Compressed Air System Maintenance

When I was seventeen my grandfather took me to a used are dealership and helped me buy my first car. It wasn’t anything special, as it was a 1996  Chevrolet Lumina. It had its fair share of bumps and bruises, but the bones were solid. We took it home and he taught me how to do all the basics, we changed the oil, oil filter, air filter, brakes, pretty much every fluid we could, we changed.

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You see my grandfather retired from Ford Motor Company after 50+ years of service. And he always said, “If you treat it right, it will treat you right.”; and I’ve lived by that ever since.

Just like a car, air compressors require regular maintenance to run at peak performance and minimize unscheduled downtime. Inadequate maintenance can have a significant impact on energy consumption via lower compression efficiency, air leakage, or pressure variability. It can also lead to high operating temperatures, poor moisture control, and excessive contamination.

Most problems are minor and can be corrected by simple adjustments, cleaning, part replacement, or the elimination of adverse conditions. This maintenance is very similar to the car maintenance mentioned above, replace filters, fluids, checking cooling systems, check belts and identify any leaks and address.

All equipment in the compressed air system should be maintained in accordance with the manufacturers specifications. Manufacturers provide inspection, maintenance, and service schedules that should be followed strictly. In many cases, it makes sense from efficiency and economic stand-points to maintain equipment more frequently than the intervals recommended by the manufactures, which are primarily designed to protect equipment.

One way to tell if your system is being maintained well and is operating properly is to periodically baseline the system by tracking power, pressure, flow (EXAIR Digital Flowmeter), and temperature. If power use at a given pressure and flow rate goes up, the systems efficiency is degrading.

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Air Compressor

Types Of Maintenance

Maintaining a compressed air system requires caring for the equipment, paying attention to changes and trends, and responding promptly to maintain operating reliability and efficiency. Types of maintenance include;

  1. Poor Maintenance – Sadly, some plants still operate on the philosophy, “If it isn’t broke, don’t fix it.” Due to the lack of routine preventative maintenance, this practice may result in complete replacement of an expensive air compressor as well as unscheduled and costly production interruptions.
  2. Preventive  Maintenance – This type of maintenance can be done by plant personnel or by an outside service provider. Usually, it includes regularly scheduled monitoring of operating conditions. Replacement of air and lubricant filters, lubricant sampling and replacement, minor repairs and adjustments, and an overview of compressor and accessory equipment operation.
  3. Predictive  Maintenance – Predictive maintenance involves monitoring compressor conditions and trends , including operating parameters such as power use, pressure drops, operating temperatures, and vibration levels. The Right combination of preventive and predictive maintenance generally will minimize repair and maintenance costs.
  4. Proactive Maintenance – If a defect is detected, proactive maintenance involves looking for the cause and determining how to prevent a recurrence.

Unfortunately, even the best maintenance procedures cannot eliminate the possibility of an unexpected breakdown. Provisions should be made for standby equipment to allow maintenance with out interrupting production.

If you would like to discuss improving your compressed air efficiency or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer
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Images Courtesy of Tampere Hacklab

6 Basic Steps for Good Air Compressor Maintenance (And When to Do Them)

A production equipment mechanic with the 76th Maintenance Group, takes meter readings of the oil pressure and temperature, cooling water temperature and the output temperature on one of two 1,750 horsepower compressors. (Air Force photo by Ron Mullan)

In one of my previous jobs, I was responsible for the operation of the facility.  One of my biggest responsibilities was the air compressor because it supplied pressurized air though out the facility to feed the pneumatic systems.  Like with many industries, the compressor system is the life blood of the company.  If the compressor fails, the whole facility will stop.  In this blog, I will share some preventative maintenance items and schedules for your air compressors.

Because the cost to make compressed air is so expensive, compressed air systems are considered to be a fourth utility.  And with any important investment, you would like to keep it operating as long and efficiently as possible.  To do this, it is recommended to get your air compressor a “checkup” every so often.  I will cover some important items to check as well as a recommended schedule for checking.  Depending on the size of your air compressors, some items may or may not apply.

1. Intake filter:  The intake filter is used to clean the air that is being drawn into the air compressor.  Particles can damage the air pump mechanisms, so it is important to have the proper filtration level.  But, as the intake filter builds up with debris, the pressure drop will increase.  If they are not properly monitored and cleaned, the air flow will be restricted.  This can cause the motors to operate harder and hotter as well as reduce the efficiency of the air compressor.

