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F
A Q
FREQUENTLY-ASKED
QUESTIONS ABOUT DRY ICE BLASTING
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on any question to jump to that section. Para Preguntas Frecuentas
pulsar aquí.
What
is dry ice?
What
is dry ice blasting?
How
do I store dry ice?
Why
would I use dry ice instead of a traditional blast media?
How
does the process work?
What
happens to the contaminate?
Do
the contaminates or dry ice pellets ricochet?
Will
dry ice blasting damage the substrate?
Can
you use Cold Jet dry ice blasting systems to clean hot tools online?
Does
dry ice blasting cool the substrate?
Will
dry ice blasting cause thermal stress to my tools?
Will
the process create condensation?
What
equipment will I need?
How
much air will I need?
Where
can I find dry ice pellets?
Does
using pellets have an advantage over using block dry ice?
Are
there differences in effectiveness of dry ice pellets vs. block
dry ice granules?
What
is the difference between a single-hose system and a dual-hose system?
How
big is a Cold Jet dry ice blasting machine?
Is
it safe to use dry ice blasting outside?
What
influence does pellet size, air pressure, and pounds per minute
have on system efficiency?
Which
is more efficient, pellets or nuggets?
What
is dry ice?
Dry Ice is the
solid form of Carbon Dioxide. Dry Ice is a colorless, tasteless,
odorless gas found naturally in our atmosphere.
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What
is dry ice blasting?
Dry ice blasting is similar
to sand blasting, 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.
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How
do I store dry ice?
Dry ice pellets are delivered
to your plant in sealed insulated containers. Depending on the climate,
the pellets will last in their container for 5 to 12 days. Once
the seal is broken, the ice should be used in 1 to 3 days.
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Why
would I use dry ice instead of a traditional blast media?
Most other blast media
leave secondary waste behind. Dry ice sublimates (vaporizes) upon
impact with the surface. All that remains is the contaminate you
are removing. Also, since dry ice vaporizes on impact, the process
can be used to clean complicated cavities where typical grit blast
media will become trapped.
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How
does the process work?
Unlike other blast media,
dry ice has a temperature of -109°F (-78.3°C). Because of
the temperature difference between the dry ice particles and the
surface being treated, thermal shock occurs during the process of
dry ice blasting. This causes a breakdown of the bond between two
dissimilar materials.
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What
happens to the contaminate?
Contaminates can be dry,
wet, hard or soft. Dry contaminates will break up into small chips
and can be swept up or vacuumed. If the particles are large enough,
they do not become airborne. If the contaminate is wet, such as
grease or oils, the Cold Jet® stream will move or
push the liquid away much like a high pressure water stream would,
except that the surface where the contaminate was will be dry and
clean. To prevent redeposition, the operator should work in a methodical
way, from the top down.
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Do
the contaminates or dry ice pellets ricochet?
Upon impact, dry ice pellets
sublimate to a gaseous state and therefore dry ice particles typically
do not ricochet. The removed contaminant is usually washed away
by the blast jet stream and does not come directly back into the
blast gun vicinity; however, safety glasses must be worn at all
times during the operation of the machine.
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Will
dry ice blasting damage the substrate?
The Cold Jet®
dry ice blasting process will not damage the substrate. The size
of the dry ice pellets and their velocity can be optimized to remove
the contaminate while being non-abrasive to the substrate. The Cold
Jet® process can clean delicate chrome or nickel
plated tools, soft aluminum or brass alloys, wire insulation, and
even circuit boards without causing damage.
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Can
you use Cold Jet® dry ice blasting to clean hot tools
online?
Yes. In fact, dry ice
blasting cleans faster when the substrate is hot.
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Does
dry ice blasting cool the substrate?
Yes, but not dramatically.
The amount of cooling depends on the substrate material, the dwell
time of the dry ice blast stream, and the dry ice usage. For example,
a 30 inch (76.2 cm) by 30 inch (76.2 cm) rubber mold may have an
initial temperature of 325°F (162.8°C). After the tool has
been blasted clean (approximately 12 minutes), the temperature of
the mold is about 300°F (148.9°C).
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Will
dry ice blasting cause thermal stress to my tools?
Generally, no. The temperature
change of the surface being cleaned is small and the corresponding
tensile stress will be well below the point of what most molds will
encounter during normal heat treatment.
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Will
the process create condensation?
Condensation occurs when
the temperature of the substrate falls below the dew point. The
dew point varies with climate and the daily weather patterns. When
cleaning hot substrates, condensation will rarely occur because
the temperature of the surface will stay above the dew point. If
condensation does form, you can control it by using heaters, heat
lamps, or warm air knives.
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What
equipment will I need?
The system will come complete
from Cold Jet. The only other items you will need are plant air,
electricity, and dry ice pellets.
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How
much air will I need?
ColdJet's single-hose
Radial Feed Series and dual-hose Venturi system typically operate
at 80 psi (5.5 bar) with 150 scfm (4.25 m3/min), but low flow nozzles
are available, which require only 100 scfm (2.83 m3/min) at 80 psi
(5.5 bar).
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Where
can I find dry ice pellets?
Dry ice pellets are available
all over the world. In the United States, call +1-800-SEND-ICE (+1-800-736-3423)
or +1-513-831-3211 for a location near you.
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Does
using pellets have an advantage over using block dry ice?
