Dry ice-blasting is a form of cleansing carbon dioxide, in which dry ice, a carbon dioxide solid form, is accelerated in a pressurized air stream and is directed at the surface in order to clean it. An alternative medium for non-abrasive blasting is ice water, known as ice blasting.
This method is similar to other forms of abrasive blasting such as sand blasting, plastic bead blasting, or sodablasting replaced with dry ice as a blasting medium. Dry ice blasting leaves no chemical residue as dry ice sublimes at room temperature.
Video Dry-ice blasting
Method
The blast of dry ice involves pellets at very high speeds. Dry ice pellets are actually quite soft, and much less than other media used in blast cleaning (ie sand or plastic pellets). Once affected, the pellets propagate almost immediately, transferring minimal kinetic energy to the surface at impact and producing minimal abrasion. The sublimation process absorbs large amounts of heat from the surface, producing a shear stress due to thermal shock. It is assumed to improve cleaning because the topsoil of dirt or contaminants is expected to transfer more heat than the underlying substrate and peel more easily. The efficiency and effectiveness of this process depends on the thermal conductivity of the substrate and contaminants. Rapid changes in circumstances from solid to gas also cause microscopic shock waves, which are also thought to help remove contaminants. Dry ice blasting is non-abrasive, nonconductive, and non-flammable. Dry Ice Blasting does not produce any additional waste or secondary contamination such as media and water blasting.
Maps Dry-ice blasting
Tools
The ice used can be in the form of solid or shaved pellets from larger ice blocks. The shaved ice blocks produce a denser, more refined ice medium than a solid pellet system.
Dry-ice blasting technology can trace its roots to conventional abrasive blasting. The difference between an abrasive-blasting machine and a dry ice-blasting machine is how they handle the explosive media. Unlike sand or other media, dry ice is commonly used at its sublimation temperature. This means that the pressurized hopper system has the potential to cause harmful pressure (see dry ice bombs). Other differences include a system for preventing ice from the formation of jam-like snowballs, and different materials to allow operation at very low temperatures.
A two-hose dry ice coating was developed before a single hose system. This approach is very similar to a suction-feed abrasive explosion system. The compressed air is sent in one hose, and the ice pellets are sucked out of the second hose by the venturi effect. Compared with a single hose system, a two-hose system provides less powerful ice particles (about 5% for a given air supply). For the amount of compressed air provided, the two-hose system can have fewer vertical distances between the engine and the applicator. For most systems currently available, this limit is more than 25 feet. Two-hose systems are generally cheaper to produce due to a simpler shipping system. This system is rarely seen today because it is less efficient in most applications. Their main advantage is in allowing finer ice particles to be sent to the applicator because the ultimate combination of warm air with cold ice produces less sublimation in the hose. This system allows a smoother surface to be cleaned like a semiconductor.
The single hose technology was developed by Cold Jet, LLC in 1986, and used a single hose to deliver a blast of dry air and ice. Single-hose dry-ice blasters share many of the advantages of a single-hose abrasive-blast system. To avoid potential dangers from pressurized hoppers, one-hose dry-ice blasters make use of fast cycling airlock. A single hose system can use longer hoses than dual hose pairs without significant pressure drop when ice leaves the hose. The extra strength comes with the increased cost of complexity. A single hose system is used if more aggressive cleaning is an advantage. This allows more heavy buildup to be cleaned and allows the buildup to be cleaned faster.
Usage
Dry ice blasting can be used to clean food processing equipment to effectively decontaminate the surface of Salmonella enteritidis E. coli , and Listeria monocytogenes so that these microorganisms are not detected using conventional microbiological methods. It can also be used to clean up some equipment without disassembly and without causing a fire or electric hazard. EPA recommends dry ice blasting as an alternative to various types of solvent based cleaning. Dry ice blasting can clean many objects with different geometries and complexes at once. Because sublimation blast media without dry ice blasting residues are found to be used in semiconductor and aerospace industries.
Security
Carbon dioxide is increasingly toxic starting at concentrations above 1%, and can also replace oxygen that results in asphyxia if equipment is not used in a ventilated area. In addition, because carbon dioxide is heavier than air, exhaust ventilation must be at or near the soil surface to efficiently remove the gas. At normal pressure the dry ice is -78 Â ° C (-108 Â ° F) and should be handled with an isolated glove. Eye and ear protectors are required to use dry dry dry equipment safely. Compared to other blasting cleaning methods, dry ice blasting produces less waste products and does not require blasting media cleaning. The waste product can be swept, emptied or washed depending on containment.
History
The first patent on dry-ice technology is AS. Patent 2,421,753 , published in 1947.
The first patents on the development and design of modern dry-ice blast technology technology were provided to David Moore of Cold Jet, LLC in 1986, 1988 ( US Pat. No. 4,617,064 and US Pat. 4,744,181 ).
See also
- Carbon dioxide cleaner
References
External links
- Blasting with Solid CO 2 Flyer, from Fraunhofer Institute
- Messer Group 2007 article on Dry Ice Blasting (pdf, pp 8-12)
Source of the article : Wikipedia
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