Metal powders are widely used in a number of production processes. These include additive manufacturing, brazing, cold spray, filters and foams, metal injection moulding, and plasma and thermal spray operations. Metal powders also have application in co-deposition, hot isostatic pressing, laser cladding, and the production of diamond catalysts and solid oxide fuel cells. Within these operations, conveying metal powders is often a critical part of the production process.
Metal powders are metals or metal alloys in powdered form. Common forms include primary metals (i.e., stainless steel, manganese, etc.), primary alloys (i.e., cobalt alloys, copper alloys, etc.), binary alloys (i.e., iron-chromium, iron-nickel, nickel-copper, etc.), and others. Many grades are available in a variety of particle sizes. Depending upon the metal and grade, the bulk densities of metal powders can vary significantly.
Conveying metal powders: issues to be addressed
Key issues to be addressed when conveying metal powders include the following:
- Containing material to prevent spillage and dusting during transfer
- Avoiding cross contamination of the powder during transfer
- Avoiding explosion risk
- Protecting workers from inhaling hazardous powder
- Easy cleaning of the conveyor during changes of material
- Having the ability to transfer powders with high bulk densities
- Having to convey material in an inert atmosphere
These issues can be addressed in varying degrees by both mechanical and pneumatic conveying systems. However, pneumatic systems may be challenged when it comes to moving metal powders of high bulk density.
Conveying metal powders: mechanical conveying solutions
Mechanical conveying solutions which have proven effectiveness in conveying metal powders include the following:
- Bucket elevators
- Aeromechanical conveyors
Bucket elevators offer a good way to transfer significant amounts of metal powder vertically and horizontally. The TipTrak™ line of positive discharge elevators from UniTrak offers the following advantages:
- Full containment and zero spillage of material during transfer. TipTrak™ Monocoque (fully sealed and gastight) units and TipTrak™ PEC (fully enclosed) units safely contain metal powder dust, while the fully interlocking bucket assemblies assure zero spillage of material.
- No cross-contamination of material during transfer. The fully sealed and fully enclosed designs of TipTrak™ Monocoque and PEC units protect material as it transits through the conveyor.
- Reduced explosion risk. TipTrak™ Monocoque elevators comply with the requirements of ATEX Zones 1, 2, 21 and 22 (metal powder falls under ATEX zones 20-22; TipTrak™ Monocoque elevators comply with the requirements of ATEX zones 21 and 22). These elevators have a number of explosion-proof features, including anti-static drive assemblies, explosion-proof drive motors, explosion relief vent panels, and more.
- Trouble-free transfer of high bulk density material. Unlike pneumatic conveyors which can have difficulty in moving high bulk density powders, TipTrak™ elevators have the power to easily move these difficult-to-handle powders.
- Conveying material in an inert atmosphere. By virtue of their fully sealed and gastight design, TipTrak™ Monocoque elevators can be charged and operated with an inert gas.
Powderflight aeromechanical conveyors from UniTrak offer a good way to move moderate volumes of metal powders. Operating on the principle of a fluidized airstream, these mechanical units mimic pneumatic conveyors with their mode of operation. The fully enclosed tube of the conveyor protects powders from cross-contamination while eliminating dusting into the surrounding environment. Complying with ATEX Zone 22, these conveyors can significantly reduce the explosion risk associated with moving hazardous metal powders.
If conveying metal powders is an aspect of your operations, UniTrak can help. With close to 50 years’ experience and thousands of installations worldwide, we can bring our expertise to bear on your conveying challenges. To find out more about how we can assist you, please contact our sales team directly.