Yes! Using only 1.5 to
2.5 pounds (0.68 to 1.14 kg) of pellets per minute, Cold Jet's single-hose
pellet blasting systems can clean two to five times faster than
a two-hose block dry ice shaver system. The single-hose system has
superior cleaning capability and can significantly reduce production
downtime and correspondingly yield thousands of dollars in production
savings beyond what is attainable with a two-hose block dry ice
system. Below is a comparison study of Cold Jet's single-hose dry
ice pellet based system versus a competitor's two-hose shaved dry
ice block system. The test was done on both sides of a single two-tire
press. Both tests were done by the same operator.
| |
ColdJet's
Single-Hose Pellet Blasting System |
Two-hose
Dry Ice Block Shaving Blast System |
| Top
half side wall cycle |
4
min. 10 sec. |
11
min. 40 sec. |
| Nozzle |
low
pressure |
round
|
| Blasting
Pressure |
60
psi / 4.14 bar |
70
psi / 4.83 bar |
| Pellet/block
feed rate |
50%
|
60%
|
| Bottom
half side wall cycle |
4
min. 25 sec. |
11
min. 0 sec. |
| Nozzle |
low
pressure |
round
|
| Blasting
Pressure |
60
psi / 4.14 bar |
85
psi / 5.86 bar |
| Pellet/block
feed rate |
50%
|
60%
|
| Total
cleaning cycle |
8
min. 35 sec. |
22
min. 40 sec. |
| Total
dry ice usage |
27.6
lbs / 12.5 kg |
44 lbs / 20 kg |
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Are
there differences in the effectiveness of dry ice pellets vs. block
dry ice granules?
Yes! The differences are
significant when it comes to adapting the pellet size and aggression
level to the needs of a particular application. Shaving dry ice
blocks produces only a snow-like blast granule that is limited to
thin layer contaminate removal. A Cold Jet® single-hose
dry ice blasting system mechanically feeds a 3mm diameter pellet
into the blast hose. The particular hose and blasting nozzle being
used govern the actual pellet size impacting the surface.
For a more technical
explanation of the difference in effectiveness between pellets and
block shaved dry ice, click here.
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What
is the difference between a single-hose system and a dual-hose system?
In a dual-hose Venturi
Series dry ice blasting system, an ejector type nozzle, similar
to a conventional abrasive media blasting nozzle, is used to combine
the compressed air stream with the dry ice particle carrying vacuum
stream created by the ejector. In Cold Jet's single-hose Radial
Feed Series dry ice blasting systems, the dry ice pellets are mechanically
fed into the air stream. No energy is wasted creating a vacuum to
pull the pellets through a separate line. A significant drawback
of a two dual-hose system is the limitation on blast hose length.
Because the dual-hose ejector nozzle relies on a vacuum to pull
the pellets into the air stream, the hose length cannot go much
beyond 25 feet (7.62 meters) before pressure losses through the
pellet hose overcome the maximum vacuum capability of an ejector
nozzle. For a more technical explanation of the difference between
a single-hose dry ice blasting system and a dual-hose dry ice blasting
system, click here.
>>Top How
big is a Cold Jet® dry ice blasting machine?
- The Cold
Jet® VSH is 34 inches / 86 cm (L) by 20 inches
/ 51 cm (W) by 38 inches / 96.5 cm (H)
- The
Cold Jet AeRO 75 is 34 inches / 86
cm (L) by 20 inches / 51 cm (W) by 40 inches / 101.5 cm (H).
- The Cold
Jet AeRO 30 is 25 inches / 63.5 cm
(L) by 17 inches / 43.2 cm (W) by 30 inches / 76.2 cm (H).
All three
units are easily moved from one area to another.
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Is
it safe to use dry ice blasting outside?
Yes. CO2 dry
ice pellets are safe to use in outdoor blasting applications. In
fact, many organizations have given Cold Jet® their
stamp of approval for the use of pellets in outdoor blasting applications,
including the California Environmental Protection Agency.
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What
influence does dry ice pellet size, air pressure, and pounds per
minute have on system efficiency?
Dry ice pellet size is
usually optimum at 3 mm, the size that is available commercially
for pick up or delivery. When a smaller pellet (particle size is
desired) it is usually accomplished by using a 3/4" (1.9 cm)
blast hose (1" (2.54 cm) is standard), a blast hose with a
ribbed interior or a nozzle that accomplishes this, or a combination
of these 3 parameters. This is often done to work on a thin coating
or to protect a sensitive surface.
Air pressure
has a direct effect on the velocity of the dry ice particles and
the velocity of the particles has a direct effect on the energy
being imparted to the surface, which can mean both higher removal
rates and also a greater potential for surface damage.
Pounds/kg per
minute of dry ice delivery can be optimized. There is an optimum
setting that is related especially to the particular nozzle (and
other parameters being used) and also highly related to the application.
A higher setting beyond the optimum does not translate into a higher
removal rate. In most cases a higher than optimum setting of dry
ice delivery will cause the particles to decrease in velocity and
therefore decrease the removal rate, and, of course, will cost more.
Many nozzles and applications are optimized between 2-3 pounds (1
to 1.5 kg) per minute.
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Which
is more efficient, pellets or nuggets?
We use the term pellets to mean dry ice formed in 3mm-diameter extrusions
or less. The 3 mm size is available commercially for pick up or
delivery, and while smaller sizes do have value for selected applications
they do not transport well enough and are not in high enough demand
be sold commercially. Sizes larger than 3 mm in diameter are generally
referred to as nuggets and they are too large for blasting as they
do not develop as much velocity and they induce surface damage more
readily.
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