When using the conventional damp blasting method water or vapour is injected in small quantities, 30 kg/h at most, into the blasting hose.
This water mist being distributed most finely encases the blasting grain. When the grain that is accelerated by the nozzle impinges on the surface the dust generated by bursting is bound by up to 95%.
The injection pressure required to wet the dry abrasive compressed-air stream amounts to a maximum of 35 b. The amount to be injected can be adjusted according to the dust volume.
In case of vapour wetting the compressed-air/abrasive stream is heated additionally so that the surface dries immediately after the impact of the wet abrasive. This mainly avoids deposition of sludge residuals on the surface. The vapour causes the chlorides and sulphates being in the mains water to be removed. By this, metallically polished blasted steel surfaces tend to renewed surface oxidation only much later compared to damp blasting with water.
Schematic presentation of damp blasting
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