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. Also,
it can viewed in the example below:.
Step #1 - Energy Transfer
With
dry ice blasting, 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 during dry ice blasting of the dry ice pellets
hitting the contaminant creates a micro-thermal shock (caused by
the dry ice temperature of -79º C) 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 of dry ice blasting 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.
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