Deflating costs
Installed compressed air units practically always offer some potential for optimization

Considerable potential for saving energy lurks in the compressed air networks of small and large-size companies alike — and exploiting this pays off. In doing so, intelligent compressed air management is just as important as the equipment engineering. PROCESS has put together some of the current offers on the market.
Hans-Jürgen Bittermann
It is exciting to see how new areas of application for compressed air are constantly being identified,” says Wolf Dietrich Meier-Scheuven, managing partner at Boge. As an example, he cites PET containers and bottle production: “Glass bottles are increasing becoming less important, and modern high-pressure blow molding engineering requires significant amounts of compressed air at high pressure.” Yet there is also much which can be done on plant which is already installed. “A major issue in the sector is and remains the buzzword of ‘energy efficiency’,” observes Matthias Zelinger, a German Engineering Federation (VDMA) expert working in the Compressors, Compressed Air and Vacuum Technology sector. He believes that the potential savings on compressed air can be between five and 50 per cent. The manufacturers now consider that they are well-prepared in this area, offering management tools, professional audits, analysis methods and remote monitoring systems. “The notion of ‘lifecycle management’ is playing a key role,” adds Zelinger. According to Meier-Scheuven, this means that the transparent compressed air unit is now already available as an option: “Display, monitoring and remote servicing are expandable tools which can help in making compressed air supply even more safe, even more comprehensible and even more easy to use now and in the future.”

Compressed air and costs

To keep a constant check on the costs and quality of compressed air, Kaeser offers the Sigma Air Manager (SAM). Usually several compressors and processing plants operate together in a modern compressed air unit. This means that the right coordination is critical, since this is where the greatest potential lies for making savings on energy and costs in generating compressed air.

The SAM — a high-level controller and web server in one — was developed to exploit this potential as far as possible. It combines energy-saving pressure band control with clear data display, and matches the operation of the compressors and additional system components to one another. Unnecessarily high end-pressure is avoided. The controller is effective down to differences in pressure band of only +0.1 bar. This is highly economical, since reducing the maximum pressure by 1 bar means six per cent less energy consumption.

The SAM hardware basis comprises an updatable industry PC with high computing power and a large working memory. Depending on the requirements, the system can be supplied for up to four, eight or 16 compressors. In addition, the long-term analysis tool Sigma Air Control plus makes it possible to trace back and evaluate network pressure, behavior in load/no-load operation, energy consumption and load on the compressors over periods of up to one year.

Beneficial use of contracting

Many manufacturers offer compressed air contracting — but not all providers are happy about this side of their operations, and there is even some talk of sluggish sales on the contracting side. Nevertheless, it is still the case that operators whose levels of demand can be estimated reliably are able to make beneficial use of all-inclusive, worry-free packages of this type. Atlas Copco advises adopting the following approach: before the compressed air contracting model can be jointly worked out, the current and future profile of compressed air usage needs to be established.

They also advise that dynamic consumption patterns need to be known. Clarification is also needed regarding what quality of compressed air is required, and whether the work involves single-shift or multiple-shift operations. For existing operations, the compressed air profile can be analyzed using the so-called AirScan method, a service offered by Atlas Copco to determine the profile
of compressed air demand over a seven-day period.

EnBW provides a practical example relating to contracting, the client being Honeywell Speciality Chemicals Seelze. The starting-point for the joint development of the compressed air supply project was an extensive energy consultancy report carried out by EnBW and looking at electricity and compressed air. On the basis of this information, the chemicals company decided to have a more in-depth compressed air study carried out. Building on this, EnBW developed a client-specific compressed air supply concept. Using the remote monitoring system ICM (Integrated Contracting Management System), all operating statuses are recorded, evaluated and archived in the central EnBW control room for contracting facilities. This creates additional data transparency in operations for the client, and facilitates rapid response to possible deviations. Payment for compressed air is on the basis of the quantity used — like electricity from the socket.

Moving away from oil

With engineering processes, contamination of the medium to be compressed is generally undesirable. The manufacturer Haug has noticed that, as a result, oil-free compression is becoming increasingly widely-used. In addition to Haug crosshead-construction process gas compressors, today’s users are employing trunk piston type compressors in the lower performance range up to 30 kW. The advantages of these compressors lie in their highly compact and simple design. To minimize the friction arising in the crank gear, sealed rolling bearings with lifetime lubrication are employed (similar to those on electric motors). This means that there is no oil anywhere in the compressor.

Boge has similarly noted the advances being made by oil-free compressors (dry running). They see the reason for this being simply that the number of situations requiring compressed air produced directly and oil-free is steadily increasing — the spectrum ranges from pharmaceuticals and the chemical industry through to chip production. A further argument favoring dry running compressors is the lower operating costs — a point emphasized by sector representatives.

In the oil-free compressor segment, Boge is expanding its existing portfolio into the lower-performance range. In the 45 kW power range, the SO oil-free screw compressors will guarantee clean compressed air in future, and for requirements below this the K piston compressor is ideal, with its compact design and featuring an innovative re-launch of the drive mechanism (lifting piston using the slide rod principle, rotating like a screw compressor). These piston compressors produce absolutely oil-free compressed air using a completely new principle, and are suitable for use in the healthcare and food sectors (2.2 to 5.5 kW power output).

An innovation from Atlas Copco is type ZT50 VSD FF oil-free compressors: the compressors work with an energy-saving speed governor and supply the compressed air system with constant pressure. An integrated dryer comes as standard. “Our clients can’t afford to have reject products simply because oil has got into the manufacturing process somewhere along the line,” observes Reimund Scherff, manager of Business Line Oilfree Air. “They don’t want production downtimes, delays or lengthier delivery periods, and they certainly don’t want to damage their image in any way.”

The manager is therefore convinced that practically no industrial operation needing to use a compressed air system can afford to be without oil-free compressors. In his view, this also includes practically all sectors of the processing industry.

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Correct condensate management naturally also forms part of an optimal compressed air supply. A specialist in this area is Beko, with its Öwamat oil-water separator. It satisfies the German statutory requirements regarding introduction of cleaned condensate into the communal waste water system; the only remaining obligation is for operation of the unit to be notified to the water authorities responsible. “This makes the Öwamat clearly superior to conventional light fluid separators conforming to DIN 1999 or to simple gravity separators,” explains Thomas Buschmann, Beko product manager.

Containerized units

For mobile or non-installed uses, there are fully-engineered compressed air units on the market, being offered for instance by Boge as connection-ready containerized solutions which come with everything which an up-to-date compressed air supply might need, and available in various operator models.

VPT Compressors is also placing its trust in the instructive benefits of the container concept: the unit can be pre-assembled and tested in the works plant under defined, clean conditions — increasing the quality and reliability of the engineering. A further advantage is that the future operator knows at an early stage where the interfaces for gas admission/gas discharge and for electricity and coolant water are located. This makes installation and taking into service particularly easy and cost-favorable. “Eight out
of ten units leaving our works today are containerized,” comments Managing Director Carsten Kollenbach, explaining the level of demand from customers for this concept.n