Frozen clean

Dry ice is pure, liquid carbon dioxide (CO2) that is super-compressed until it becomes a solid. It does not turn back into a liquid when it warms, but rather skips this step and turns into a gas.

The process is called sublimation. For dry ice blasting this means no mess, which puts dry ice blasting in a league all it’s own when it comes to cleaning equipment indoors, or in any area where a buildup of cleaning waste is undesirable.

EcoJet restored the famous Toronto statue, Rising, using dry ice blasting. The technique is perfect for applications where the substrate must not be damaged and water is undesirable.

Other forms of blasting, such as sandblasting, generally rely on the hardness and angularity of the cleaning media combined with air pressure that works to pulverize and remove the contaminate. Sand blasting is a very fast method of removing paint, and prepping metals for re-painting as it creates a profile in metal for better paint adhesion, but is a very ineffective as a cleaner as it creates secondary waste and damages almost all substrates. Power washing is much better for cleaning than sand blasting in many situations, but delivers its own set of problems. When water as a waste byproduct is problematic, when water is a scarce resource or when the high pressures required to clean some contaminates may damage the substrate, one may have to rule our power washing as an option. When we look at dry ice blasting and the four basic principles by which it operates, we can see what set it apart from the others:

• Thermal differentials between the contaminate and the substrate
• Explosive sublimation
• Hardness of media
• Air pressure

The temperature of dry ice is -80C. The extreme cold causes the contaminate to shrink and detach itself from the substrate. The explosive sublimation process of the solid CO2 converting to a gas (800 times its volume in one millisecond), coupled with the high pressure airstream, works to blast the contaminate from the surface. The hardness of media plays a lesser role in the process as the dry ice is relatively soft (only about as hard as a fingernail). This however, is what makes it such a great method of cleaning – it is fast, sterile and won’t damage most surfaces.

Dry ice blasting used CO2 captured as a byproduct from such other industrial processes as ammonia, fertilizer, natural gas production and large scale fermentation processes. That means dry ice blasting adds absolutely no greenhouse gas to the atmosphere that was not already there. As well, unlike water, sand, and soda blasting, it creates no secondary waste stream. It is non-abrasive, non-conductive, non-toxic, non-flammabl, and non-waste-generating. It is safe for use in sterile environments such as food and pharmaceutical facilities. It is also safe for use on live electrical components. When used on machinery, the equipment can be running and can even be hot (in fact, it is better if it is hot). Machinery rarely needs disassembly before cleaning with dry ice blasting.

Now that we understand most of what separates dry ice blasting from all other forms of abrasive blasting methods, we have to talk about what can put this advanced technology out of reach of most plant managers, maintenance superintendents and homeowners: the price.

To purchase a dry ice blasting machine you are looking at a $30,000-$40,000 buy-in. EcoJet strongly endorses ColdJet products for the way they are able back their product line. ColdJet have been in the game a long time and are trendsetters in this industry. The standard equipment package includes a blasting machine an after cooler, a few lengths of blast hose and a few nozzles. This does not include an air supply, but for rental operations providing compressors, this is probably not a problem. For air supply you will generally need a compressor that can supply 120 PSI at 160 CFM.

As $2,500 per day when a compressor, a supervising technician and all the required ice are thrown in.

Operating dry ice blasting equipment is pretty simple. Once you understand the basic principles of how dry ice reacts with moisture and the atmosphere, you will have a much easier time troubleshooting problems in the field.

Basic operation lesson one is, water and dry ice are arch-enemies. Operators need to be warned against filling up the hopper then going for lunch. When they get back, their hopper full of nice fluffy ice pellets will have turned into a frozen block of hair-pulling frustration.

Dry ice blasting is widely used to clean the following kinds of equipment:

Power generation:

• Turbines
• Compressors and generators
• AC/DC motors
• Circuit breakers
• Switch gear
• Transformers
• Rotors and stators
• Insulators
• Field frames
• Substation isolators and bushings

Rubber and plastic:

• Moulds of all kinds
• Tilt-back and lift presses

Food and beverage processing:

• Slicers and dividers
• Pack-off tables
• Labelers and gluers
• Ovens and conveyors
• Mixes and baggers
• Ishida weighers
• Bottling lines

Contract cleaning:

• Fire and smoke restoration
• Mould remediation
• Odour elimination
• Water damage
• Lead paint abatement
• Adhesive and tar removal
• Corrosive contaminants removal
• Plant shutdowns

Foundry and forging:

• Removing resins and release agents
• Permanent aluminum moulds
• Semi-solid castings and forging dies
• Core boxes and vents
• Refractory coatings
• Shell Core moulds
• Die cast tooling
• Conveyors

Medical:

• Medical stints and implants
• Thermoplastic injection moulds
• Titanium, stainless and PEEK products
• Surgical tools and instruments
• Thermoset injection moulds
• Deflashing and deburring
• Liquid injection silcone moulds
• Catheter tips
• Manifolds

About the author
Mike McGraw is a partner in EcoJet Dry Ice Blasting. EcoJet is based in the Greater Toronto Area with nationwide service. McGraw can be reached at 1-888-641-6777 ext. 212 or
mike@ecojetinc.com.