pipe compound, and dirt are some of the contaminants that can damage valve
parts and other close fitting parts of downstream devices. In the compressed
air system, hard particles assault equipment and piping. The result is damage to the system. Particles in a compressed air system can:
1.Plug orifices of sensitive pneumatic instrumentation.
2.Wear out seals.
3.Erode system components.
4.Decrease air dryer capacity.
5.Foul heat transfer surfaces.
6.Reduce air tool efficiency.
7.Damage finished products.
Compressed air contaminants combine inside the air system forming sludge. Sludge clogs pipes and valves causing valves to jam. A filter will remove all foreign matter and allow clean dry air to flow freely. Clean, dry air protects the air system, reduces maintenance costs, and increases finished product yields. It should be installed in the line upstream from all working
devices and in such a way that it cannot be bypassed to avoid damage to those devices. The filter capacity should be large enough to handle the required flow of air. In order to properly size a filter for a particular application, the maximum allowable pressure drop that can be caused by the filter should be established.
Construction and Working of Pneumatic Filter
(Refer to Figure 5.5.) Construction of air filter is shown along with its major parts. Air enters from an inlet port and is directed to inside the filter. The compressed air has to pass through the filter element, as there is no other
way to pass out. In this course of air passage, the air comes in contact with the element of the filter and finally after removal of all the impurities from air, the compressed air is directed outside by means of an outlet port.
Moisture present in the air is blocked by the filter and it can be manually drained out by simply operating the manually operated drain plug
1. General-Purpose Filters
General-purpose filters remove harmful water condensate, pipe scale, dirt, and rust from your compressed air system. This prevents corrosive damage to compressed air equipment and finished products. Typically, general-purpose filters are installed upstream of regulators to prevent valve failure. They are also used as pre-filters to oil removing and coalescing filters to ensure high efficiency and long element life in applications such as
paint spraying, instrumentation, and pharmaceutical.
2. Compressor Intake Filter
The first line of defense is the intake air filter, which reduces the bulk contaminant load protecting the compressor from dirt and solids.
3. Coarse Coalesce Filter
A coarse coalescing filter separates large water and oil droplets from the compressed air stream before the coalescing filter. The coarse coalescer also removes large solids.
4. Coalescing Filter
Coalescing filters function in a different way from general-purpose filters. Air flows from inside to outside through a coalescing media.
Coalescing by definition means “to come together.” It is a continuous process by which small aerosols come in contact with the fibers in the filter media uniting with other collected aerosols and growing to emerge as a
droplet on the downstream surface of the media which by its weight is gravitationally drained away. For maximum performance and efficiency, coalescing filters should be preceded by a general-purpose filter.
5. Vapor Filter (Charcoal Filter)
A vapor filter removes organics from the air stream. Organics like taste and odor need to be removed from breathing air systems. In general, industrial applications of vapor compressed air filters remove hydrocarbons and other organic chemical vapors from the air system. Depending on the airflow, vapor filters need to be replaced every few months because of the effectiveness of the activated carbon degrades as it absorbs.