18-06-2012, 01:49 PM
Seminar on Carbon Dioxide (Dry-Ice) Blasting
Carbon Dioxide (Dry-Ice) Blasting.pdf (Size: 316.54 KB / Downloads: 170)
Basic Principles of Operation
Dry-ice particle blasting is similar to sand
blasting, plastic bead blasting, or soda blasting where
a media is accelerated in a pressurized air stream (or
other inert gas) to impact the surface to be cleaned or
prepared. With dry-ice blasting, the media that impacts
the surface is solid carbon dioxide (CO2) particles. One
unique aspect of using dry-ice particles as a blast
media is that the particles sublimate (vaporize) upon
impact with the surface. The combined impact energy
dissipation and extremely rapid heat transfer between
the pellet and the surface cause instantaneous sublimation
of the solid CO2
into a gas.
Equipment/Materials
There are two general classes of blast machines
as characterized by the method of transporting
pellets to the nozzle: two-hose (suction design) and
single-hose (pressure design) systems. In either
system, proper selection of blast hose is important
because of the low temperatures involved and the
need to preserve particle integrity as the particles
travel through the hose.
In the two-hose system, dry-ice particles are
delivered and metered by various mechanical means
to the inlet end of a hose and are drawn through the
hose to the nozzle by means of vacuum produced by
an ejector-type nozzle. Inside the nozzle, a stream of
compressed air (supplied by the second hose) is sent
through a primary nozzle and expands as a highvelocity
jet confined inside a mixing tube.
Repainting Machines, Machine Tools, and
Equipment
Complete machines can be cleaned without
removing the factory paint and made ready for repainting
with little or no other preparation such as masking
or rinsing.
Dry-ice blasting is much faster and more
thorough than manual preparation, has no airborne grit
to ruin bearings and other moving parts, and does not
“short-out” motors and electrical controls like water
blasting does.
Applications for Dry-Ice Blasting
In simple terms, dry-ice blasting is not a paint
stripper. While isolated success cases exist in paint
stripping using blast pressures from 150 to 300 psi (1
to 2 MPa), most results indicate partial to complete
failure to remove topcoats at profitable rates, and
failure is even more likely when the goal is to completely
remove a primer.