The right inline air compressor filter solution - Atlas Copco USA

Particulates: Particulates in compressed air are small pieces of material like dust, dirt, and/or pollen, as well as loose metal pieces. Depending on the sensitivity of your application and or process, contact with particles can be damaging to the end product. They can also cause delays in production and quality control issues, as well as unsatisfied customers.

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Aerosols: Aerosols consist of small droplets of liquid found within a compressed air system, especially in oil-injected machines. Aerosols are created from lubricant. Therefore, oil used in the compressor can be harmful to both products and people if not treated properly.

Vapors: In a compressed air system, vapors consist of lubricants as well as any other liquid that has converted to a gas. Such vapors require a special carbon activated filter in order to be removed from the system.

Now that we have a better understanding of the contaminants above, let us take a look at what types of filtration methods are used.

There are three main mechanisms utilized in dry particulate filters to remove solid particles from compressed air. These three forces contribute to the overall efficiency of the filter.

Inertial Impaction: Inertial impaction is a process where particles that are too heavy to flow with the compressed air stream get trapped in the fiber media of compressed air. The larger the particles are, the easier it will be to separate them.

Interception: Smaller particles can follow the air stream. However, if the diameter of a particle is larger than the gap of the filter media, it will get caught by the filter media. This makes it easier to eliminate larger particles than smaller ones.

Diffusion: Diffusion happens when small particles move erratically throughout the surface, instead of following the compressed air stream. This irregular movement path is caused by the particles colliding with other gas particles, an occurrence called Brownian movement. Since the particles have a free-range of motion, it is more likely that they become intercepted and removed by the filter media. Through diffusion, separation of smaller particles is easier than separating larger ones. 

Two types of filters are used to remove aerosols and vapor. Coalescing filters are utilized to remove liquids as well as some particulates, while vapor filters use adsorption to remove vapors from compressed air.

Coalescing: Coalescing filters are used to remove aerosols and particulates, but are not effective in the removal of vapors. The coalescing process consists of bringing small droplets of liquid together in order to form large droplets. As the droplets increase in size, they fall from the filter into a moisture trap, resulting in a cleaner and dryer compressed air stream.

Adsorption: Adsorption is a chemical process used to remove gaseous lubricants or vapors. This process involves vapors bonding with the surface of the media (adsorbent). Activated charcoal filters are commonly used since they attract oil vapor.

As the oil vapor covers the surface of the activated charcoal over time, it is essential to change the filter before it becomes saturated. If not, this would lead to a breakthrough of the oil into the air system.

It is also necessary to use a dust filter after the activated charcoal filter. This is because small charcoal particles could break out and enter the air stream.

To assess the potential damage oil can cause to your compressed air system, it's important to understand your equipment and basic industry requirements. If your industry has strict health codes and or your equipment is sensitive to oil / vapor exposure, it is crucial to use proper filtration.

Let’s take a closer look at lubricants and understand the effects they can have on your end product. Similar to particulates,lubricants can enter your compressed air system from ambient air as well as from the compressor itself. Facility operations, like a motor exhaust, release hydrocarbons like oil aerosols into the ambient air, which can compromise air quality and cause equipment failure.

Oil injected air compressors will also release lubricants into the compressed air system, resulting in increased operational and maintenance costs. Industries such as electronics and semiconductor are especially exposed to lubricant contamination, which can result in product loss, missed deadlines and unsatisfied customers.

FRLs, such as this ASCO Numatics 651/652/653 Series air preparation manifold, are often the forgotten parts of a plant’s pneumatic system, but they have a big impact on machine efficiency and productivity.

FRL 101:The Basics

FRLs provide point-of-use control of air pressure and cleanliness in pneumatic networks. They are located upstream from the directional control valves, manifold, cylinders, and actuators. Virtually every pneumatic device requires some type of air preparation and pressure control.

Today’s FRLs use modular components that are placed in-line in one assembly. Typically, after the shutoff valve, the filter is the first component in the air line; then the regulator; and finally, the lubricator.

Contact us to discuss your requirements of inline compressed air filter. Our experienced sales team can help you identify the options that best suit your needs.

Filters are available in different varieties to let them remove oil, particulates, water, and odors from the compressed air. Particulate filters remove particles from the air stream and are available in pore sizes of 5, 25, and 40 microns. Coalescing filter pore sizes are smaller, ranging from 0.01 to 1.0 microns, to extract moisture and oil drops that can impact pneumatic performance. Adsorption filters, although rarely used, employ activated carbon to eliminate odors and residual oil vapor in the air.

