Frequently Asked Questions
- What is CO2 blasting?
- How does it remove contaminants?
- How does this differ from how sandblasting works?
- What happens to the dry ice once it strikes the surface?
- What happens to the contaminant?
- Does the process damage the substrate?
- Does the CO2 cool the substrate?
- Will the process create condensation?
- How is dry ice made?
- How are dry ice pellets made?
- How is block dry ice converted to blastable granules?
- Does block dry ice have advantages over pellets?
- Are there differences in the cleaning effectiveness of dry ice pellets vs. the granules produced by the SDI-5?
- How did the dry ice blasting technology originate?
- How much air will I need to clean effectively?
- What blasting pressures are possible?
- How much dry ice should I expect to use?
- Can I vary the dry ice consumption rate?
- How do I store my dry ice?
- Will I need an air dryer?
- How much regular maintenance is required?
- Does CO2 replace sandblasting / bead blasting / water blasting, etc.?
- What are the primary safety issues relating to the use of dry ice blasting systems?
- Is the system noisy?
- Do the contaminants or dry ice particles ricochet?
- Does the process generate static electricity?
- Is it okay to blast in an enclosed area?
What is CO2 blasting?
It is a process in which dry ice particles are propelled at high velocities to impact and clean a surface. The particles are accelerated by compressed air, just as with other blasting systems. Today, most applications are able to use standard shop air, in the 30 - 100 psi range.
PageTopHow does it remove contaminants?
It depends on what you're cleaning. If you're 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 overcome the bonding strength and literally pop the coating off from the inside out. If you're 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 compress and mushroom out, creating a high velocity snow flow that actually flushes the surface.How does this differ from how sandblasting works?
Sandblasting 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 1% of our atmosphere.What happens to the contaminant?
People sometimes think it disappears too, but it does not. All cleaning involves the relocation of dirt. When you mop a floor, the dirt moves from the floor to the mop to the water in the bucket. With dry ice, the dirt moves from an undesirable area to an area where you can better deal with it. If it is a dry substance, it generally falls to the floor where it is swept away or vacuumed during normal maintenance. If it is a wet substance like grease, you take a methodical approach similar to hosing down a driveway. You start at one end and guide the grease to the other end where it is vacuumed or squeegeed up.Does the process damage the substrate?
Generally no, but it depends on the substrate. There is an energy threshold at which disbonding will occur and a threshold at which damage will occur. When the disbonding threshold is lower than the damage threshold, you can clean. If the reverse is true, damage can occur. Adequate traing of the technician is required to assure that no damage occurs to the cabinet components.Does the CO2 cool the substrate?
Yes, but generally not as much as you might think. The amount of cooling is dependent upon three main factors: mass of the targeted surface, dwell time, and ice usage rate. Generally cooling is not a concern and only rarely does it affect cleaning performance.Will the process create condensation?
Once again, it depends on the mass of the object you're blasting, your dry ice usage rate, and your dwell time. There will be condensation if you cool the substrate below the dewpoint (the dewpoint varies depending on local climate). Wickens Industrial has developed our air preparation unit to eliminate,as much as possible, condensation concerns. In addition we record the dew point before commencing cleaning operations in order to anticipate the production of condensation.How is dry ice made?
It is made from liquid carbon dioxide. Dry ice 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.How are dry ice pellets made?
Pellets are made by taking liquid CO2 from a pressurized storage tank and dropping it to ambient pressure to produce snow. The snow is then pushed through a die to make pellets. The Triventek system is a mechanical extruder process in which the pellet extrudes through 3 easily interchangeable die plates.How is block dry ice converted to blastable granules?
When you pull the trigger on the SDI-5, an actuator engages the ice, pushing it into the cutting face (the granulator) which produces particles that look much like raw sugar crystals, about 10 mils in size. Because the granulator only operates when the trigger is engaged. The SDI-5 is a patented system, the only blasting unit on the market capable of starting with block dry ice to create a blastable medium.Does block dry ice have advantages over pellets?
