Process control for cryogenic decoating

摘要

Operation of processes for removal of adherent coatings from articles by cryogenic embrittlement of the coatings and blasting of the embrittled coatings with impact media impelled by one or more rotating throwing wheels in a closed treating chamber are disclosed, wherein the chamber is initially cooled down progressively to a supercold preset temperature level considerably below that required for embrittlement of the coatings. In a preferred batch operation the throwing wheel or wheels are rotated in the absence of media fed thereto during an initial stage of the operating cycle. The supercold preset temperature level is controllably maintained for a prefixed time period for prechilling the coated articles. At the end of said prechilling preset time period the blasting of the coated articles is initiated. The blasting is continued for a fixed time period; during part of said blasting time period the temperature of the chamber is permitted to rise to a second preset level and while continuing the blasting the introduction of refrigerant into the vessel is discontinued.