Lubricators are installed to introduce small amounts of clean oil into the air stream. The oil cleans and protects downstream components from wear and corrosion.

Regulators set the incoming air pressure to the desired level for the cylinders and actuators operating machinery. Because pressure in the plant’s air drops frequently and varies, consistent pressure regulation is essential to ensure appropriate machine reaction times and speeds. The regulator is typically set slightly below minimum plant air supply pressure. Regulating to the correct pressure for the application also allows users to optimize energy consumption.

The ASCO Numatics 653 Series of air preparation products from Emerson lets users power more products from the same Filter-Regulator or Lubricator (FRL), or reduce pressure drop across the system, both of which can save energy and costs.

FRLs: Six Key Criteria

There are six key criteria engineers must consider to ensure they get the best FRLs needing the least maintenance:

The operating environment. The operating environment makes a big impact on which FRL is selected. It’s essential that the FRL’s components use appropriate materials and construction. First, will the assembly be located indoors or outdoors? If outdoors, consider the range of the operating temperature. Extreme hot or cold conditions requires components with high- or low-temperature ratings. Oil rig components and other exposed to the oceans must withstand saltwater corrosion. If indoors, caustic or chemical environments demand the FRLs use different types of seals or are mounted inside protective enclosures.

Proper pressure specification. Is your plant’s air-supply pressure a normal 125 psig or less? Or is it a high-pressure system? Most FRL components are designed to handle pressures up to 145 psig in standard sizes and configurations. However, some plant air supplies are rated at up to 250 psig. That means a high-pressure regulator and filter should be specified. Some new FRLs handle up to 300 psig.

Lubrication. Do your pneumatics require a lubricator? If you decide your machine’s pneumatic valves and cylinders require lubrication, a lubricator will be needed in the FRL assembly. The lubrication also acts like a detergent in the air system. As you continuously lubricate, the clean oil washes out contaminants that would cause the valves and cylinders to stick. If using this approach, a 5-micron particulate filter is usually sufficient.

If the pneumatics do not require lubrication, both particulate and coalescing filters are suggested. The coalescing filter helps remove the contaminants the lubricant would wash out.

Shutdown valves. Lockout valves are frequently required on a machine’s pneumatics. These components vent the air off equipment and are typically operated manually or electrically. When activated, these valves ensure no components downstream of the FRL will receive air. The objective is to exhaust air from the machine if there is a mechanical jam or if an operator enters the area.

Shutoff or isolation valves (low-flow exhaust) are installed on the upstream side of the FRL assembly while lockout valves (high-flow exhaust) are installed downstream.

Lockout valves come in quick-exhaust or soft-start quick-exhaust versions. With today’s modular architecture, it is easy to add shutoff, isolation, and/or lockout valves to the FRL assembly. Adding these devices is an application-specific decision and typically dictated by machinery components.

Correct air flow. The air flow rate is an important consideration in selecting FRL components. Engineers should ensure the FRL is properly sized to match the required machine air flow. Accurately calculating a machine’s air-flow requirements is complex and laborious for most equipment designers. Flow is determined by the air volume needed to fill and exhaust the pneumatic component and required response times.

For example, if a machine has a pneumatic cylinder with a 2-inch bore and 24-in. stroke, and you want to extend the cylinder through its entire stroke in 5 sec. at 60 psig, it requires a flow rate of about 2.5 scfm. However, if the same cylinder under the same conditions must travel through its stroke in 100 msec., the flow rate jumps from 2.5 to about 135 scfm. This does not include valve-to-cylinder tubing.

The FRL flow rate depends on the inlet pressure and pressure drop. Flow rate increase is directly proportional to increases to inlet pressure and/or pressure drop (known as ∆P). The FRL’s flow rate must be sized to peak demand, not average or mean demand.

Generally, equipment engineers size FRLs by matching their port size to the valve manifold’s or cylinder’s port size. Some simply rely on past experience. Accurately calculating the FRL’s air flow may take more time and effort but it will make the pneumatics more cost effective and efficient.

Most manufacturers offer FRL series with overlapping port sizes. Although each larger series offers significantly more nominal flow rates, changing port size within a series minimally alters flow capacity and can be more convenient for plumbing purposes.

Filter replacement. Our experience is that filter elements in a plant’s pneumatic system do not get replaced at the intervals required to maintain peak performance. This can lead to inefficient machine performance and possible downtime. Often equipment operators don’t know filter maintenance is required, so reliance on preventative maintenance programs is encouraged. Some FRLs have visual or electronic ∆P indicators or system pressure switches to alert maintenance personnel. In addition, today’s FRLs use modular components that make maintenance easier.

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