An Overview of Dry Ice Blasting
Dry ice blasting (also known as CO2 blasting) is a relatively new cleaning process using solid CO2 pellets. It is primarily used for industrial use in a variety of applications. The pellets sublimate (convert directly from a solid blast pellet to a vapor (CO2) leaving no residue. The process is superior to sand blasting, glass bead blasting and other types of cleaning methods for numerous reasons.
Today, the dry ice method of cleaning is quickly becoming favored for environmental as well as production reasons. Because of tremendous environmental regulations, industry has needed to minimize wastes. Also, there is a growing consciousness that many are placing now on the global environmental impact of their production practices. However, these benefits are accentuated due to the tremendous performance gains through dry ice blasting — little or no production downtime, quality of clean and minimized damaged to equipment.
What Is Dry Ice?
Dry ice pellets are made by taking liquid carbon dioxide (CO2) from a pressurized storage tank and expanding it at ambient pressure to produce snow. The snow is then compressed through a die to make hard pellets.
With the dry ice blasting process, dry ice (CO2) particles are propelled to supersonic speed impacting and cleaning a surface. The particles are accelerated by compressed air, just as with other blasting methods. Overall, there are three steps involved in dry ice blasting.
Step #1 – Energy Transfer
Dry ice pellets are propelled out of the blasting gun at supersonic speed and impact the surface. The energy transfer knocks off the contaminant without abrasion. The force of this impact is the primary means of cleaning.
Step #2 – Micro-Thermal Shock
The cold temperature of the dry ice pellets hitting the contaminant creates a micro-thermal shock (caused by the dry ice temperature of -109F) between the surface contaminant and the substrate. Cracking and delamination of the contaminant occurs furthering the elimination process.
Step #3 – Gas Pressure
The final phase has the dry ice pellet explode on impact, and as the pellet warms it converts to a harmless CO2 gas, which expands rapidly underneath the contaminant surface. This forces off the contaminant from behind. The contaminant is then relocated, typically falling to the ground. Since the dry ice evaporates, only the contaminant is left for disposal.