Yes. It is easier to transport. Block dry ice has a longer shelf life. Pellets have a higher surface-to-mass ratio which makes them more hydroscopic, meaning they attract water. When stored, this causes them to sublimate (turn into a gas) faster than block. Block machines are larger and more complex and consequently are much more expensive to purchase and operate.Are there differences in the cleaning effectiveness of dry ice pellets vs. the granules produced by the SDI-5?
In about 75% of the applications, users do not choose dry ice media based on its cleaning effectiveness because there is little or no difference. In the remaining cases, pellets work better in some of the applications, granules in others. Generally speaking, pellets are more effective with thick hard to remove contaminants as the greater mass behind each individual particle more readily travels all the way through the contaminant to disbond it. Because the granules are smaller than the pellets, they produce a significantly greater number of surface impacts and are therefore better at removing common contaminants found on switch gear and in transformer vaults.How did the dry ice blasting technology originate?
Dry ice blast cleaning originated at Lockheed in the 70's when a coatings engineer, Calvin Fong, was researching ways to strip paint off aircraft. The technology did not become commercially available until Alpheus bought the license and patents from Lockheed and introduced it to the marketplace in 1987.How much air will I need to clean effectively?
It is typical to operate at about 90 psi with 130 cfm, however your needs will depend on your application.What blasting pressures are possible?
Our standard gun configuration is rated up to 200 psi which is well above the 80-100 psi generally used.How much dry ice should I expect to use?
This is an important question to ask because the amount of dry ice needed to clean effectively can vary dramatically within from gear to gear. Generally we expect to use 1½-2 pounds per minute while the trigger is engaged. Of course, when you are cleaning, you won't be pulling the trigger constantly. At a rate of 2 pounds per minute with 50% trigger time, you would use 60 pounds of dry ice in an hour.Can the dry ice consumption rate be adjusted?
Yes, the rate can easily be adjusted at the control panel on the SDI-5.How do I store my dry ice?
Since dry ice is -109°F, putting it in a freezer doesn't really help. The best way to extend your shelf life is to store the ice in an insulated bin. Depending on the quality of the bin and how much ice you are storing, your loss due to sublimation should range from 2% to 10% per day.Will I need an air dryer?
Yes a properly designed and set up air preparation system is critical to safe energized electrical cleaning. Wickens Industrial has developed a system that exceeds the requirements to clean safely and effectivly.Does CO2 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 each do the job of the other? Perhaps, but the ideal toolbox would include each, because each has specific capabilities that it does better than any of the others. Electrical utilities have progressed through the use of all of these formats particularily in substation contamination problem areas the applicability of dry ice technology lends itself to voltages to 28 kv and light contaminants. .What are the primary safety issues relating to the use of dry ice blasting systems?
One issue is the temperature of the dry ice. At -109°F, we recommend you never handle it directly without gloves. Proper PPE for the contaminant involved is required and just as in sand blasting or steam cleaning, the gun should never be pointed at anyone or serious injury could occur. The issue that comes up most often is noise.Is the system noisy?
Yes. Noise is a function of air volume and air velocity. Within the nozzle, the stationary air is sheared by the high velocity air causing turbulence which creates noise. The level can range from 80 - 130 db. Hearing protection is required.Do the contaminants or dry ice particles ricochet?
As long as it strikes the surface head on, dry ice does not ricochet because it sublimates (turns into a gas) 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 is recommended at all times.Does the process generate static electricity?
Yes. Any dry air process will generate static electricity and dry ice blasting is no exception. In the Wickens Industrial system we have assured that both the blasting unit, vehicle and cabinet are properly grounded.What should I do if my blast hose is cracked?
Replace it. The hoses carry high pressure air and could lead to problems if cracked or abraded.Is it okay to blast in an enclosed area?
Yes, with proper ventilation. Because CO2 is 40% heavier than air, placement of exhaust vents at or near ground level is recommended when blasting in an enclosed area. In an open shop environment, existing ventilation is sufficient to prevent undue CO2 buildup.Copyright ©2004 Wickens Industrial Limited. All rights reserved.