coating layer itself, an d at the interface between the coating and the substrate, causes instant fracturing and separation of coating material from the surface. In general, if a coating or contaminant is CHEMICALLY bonded to a surface, dry ice particle blasting will NOT effectively remove the coating. If the bond is PHYSICAL o r MECHANICAL in nature, such as a coating of rubber residue which is "anchored" into the porous surface of an aluminum casting, then there is a good chance that dr y ice blasting will work. Contaminants which are etched, or stained into the surfaces of metals, ceramics, plastics, or other materials typically cannot be removed with dry ice blasting. If the surface of the substrate is extremely porous or rough, providing strong mechanical "anchoring" for the contaminant or coating, dr y ice blasting may not be able to remove all of the coating, or the rate of removal may be too slow to allow dry ice blasting to be cost effective. The classic example of a contaminant that does NOT respond to dry ice blast-ing is RUST. Rust is both chemically and strongly mechanically bonded to steel substrate. Advanced stages of rust must be "chiseled" away with abrasive sand blasting. Only the thin film of powderized "flash" rust on a fresh steel surface can be effectively removed with dry ice blasting. 4.2.1.1. Inductio n (venturi) and direct acceleration blast systems - the effect of the typ e of system on available kinetic energy In a two-hose induction (venturi) carbon dioxide blastin g system, the medium particles are moved from the hopper to the "gun" chamber by suction, where they drop to a very low velocity before being induced into the outflow of the nozzle by a large flow volume of compressed air. Some more advanced two-hose systems employ a small positive pressure to the pellet delivery hose. In any type of two-hose system, since the blast medium particles have only a short distance in which to gain momentum and accelerate to the nozzle exit (usually only 200 to 300 mm), the final particle average velocity is limited to between 60 and 120 meters per second. So, in general, two-hose systems, although not so costly, are limited in their ability to deliver contaminant removal kinetic energy to the surface to be cleaned. When more blasting energy is required, these systems must be "boosted" a t the expense of much more air volume required, and higher blast pressure is re-quired as well, with much more nozzle back thrust, and very much more blast noise generated at the nozzle exit plane. The other type of solid carbon dioxide medium blasting system is like the "pressurized pot" abrasive blasting system common in the sand blasting and Plas-ti c Media Blasting industries. These systems use a single delivery hose from the hopper to the "nozzle" applicator in which both the medium particles and the compressed air travel. These systems are more complex and a little more costly than the inductive two-hose systems, but the advantages gained greatly outweigh the extra initial expense. In a single-hose solid carbon dioxide particle blasting system, sometimes referred to as a "direct acceleration " system, the medium is introduced from the hopper into a single, pre-pressurized blast hose through a sealed airlock feeder. The particles begin their acceleration and velocity increase

DOI link for coating layer itself, an d at the interface between the coating and the substrate, causes instant fracturing and separation of coating material from the surface. In general, if a coating or contaminant is CHEMICALLY bonded to a surface, dry ice particle blasting will NOT effectively remove the coating. If the bond is PHYSICAL o r MECHANICAL in nature, such as a coating of rubber residue which is "anchored" into the porous surface of an aluminum casting, then there is a good chance that dr y ice blasting will work. Contaminants which are etched, or stained into the surfaces of metals, ceramics, plastics, or other materials typically cannot be removed with dry ice blasting. If the surface of the substrate is extremely porous or rough, providing strong mechanical "anchoring" for the contaminant or coating, dr y ice blasting may not be able to remove all of the coating, or the rate of removal may be too slow to allow dry ice blasting to be cost effective. The classic example of a contaminant that does NOT respond to dry ice blast-ing is RUST. Rust is both chemically and strongly mechanically bonded to steel substrate. Advanced stages of rust must be "chiseled" away with abrasive sand blasting. Only the thin film of powderized "flash" rust on a fresh steel surface can be effectively removed with dry ice blasting. 