2. Compressor Oil:  This would be for flooded screws and reciprocating compressors that use oil to operate the air pump.  Most systems will have an oil sight gauge to verify proper levels.  In larger systems, the oil can be checked for acidity which will tell you the level at which the oil is breaking down.  The oil, like in your car, has to be changed after so many hours of operation.  This is critical to keep the air pump running smoothly without service interruptions.

3. Belts and Couplings:  These items transmit the power from the motor to the air pump.  Check their alignment, condition, and tension (belts only) as specified by the manufacturer.  You should have spares on hand in case of any failures.

4. Air/Oil Separators:  This filter removes as much oil from the compressed air before it travels downstream.  It returns the oil back to the sump of the air compressor.  If the Air/Oil Separator builds too much pressure drop or gets damaged, excess oil will travel downstream.  Not only will the air pump lose the required oil level, but it will also affect the performance of downstream parts like your air dryer and after cooler.

5. Internal filters:  Some air compressors will come with an attached refrigerated air dryer.   With these types of air compressors, they will place coalescing filters to remove any residual oil.  These filters should be checked for pressure drop.  If the pressure drop gets too high, then it will rob your compressed air system of air pressure.  Some filters come with a pressure drop indicator which can help you to determine the life of the internal filter element.

6. Unloader valve:  When an air compressor unloads, this valve will help to remove any compressed air that is trapped in the cavity of the air pump.  So, when the air compressor restarts, it does not have to “work” against this “trapped” air pressure.  If they do not fully unload, the air compressor will have to work much harder to restart, wasting energy.

Preventative maintenance is very important, and checks need to be performed periodically.  As for a schedule, I created a rough sequence to verify, change, or clean certain items that are important to your air compressor.  You can also check with your local compressor representative for a more detailed maintenance schedule.

Daily:

  • After stopping, remove any condensate from the receiver tank.
  • Check oil level.

Monthly:

  • Inspect cooling fins on air pump. Clean if necessary
  • Inspect oil cooler. Clean if necessary

Quarterly:

  • Inspect the inlet air filter. Clean or replace if necessary.
  • Check the belt for tension and cracks. Tighten or replace.
  • Check differential pressure indicators on outlet compressed air filters.

Yearly:

  • Replace Air Inlet Filter
  • Replace the air-oil separator
  • Test safety valves and unloader valve
  • Replace compressed air filters
  • Change oil
  • Grease bearings if required

Keeping your air compressor running optimally is very important for pneumatic operations and energy savings.  I shared some important information above to assist.  Another area to check would be your pneumatic system downstream of the air compressor.  EXAIR manufactures engineered products that can reduce air consumption rates.  You can contact an Application Engineer to discuss further on how we can save you energy, money, and your air compressor.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

About Air Compressors: Air Intake Best Practices

Take a second and think about where the air compressor is located within your facility.  It is more than likely not a major focal point displayed prominently in the floor layout. There is a better chance it is tucked away in a corner of the facility where operators seldom travel.  No matter the type of air compressor, it still has an intake where it pulls in the ambient air from around the compressor then sends it through some process and on the demand side of your compressed air system.  These intakes can easily be placed out of sight and out of mind especially in older facilities that were designed when compressors were loud and the piping layout kept them away from operators due to sound level restrictions.

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Antique Air Compressor (Not safe for use!)

That’s why your compressor manufacturer supplies a specific grade of air inlet/intake filter, and this is your first line of defense. If it’s dirty, your compressor is running harder, and costs you more to operate it.  If it’s damaged, you’re not only letting dirt into your system; you’re letting it foul & damage your compressor. It’s just like changing the air filter on your car, your car needs clean air to run correctly, so does your compressor and the entire demand side of your compressed air system.

According to the Compressed Air Challenge, as a compressor inlet filter becomes dirty, the pressure drop across the inlet increases, this is very similar to the point of use compressed air filters.  The inlet filter on the compressor is the only path the compressor has to pull in the air, when restricted the compressor can begin to starve for air very similar to if you only had a small straw to breath through and told to run a marathon.  A clogged inlet filter can give false symptoms to compressor technicians as well.

The effects can mimic inlet valve modulation which result in increased compression ratios. If we were to form an example based on a compressor with a positive displacement, if the filter pressure drop increases by 20″ H2O, a 5% reduction of the mass flow of air will be present without a reduction in the power being drawn by the compressor. This all leads to inefficiency which easily amounts to more than the cost to replace the depleted inlet air filter.

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Compressed Air System

Where you place the filter is just as important as how often you replace it.  There are some tips to be used when mounting the inlet filter.

