Frequently Asked Questions (FAQ)

 

Frequently asked questions about Dry Ice, Dry Ice Production and Dry Ice Blasting.

• Q: What is dry ice?

• A: Dry Ice is the solid form of Carbon Dioxide (CO2). CO2 is a colorless, tasteless, odorless gas found naturally in our atmosphere.

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• Q: What is dry ice blasting?

• A: 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 and clean a surface.

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• Q: Why would I use dry ice instead of a traditional blast media?

• A: Most other blast media leave secondary waste behind. Dry ice sublimates (vaporizes) upon impact with the surface. All that remains is the contaminant you are removing, displaced from the substrate. 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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• Q: How does the process work?

• A: 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, breaking the bond between two dissimilar materials.

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• Q: What happens to the contaminate?

• A: : Contaminants can be dry, wet, hard or soft. Dry contaminants 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 contaminant is wet such as grease or oil, the dry ice stream will move or push the liquid away much like a high pressure water stream would, except that the surface where the contaminant was will be dry and clean. To prevent re-deposition, the operator should work in a methodical way, from the top down.

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• Q: Does the contaminant or dry ice pellets ricochet?

• A: 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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• Q: Will dry ice blasting damage the substrate?

• A: : The 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 contaminant while remaining non-abrasive to the substrate. The dry ice blasting process can clean delicate chrome or nickel plated tools, soft aluminum or brass alloys, wire insulation and even circuit boards – all without causing damage.

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• Q: Can you use dry ice blasting to clean hot tools online?

• A: Yes. In fact, dry ice blasting cleans faster when the substrate is hot.

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• Q: Does dry ice blasting cool the substrate?

• A: 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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• Q: Will the temperature reduction damage the hot mold?

• A: 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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• Q: Will the process create condensation?

• A: 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 blow off devices.

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• Q: Is it safe to use dry ice blasting outside?

• A: Yes. CO2 dry ice is safe to use in outdoor blasting applications.

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• Q: Is it okay to blast in an enclosed area?

• A: 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 environment, existing ventilation is sufficient to prevent undue CO2 buildup. Even though CO2 is non-poisonous, it does displace oxygen in the atmosphere.

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• Q: What are the primary safety issues when dry ice blasting?

• A: One safety issue is to protect workers from moving parts. Dry ice blasting equipment is designed so that workers do not have access to moving parts without shutting down the system. Another concern is the temperature of the dry ice. At -109°F (-78.3°C), we recommend wearing gloves when coming in contact with the dry ice. Eye and ear protection should be worn at all times.