![]() | |||||
|
| |||||
What
is Dry Ice? It is
frozen carbon dioxide (CO2). Carbon Dioxide is a gas which is natural to our atmosphere.
It is inert. It is non-conducive. Nearly all dry ice that is used in dry ice blasting
is recycled from factories and industrial processing. How
is dry ice made? It
is made from liquid carbon dioxide. CO2 exists as a liquid only under high pressure.
When it drops to ambient pressure (the normal pressure that surrounds us), approximately
half turns to gas and half turns to solid. The solid, usually in the form of fluffy
snow, is then compressed to form dry ice blocks, pellets or nuggets. What
is Dry Ice Blasting?
It is a process in which particles of solid carbon dioxide (dry ice) are propelled
with high velocity air (usually 80-100 psi) to impact and clean a surface. How
did the technology originate?
It originated at Lockheed in the 70's when a coatings engineer, Calvin Fong, was
researching ways to rejuvenate aircraft primer. The technology was introduced
commercially in 1987. What
is FreezeBlasting?
Freezeblasting is another name for dry ice blasting. Freezeblasting is a registered
trademark of American FreezeBlast, Inc. How
does dry ice blasting remove contaminants?
When removing a brittle contaminant such as paint, the process creates a compression
tension wave between the coating and the substrate. This wave has enough energy
to literally pop the coating off from the inside out. When removing a malleable
or viscous coating such as oil, grease, or wax, the cleaning action is a flushing
process similar to high pressure water. When the particles hit, they create a
high velocity ice flow that flushes the surface. How
is this different from how sandblasting works?
Sand blasting is similar to using an ice pick whereas dry ice blasting is similar
to using a spatula. Sand cuts or chisels away the contaminant. Dry ice lifts it
away. What
happens to the dry ice once it strikes the surface? It sublimates and returns to the atmosphere as carbon
dioxide (CO2) gas. CO2 is a naturally occurring element that constitutes less
than 4/100th of 1% of our atmosphere. What
happens to the contaminant?
It moves from an undesirable area to an area where it can be dealt with more easily.
If it is dry, it usually falls to the floor and is swept up or vacuumed during
normal maintenance. If it is a wet substance such as grease, a methodical approach
similar to hosing down a driveway is required. Start at one end and guide it to
a collection point for disposal. Does
dry ice blasting damage the substrate?
Generally no. If the energy threshold at which disbonding will occur is lower
than the threshold at which damage will occur, the surface can be cleaned safely.
If the reverse is true, damage can occur. A lot of dry ice blasting applications
involve production equipment (cast iron, tool steel, tool grade aluminum), but
we also have great success with softer substrates such as plastics, wiring, pure
copper, and fabrics. Can
dry ice blasting be used to clean hot on line? Absolutely. Most contaminants have weaker adhesive
strength when hot, so cleaning a hot substrate is almost always faster than cleaning
a cold one. Also, dry ice sublimates on impact, so there are no worries about
grit entrapment as there would be if using sand, glass beads, or other abrasive
media. Does
the dry ice cool the substrate?
Yes, but generally not as much as you might think. The amount of cooling depends
upon three main factors: a) mass of the targeted surface; b) dwell time; and c)
ice usage rate. Typically, a tire mold may drop from 350°F to 325°F during cleaning.
With a very thin mold, the drop can be much greater. Generally, however, cooling
is not a concern and rarely does it affect cleaning performance. Will
the temperature drop damage the substrate?
It is unlikely, but it depends on the mass of the targeted object. Heavy molds,
will not be harmed because the drop in temperature is insignificant when compared
to the mass of the mold. With thin substrates where tolerances are critical, some
testing may be required to determine if the drop in temperature would structurally
alter the surface. What
are the best cleaning applications for dry ice blasting? Dry ice blasting excels at cleaning production equipment
online, because it eliminates the need for masking, cool down and disassembly.
Users minimize downtime, which maximizes production efficiency. The range of cleaning
applications for dry ice blasting is remarkable as demonstrated by just a small
sampling of the various uses of dry ice blasting : core boxes; coater cups; printing
presses; food processing mixing equipment; tire molds; and payload fairings for
a missile system. Dry ice blasting is also widely used by the nuclear industry
for decontamination and by the utility industry and the U.S. Navy for cleaning
energized switchgear. Any time waste volume or health risks are a concern, the
viability of dry ice blasting should be examined. Because CO2 disappears on impact,
it creates no additional waste. Competing processes such as grit blasting or solvents
often present disposal problems or health hazards. How
is dry ice blasting used in the printing industry? The process is used to remove ink (wet and dry),
spray powder, paper dust, and coatings from web presses and sheet-fed presses.
