Compressor Issues Get New Airing

Plants increasingly re-evaluate economic and technical factors

By Seán Ottewell, Editor at Large

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For the future, Beals sees more plants considering compresssor automation and over-the-fence air. "However, based upon my experience, it is still very hard in the U.S. to get capital for compressed air systems or other utilities until it's absolutely necessary — and this is holding back improvements in compressed air system efficiency."

To help plants achieve optimum cost and energy savings, compressor maker Gardner Denver, Wayne, Pa., offers a ten-point guide: 1) carry out an air audit; 2) specify the correct receiver size; 3) be aware of network pressure; 4) size downstream equipment correctly; 5) perform regular maintenance; 6) conduct weekly checks on downstream filters; 7) use the right technology; 8) don't buy on price; 9) eliminate off-load running; and 10) focus on leak reduction.

Gardner Denver notes that chemical and pharmaceutical operations increasingly are installing its Reavell high-pressure compressors and boosters (Figure 2). Typical uses include air and other industrial gas compression, gas recovery systems, inert gas blanketing and cryogenic cooling systems.

"A large part of our business is supplying high-pressure compressors and boosters (up to 6,000 psi/350 hp). The key issue here is sizing: the solution must be suitable for the application," explains Paul Green, sales manager, high pressure products Americas.

"The key is to optimize the available gas pressure and size and to configure the machine to ensure its operating parameters are the most efficient, which ensures not only reliability but keeps operating costs to a minimum," he adds.

A focus on initial capital cost can undermine achieving efficiency and optimization, Green warns. "Many markets are still very conservative and there can be issues with getting customers to accept using higher-speed compressors/boosters despite their advantages, such as less bearing and piston wear, higher reliability and lower maintenance costs."

"Customers do look very closely at the purse strings. But a lot of this depends on where the money is coming from and which people within the company you are actually speaking with. It also depends on how critical the application is. For example, we have been asked to repair broken machines that under normal circumstances might be switched out for new models, but the money was there in the service budget so they were repaired rather than replaced."

In another example, the company replaced a 300-hp compressor that was running at 100% all the time with two 150-hp compressors in a lead-lag configuration. The second machine comes on-line only to meet certain pressure demands; the company involved is saving 30–40% on compressed air energy costs as a result.

"Maintainability is a key factor in looking at 'through life costs' of any piece of equipment and is a key feature of all Reavell products," notes Green. For example, the 100-hp (75-kW) 5,000-psig 100-scfm 5437 model can be totally stripped and rebuilt in a day and a half, he notes; a valve change takes just five minutes and a three- or four-stage piston ring can be replaced in just 15 minutes, he adds.

The high-pressure Reavell products all are oil lubricated but Green believes this isn't the drawback users presumed in the past. "Not all chemical applications necessarily require 100%-oil-free air and, with high-pressure Reavell compressors, they have an oil carry-over of less than 2–3 ppm, which is easily removed with final filters. This is down from 20 ppm only a few years ago and getting even better as a result of new ring materials that don't require the same level of lubrication. So there are definitely cases now where people automatically assume they need oil-free, but in reality the required air purity can be achieved through suitable filtration. And this is an argument that we are winning now," he says.

Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at


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