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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.

Maintaining Adequate Airflow

Prevent and Eliminate Air Supply Restrictions
Common causes of restrictions:

  • The air supply hose is too long (>20 ft.) or there is more than one coupler.
  • The ID of the hose is too small for tool PSI/SCFM requirements.
  • The air connections or fittings have an ID that is too small.
  • Too many air connections or fittings are being used.
  • When an inline filter is being used, the unit may be too small, or the filter element may be plugged.
  • When an inline regulator is being used, the unit may be too small, not adjusted properly, or defective.
  • The air supply hose, air fitting, air tool inlet, or air tool exhaust may be plugged.
  • If the air tool has a speed regulator, it may be closed.
  • Insufficient air supply or drop-line diameter (ID) may be too small for the air tool PSI/SCFM requirements.
  • Coupler/plug should have maximum flow to eliminate air restriction to the tool.

Air Supply Hose

  • Use the air supply hose with the correct ID as recommended by the air tool manufacturer.
  • Use the shortest air supply hose possible for the task being performed.
  • Longer air supply hoses (>20 ft.) require larger IDs to compensate for line pressure drop.
  • Coiled air supply hoses appear much shorter than they actually are. When using a coiled hose, make sure that the ID is large enough to compensate for the length (see Figure 9).

Pneumatic Tool Startup Check List

  1. Examine the pneumatic tool before attaching the air hose.
    • The pneumatic tool should not be operated if any parts, such as the muffler assembly and guards, are missing; doing so will cause the tool to operate improperly.
  2. Check the air pressure at the regulator/filter if there is one:
    • The tool will not operate efficiently unless the air pressure at the tool is 90 PSI at the proper SCFM while under load.
    • Never operate the tool at a higher PSI than recommended by the manufacturer. This will cause premature tool wear and may be dangerous to the operator.
  3. Examine the air hose:
    • If there are tears or if the connections are loose, the hose should be replaced. if the hose is damaged or broken, a serious injury could result.
    • Hose length should be as short as possible and not exceed 20 ft. For every additional 20 ft. of hose length, the air pressure drops by approximately 50 percent.
    • Do not use a coupler to increase hose length; each coupler equates to an additional 15 ft. of hose length, thereby reducing air pressure and SCFM.
    • When the tool is connected to the air line, check for air leaks in the hose and coupler/plug.

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


Information provided by Saint-Gobain Abrasives, Dynabrade Inc., and U.S. Dept. of Energy.

Pneumatic Tool Preventive Maintenance


Provide a Good Air Supply:
  1. Reduce or eliminate condensation (moisture) from the air supply by using:
    • Water traps and drains
    • After-coolers
    • Refrigerated air dryers
  2. Prevent debris from entering the air motor:
    • Filter the air.
    • Keep the air inlet connections, plugs, and couplers clean, free of dust and debris.
    • Keep exhaust mufflers and elements in place. Muffler elements provide a barrier that prevents dust from being pulled into the air motor.
    • Do not use compressed air to blow off the tool; this could force debris into bearings.
    • Do not remove exhaust mufflers/elements to use as blowoff tools.
  3. Lubricate the air motor:
    • Use an automatic lubricator to supply the correct weight and amount of air motor oil if the environment permits it. If it does not, then manually lubricate tool (two to three drops throughout the day) directly into the air inlet, for example, at startup, morning break, lunch, afternoon break, and end of shift. Note: The muffler assembly should be removed during this process so that the oil will not clog it. This should be done in an enclosed area so that the exhausted air will not recirculate into the plant and cause finishing issues.
  4. Eliminate any blockage of airflow, in or out:
    • Keep the tool's air inlet clear of any debris.
    • Clean or replace exhaust muffler elements as needed. Never remove or operate tool without one.
  5. Lubricate gears, sleeves, bearings, and sliders:
    • Use the manufacturers-specified lubricant and apply the suggested amount at the recommended interval. Note: This is usually found in technical support literature, such as tool manuals and parts pages.
  6. Use the tool, accessory, or related product as specified by the tool manufacturer:
    • Adhere to the specified maximum operating air pressure.
    • Adhere to the specified maximum operating RPM for all tools and accessories, such as grinding wheels, mounted points, cutoff wheels, abrasive sanding discs, and backup pads.

Information provided by Saint-Gobain Abrasives, Dynabrade Inc., and U.S. Dept. of Energy.

The Perfect Air Hose

  • The ideal hose ID is ⅜ in.
  • The air hose should be as short as possible and not exceed 20 ft. in length. For every additional 20 ft. of hose length, the air pressure drops by approximately 50 percent.
  • Never use couplers to extend the length of the hose, each coupler equates to adding 15 ft. of hose length.
  • The air hose can be either rubber or synthetic, the attributes are:
    • Rubber
      • Durable
      • Wear-resistant
    • Synthetic
      • Lightweight
      • Flexible
      • Ergonomic
    • Connections on a hose should be maximum-flow couplers and plugs that will eliminate airflow restrictions.


    Information provided by Saint-Gobain Abrasives, Dynabrade Inc., and U.S. Dept. of Energy.

About the Author

Dennis Walsh

Sr. Corporate Application Engineer

1 New Bond Street

Worcester, MA 01615

(800) 551-4413