quote:I'd be a little concerned over the temperature and surface brittleness or shrinkage it might create on cast components with dry ice being at -109 degrees F. I see it's aggressive enough to strip the paint from the rear cover, but does the gearbox get down to really low temperature?
Ah ha, Julian the engineer raises interest points.
Yes, it does in fact create a surface shrinkage and it is damn cold.
From Wiki:
Dry-ice blasting involves propelling pellets at extremely high speeds. The actual dry-ice pellets are quite soft, and much less dense than other media used in blast-cleaning (i.e. sand or plastic pellets). Upon impact, the pellet sublimates almost immediately, transferring minimal kinetic energy to the surface on impact and producing minimal abrasion. The sublimation process absorbs a large volume of heat from the surface, producing shear stresses due to thermal shock.[1] This is assumed to improve cleaning as the top layer of dirt or contaminant is expected to transfer more heat than the underlying substrate and flake off more easily. The efficiency and effectiveness of this process depends on the thermal conductivity of the substrate and contaminant. The rapid change in state from solid to gas also causes microscopic shock waves, which are also thought to assist in removing the contaminant. Dry Ice Blasting is nonabrasive, nonconductive and nonflammable. Dry Ice Blasting generates no additional waste or secondary contamination unlike media and water blasting.
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I was not present during the process, but as the specks of dry ice immediately boil off to gas with the energy of impact, I can't imagine the underlying surface sees any temperature change of any concern. The process is used onsite for food production facility equipment; doubtful companies would submit to the process if it was in any way going to affect the integrity of their equipment. Speaking with the shop, they told me the host item does get a chill, but local to the blasting area and very short lived. Nozzle pressure is about 60 pounds.
As for finding a dry ice blasting operator, that does seem to be difficult. I did online research and stumbled upon my shop here in Fresno.
There is this online listing that may help in one's search:
http://www.blastcleaningdirect...om/Countries/USA.htm
Larry