Dry ice is the solid form of carbon dioxide (chemical formula: CO2), comprising two oxygen atoms bonded to a single carbon atom. CO2 is a colorless, tasteless, odorless gas found naturally in the atmosphere.
Dry ice pellets are shot out of a nozzle with compressed air. This process can remove residues from industrial equipment. Examples of materials being removed include ink, glue, oil, paint, mold and rubber. Dry ice blasting can replace sandblasting, steam blasting, water blasting or solvent blasting and cleaning.
Other blast media leave behind secondary waste. Dry ice vaporizes (sublimates) upon impact. All that remains is the contaminate you want to remove. And since dry ice vaporizes on impact, dry ice can be used to clean complicated cavities where other blast media might become trapped.
The frigid temperature of the dry ice pellets (-78.5°C or -109.3°F) being blasted at high velocity through a blasting gun using compressed air hit the surface of the material causing a mirco-thermal shock between the surface contaminate and the substrate. The substrate which is warmer causes the dry ice to convert back into a harmless CO2 gas. The gas expands to nearly 800 times the volume of the original pellet and the surface contaminate is lifted by the CO2 from behind and falls away from the surface. Since the dry ice has now evaporated (CO2 gas), the only clean up that remains is the contaminate, which can easily be swept away!
Contaminates that are dry, wet, hard or soft can be swept up, vacuumed or sprayed away. The surface where the contaminate was will be dry and clean.
The dry ice blasting process will not damage the substrate.The size of the dry ice pellets and the velocity that it hits the substrate can be changed to remove the contaminate while being non-abrasive to the substrate.
The process actually cleans better and faster when the substrate is hot. Most contaminants have weaker adhesive strength when hot. In many applications, you may be able to clean three to five times faster hot than cold. Because dry ice sublimates on impact, entrapment of the blasting media is not an issue, so cleaning can be done online.
Yes, but not that much. The amount of cooling depends on the substrate, the dwell time of the dry ice blast, and ice usage. For example, a tire mold may start at 350°F and drop to 325°F during cleaning.
Generally, no. The temperature change of the surface being cleaned is small and the corresponding tensile stress will be well below the point of what most molds will encounter during normal heat treatment.
Condensation will occur when the temperature of the substrate falls below the dew point. The dew point varies with climate. When cleaning hot substrates, condensation will only occur when the temperature of the surface stays above the dew point. You can control condensation by using heaters or heat lamps.
Yes, with proper ventilation. Because CO2 is heavier than air, placing exhaust vents at or near ground level is recommended. In an open indoor environment, existing ventilation is usually ok to prevent extra CO2 buildup. CO2 is non-poisonous, but does displace oxygen in the atmosphere.
The noise that is created is a function of the air volume and the air velocity. In nozzle, the stationary air is sheared by the high velocity air causing turbulence which creates noise. Appropriate hearing protection should be worn.
A two-hose system which runs one hose for compressed air and the other to the feeder with dry ice, generally delivers the dry ice pellets with less force and has some limitations on vertical distance between the machine and applicator. Single-hose system aggression is also ideal for removing heavier build-up or for blasting at a vertical elevation where the machine is at a lower level than the blasting surface.