External abrasive storage in abrasive blast cabinets refers to situations where abrasive is stored outside of the blast cabinet. In a direct pressure abrasive delivery system where a pressure pot and the external abrasive storage are used, all the abrasive is removed from inside the cabinet each time it exits the nozzle which allows the use of many different pressure pot sizes. Because the pot is sealed when blasting, it must stop blasting to refill the pot. As you can imagine, running more than one nozzle on any pressure pot means the pot empties faster. When the pot is filled again and re-pressurizing, operation downtime brings production to a standstill. This is why most automated machines use siphon delivery that uses no pressure pot assembly.
The item used to remove the abrasive from the cabinet is normally a pneumatic conveyor and cyclone separator reclaimer. These remove the abrasive, separate the dust from the abrasive and recycle the abrasive over and over without loss of abrasive. The cyclone is the most efficient mechanical separator reclaimer available today and when built correctly is a pneumatic dry centrifuge.
Advantages of External Abrasive Storage
- Dries the abrasive each time it’s used – a must have feature for ultra-fine abrasive
- Aerates the abrasive allowing fine abrasive to flow by doubling the physical volume
- Works well with a pressure pot that makes vapor each time the pot is pressurized
- Allows the use of larger pressure pots for longer pot run times
- Has the lowest abrasive usage of any type of machine other than Wet Blasting
- Better cabinet visibility with true down-draft air movement through the cabinet that is necessary when using fine and ultra-fine abrasives
- Easy operator cyclone efficiency settings allowing removal of the abrasive when the abrasive size is no longer producing the correct surface finish on the part
- Works well with abrasive size that have a low Angle of Repose, fine and ultra-fine abrasive all below 150 mesh in size are good examples
- Allows the use of soda and plastic with many advantages needed for these two types of special application abrasives
Given the list above, you may be wondering why anyone would use anything besides direct pressure with external abrasive storage. Well, unless you have an application that requires direct pressure using external abrasive storage the siphon delivery cabinet, open to atmosphere that doesn’t need to stop and refill a pressure pot every 15 minutes, is faster at the end of the day.
To Sum It Up
When the model application requires direct pressure delivery with external abrasive storage this Media Blast machines are ideal solutions. Keep in mind, if you use a machine model incorrectly the equipment will have a higher cost, increased maintenance and another machine model will have a higher daily production output. Using a direct pressure machine with pneumatic conveyor incorrectly can make some manufactures that only offer pneumatic conveyors very happy with the replacement parts business.