Abrasive is consumed over time as it cycles through the blast machine and abrades the work. Cast steel shot and grit, perhaps the most common abrasive media used in centrifugal blast machines, becomes smaller and more fractured each time it impacts the work and recycles through the blast machine reclaim system and abrasive hopper. A low abrasive level in the storage hopper means the shot does not have to wait in line. In other words, the shot will cycle through the equipment more frequently as compared to a high or properly filled abrasive hopper. The media simply breaks down faster when proper abrasive levels are not maintained. So you get “less bang for your buck”. More cycles per hour means the abrasive that is doing the work breaks down faster. In a full hopper situation the abrasive recycles less and lasts longer.
Proper abrasive levels mean that the size distribution of abrasive cleans the work faster and more effectively. The proper size distribution of shot means there is a mixture of new larger media with smaller media particles. This mixture allows for the best coverage or scattering of impacts on the work. When a proper distribution of media is thrown at the work, the cleaning is much more effective which in turn allows for faster line speeds and consequently higher productivity. When abrasive levels are low the distribution of particle sizes is tilted to the smaller end of particle sizes. The absence of larger particles effects the size distribution resulting in slower line speed or decreased productivity. A tell tale sign that abrasive levels are not proper is when the operator notices it is taking longer to clean the work. Simply put; running the machine faster and therefore for less time decreases overall machine operating cost.
An operating mix that is heavily weighted to fine particles and abrasive dust is more abrasive to the blast equipment than a properly maintained operating mix associated with full media hoppers. Fine particles and dust act less like high velocity media impacting the work and more like sandpaper working to wear the blast wheels and reclaim system in the equipment. In a low hopper condition it will take longer to clean thereby allowing more time for the abrasive dust to work on the machines wear components, particularly with the blast wheel.