Senin, 03 Maret 2008

Dry Ice Blasting - Foundry Industry's Innovative Cleaning Method

by Russell Murray

Dry ice blasting (also known as CO2 blasting) in the foundry industry provides some excellent benefits. That is because some of the cleaning challenges including the cleaning of molds for metal, plastic or rubber castings can be daunting. Here are a couple of examples of cleaning challenges:

- core boxes and core machines covered with sand, binder or carbon build-up
- plastic and rubber molds and vents caked in mold release and grease and residues

Traditional methods of cleaning have included hand scraping and scrubbing, use of chemicals and sand blasting. The drawbacks of these methods include the following:

- Labor intensive - Typically, items need to be taken off-line and cleaned.
- Downtime - The extensive time required to effectively disassemble, clean molds and than reassemble, results in costly production losses.
- Mold wear - Sand blasting can etch or wear down mold surfaces.
- Grit entrapment - Sand blasting can become entrapped and become difficult to remove.
- Liability - The use of chemicals poses safety hazards.
- Cost - Chemicals are expensive. Plus, they become an additional contaminated waste disposal cost.

The Dry Ice Blasting Process

Dry ice blasting is a relatively new cleaning process using solid CO2 pellets (known as dry ice). It is primarily used for industrial use in a variety of applications. The pellets sublimate (convert directly from a solid blast pellet to a vapor (CO2) leaving no residue.

The process involves propelling dry ice particles from a blasting gun at supersonic speed to impact and clean a surface. The particles are accelerated by compressed air, similar to other blasting systems.

The micro-thermal shock (caused by the dry ice temperature of -79� C), the kinetic energy of dry ice pellets and the air pressure break the bond between the coating and the substrate. It pops off the coating from inside out and the air stream removes it from the surface.

Dry Ice Blasting: The Perfect Solution

Dry ice blasting addresses each of the major issues regarding mold cleaning and produces the following benefits:

- Benefit #1 - Reduced labor hours. The dynamics of cleaning with dry ice can dramatically reduce time requirements. The actual cleaning is faster. There is no need for disassembly/reassembly of equipment.

- Benefit #2 - Reduced downtime through cleaning in place. Any cleaning labor for scrubbing and scouring is eliminated. Also, the time required to move equipment to a staging area for cleaning is eliminated. Production gains can be extremely significant.

- Benefit #3 - Reduced equipment damage. Dry ice pellets do not chisel away contaminants as sand blasting does. Instead, CO2 pellets penetrate the contaminant, fracture into small particles when they impact the base material and instantly sublimate. The contaminants are removed in a lift and flush action. Also, CO2 cleaning can be performed regularly; thereby, virtually eliminating the problem of completely plugged vent holes.

- Benefit #4 - Elimination of grit entrapment. Since the dry ice pellets returns to a vapor upon contact, there is no cleaning material that could be entrapped in the equipment.

- Benefit #5 - Reduced liability. Chemical solvents can be eliminated removing the dangers they pose to workers. Also, dry ice poses no risk around electrical circuits.

- Benefit #6 - Reduced costs. Dry ice sublimates eliminating a secondary waste stream thus minimizing waste disposal costs. Also, the cost of solvents is eliminated.

About the Author

Russell Murray is Director of RSG Technologies, a dry ice blasting equipment provider and also offering dry ice blasting rental equipment.

Tidak ada komentar: