While most folks think this old adage applies only to personnel not being familiar with the OPERATION of machinery, it’s also a reminder that ‘operating it right’ necessarily includes keeping up with regularly scheduled preventive maintenance. This includes pretty much anything with moving parts and components in a system that fluids might flow through. But today, I’m going to focus on certain parts of a typical industrial compressed air system. Failing to change oil in an industrial air compressor, for example, will “let the smoke out” just as fast (and sometimes faster) than anything a day-to-day operator can do to it.
The folks at Compressed Air Challenge are dedicated to (and this is right from their website) “helping you enjoy the benefits of improved performance of your compressed air system.” Their “Best Practices For Compressed Air Systems” stresses the importance of:
Proper maintenance as a means to ensure operational efficiencies and systems reliability.
Continuous checks for preventive maintenance items.
Implementing a detailed system maintenance program, including schedules of required maintenance, and records of its performance.
And that’s just from the introduction. It goes on to list the major components that should be included in this program: the compressor, heat exchanger surfaces, lubricant, lubricant filter, air inlet filter, motors, belts, and air/oil separators. The steps for properly maintaining these components range from standard housekeeping practices, to mechanical operations that are typically performed by trained operators, to services that might be best handled by qualified manufacturer’s representatives:
Cleaning: The air compressor itself, and any heat transfer surfaces, have to be kept clean & free of contaminants. Moving parts generate heat, and dirt, scale, corrosion, etc. are essentially insulation that’ll prevent that heat from being dissipated.
Lubrication: It’s critical to service the lubricant & any lubricant filtration per the manufacturer’s specifications. Again – not doing this is one of the best ways to “let the smoke out” of any machine.
Power transmission components: Regular inspection, including alignment checks, of belts & couplings is probably the 2nd best way (next to lubrication maintenance) of keeping the moving parts of the air compressor, and its drive, in good working order.
Intake filter: An air compressor will try to compress anything that’s drawn in with its air intake. If it pulls in particulate, that can damage internal surfaces, especially moving parts with tight tolerances to each other, like pistons & cylinders, scrolls & casings, rotary screws & chambers, impellers & volutes, etc., depending on the type of compressor. Plus, anything that makes its way into your compressed air header will also have a chance to foul up your pneumatic tools & devices, and get on anything that you use compressed air to blow off.
Motors & drives: Simply put, if you can’t turn the shaft of the compressor, it won’t compress any air. Periodic checks of electric motor windings, bearings, ‘soft start’ capacitors, phase converters, etc., are among the basic maintenance items that operators can inspect.
In addition to the compressor itself, the air distribution system should be properly maintained as well:
Filtration: The intake filter is there primarily to protect the compressor. Many times, the aforementioned tight tolerances between the moving parts in the air end will result in (hopefully) small amounts of particulate being carried over into the compressor discharge. There’s usually a main particulate filter, along with a dryer (for entrained moisture – the intake filter won’t do anything about that either), and possibly even a coalescing filter for oil & oil vapor. Good engineering practice calls for servicing those filters when the differential pressure across them reaches a certain value (5psid is a common one), but those elements, being relatively inexpensive, can also be replaced during regularly scheduled downtime as well.
Leak detection & repair: Leaks make the compressor run harder, so any reduction in the amount of compressed air leakage will, by definition, reduce the wear & tear on the compressor. EXAIR makes it easy to find them with the Ultrasonic Leak Detector.
Filtration Part 2: Don’t forget about contaminants that can enter the system downstream of the compressor, too. Iron pipe headers are subject to internal corrosion, which can result in rust particulate. Environmental pollution can enter if flanges or fittings are broken & made up during maintenance. Point of use filtration, like EXAIR Automatic Drain Filter Separators, can keep this debris (and any moisture that’s not removed by the compressor’s dryer) out of your pneumatic tools & products.
Compressed air is expensive enough without throwing in a bunch of easily preventable repair costs. Schedule time for maintenance, or it’ll schedule the time for you…and it may even send you a ‘smoke signal’ when it’s ready. If you’ve got questions about getting the most out of your compressed air system, we’ve got answers.
If you have been around compressed air systems, our blogs, or even optimized installations of point of use compressed air products, you will see point of use filtration in place. These filters come in a plethora of sizes, shapes, and specifications. Here at EXAIR we recommend to always keep a point of use filtration solution in place. This would include an auto-drain filter separator, as well as an oil removal filter.
So why do we have two instead of one? Could you use just the oil removal filter rather than two? Well, the answer lies in an optimized installation that will also carry with it a lower total cost of ownership. The auto-drain filter separators from EXAIR have a filter element which takes the air to a 5 micron level of filtration. (Except for the model 9004 which filters down to 20 micron.) The Oil Removal Filters have a coalescing filter element which filters to a 0.3 micron level for the finest debris/mists that may be contained within the compressed air stream. One reason for the separation is when a system is oil-free, the finer filtration level may not be needed. Also, by catching the bulk of material with the standard auto-drain filter and then leaving the finer filter to catch the residual amounts liquid that had been finely atomized within the stream of compressed air. This finer filter costs more so using it to catch larger particulate and risking it becoming clogged quicker will increase the total cost of ownership of the point of use compressed air product it is hooked to, hence never first and sometimes last. After the point of use filtration then placing the point of use pressure regulator and solenoid valves are next. This is all a better way to reduce risk of these being damaged from dirt and contaminants in the air lines. Total cost of ownership reductions all point to a better sustainability of any product.
