Cleaning is an important and necessary step in the process of manufacturing as well as repairing and finishing ships. The traditional method of cleaning by dry sand shows the greatest inadequacy of environmental pollution. This is why the authors of Pha Rung Shipbuilding One-Member Limited Company have researched, designed, and fabricated a wet sand blaster to replace the traditional dry sand blasting method.
The structure of the wet sand blaster includes: sand separator with the capacity of 8-10 m3/hour; sand blasting machine with the capacity of 0.2 m3, working pressure of 6.5 kg/cm2; 170 bar water pressure pump; nozzle (sand, water) with 3 holes, and the hole size of 0.5 mm; water spray system with the hole size of 0.35 mm.
The operating principle of the wet sand blaster is as follows: to pump high-pressure water, then open the pneumatic valve of the sand blasting machine. As the result, sand and water will come out from the nozzle at the same time. The user controls how much water and sand to clean the surface. After cleaning the hull with the wet sand blaster, the surface of the hull will appear acute leaks, so the authors continue to spray dry sand to ensure the roughness before painting. The water spray system is operated during this period to prevent dust from entering the environment.
Although the cleaning efficiency of the wet sand blasting method is only 80% of the dry sand blasting method, the greatest advantage that this method provides is to ensure a working environment for workers. This is an important criterion for putting the wet sand blasting method into use and completely replacing the dry sand blasting method to clean the hull in practice.
Nguyen Luu (Hai Phong Department of Science and Technology)