Beyond the Roll: Dry Ice Blasting for Maintenance and Cleaning
- Published: June 25, 2020
By Jeff Paduano, President at ARCS
At my company, we get asked a lot if dry ice can be used for roll cleaning. The answer is no – it will lead to damage and cylinder delamination. We work very closely with many top anilox roll manufacturers, and not one of them recommend dry ice for cleaning their rolls either.
For the record, the most effective roll cleaning methods on the market today include chemical wash and ultrasonic equipment, On-press and off-press baking soda systems, and a newer technology which uses lasers to remove dried inks and coatings.
This article goes “beyond the roll” and discusses the pros and cons of using dry ice for industrial maintenance and cleaning applications addressing common questions asked.
How does dry ice blasting work?
Have you ever done any sand blasting? Dry ice blasting is based on the same concept. The difference between these two forms of blasting involve the type of equipment and blasting media used.
Dry ice blasting uses a dry ice blaster which gets filled with dry ice pellets. When the machine is used, three processes happen at the same time:
- Kinetic – When dry ice pellets are accelerated in a jet of compressed air and strike a hard surface, the pellets crack and loosen the coating or soil on the substrate being cleaned.
- Thermal – The extreme low temperature (-79˚C/-110˚F) of the pellets makes the coating brittle and loosens it, allowing for the dry ice to dislodge the coating or soil.
- Sublimation – Dry ice permeates the coating and immediately sublimes, which means that the dry ice instantly goes from a solid state to a vapor state. This resulting increase in volume creates an “explosive” effect that lifts the coating off of the surface.
I’ve heard dry ice blasting doesn’t require any containment or clean-up – is this true?
Not quite. It is true that because dry ice media “disappears” containment and clean-up are much easier than other cleaning methods. For instance, no wastewater, spent media, or any type of secondary waste gets generated. However, you still must ensure any sensitive areas near the location to be cleaned are protected. The goal is to keep any debris the dry ice targets inside the work zone. Simple containment measures such as surrounding the workspace with welding curtains can accomplish this. Technique also matters – blasting downwards keeps most debris on the floor.
When done properly, post-blasting clean-up is a snap – most times the residual waste gets swept up and thrown away in standard waste containers since nothing gets rewetted or liquified.
What safety measures must be taken when dry ice blasting?
Operators must protect their hearing, eyes and skin when blasting. It is also a good idea to wear a face shield. When handling the ice heavy duty gloves get worn. Anyone near-by during the blasting process would also need hearing protection.
Is dry ice suitable for confined spaces or hard to reach areas?
Yes – but be aware that dry ice will replace the oxygen in an enclosed space with carbon dioxide. Either extra air ventilation or wearing a supplied air respirator system will solve this problem.
I already own a sand (or soda) blaster – can I use this with dry ice?
No. Dry ice blasting equipment is unique and engineered to run an ultra-cold media (remember, Dry Ice registers -110°F!).
What else do I need to run a dry ice blaster?
A large volume of clean and dry compressed air and a standard electrical outlet. Dry ice blasters are controlled with electricity (on/off, consumption rates, blast pressure), but the ice itself is fed from the hopper to the metering valve and then “delivered” onto the surface using compressed air.
To do a large job its best to blast at a high pressure and use a large nozzle. Typically, a minimum of 185 CFM (cubic feet per minute) air volume is needed. Most plants we work with own compressors large enough to produce this amount. If you do not know your CFM, you can also calculate this value if you know the HP of your compressor motor: 1 HP = 4 CFM.
However, some plants schedule their dry ice projects off hours or on weekends to not interfere with air supply needs of other departments and operations.
The quality of the air supply is just as important. Any moisture or oil residue in the air supply line can lead to flow and clumping issues. Once this happens, the machine hopper usually needs to get emptied and start over. Most of our clients do not have this problem since their other pneumatic powered equipment also has this same requirement, however, a simple in line air filter/moisture separator can be installed if necessary.
How is dry ice packaged? How long of a “shelf life” can I expect?
We work with several dry ice producers around the country. All of them load the ice into heavy duty rolling thermal bins and have a minimum order requirement of 500 lbs.
Due to sublimation, a daily “loss” of 5 percent occurs no matter how or where its stored. As the dry ice sublimates, it begins to clump up. Usually a bin will last up to five days before it is too difficult to break up and pour into the machine hopper.