4.2.1.1. Inductio n (venturi) and direct acceleration blast systems - the effect of the typ e of system on available kinetic energy In a two-hose induction (venturi) carbon dioxide blastin g system, the medium particles are moved from the hopper to the "gun" chamber by suction, where they drop to a very low velocity before being induced into the outflow of the nozzle by a large flow volume of compressed air. Some more advanced two-hose systems employ a small positive pressure to the pellet delivery hose. In any type of two-hose system, since the blast medium particles have only a short distance in which to gain momentum and accelerate to the nozzle exit (usually only 200 to 300 mm), the final particle average velocity is limited to between 60 and 120 meters per second. So, in general, two-hose systems, although not so costly, are limited in their ability to deliver contaminant removal kinetic energy to the surface to be cleaned. When more blasting energy is required, these systems must be "boosted" a t the expense of much more air volume required, and higher blast pressure is re-quired as well, with much more nozzle back thrust, and very much more blast noise generated at the nozzle exit plane. The other type of solid carbon dioxide medium blasting system is like the "pressurized pot" abrasive blasting system common in the sand blasting and Plas-ti c Media Blasting industries. These systems use a single delivery hose from the hopper to the "nozzle" applicator in which both the medium particles and the compressed air travel. These systems are more complex and a little more costly than the inductive two-hose systems, but the advantages gained greatly outweigh the extra initial expense. In a single-hose solid carbon dioxide particle blasting system, sometimes referred to as a "direct acceleration " system, the medium is introduced from the hopper into a single, pre-pressurized blast hose through a sealed airlock feeder. The particles begin their acceleration and velocity increase

coating layer itself, an d at the interface between the coating and the substrate, causes instant fracturing and separation of coating material from the surface. In general, if a coating or contaminant is CHEMICALLY bonded to a surface, dry ice particle blasting will NOT effectively remove the coating. If the bond is PHYSICAL o r MECHANICAL in nature, such as a coating of rubber residue which is "anchored" into the porous surface of an aluminum casting, then there is a good chance that dr y ice blasting will work. Contaminants which are etched, or stained into the surfaces of metals, ceramics, plastics, or other materials typically cannot be removed with dry ice blasting. If the surface of the substrate is extremely porous or rough, providing strong mechanical "anchoring" for the contaminant or coating, dr y ice blasting may not be able to remove all of the coating, or the rate of removal may be too slow to allow dry ice blasting to be cost effective. The classic example of a contaminant that does NOT respond to dry ice blast-ing is RUST. Rust is both chemically and strongly mechanically bonded to steel substrate. Advanced stages of rust must be "chiseled" away with abrasive sand blasting. Only the thin film of powderized "flash" rust on a fresh steel surface can be effectively removed with dry ice blasting. 4.2.1.1. Inductio n (venturi) and direct acceleration blast systems - the effect of the typ e of system on available kinetic energy In a two-hose induction (venturi) carbon dioxide blastin g system, the medium particles are moved from the hopper to the "gun" chamber by suction, where they drop to a very low velocity before being induced into the outflow of the nozzle by a large flow volume of compressed air. Some more advanced two-hose systems employ a small positive pressure to the pellet delivery hose. In any type of two-hose system, since the blast medium particles have only a short distance in which to gain momentum and accelerate to the nozzle exit (usually only 200 to 300 mm), the final particle average velocity is limited to between 60 and 120 meters per second. So, in general, two-hose systems, although not so costly, are limited in their ability to deliver contaminant removal kinetic energy to the surface to be cleaned. When more blasting energy is required, these systems must be "boosted" a t the expense of much more air volume required, and higher blast pressure is re-quired as well, with much more nozzle back thrust, and very much more blast noise generated at the nozzle exit plane. The other type of solid carbon dioxide medium blasting system is like the "pressurized pot" abrasive blasting system common in the sand blasting and Plas-ti c Media Blasting industries. These systems use a single delivery hose from the hopper to the "nozzle" applicator in which both the medium particles and the compressed air travel. These systems are more complex and a little more costly than the inductive two-hose systems, but the advantages gained greatly outweigh the extra initial expense. In a single-hose solid carbon dioxide particle blasting system, sometimes referred to as a "direct acceleration " system, the medium is introduced from the hopper into a single, pre-pressurized blast hose through a sealed airlock feeder. The particles begin their acceleration and velocity increase