Nozzle Maintenance before Painting Process

 The Reason of the Nozzle Failure
Firstly, erosion: when the high velocity of the liquid goes through the metal surface of the nozzle holes, it will cause the erosion of the nozzle hole resulting in the reduction of the spray gun nozzle, pressure and disorder of the spray state. Probability of erosion depends on the hardness of the liquid, spray pressure, the kinds and amounts of chemical materials. Furthermore, the particulate impurities in the liquid may also cause the punished erosion of the nozzle. Secondly, accidental damage: incorrect use and untimely maintenance are the main reasons for the nozzle accidental damage. Although the nozzle opening is typically designed into saucer shape, the offset of the fan nozzle structure is easy to be damaged. Thirdly, corrosion: when spray and wash the workpiece with chemical materials, these chemical materials can also cause corrosion of the nozzle material. Fourthly, obstruction: chemical materials and impurities are piped in internal or external edge of the nozzle resulting in clogging of the nozzle. This will affect the shape of the fan spray nozzle, which affects the spray pressure. Fifthly, temperature: nozzle has worked for a long time under high or abnormal temperature causing the damage of nozzle due to the softening of material.

Identification of the Nozzle
When the spray pump is running at its rated capacity, the spray pressure of the nozzle will be reduced with the expansion of the nozzle aperture. For the damaged nozzle, even if the nozzle is more than 30% of its rated flow, the change in the state of atomization is also difficult to be recognized by eyes. The best method to identify the nozzle is to observe the change of pressure in the sprinkler pipe. When comparing the different nozzles in the same pre-treatment system, the location and accuracy of the pressure gauge is essential. Usually pressure gauge should be placed in the front end of the spray tube. When judge of the pressure variation of the spray conduit, we should take intact nozzles spray pressure as a reference, and discriminate the problems of nozzle by the difference between the actual pressure and the reference pressure.

Exclusion of Nozzle Problem
Because it is difficult to directly observe the problems of nozzle, so we must pay attention to the selection of the nozzle. Select the appropriate nozzle, and also make a complete set of maintenance and replacement program. Regularly check the nozzle: including regular cleaning nozzle and regularly check the nozzle appearance damage. A few processes (such as pre-skimmed, skimmed) should be carried out in the general pre-processing production. The regular replacement of nozzle: frequency of nozzle replacement depends on the environment, the composition of the spray liquid and nozzle material. If the temperature is higher, or the spray liquid contains impurities, the number of nozzle replacement is relatively frequent.