Sandblasting metals and static current

Cause, risks and measures to avoid them

In the blasting process with metallic abrasive static currents are generated mainly due to the transfer of different materials electrons traveling in hoses and pipes up to the nozzle and the presence of powders which are poor conductors of electricity and tend to accumulate static electricity during mixing, sieving, filtration and transport. The causes are due to the high velocity of the vortex motion of granigle and powders (80 m/s), to the strong friction which is formed before and during implantation on the surface to be blasted, to their forced flow in pipes and hoses, compressed air dry, the swirling whirl of dust and grit in the plant and abrasive blasting dust recovery, finally to the shoes worn by the operator. The size of the powder particles ranging from 1 a 1000 micron; the dust > 10 Micron is visible and easily deposited on the ground, while that < 10 microns is invisible and remains suspended in the air for a long time.

What are the risks

If the static current is not controlled, It can also cause some shock to the operator and in the manual and automatic systems can cause problems to the smooth flow of grit and dust separation, with possible triggering of sparks and explosions due to potential in the presence of paint residues, Organic abrasives and metal powders of other nature. Since the accumulation of surface electrical charges, the energy is quite low and extinguished quickly.

Come prevent

With the grounding of flexible nozzles with a cable increases the resistance < 50 hms. To avoid the accumulation and the formation of sparks is advisable to check the electrical resistance at least once a year for fixed installations while for portable ones it must be checked at each start of work. Rarely Sanders cause shock if that worker wearing proper shoes.