According to a recent United States Department of Energy (DOE) publication, compressed air systems account for 10% of the nation's electrical consumption and roughly 16% of our industrial motor system energy use. Seventy percent of our manufacturing facilities use compressed air in their production process.
Compressed air audits of industrial plant air systems generally uncover large energy-saving opportunities that have relatively low costs to implement. The same DOE report states, "In small- to medium-sized industrial facilities, approximately 15% of compressed air system usage can be saved with simple paybacks of less than two years. In larger facilities, these savings could range from 30% to 60% of current system usage."
Additional benefits include providing the plant with an adequate supply of air where and when it's needed, as well as reducing compressor run time.
Goals and metrics
Generating and maintaining management support for a compressed air audit program requires a business case. It's important to establish meaningful and measurable goals to monitor the results and show progress from the baseline data taken at the beginning of the program. These measurements must indicate initial positive results as well as longer-term positive results to ensure continuous improvement in the techniques and procedures used.
Metering air use
This is one of the most meaningful measurements because energy costs are so high. The newest flow-measuring technology has zero insertion loss, thus saving energy. Metering compressed air consumption before and after an audit is mandatory for ensuring the program is effective. Without metering, the plant won't be able to quantify its efficiency gains. Metering also will indicate when the program is going awry — compressed air demand exhibits an anomalous increase.
There are metering systems available that measure the compressor's electrical consumption and other systems that measure the compressor's air flow. In either case, metering and measurement must be included as part of the program.
When a production process needs air, it must be available at the correct pressure to avoid losing valuable production output. Correlating lost output to air system deficiencies is another meaningful measurement that most managers will understand.
An in-house compressed air audit should
involve a team of people who have a
stake in the air system.
A properly designed and well-maintained compressed air system provides reliable operations during its entire life cycle. When waste forces compressor run times to increase, reliability and total life-cycle cost suffer. That's why tracking total cost of ownership is another valuable measurement.
Improved air quality
Many components in a compressed system depend upon clean, dry air if they are to operate effectively. A poorly maintained air quality system will result in a shortened life for sensitive components and lead to higher replacement and repair costs. Every aspect of the plant operation suffers from poor compressed air quality. Tracking historical compressed air tools/components repair and replacement costs can help support a business case for compressed air audits. Once management understands and supports your business case for implementing a compressed air audit program, it's time to get started with field work.
Air = uptime
Build your case for an audit around sound
business principles, such as asset reliability.
It's useful to form one or more teams made up of the people affected by the compressed air system. The team could include personnel from operations, maintenance, safety, engineering and management. You may even consider inviting accounting and purchasing.
Once the team of stakeholders is named, it should map out the process of producing and using compressed air throughout the facility. This process is called compressed air mapping and uses existing documentation, energy information, work order history and interviews of the people involved with compressed air to provide a total system overview and understanding. Compressed air mapping provides the big picture.
Compressed air mapping offers several benefits:
- People start to see how their piece of the operation affects the entire system.
- It quickly identifies obvious areas of waste.
- Missing documentation and drawings can be located or reproduced.
- It raises the level of communication.
- Components may be assessed in the context of an entire system.
- It develops a strategy for operating an efficient compressed air system.
Unless plant personnel have a detailed and thorough knowledge of compressed air system design, it may be advantageous to hire a qualified firm that has experience in this area for the initial assessment. In addition, an outside contractor can serve as an independent auditor on an annual basis to ensure that your compressed air program continues to meet its goals.
When evaluating audit contractors and the solutions being proposed, it's important to identify any manufacturer's affiliations that might be involved. An independent company often can provide unbiased information that allows you to choose among several types of solutions.
Make sure to ask for copies of several of the firm's customer reports. These should contain the information that you've determined you want, as well as specific cost-effective action recommendations. A lot of the savings is usually gained with very little or no capital cost.
Leaks will always be part of any compressed air system. It's important to develop a regularly scheduled program for detecting, tagging and repairing them. Inexpensive ultrasonic leak detectors are now widely available and easy to use, even in noisy plant environments. In-house resources generally can handle this task; however, several service companies also specialize in offering this service.
Don't confuse an air leak survey with a compressed air system audit. Fixing leaks saves energy, but the problems that exist in other areas of the system can consume even more energy than leaks. Addressing the system in toto accomplishes the real long-term gains.
Air system management
Improving compressed air system efficiency isn't a one-time event; it's an ongoing process. Managing and maintaining the compressed air system must be a continuous effort. Using tools, such as compressed air mapping, helps ensure teamwork and management support for your efforts.
Kelly Paffel is the technical manager at Inveno Engineering, LLC. Mr. Paffel is a recognized worldwide authority in industrial steam systems. He has has 35 years of experience in steam, compressed air systems and power operations. Mr. Paffel has achieved Steam System Level V certification in Steam Systems and is also is also a member of the Department of Energy’s (DOE) Steam Best Practices Committee and Steam Technical Committee.
Figures courtesy of Plant Support and Evaluations.