continuous phase increases with the increment of the spray pressure and the decrement of the width of nozzle.3) The experimental system of high-pressure airless spray is constructed, and the methods are proposed to evaluate the atomization characteristics of paint. The experiments have been done due to different nozzles with variable equivalent diameters and different spray pressures. Experimental results show that the Sauter Mean Diameter (SMD) and characteristic diameters decrease with the increment of the spraying pressure, and increase with the increment of the equivalent diameter of nozzle. The relative size range is influenced significantly by the spraying pressure, and such size decreases with the increment of spray pressure, making the atomizing particle more uniform.4) The coating for the oil and gas pipeline prevents it from corrosion and reduces friction, so the parameters of quality have been proposed in order to analyze the coating effects. The experiments have been conducted on different nozzles with different spray pressures and spray distances. Experimental results show that the coating of high-pressure airless spray is smooth, the roughness decreases significantly, and the values of Ra reduces with the increment of the spray pressure. The effect of coating is the best when the spray distance is 300mm. There are no breakages in the anti-impact test, and the adhesion of the coating are in good condition. The adhension force decreases with the increment of spray distance and increases with the increment of spray pressure.