Dry Ice / CO2 Blasting Questions

A. Operation in an open facility poses no problem to human respiration. Now, CO2 is almost inert (remember it is used as a protecting atmosphere for weldments) so it poses no harm to metals. Only complaint in our opinion would be its very low efficiency to remove very adherent soils or stains and its high noise and cost.

A. When investigating dry ice blasting, keep in mind there are different types of this technology. It's very similar to water blasting in that there are small units like pressure washers and big units like hydroblasters .... and everything in between.

Rather than dealing with GPM and PSI, dry ice blasting deals with CFM and PSI.

I watched a demo comparing a smaller unit (125 psi) and what I'd consider a monster at 300 psi/350 cfm, if memory serves me correctly. The test was to clean a tar pot on a trailer used for roofing tar. In the time it took for the small unit to clean a patch not much bigger than your hand, the bigger unit cleaned the rest of the trailer.

Dry ice blasting is a loud and somewhat expensive. Other than that, I think it has a lot of merit and is worth a look. Just be sure you are comparing apples to apples in pressure and flow.

Thank you Mr. Marrufo and Mr. Turner for your input.
We would be looking at a smaller dry ice unit (125 psi).
Has anyone who operated the equipment complained of, or had any back or shoulder issues?

Reading between the lines it seems that maybe you should go first on that one, Archy :-)

Thanks, Archy; that's exactly the kind of response I was hoping for.

A. We offer dry ice blast cleaning (or CO2 Cleaning) as a service business in the New England Region. We have not had any problems with injuries from using the system. Extended periods of operation do require that the operator take breaks, and care should be taken to ensure that the operator is not in unnatural positions for extended periods of time.

Protective equipment is a must, including ear, face and hand protection. The blasting noise is quite loud, (around 200 db) and ice pellets and debris often fly back in the face of the operator. Depending on what is being cleaned, a respirator may be advisable.

Steel molds generally clean quite well. Dry ice is NOT abrasive so the integrity of the mold geometry is protected. Molds can be cleaned in the press, while still hot, or after removal.

You may elect to begin trying this technology on a service basis before actually purchasing a machine. This will give you a good chance to learn about the technology, evaluate the results and see it in use before investing in the equipment. There are a number of service companies across the country, like us, that will come to your facility and clean your molds for you.

Dry ice must be ordered in advance and pricing and delivery can vary considerably from region to region and also based on the volume that you consume. It is wise to identify ALL sources of local supply before you order a machine so that you fully understand the costs, lead times and options available to you in your local market. Remember, dry ice is a perishable commodity.

A. It is not possible to use the usual Hopper that is used for generalized blasting when blasting with dry ice as the pellets have different chemical and physical properties as when compared to maybe sand or grit.

What you will need is a specially designed pneumatic hopper to blast with dry ice.

Regards,

A. You cannot add dry ice directly to the hopper. There needs certain engineering in mixing dry ice and compressed air. In India, generally pellets are not available. Even if available locally the density would not be enough. Dry ice blasting is non abrasive. It removes coating or contaminants. Removing paint is one of the applications while cleaning without removing the paint is another. If paint is loosely held it normally peels off while blasting.

A. Hello, Yashodeep. Good luck with your project. You could conduct a computerized literature search of the published literature. Alternately, if you know a likely journal, and I think the "Journal of Protective Coatings & Linings " is a good one, you could contact them about relevant articles. I have a copy of their Technical Information Packet Service, TIP-38, "Specialized and Novel Methods of Surface Preparation" and it includes the following three papers: "Ice Blast Technology"  and "Perspectives on Surface Preparation with CO2 Blasting", both from the Dec. '90 Proceedings;  and "Ice Blasting is One Step in Restoring Historic Site" from JCPL Column Innovative Practice Oct. '93.