Not for knuckleheads

Emerging trends in compressed air systems range from more efficient compression and conditioning equipment to greater reliability with lower maintenance to improved product quality via cleaner, drier air. But to take full advantage of these powerful improvements, industry experts, consultants and users say the first step is to understand what you've got in your plant.

Although awareness about the significance of compressed air costs has increased, and sources of solid information like the Compressed Air Challenge are available (www.compressedairchallenge.org), most industrial systems are still far from optimized. "We've audited a thousand plants in 18 years and have a lot of data", says Hank van Ormer, president, Air Power USA (www.airpowerusainc.com). A 30% reduction in electric cost and less than one year payback is typical.

With that kind of incentive, it's worth taking a harder look at your plant's air requirements and doing a system analysis to see how much air is going where, pressure drops, loss ratios and contaminants. If your auditor is competent and unbiased, you may be surprised how little you need to spend to impress your boss with significant improvements.

Figure 1. A thorough audit calls for at least one mass flowmeter with programmer; pressure, temperature, dewpoint, voltage and amperage sensors; and a datalogger.

If your system is old or decrepit enough, it may be easy to find quick fixes with less than one-year paybacks, but it's wiser to perform an audit or have one done by a consultant, compressed air equipment supplier or other trusted source.

Many end users rely on advice from equipment vendors. "In our experience, an air audit pays for itself in less than a year, often six months or less," says Larry McNett, marketing services, Gardner Denver (www.gardnerdenver.com). Many plants have not had a professional audit and may not have the tools or expertise (Figures 1 and 2). "Even when in-plant maintenance has done an audit, we find they're losing energy with outdated piping, ill-fitting valves and leaks", McNett says. 'The average potential energy savings is about 15-25%. Equipment vendors' auditors may come from the company itself or a local distributor, and vary in expertise and impartiality. "End users are much more aware of energy, and we see the impact", says Harish Shah, advisory engineer, Sullair (www.sullair.com). "They're asking us to work with them to evaluate their systems and help them lower their operating costs. We provide this service via distributors or factory people, depending on the size of the system, often at no charge."

Find wise guys

Independent consultants caution potential clients to be aware of vendors' motives. "Though savvy customers know the sales guy is biased, most discount or ignore the fact that the vendor is only obligated to tell you the truth as it applies to convincing you his system is the best one to solve your problems," says Ron Wroblewski, P.E., a consultant for Productive Energy Solutions, Madison, Wis. "The rules of the engagement are such that he is not obligated to tell you a $5,000 receiver can solve your pressure fluctuations as well or better than his $50,000 compressor."

Not obligated, perhaps, but it's not unheard of for vendors to put end users' needs first. They increasingly are realizing their health depends on the wellbeing of their customers. "We analyze what you have by monitoring," says Harold Wagner, national sales manager, Kaeser Compressors (http://us.kaeser.com). "We have done many systems where we have made changes in the configuration and control and not sold any machines."

Some companies strike pay dirt by mining government programs. Under pressure to identify cost-reducing programs with short paybacks, Kurdzeil Industries, Rothbury, Mich., reconsidered the results of an energy audit performed a few years ago by University of Michigan graduate students as part of a U.S. Department of Energy program (such programs continue, see www.oit.doe.gov/bestpractices).

"The compressors were near the top of the payback potential", says Jim Urquhart, Kurdzeil senior electrical engineer. They set up their five old compressors on a sequencer and put a variable-speed unit on top of them for trim. The trim compressor ramps up and down to satisfy demand based on a mass flowmeter and pressure transducer on the main supply line. Urquhart says, "We're saving $50,000-$60,000 annually, enough for the project to pay for itself in a year."

Regardless of the audit source, system knowledge is absolutely essential. "An air system is not a simple thing, and it's not a commodity", says Frank Athearn, vice president, marketing and sales, Cooper Compression (www.coopercompression.com). "Each system is different. Like many engineering problems, there may be a range of cost-effective options. But there's only one best solution."

Often, the recommended solutions will depend on the source of the audit. Try to get an unbiased audit.Plants' air requirements vary significantly from shift to shift and even minute to minute, and most plants supply them with more than one compressor. For the highest operating efficiency, air pressure should be held as low and constant as possible under these varying load conditions. The potential energy savings are significant: every 2 psi reduction in compressor outlet pressure can reduce input power by 1%.