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2006-11-01 - Air Force print News Story

A cold day in Hill: ice blaster saves money, manpower By Bill Orndorff 309th Maintenance Wing

HILL AIR FORCE BASE, Utah -- To remove sealant from F-16 wings, the 574th Aircraft Maintenance Squadron is replacing elbow grease and plastic scrapers with dry ice.

The process, which blasts material with dry ice pellets, saves time, money and manpower, and is easy to clean up. Hill officials say it has already paid for itself.

"This is so much easier," said Dennis Hathaway, F-16 Wing Shop supervisor. "I used to crawl into a hole and scrape these wings upside down when I could have just stood up and blasted it. Scraping sealant by hand is one of the worst jobs for a sheet metal mechanic - it uses too much manpower and can cause carpal tunnel syndrome."

Manufactured by Cold Jet, from Loveland, Ohio, the machine cost $27,000. The ice pellets, purchased in a 600-pound container from a Salt Lake City ice company (Airgas Dry Ice), are 40 cents a pound.

F-16 wings brought into the shop have the sealant removed before they are repainted with fuel-resistant paint. Mr. Hathaway estimates that an entire F-16 wing could be blasted in four shifts by one person. Scraping took four shifts and three to four people per shift.

"In man-hours, the machine was almost paid for after the first use," Mr. Hathaway said. "The shop does six or seven wing skins per year; now all will be done by blast instead of scraping."

To remove the sealer, the pellets are driven at 3.5 pounds per minute. The machine, which isn't much bigger than a mid-sized barbecue grill, is capable of operating at one-half pound per minute up to seven pounds per minute. The ice is blasted through a blast swath nozzle using building-supplied air pressure at 80 pounds per square inch.

"The sealer is in a dry state, so once it's removed, it can be swept up and placed in the trash," said Marion Long, 574th AMXS Structures Section chief. "There's no biohazard or bead media to contain, and it's safe to use on aluminum as thin as 30/1000ths of an inch."

Workers don't need to wear a hazardous material suit to operate the blaster - the only extra equipment needed is a face shield, to protect against sealant residue particles, thick gloves for handling the dry ice and hearing protection.

Not much larger than a grain of rice, the dry ice pellets are formed from frozen carbon dioxide. Frozen at minus-109.3 degrees, the dry ice causes material like the sealant to shrink and lose adhesion from the sub-surface, according to the Cold Jet Web site. At the same time, the temperature of the sub-surface causes the dry ice to convert back into carbon dioxide gas or "sublimate." As the dry ice pellets sublimate, only the removed material remains.

With the blast pressure adjusted to 3.5 pounds per minute, the dry ice pellets remove only the sealant and don't affect the paint, Mr. Long said. Dry ice blast machines are used often in the southern United States to remove mold spores from walls or other objects without damaging the surface.

Indeed, one Salt Lake City business has used dry ice pellets for a gentler job - removing soot from book covers.

Hill is home of the Ogden Air Logistics Center, which specializes in sustaining aircraft including the F-16, A-10, C-130 and newly arrived F-22A.

Link directly to the article Hill Air Force Base