This prevents web breaks, improves product quality, reduces maintenance time,
and provides for faster make-readies. What
are some examples of applications where dry ice blasting does not work well? You cannot etch or profile most surfaces using dry
ice blasting. If you clean large quantities of small parts, ultrasonics or parts
washers are probably more efficient than dry ice blasting. Because the technology
is primarily a line-of-sight cleaning process, you generally must be able to see
what you're cleaning to clean effectively with dry ice blasting, although recent
advances in nozzle technology provide cleaning options not previously available.
Can
dry ice blasting remove paint?
Yes, however, the removal rate is dependent on many factors including: the underlying
surface profile of the substrate the thickness of the coating the adhesive bond
strength of the coating and the cohesive strength of the coating (generally a
function of age). Paint removal rates can vary dramatically, from 300 square feet/hour
down to 1 square foot/hour. Will
dry ice blasting remove greases and oils?
A methodical approach similar to hosing down a driveway is used if dry ice blasting
is to be effective on wet contaminants. The operator will start at one end and
work the grease to the other end where it can pass through a grate or be vacuumed
or squeegee-d for disposal. The operator may use a paper or plastic backdrop to
catch the wet contaminant as it is removed from the substrate. Will
dry ice blasting remove weld slag?
Weld slag removal is an excellent dry ice blasting application and is used by
numerous manufacturers, usually in transportation-related industries. Dry ice
pellets are generally the preferred media. Can
dry ice blasting be used to remove rust?
It tends to remove the loosely adhered oxidation and salts, but will not remove
the deeply adhered oxidation. You will not get a white metal finish. To do that
the surface metal must be removed, something dry ice blasting cannot do. Of course
in many applications, this is a major advantage because it preserves the surface
integrity of the substrate. Will
dry ice blasting clean glass?
It can, but some prior testing is required to avoid shattering the glass. One
dry ice blasting application being used today is to clean glass monitors before
applying a non-glare coating. Others use it in general maintenance to remove oil
and grease from glass dials on control panels. To clean glass, it is important
to remember that a certain impact energy is required to disbond the contaminant.
If that energy level is high enough to also shatter the glass, this process should
not be used. Can
dry ice blasting be used to clean wood?
Hard woods have been successfully cleaned. For softer woods, the operation must
be finessed, using flakes and low compression. Dry ice blasting is ideal for mold
remediation programs and fire restoration. Does
dry ice blasting replace sandblasting/beadblasting/waterblasting, etc.? They are all tools in the toolbox. Consider that
there are many types of hammers: ball peen; tack; claw; sledge; and so on. Could
one do the job of the other? Perhaps, but the ideal toolbox would include each,
because each has specific functions that it performs better than any of the others.
Dry ice blasting equipment should be in your toolbox if you are concerned with
downtime, entrapment, waste volume, or equipment damage. Is
dry ice blasting noisy?
Generally speaking, yes. However, significant advances have been made which have
reduced required air volumes to as low as 12 CFM. This has, in turn, reduced associated
noise levels. Is it okay to blast in an enclosed area? Yes, with proper ventilation.
Because CO2 is 40% heavier than air, placement of exhaust fans at or near ground
level is necessary when blasting in an enclosed area. In an open shop environment,
existing ventilation is sufficient to prevent undue CO2 buildup. Do
the contaminants or dry ice particles ricochet? If they strike the surface head on, dry ice particles
generally do not ricochet because they sublimate on impact. As for the contaminant,
you usually do not see or feel it as it disbonds and leaves the substrate, however,
it is removed with some force, which is why eye protection should always be used
when blasting. Does
the process generate static electricity?
Yes. Any dry air process will generate static electricity and dry ice blasting
is no exception. As long as both the blasting unit and the piece being blasting
is properly grounded, it is unlikely to have static discharge problems. As an
added precaution, rubberized gloves and rubber-soled shoes offer additional protection
for the operator. Does
dry ice blasting contribute to the greenhouse effect? The environmental impact of dry ice blasting is
overwhelmingly positive. Dry ice is made from CO2 which is widely recognized as
a greenhouse gas. It is important to understand, however, that most of this CO2
has been recaptured as a byproduct of other industrial processes. If not purchased
by dry ice manufacturers and used to make dry ice, it would simply be released
directly into the atmosphere. By using it as a blast cleaning medium, we are essentially
recycling the CO2, giving it a second useful life. Does
dry ice blasting provide other environmental benefits? Indeed it does. Dry ice blasting greatly reduces
solvent use. Tinker Air Force Base, has reported that dry ice blasting has reduced
their solvent use by 1,700 gallons annually. Hill Air Force Base reports even
greater savings of 2,800 gallons per year. Unlike sand or other grit media, dry
ice adds nothing to the waste stream because it disappears on impact. This means
dramatic reductions in hazardous waste volume. A person that works in the petroleum
industry reports that, when they used sandblasting, they measured their waste
volume by the boxcar. Upon switching to dry ice blasting, they began measuring
their waste volume by the barrel. | |||||
Design by Amazon Affinity Inc. | |||||