The impact of compressed air on pneumatic tools and abrasive performance

Figure 1: Two controlled evaluations were conducted on 1018 carbon steel flat stock to show the direct impact pneumatic air has on abrasive performance.

A compressed air system must be able to deliver an adequate volume of air in standard cubic feet per minute (SCFM) increments and maintain the proper operating pressure in pounds per square inch (PSI) to supply all compressed air requirements for a facility and its related applications. Knowing the proper requirements for optimizing the compressed air system is essential to meet all air needs.

There is a common misconception that if the line pressure (PSI) is high, all air requirements will be met. This is false ‒ in fact it is a combination of both PSI and SCFM. Not only does the size or horsepower of the compressor make an impact, several other critical factors have a direct effect. These include the air receiver tank capacity, main trunk line diameter, drop-line diameter to manifold, plug/couple type, inside diameter (ID) and length of hose to tool, and whether the facility has a loop system.

A proper air system is important for delivering optimal abrasive performance when using a pneumatic tool for grinding or sanding. Pneumatic tools have an air requirement to operate at maximum efficiency under load, which is 90 PSI with the proper SCFM for the tool being used. If one or both criteria are not met, either the grind cycle/takt time will increase, removal rates will decrease, or both will occur, causing lower performance and higher costs.

To prove that PSI has a direct impact on abrasive performance, two controlled evaluations were conducted on 1018 carbon steel flat stock using the parameters shown in Figure 1. (All images are available in the slideshow.)

Test results in Figure 2 show a significant removal difference between the air pressures. This is further demonstrated by the sparks visible in Figure 3, which correlate directly to removal rate; for example, more sparks indicate a greater removal result. Figure 4 shows the percentage improvements and percentage savings difference per PSI, which are significant.

To demonstrate that PSI is not the only factor that has a direct impact on airflow and abrasive performance, a controlled evaluation was conducted with two different coupler/plug assemblies – maximum flow and standard/tapered on a 304 stainless steel weld using the parameters shown in Figure 5.

Three weld removal evaluations were conducted with each type of coupler/plug assembly (maximum flow and standard/tapered) at 90 PSI/43 SCFM to determine the impact of the orifice diameter on cycle time/takt time. The results are shown in Figure 6.

Note that the standard/tapered plug orifice diameter is approximately 35+ percent smaller than the maximum flow one as shown in Figure 7. This difference has a direct impact on tool and abrasive performance, as seen in the stainless steel weld (Figure 8) removal evaluations. The maximum flow assembly removed the weld in less than half of the cycle/takt time.

Providing maximum airflow to the tool optimizes the performance of the abrasives on the tool. Depending on the material being ground, the grit size used, and the abrasive type, the improvement in productivity gained by switching from a standard tapered plug to a maximum flow plug could exceed 100 percent. If using a standard tapered plug, productivity could be reduced by more than 50 percent.

The following suggestions and recommendations can assist in maintaining maximum performance of a pneumatic tool and abrasive.

Figure 2: Test results in show a significant removal difference between the air pressures.

Prevent and Eliminate Air Supply RestrictionsCommon causes of restrictions:

Air Supply Hose

Air supply is critical to the performance of the tool. Without proper PSI and SCFM, the tool will not operate efficiently.