METHOD FOR ABRASIVE-GAS TREATMENT AND NOZZLE APPARATUS FOR PERFORMING THE SAME Russian patent published in 2005 - IPC

FIELD: cleaning of large-size metallic constructions such as ships, tanks for oil products, sheets and so on due to removing from them different coatings, deposits, stains in different media including sea water, aggressive media, gas atmosphere and at condition under pressure.

SUBSTANCE: method comprises steps of supplying compressed gas; speeding up flow up to supersonic velocity values, expanding it, mixing abrasive with compressed gas and ejection of abrasive-gas mixture onto treated surface. Gas flow is mixed with abrasive before speeding-up for preparing abrasive-gas mixture whose expansion is realized until pressure value lower than that of environment. Addition of gas from environment is controlled. Speeding up of abrasive-gas mixture is stopped after achieving velocity of mean-mass particles of abrasive consisting 0.7 - 0.95 of gas velocity. At speeding up and expanding in each cross section of gas flow abrasive concentration in mixture is sustained in range 0.01 -1 vol.%; total pressure P* of gas flow is sustained by value no less than limit pressure Pl and reduced gas velocity λ is sustained by value no more than limit reduced velocity λr determined according to given relation.

EFFECT: enhanced efficiency due to elimination of sudden changes of pressure, uniform mixing of abrasive and gas, complete usage of energy of compressed-gas pressure, increased surface area of treated surfaces.

11 cl, 6 dwg, 2 ex