The first abrasive used for blasting, this is over 100 years ago
The main characteristics of sand usually used for blasting are:
1) It is a low cost product, easily found, already classified and, in some cases, washed for relative purification.
2) Its low cost does not justify accurate industrialization, making the classification unreliable with the occurrence of impurities such as oxides and saltpeter.
3) The biggest drawback of sand is the presence of free silica in its constitution, whose penetration into the pulmonary alveoli causes the disease called “silicosis”, irreversible and therefore incurable. The same is not true of other materials such as glass, steel shot, aluminum oxide and organic abrasives, which are eliminated as they do not contain free silica. The health hazards of the operator are such that, in the United States and other developed countries, their use is strictly prohibited, and there are already restrictions in Brazil by CETESB, FEEMA and some CIPAs and other organizations that oversee for health.
4) Another important point to consider is the ease with which sand fragments, especially when using nozzles on pressure jet machines.
Using pressures of 100 p.s.i. (7kg / m2) adopted to achieve operational efficiency after the first cycle, 70% of the total is pulverized, and a second use is usually only allowed before the material is completely replaced.
5) Rapid spraying with intense fines not only reduces process efficiency but increases operator risk, makes any reclassification process difficult and, in equipment, requires exaggerated handling capabilities. exhaust (internal visibility) and dust collection (collecting filters).
6) The amount of dust generated when operating in the open air causes intense air pollution which, when carried by the wind, can reach great distances.
7) For the same reason, albeit with large exhaust capacities, which ensure internal air circulation speeds of the order of 880 ft / min. (25 m / min) there is a settling of dust on the hard-to-remove parts and cabin floor, as well as the accumulation of large columns in the collector, with all collection and transport problems.
8) Even more with sand, it is almost impossible to obtain a uniform and repetitive anchor pattern, which is essential to meet the usual specifications of surface preparation for more responsible coatings.
9) Of course, sand is indispensable when cleaning outdoor parts. The difficulties of recovery make the use of more expensive materials prohibitive. In this case, special attention should be paid to operator protection systems, avoiding the use of simple filter masks that always allow the passage of the finest particles that are exactly the most harmful. Just the presence of helmets and filters is not enough, should be adopted, in parallel, strict safety standards and training, informing operators of the seriousness of the risks to their use and maintenance of available equipment.