The air leaving a pneumatic system is typically unsuitable for any intended use. Wet, dirty, and incorrectly pressured compressed air can damage downstream equipment because it is wet, dirty, and at the wrong pressure. Compressed air is conditioned using an FRL (Filter, Regulator, Lubricator). The FRL system consists of three separate units that carry out different phases of conditioning: filtration, regulation, and lubrication. It does not always come as a single unit, even though it is frequently used that way. An individual regulator or a filter-regulator unit is used. Modern pneumatic systems with self-lubricating equipment rarely use lubricators.
Filter
For downstream equipment to last as long as possible, proper filtration is crucial. Typically, filters are installed upstream of other conditioning equipment since filtration is the first stage. The system operates by creating a cyclonic action in the incoming air. Heavy contaminants are deposited at the bottom of the bowl as a result. The compressed air is then forced through a filter mesh of sufficient size, effectively removing contaminants. Depending on the type of filter, accumulated contaminants and moisture are removed in either manual or self-draining ways. When draining manual filters, the machine must be turned off before the filter can be drained, but with self-draining filters, the filter is drained automatically by a float-controlled valve. In terms of filtration level, there are three types of filters.
A general-purpose filter that removes dust, oil, and water as well as particulate matter and water Oil removal filters that remove both oil and vapor Filters that remove both oil and vapor as well as dust, oil, and water
Pressure regulator
In this system, the air pressure that is supplied to downstream equipment is regulated. Fluid power applications such as blow guns, pneumatic cylinders, and air logic valves require this unit. There are two types of regulators: pressure-reducing valves and regulators. A regulator’s control knob is used to set the desired pressure for an application. The knob adjusts the internal diaphragm and needle valve assembly to ensure the correct output pressure. There are two types of regulators: relieving and non-relieving. Regulators that relieve pressure can be adjusted from high to low pressures. Overpressure downstream will be exhausted when necessary by these regulators. The downstream pressure cannot be relieved by non-relieving regulators, however. It is therefore necessary to use other methods of releasing trapped air. There are two types of regulators: single regulators and two-in-one regulators.
Lubricator
A micro-fog lubricator and an oil-fog lubricator are both types of lubricators. In oil-fog lubricators, oil is directly deposited into the air stream as relatively large droplets. Micro-fog lubricators, however, first atomize oil droplets to about 2m in size before introducing them into the airflow. To reduce the friction generated by moving components, lubrication is necessary. To extend the life of air-driven equipment such as valves and air motors, lubrication is necessary. In most cases, pneumatic systems do not require lubricators, since they are self-lubricating.
Size of the filter element
As the filter element size increases, the level of filtration increases. The smaller the filter element size, the greater the level of filtration required. All particles larger than 40m would be filtered out by a 40m filter. In addition to filter size, pressure is also affected by filter size. The finer the filter, the greater the pressure drop. Filter sizes should therefore be selected based on the acceptable pressure drop for an application. A filter’s manufacturer usually specifies its expected pressure drop. Using a higher-power compressor can compensate for applications requiring both high pressure and maximum filtration. Filter elements can be classified according to their size and level of filtration as follows:
Generally speaking, these filters come in sizes of either 40m or 5m. The size 40m filter effectively removes particulate matter and 90% of water. Particulates and water in compressed air are removed by a 5 m-sized filter.
Filters for oil removal (coalescing): These 0.3m-sized filters remove oil, water, and particulates. A filter of this type is necessary for applications where oil is a damaging contaminant, such as spray painting and breathing apparatus.
Filter for vapor removal: The size of this ultra-fine filter is 0.01m. Besides particles, oil, and water, it is also capable of filtering out vapor.
For applications such as food and pharmaceuticals that require high levels of purity, activated carbon filters are used. As well as removing odor and taste, they are also capable of removing impurities.
Pressure rating
Different applications require different pressures of compressed air. As soon as the appropriate minimum operating pressure is determined, it is crucial that air is supplied at constant pressure, regardless of fluctuations in the upstream pressure. The standard range of pressures regulated by regulators is 0.05 – 1Mpa. In general, they are available at operating pressures of 0.1, 0.2, 0.4, 1.0, and 1.6Mpa. It is the maximum pressure above which the regulator cannot operate, or it may be damaged. A regulator’s pressure ratings should be known before selecting it for a particular application.
Port size
An FRL unit’s flow rate is determined by its port size. Selecting an FRL of a port size is dependent on the flow rate required for a process or system. In general, the larger the port side of the selected unit, the higher the flow rate required. Gas flow factor formulas can be used to determine the port size for a given flow rate.
Lubricator type
In heavy-duty applications, such as cylinders with heavy loads and single tools, oil-fog lubricators are best suited. For level runs and short distances, they are ideal.
On the other hand, micro-fog lubricators are ideal for complex, multi-component systems. Long distances and non-level runs are best suited to them.
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