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Compressed Air

Operation and Maintenance Tips

  1. Do a Compressed Air Audit
  2. Find and Fix Leaks
  3. Change the Mode of Compressor Operation
  4. Add a Storage Receiver
  5. Determine Your Actual Requirements
  6. Eliminate Wasteful Uses
  7. Lower the Operating Pressure
  8. Keep the Heat
  9. Examine the Air Dryer
    Compressed Air Energy Efficiency Reference Guide
  10. Slow the Flow
  11. Repair or Replace Condensate Drains
  12. Upgrade Piping and Connectors
  13. Replace or Upgrade Filters
  14. Turn Off Compressors
  15. Smaller is Better
  16. Follow a Systematic Inspection and Maintenance Schedule
  17. Use AIRMASTER+ to Optimize Your System

1. Do a Compressed Air Audit

This should be the starting point and will allow you to gather basic information on your system. An audit should help you determine the current operating costs of your system and identify any areas for improvement. For more information, see Compressed Air System Audit, or read these sections in the Compressed Air Challenge (CAC) publication, Improving Compressed Air Performance – a Sourcebook for Industry (referred to in these web pages as the “CAC Sourcebook”):

  • Baselining Compressed Air Systems;
  • Determining Your Compressed Air System Analysis Needs; and
  • Guidelines for Selecting a Compressed Air System Provider.

Most compressed air system vendors in Canada have access to a compressed air auditing service or are developing such a service. In some cases, the cost of the audit might can be shared by Natural Resources Canada and/or your local power utility.

2. Find and Fix Leaks

Leaks waste an estimated average of 25 percent of compressed air. You can often dramatically reduce compressed air use by fixing leaks inexpensively. For more information, read Compressed Air System Leaks in the
CAC Sourcebook. For information on leak-detection equipment, see Purchasing Leak Detection Equipment.

At $.05/kWh:

  • a $100/year leak cannot be felt or heard
  • a $400/year leak can be felt but not heard
  • a $700/year leak can be felt and heard

From Fundamentals of Compressed Air Systems course notes, Compressed Air Challenge

When you find a leak, mark it with a tag. (See Tagging the Leaks). Write on the tag the date, system pressure, size of the leak, system fluid, location (e.g., at the gasket, on the run of a tee, etc.), and how much the leak is costing you. This will encourage you to fix the bigger leaks rapidly.

Note that fixing leaks may not result in energy savings if you do not control the operating pressure. Without control, fixing the leaks will simply cause your system to run at a higher pressure.

3. Change the Mode of Compressor Operation

The operating mode (or method of controlling the compressor) can have a big effect on how much energy is consumed. The wrong choice of operating mode can limit the savings gained by other efficiency measures such as fixing leaks. Converting your existing compressors or purchasing a new compressor capable of running in a more efficient mode can save significant operating costs. For more information, read Compressor Operating Modes in
How Much Will I Save?

4. Add a Storage Receiver

Storage receivers (or storage tanks) can lower compressed air costs and provide pressure stability. A storage receiver buffers supply by handling short-term spikes in flow rate exceeding the compressor capacity. With a storage receiver, the compressor can be sized to handle a lower flow rate rather than the spike. For more information, read Compressed Air Storage in the
CAC Sourcebook. For an idea of the possible savings, see
Compressor Operating Modes in How Much Will I Save?

5. Determine Your Actual Requirements

Your system audit can help you find out who needs how much compressed air, what pressure they need, and where and when they need it. From the audit, you can devise a strategy to maximise efficiency. For more information and an example of supply strategies, read Sample System Profile in Compressed Air System Audits.

6. Eliminate Wasteful Uses

Often, compressed air is wasted because it is handy and easy to use. Most end users are surprised when they find out how much compressed air systems cost to operate. Since it takes 7-8 hp of electrical energy to produce 1 hp of end effect of compressed air, think carefully about whether compressed air is the most efficient way to meet your need. Examples of potentially inappropriate uses of compressed air (taken from the CAC Sourcebook) include:

  • Open blowing
  • Sparging
  • Aspirating
  • Atomising
  • Padding
  • Dilute-phase transport
  • Dense-phase transport
  • Vacuum generation
  • Personnel cooling
  • Open hand-held blowguns or lances
  • Diaphragm pumps
  • Cabinet cooling
  • Vacuum venturis.

For alternatives, read Potentially Inappropriate Uses of Compressed Air in the CAC Sourcebook. For an idea of possible savings, read Compressed Air System Leaks and End Uses in [Title and Link to EGI Web page]. A videotape and CD suited to staff meetings, highlights wasteful practices and is available from the Natural Resources Canada's Office of Energy Efficiency. The U.S. Department of Energy Web site also has a tip sheet Alternative Strategies for Low-Pressure End Uses.

7.Lower the Operating Pressure

Rule of thumb: decreasing operating pressure by two psi cuts compressor energy input by one per cent.

