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.
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.