  1. The filter can be placed on the compressor, but the inlet pipe should be coming from an external area to the compressor room or even the building if possible. The inlet should be free from any contaminants as well.  Some examples that are easy to overlook are nearby condensate discharges, other system exhausts and precipitation.
  2. Depending on the type of compressor being used, a lower intake air temperature can increase the mass flow of air due to the air density.  A compressor that is lubricant injected is not susceptible to this due to the air mixing with the warmer lubricant before being compressed.

If you would like to discuss improving your compressed air efficiency or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer
Send me an email
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Twitter: @EXAIR_JS

 

Images Courtesy of  the Compressed Air Challenge and thomasjackson1345 Creative Commons.

How a Centrifugal Compressor Works

Continuing our series on different types of air compressors, today’s blog will feature the centrifugal compressor.  The centrifugal compressor is classified as a dynamic compressor.  Dynamic compressors are designed to work with  a continuous flow of air that has its velocity increased by an impeller rotating at a very high speed.

The centrifugal compressor works by transforming the kinetic energy and velocity into pressure energy in the diffuser.  The air passes through the inlet guide vanes being drawn into the center of a rotating Impeller with radial blades and is then pushed outward from the center by centrifugal force. This radial movement of air results in a pressure rise and the generation of kinetic energy.  The kinetic energy is also converted into pressure by passing through the diffuser.

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Sample Centrifugal Compressor

Multiple stages are required to raise the pressure to a sufficient level for typical industrial plant requirements.  Each stage takes up a part of the overall pressure rise of the compressor unit.  Depending on the pressure required for the application, a number of stages can be arranged in a series to achieve a higher pressure.

The most common centrifugal air compressor has two to four stages to generate pressures of 100 to 150 PSIG and incorporates a water cooled inter-cooler and separator between each stage to remove condensation and cool the air prior to entering the next stage.

Centrifugal compressors are the near middle of the road regarding efficiency, their typical operating cost is 16 to 20 kW/100 CFM.  The most efficient compressor type is the double-acting reciprocating and costs 15 to 16 kW/100 SCFM and the least is the Sliding Vane which costs 21 to 23 kW/100 SCFM.

Advantages of the centrifugal air compressor:

  • Up to 1500 HP systems are available
  • Price per HP drops as system size increases
  • Supplies lubricant-free air
  • Special installation pads are not required for installation

Disadvantages of the centrifugal air compressor

  • Costs more Initially
  • Requires specialized maintenance
  • Due to high rotational speeds (can exceed 50,000 RPM) precision high speed bearings and vibration monitoring are required

EXAIR recommends contacting a reputable air compressor dealer in your area to discuss your volume and pressure requirements to determine the best size & type air compressor for your needs.

Regardless of the type of air compressor you have, EXAIR’s Intelligent Compressed Air Products® can minimize your compressed air consumption, potentially reducing the size of compressor needed, reduce noise and still deliver powerful results!   If you would like to discuss highly efficient and quiet point of use compressed air products or any EXAIR product, we would enjoy hearing from you. 

Steve Harrison
Application Engineer
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Image Courtesy of  the Compressed Air Challenge

Cold Guns for Spot Cooling or Replacing Mist Systems

By using only a source of compressed air, the Cold Gun and High Power Cold Gun produces a stream of clean, cold air 50°F (28°C) below your compressed air supply temperature. The Cold Gun is very quiet at only 70 dBA and has no moving parts to wear out. Just supply it with clean compressed air and it’s maintenance free.

How does it work, and what are the benefits?

  • The Cold Gun uses compressed air to produce a stream of clean, cold air at 50°F (28°C) below supply air temperature. Generally this will be 20°F-30°F outlet temperature.
  • They use Vortex Tube technology…no moving parts to wear out.

How A Vortex Tube WorksInstant cold air flow with no moving parts!

  • Cold flow and temperature are preset to optimize cooling capability, and are non-adjustable to prevent freeze-up during use.
  • Eliminates the expense of both the purchase & disposal of cutting fluids when replacing expensive mist systems.
  • Removes the potential for health problems associated with breathing mist & vapors, and the safety issue of slipping on a wet floor.

Cold Gun Aircoolant System selection is easy & straightforward…we offer a standard, and a High Power version to meet your specific needs.

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Four systems to choose from, to meet most any need.

We also offer Single & Dual Point Hose Kits, to further meet the needs of your application.

One of the best applications I have seen with our cold gun came from a customer in Peru. They are a gold mining operation and they were having trouble with the liquid they were using to cool a saw. Read all about it here!