To better showcase the importance of filtration, here’s a brief video I did a while back that visualizes just what one can see out of a compressed air line with minimal moisture introduced.
As you can see, keeping the point of use air filtered protects your process and decreases the total cost of ownership for your compressed air point of use product. If you would like to discuss other ways we can improve efficiency within your facility and help ensure you are getting the longest life out of your products, please contact us.
Brian Farno Application Engineer BrianFarno@EXAIR.com @EXAIR_BF
Airborne particles surround us everywhere. In a general work environment, nearly four million particles per cubic foot is floating around us at any given time. When a compressor compresses this air, the concentration increases substantially. So, compressed air is not only expensive to make, but very dirty. As the air exits your air compressor and travels into your pneumatic system, there is so much contamination that the International Standard Organization, ISO, created an Air Quality chart with Purity Classes.
This chart is easy to follow and can be found in the ISO8573-1 standard for Air Quality. It is used to select a cleanliness level for your compressed air system. The contamination is categorized into three areas; Particles, Water, and Oil (reference above). A Class is associated with a number for each category ranging from 0 (most stringent) to 9 (most relaxed). As an example, an Air Quality value of ISO8573-1:2010 [1.2.4] has a Class 1 for Particles, Class 2 for Water, and Class 4 for Oil. These Class values will show the maximum value in each category.
To define the categories in more detail, I will separate the three to discuss the origins and solutions.
Particles: For solid particles, this part comes from many different areas. The surrounding ambient air that is being drawn into the air compressor is filtered; but the intake filter will only remove large diameter particles. The smaller diameter particles will go through the filter and into the compressed air system. Another part is rust particles that occur from steel air pipes and receiver tanks. Over time, rust will flake off and create particles that can affect pneumatic equipment. Other particles can come from components inside the air compressor, valves, etc., that wear and breakdown. In the ISO column for Particles, it is separated into three different micron ranges and concentrations. The removal of particles from the compressed air is done by traps and compressed air filters. EXAIR offers two types; Filter Separators with 5-micron filtration and Oil Removal Filters with 0.03-micron filtration. There are other types of filtration systems depending on your ISO requirement.
Water: Humidity is a natural occurrence as water vapor in the surrounding air. It can be measured as a dew point temperature. This is the temperature at which water will condense and make rain. Inside an air compressor, the air is ‘squeezed”, and the amount of space for water vapor is reduced. So, it will condense into liquid form as “rain” inside the pipes. Air that comes out from an air compressor will always be saturated with water. To remove liquid water, a mechanical device can be used. Inside a Filter Separator, a centrifugal separator will spin the air and remove the liquid water. To remove water vapor, a compressed air dryer is required like a refrigerant, desiccant, deliquescent, or membrane type. Each type will have a dew point range that they can reach. As an example, a refrigerant type will reduce the dew point near 37 oF (3 oC). That means that water will not condense until the temperature reaches below 37 oF (3 oC).
Oil: This category can be found as a liquid, aerosol or vapor, and it includes more than just oil. It contains small hydrocarbons, CO, CO2, SO2, and NOX. Oil mainly comes from inside an oil-flooded air compressor. As the air passes through the compressor, it will pick up remnants of oil aerosols and carry it downstream. With high temperatures inside the air compressor, some of the oil will vaporize. Even with oil-less type air compressors, carbon vapor can still be an issue. Small hydrocarbons can come through the air intake and condense inside the system like water vapor above. To remove the liquid and aerosol type of oil, Oil Removal Filters can be used. They are designed to “coalesce” the small particles into larger particles for gravity to remove. Oil vapor requires an activated carbon to remove. These types of filter units will adsorb the vapor. This helps to remove odors as well as dangerous chemical vapors that may be in the compressed air line.
There are a variety of pneumatic systems that use the ISO8573-1 standard. This will include breathing air operations, food and beverage, pharmaceutical, and the electronic industries. If you need stringent requirement for your compressed air system, the Air Quality standard should be used by referring to the Class numbers above. This helps to dictate the types of filtration and air dryers that should be used within your pneumatic system. If you have any questions about your compressed air system, an Application Engineer at EXAIR can help.
Compressed air filters help to keep the air clean and condensate free to protect equipment from dust, dirt, pipe scale, oil and water. Even though the compressed air system will typically have a main dryer, additional treatment is often necessary. For this discussion, we will focus on the oil removal process and filter type.
After the compressed air has passed through a particulate filter, the dirt, dust and water droplets have been removed. Oil that is present is much smaller in size, and mostly passes though the particulate filter. The installation of a coalescing filter will provide for the removal of the majority of the fine oil aerosols that remain. The coalescing filter works differently than the particulate filters. The compressed air flows from inside to outside through the coalescing filter media. The term ‘coalesce’ means to ‘come together’ or ‘form one mass.’ The process of coalescing filtration is a continuous process where the small aerosols of oil come in contact with fibers of the filter media. As other aerosols are collected, they will join up and ‘come together’ and grow to become an oil droplet, on the downstream or outside surface of the media. Gravity will then cause the droplet to drain away and fall off the filter element.
Some important information to keep in mind –
Change the filter regularly, not just when the differential pressures exceeds recommended limits, typically 5 PSI
Coalescing filters will remove solids too, at a higher capture rate due to the fine level of filtration, using a pre-filter for solids will extend the life
Oil free compressors do not provide oil free air, as the atmospheric air drawn in for compression contains oil vapors that will cool and condense in the compressed air system.
If you would like to talk about oil removal filters or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.