allow the excess downstream load- or headinduced pressure to be exhausted. Nonrelieving regulators, when similarly adjusted, will not allow the downstream pressure to escape. The trapped air will need to be released by some other means, for example, by operating a downstream valve. Downstream equipment flow and pressure requirements must be determined to properly size the correct regulator for the application. Similar to filters, manufacturers offer flow characteristic charts for their products to help chose the correct regulator. A lubricator adds controlled quantities of oil or other lubricant into a compressed air system to reduce the friction of moving components. Most air tools, cylinders, valves, air motors and other air driven equipment require lubrication to extend their useful life. The use of an air line lubricator solves the
problems of too much or too little lubrication that arise with conventional lubrication methods, such as either grease gun or direct oil application. Once the lubricator is adjusted, an accurately metered quantity of atomized lubricant is supplied to the air operated equipment, and the only maintenance required is a periodic refill of the lubricator reservoir. Adding lubrication to a system also “washes away” compressor oils that travel through the system in vapor form. Mineral oils added to the system prevent synthetic compressor oil build-up on system components. When lubricators are not used in a system, a coalescing filter should be installed to remove compressor oil aerosols. Lubricators are sized by downstream flow requirements, and an analysis of air flow use must be made to accurately determine lubrication rate. After determining how much air flow is needed, a lubricator can be chosen, and once again, manufacturers’ curves will be similar to the one shown.
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FLUID POWER WORLD
The selection of an FRL assembly is based mostly on the flow rate required, and the size of the component bodies reflects this. Other than the required flow rate, construction material and component options are also considered. Often in pneumatic systems, components are sized to match connection ports on other components. For example, if your valve manifold inlet port is ¾-in. NPT, then choosing ¾-in. ports for your FRL might seem like the easy choice. However, not all filters, regulators and lubricators are created equal, and their selection should be based on the flow characteristics of the assembly, rather than port size alone. By referring to the flow charts provided by the FRL manufacturer, you can size the assembly to match the flow required. An important consideration of selecting FRL size is the flow characteristics of the regulator. Because the regulator limits and controls downstream pressure, the outlet pressure plays a critical role in the dynamic flow capability of the whole FRL assembly. If outlet pressure rises or is regulated
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too close to inlet pressure, the FRL will start to reduce flow, or even stop flowing altogether. On top of flow limitations possible with the regulator, you must calculate the flow of the filter and lubricator. Flow reductions are cumulative, as every inline component can reduce flow further, which emphasizes the importance of avoiding arbitrary FRL selection based on port size alone. Construction material of the FRL components also plays a role in selection, and some of the metals and plastics in their construction might not be compatible with the ambient air conditions of their installation location. For example, the standard polycarbonate bowl construction of most filters are not appropriate for exposure to aromatic chemicals, and nylon should be used instead. Finally, FRLs are available with many options, such as pressure gauges, drains, pressure switches and check valves, to name a few. If you’re unsure what you need, contacting the manufacturer will put you in touch with someone to help with your decisions.
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Fluid Power World Handbook 2016