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If you have an application that you believe would be better served by the use of an EXAIR Cold Gun, give us a call.

Jordan Shouse
Application Engineer
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Understanding Compressed Air Supply Piping

An important component of your compressed air system is the supply piping. The piping will be the middle man that connects your entire facility to the compressor. Before installing pipe, it is important to consider how the compressed air will be consumed at the point of use.  You’ll also need to consider the types of fittings you’ll use, the size of the distribution piping, and whether you plan to add additional equipment in the next few years. If so, it is important that the system is designed to accommodate any potential expansion. This also helps to compensate for potential scale build-up (depending on the material of construction) that will restrict airflow through the pipe.

Air Compressor
Air Compressor and Storage Tanks

The first thing you’ll need to do is determine your air compressor’s maximum CFM and the necessary operating pressure for your point of use products. Keep in mind, operating at a lower pressure can dramatically reduce overall operating costs. Depending on a variety of factors (elevation, temperature, relative humidity) this can be different than what is listed on directly on the compressor. (For a discussion of how this impacts the capacity of your compressor, check out one of our previous blogs – Intelligent Compressed Air: SCFM, ACFM, ICFM, CFM – What do these terms mean?)

Once you’ve determined your compressor’s maximum CFM, draw a schematic of the necessary piping and list out the length of each straight pipe run. Determine the total length of pipe needed for the system. Using a graph or chart, such as this one from Engineering Toolbox. Locate your compressor’s capacity on the y-axis and the required operating pressure along the x-axis. The point at which these values meet will be the recommended MINIMUM pipe size. If you plan on future expansion, now is a good time to move up to the next pipe size to avoid any potential headache.

After determining the appropriate pipe size, you’ll need to consider how everything will begin to fit together. According to the Best Practices for Compressed Air Systems from the Compressed Air Challenge, the air should enter the compressed air header at a 45° angle, in the direction of flow and always through wide-radius elbows. A sharp angle anywhere in the piping system will result in an unnecessary pressure drop. When the air must make a sharp turn, it is forced to slow down. This causes turbulence within the pipe as the air slams into the insides of the pipe and wastes energy. A 90° bend can cause as much as 3-5 psi of pressure loss. Replacing 90° bends with 45° bends instead eliminates unnecessary pressure loss across the system.

Pressure drop through the pipe is caused by the friction of the air mass making contact with the inside walls of the pipe. This is a function of the volume of flow through the pipe. Larger diameter pipes will result in a lower pressure drop, and vice versa for smaller diameter pipes. The chart below from the Compressed Air and Gas Institute Handbook provides the pressure drop that can be expected at varying CFM for 2”, 3”, and 4” ID pipe.

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Air Pressure Drop

To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer
Send me an email
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Twitter: @EXAIR_JS

 

Images Courtesy of  the Compressed Air Challenge and thomasjackson1345 Creative Commons.

About Compressed Air Dryers – What Are They and Why Use Them

All atmospheric air contains some amount of water vapor.  When air is then cooled to saturation point, the vapor will begin to condense into liquid water. The saturation point is the condition where the the air can hold no more water vapor. The temperature at which this occurs is knows as the dew point.

When ambient air is compressed, heat is generated and the air becomes warmer. In industrial compressed air systems, the air is then routed to an aftercooler, and condensation  begins to take place. To remove the condensation, the air then goes into separator which traps the liquid water. The air leaving the aftercooler is typically saturated at the temperature of the discharge, and any additional cooling that occurs as the air is piped further downstream will cause more liquid to condense out of the air. To address this condensation, compressed air dryers are used.

It is important to dry the air and prevent condensation in the air. Many usages of the compressed air are impacted by liquid water being present. Rust and corrosion can occur in the compressed air piping, leading to scale and contamination at point -of -use processes. Processes such as drying operations and painting would see lower quality if water was deposited onto the parts.

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There are many types of dryers – (see recent blogs for more information)

  • Refrigerant Dryer – most commonly used type, air is cooled in an air-to-refrigerant heat exchanger.
  • Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process).
  • Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up, and needs to be replaced periodically.
  • Heat of Compression Type – are regenerative desiccant dryers that use the heat generated during compression to accomplish the desiccant regeneration.
  • Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount water vapor in air stream.

The air should not be dried any more than is needed for the most stringent application, to reduce the costs associated with the drying process. A pressure dew point of 35°F to 38°F (1.7°C to 3.3°C) often is adequate for many industrial applications.  Lower dew points result in higher operating costs.

If you have questions about compressed air systems and dryers or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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