In this article, we examined the history and fundamental principles of air gaging as well as the various styles of air gaging systems in use today. This discussion will focus on the components that comprise a typical air gaging system and how they work together. We also will address the most common air gaging applications used in industrial environments.
Air gages, past to present, either measure flow or back pressure. Integrated air gaging systems are comprised of these basic components: air regulator, amplifiers, tooling, setting masters, connectors, and accessories. Let's take a look at each type of component and then examine various applications.
Components of an Air Gage System
All air gages employ a precision air regulator, which provides consistent air pressure to the amplifier. Depending on the system, this can be as little as 10 psi or as much as 44 psi.
In addition to the air regulator, air gages use various types of tooling that deliver a specific air flow or pressure to the surfaces being measured. The tooling, which can be plugs, rings, or other shapes, is configured and sized specifically for the work piece it's designed to measure. Air tooling is designed with its nozzles recessed, to achieve the appropriate clearance for the air pressure of the system being used and to gain protection against wear or damage to the nozzles. The tooling also features vents that let air escape from the work piece without creating spurious back pressure or restriction of flow.
Moreover, air gage tooling is designed with properly positioned nozzles. For example, two nozzles are needed to measure a diameter. The nozzles are balanced to ensure accurate and repeatable readings, regardless of the skill level of the worker using them. For instance, if a tool should be applied to the work piece radially off-center, the decrease in air flow from the closer nozzle is offset by increased flow through the further one. Hence, the flow and back pressure for the tool as a whole remains constant.
Another common component of the typical air gaging system is an amplifier. Available in several styles, including an air-electronic column, dial-type meters, or flow meter tube, the amplifier provides visual representation of the size being measured, enabling the user to take readings quickly and accurately. Back pressure systems either use columns or dials to display readings; flow systems use flow meter tubes.
If an application requires the operator to make multiple measurements, more than one amplifier must be viewed at a time. However, checking multiple measurement results from several dial readouts can be difficult. To make it easier to compare results, it's recommended that the air-electronic columns or flow meter tubes are parallel stacked, where all readouts line up vertically.
Air-electronic columns also offer a more sophisticated system for multiple-function processing, as well as output of data for printing and for SPC and other data processing uses.
Finally, setting masters are used to calibrate air gaging systems. Depending on the system, one or two masters – usually in the form of discs or rings – are employed. Usually, two masters are recommended for absolute accuracy. (See "Back Pressure Bleed System" in Part I for further explanation.)
Typically fabricated from steel, chrome, or tungsten carbide, masters are furnished to tolerances ranging from class X to XXX. Make sure you understand the lab's relationship with NIST so you'll know whether the lab's masters are directly or indirectly traceable to NIST.
Edmunds, Robert, III. "Putting Air Gages to Work." Edmunds Gages - Metrology World Article - Putting Air Gages to Work. N.p., n.d. Web. 27 June 2017.