One question you should ask is “What is the pressure of our compressed air system?” Another question is “Why?”

The pressure is often set to the maximum output of the compressor. By documenting and determining the exact end use requirements for air pressure, volume and quality it is often possible to reduce the pressure of the compressor.

According to the CAC Sourcebook, unregulated pressure usage typically accounts for as much as 50 percent of demand. Reducing pressure by 2 psi can lower energy consumption by a further 0.6 to 1.0 percent simply because less unregulated air is being consumed. This can result in a total energy saving of 1.6 to 2.0 percent.

For information how to reduce system pressure and save energy while maintaining high performance, refer to Pressure Drop and Controlling System Pressure in the CAC Sourcebook.

8. Keep the Heat

Only 20 percent of the energy input to the air compressor goes to compressed air while 80 percent of it converts into heat. If there is a need for process heat, hot water or space heat, the heat generated by the compressor can sometimes be recovered and used to supplement these requirements. For more information, read Heat Recovery and Compressed Air Systems in the CAC Sourcebook. For an idea of potential savings, read Heat Recovery in How Much Will I Save?

9. Examine the Air Dryer

The type of air dryer and how it operates can save significant energy. Air drying equipment can use as much as 20 percent of the total system power. In extreme cases of faulty or poorly-sized heatless desiccant or membrane dryers, the purge flow consumed by the dryer can be the largest single air consumer in a facility. For more information, read Air Dryers in How Much Will I Save?

10. Slow the Flow

In some cases, water and sewer charges for liquid-cooled compressors can be higher than the cost of the electricity the compressors consume. Significant savings can usually be found by controlling the water flow with a thermostatically controlled modulation valve, or by installing a closed loop cooling system.

11. Repair or Replace Condensate Drains

To have high quality compressed air, you must remove condensate collected by coolers, dryers, receivers and filters. How the condensate is removed affects the efficiency of the system. Large amounts of air can be wasted by:

  • manual drains that are always “cracked” slightly open;
  • float drains that have failed in the open position; or
  • timer drains set to drain excessively.

You can save money by repairing or replacing these drains with more efficient ones. For more information, read Condensate Drains in How Much Will I Save?

12. Upgrade Piping and Connectors

The greatest pressure loss in the system often occurs in the “dirty 30”, the last 30 feet of air line between the main distribution header and the air tools. Users demanding 115 psi and more are often surprised to learn that the local pressure at their equipment falls to 60 psi or less when they operate their tools. Upgrading poorly-sized distribution piping and replacing undersized quick couplers, hoses, filters, regulators and lubricators can improve end-user pressure, and allow for more efficient and lower main system header pressures. For more information, read Pressure Drop and Controlling System Pressure in the CAC Sourcebook.

13. Replace or Upgrade Filters

When you monitor and regularly replace compressor room filters, you can reduce operating costs. Each main filter can often add 3 to 10 psi of pressure differential to the system. This pressure differential requires an increase in compressor pressure and, as a result, increases the power the compressor uses. A high pressure differential can also interfere with compressor control and increase costs. Monitoring and replacing these filters regularly can reduce the cost of operating the system. To maintain higher system efficiency, upgrade and replace filters with low-differential filters or with an oversized filtration system.

14. Turn Off Compressors

System demands can vary greatly through a typical seven-day operating cycle. For peak periods, all compressors may be needed to maintain pressure. Yet during average periods one compressor may be enough. Often, compressors do have the option for automatic shut down under low loads. Use of this feature, or simply turning off compressors for long low-load periods such as nights and weekends, can save much energy.

15. Smaller is Better

Large compressors must often be left on to supply very small loads such as dry fire systems at night and on weekends even though there are no other compressed air demands. Large compressors can be very inefficient at such low loads, and must also use energy to supply the inevitable leaks. You can save energy by installing small independent compressors for minimum-demand hours, and by turning off the larger main compressors.

16. Follow a Systematic Inspection and Maintenance Schedule

Focus on filters, oilers, quick couple points and all other maintenance points as set out by the equipment supplier.

According to the CAC Sourcebook, “Like all electro-mechanical equipment, industrial compressed air systems require periodic maintenance to operate at peak efficiency 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. Compressed air system maintenance is similar to that performed on cars; filters and fluids are replaced, cooling water is inspected, belts are adjusted, and leaks are identified and repaired.” For more information, read Maintenance of Compressed Air Systems for Peak Performance in the CAC Sourcebook.

17. Use AIRMASTER+ to Optimize Your System

AIRMASTER+ is a software package to help you maximise the efficiency and performance of your compressed air system. The software provides a systematic approach for assessing the supply-side performance and evaluates supply-side operational costs for various equipment configurations and system profiles. AIRMASTER+ can also help you evaluate the energy saving potential of a number of corrective actions and calculates the simple payback periods. This software is free and available on the CAC Web site.

Next: Compressed Air System Audit