For abrasive blasters there’s a “sweet spot” in their metering valve which provides them the optimum flow of abrasive which then delivers the greatest efficiency and productivity. However, this sweet spot is debated among professional blasters and there seems to be two camps. One camp believes extra abrasive impacting the surface helps speed up the process and results in a faster profile. The other camp thinks it doesn’t matter.
So which camp is right?
Well, it’s a fact that a sweet spot does exist. This fact is known by realizing that too little or too much abrasive lowers efficiency; which can be tested.
Metering Too Much Abrasive
When the metering valve is open too wide – valuable, costly abrasive flows in greater than necessary quantities and is essentially wasted. This lowers efficiency which cuts into your profits.
But what about the claim that extra abrasive hitting the surface speeds up the cleaning? The truth is that too much abrasive in the airflow slows the exit velocity at the nozzle and therefore, particle impact upon the steel is diminished as well. This is inefficient.
Metering Too Little Abrasive
When the valve releases too little abrasive, the particles won’t pack enough punch to clean the surface at the rate it might have had more abrasive been in the stream.
Slowing the blasting rate reduces overall output, wastes both time and resources such compressor fuel, wear and tear and electricity costs. The system is not being used at its ideal capacity. This results in the overall project taking longer to complete. This too is inefficient.
The Ideal Mix Of Abrasive
Dialing in on the sweet spot requires more observation than technical specifications. Once the dead-man trigger is on, inspect how the abrasive exiting your nozzle appears.
If the air flow displays a lot of color, it’s probably true that there’s too much abrasive in the mixture. We recommend dialing your meter back some. An optimal mix of air and abrasive should only be slightly visible, with a mere hazy color appearing in air stream.
Using these visual cues will help you optimize your metering of abrasive and therefore your blasting efficiency as well.