Does dry ice strip paint or remove rust?
Depends. In general, dry ice blasting is considered a non-destructive cleaning method. Most paint and rust conditions require a much more aggressive approach with some exceptions. Simple surface rust or failing paint? Should work. Heavy duty rust or well bonded, thick paint? Try something else.
What is dry ice good at removing?
Dried ink, coatings, outgassing residue, oil, grease, glue, adhesive, overspray, graffiti, pollution, carbon and many other soiling conditions.
What substrates can I dry ice blast without causing damage?
Steel, aluminum, soft metals, stone and many other materials are safe for this process. Wood, fiberglass, gel coats, carbon fiber, finely engraved surfaces, brick and other delicate or soft substrates may experience damage during the blasting process. Many times, the extent of potential damage can be lessened by reducing your blast pressure or increasing your nozzle stand-off distance. When in doubt, consult an expert since the damage that may occur might not matter when compared to the pitfalls of using another cleaning method.
What applications exist for dry ice blasting? How do other companies use this process?
In certain industries, dry ice blasting is used regularly. It is the preferred method for mold clean outs in the plastics and rubber industries. It is also a great way to clean large parts – ones that do not easily fit into a standard parts washer or when strong chemicals can do more harm than good: Pans, ink trays, mixing shafts and blades, carts, vessels, conveyors, belts, chains.
It is also very popular for cleaning press frames. Dirty walls, production equipment of all types, cat walks, railings, and more!
Since dry ice blasting is a waterless process, it is also popular for electrical gear, control panels, switches, electronic components, cables, wiring and other forms of electrical maintenance.
How can this one process be effective in so many ways?
Dry ice blasting is not a “one size fits all” method. Today’s equipment has come a long way and now offers a variety of settings and nozzle configurations. You can even get an accessory that subdivides the original ice pellet into a smaller particle in order to target very delicate items such as wiring and electrical connections.
The operator also has electronic control over ice consumption and blast pressure – use less for light duty jobs and more for tough soiling conditions.
How much dry ice will I need? How long will my project take to finish?
We probably hear these two questions the most. Since no two jobs are alike, they are also the hardest ones to answer. The variables to consider include soiling condition, blast area complexity (can I perform blasting standing up, or do I have to perform the work at an elevation?), containment measures needed, lots of nooks and crannies to blast or only flat surfaces, etc.?
A bin of ice can last up to eight hours. A person can usually clean at least one square foot per minute, sometimes much more than this. Speak to an expert with your project details to gain a better understanding of production rates you can expect, material costs and ways to ensure your project goes smoothly.
Tell me more about dry ice logistics?
The biggest thing to know is that dry ice is not stockpiled waiting for people to order it. However, a good supplier will have the ability to get dry ice to your facility within 3-5 days. Keep in mind if you underestimate your need and run out before you are done, it may take another 3-5 days to get resupplied. It is always a good idea to order 10-20 percent more than you think you will need in case you encounter unforeseen circumstances.
What equipment options exist?
Dry ice equipment comes in various sizes – speak to your supplier regarding what makes the most sense for your needs. Dry ice equipment also has different price points, but it is rare when a company needs the biggest, most expensive unit available. Only looking to do one or two projects a year? Consider renting – the right supplier should offer both sales and rentals.
Is dry ice equipment difficult to operate?
Not really – but it does take some skill. Today’s machines are all PLC-controlled, so adjusting the settings has become very easy. The blasting operation does take a little “nozzle time” to get used to, but with good training and a little patience you will find it is much easier and safer to perform than dealing with hazardous chemicals and solvents.
A proven method
Dry ice blasting has been around for several decades, but its only in the last several years where we have seen it become increasingly popular and an accepted cleaning technology at many manufacturing plants. It is fast, effective, does not generate secondary waste and sometimes is the only way to solve a company’s problem.
This article is meant to be a primer for people considering using dry ice in their operation. Work with a good supplier should you have a desire to learn more about how dry ice blasting technology can help your plant benefit from this proven method.
About the Author:
Jeff Paduano is the president at ARCS, where under his direction, the company has expanded into a national systems and services provider over the last decade, with regional branch offices now in three locations. ARCS specializes in advanced technology for both on and off press roll cleaning, and also can help companies with many of their surface prep and finishing needs.
