Availability and efficiency have top priority
Overview over compressors and compressed air systems

From the user perspective, availability and efficiency are at the top of the priority list. Piston, screw and turbo compressors offer a choice of alternatives for a diverse range of applications. However, experts emphasize that there is no substitute for adequate, professional planning and design of the compressed air network. And, compressor services are also important.

Astudy conducted by Mercer Management Consulting entitled “Maschinenbau 2010” confirms that it actually is worth focusing on services. According to the study, all successful business models have a well-developed service element. For example, profits at Hanover Compressor, which markets customer solutions such as a full-service package for natural gas compressor stations, showed an annual increase of 40 percent, and turnover increased by 64 percent. Integrated solutions are also becoming increasingly more popular. According to industry sources, compressors featuring frequency control, dryers and condensate management are selling well.
What changes are driving these developments? Compressor manufacturers initially concentrated on “their” equipment. However, users now want complete, harmonized systems including the compressor, controller, air treatment and distribution at the customer site. Maintenance is another element which is often performed by the compressor manufacturer, who has specially trained service engineers, rather than by the customer. Build, own and operate schemes take this approach to its logical conclusion. The customer essentially has nothing to do with the equipment and is only interested in the key deliverables of the air supply service.
Where is the technology headed? Boge has noticed a shift in market share among the established compressor systems.

The tendency for screw compressors to replace piston compressors has been evident for a long time. However, turbo compressors are more energy efficient, and they are increasingly moving into territory traditionally held by large screw compressors. When there is large demand for compressed air, a good solution is to use turbo compressors for the basic supply and easily adjustable screw compressors to handle peak loads. Another trend is the increasing popularity of oil-free (dry running) compressors. There is now greater demand for high quality compressed air (pharmaceutical, chemicals and chip production). During the planning phase for a compressed air system, many companies do not spend enough at the outset in an attempt to reduce investment costs. This view was expressed at the 1st International Compressor User Forum which was held in Karlsruhe/Germany in 2004. Over the long term when systems are run at near maximum load, planning and installation only account for ten percent of the total cost of a compressed air supply system, and only about four percent is spent on maintenance. Energy consumption accounts for the remaining 86 percent, and according to an EU study these costs could be reduced by 25 to 40 percent. On a 90kW compressor system, users could save as much as s100,000 over a period of ten years, which is a remarkable sum. The opportunity to reduce cost is not limited to new investment projects. The German Engineering Federation (VDMA) believes that users could save substantial sums by improving existing systems, and the amortization period is significantly less then two years. Just a few figures show how quickly companies can reap the benefits (talk given by Beko/AGT Thermotechnik). Assuming an air pressure loss of 600 l/min, which occurs when air is escaping through a 4 mm hole on an 8 bar system, the energy you are wasting costs you s10,000 per year. Reduced cross sections can restrict the flow of compressed air, and this can drive up energy costs even further. These bottlenecks cause the pressure to fall, which has to be compensated for by increasing compressor output, and this in turn increases energy consumption. A pressure drop of only one bar can waste up to ten percent of compressor output, so it is easy to see how expensive these problems can be. Inadequate line cross sections and bends in the lines often reduce operating pressure, which increases operating costs. Compressed air systems that have grown over the years often contain a variety of materials, line sizes that are not optimal and a number of different couplings. All of these factors increase air flow resistance and the associated costs.
Ease of maintenance
Anyone who is planning to invest after giving all of these factors due consideration should have a look at what Kaeser Compressors has to offer. The company offers a full range of products designed to provide an efficient supply of compressed air. The portfolio includes a range of screw compressors which deliver 0.2–79 m3/min (at 7.5 bar), a complete range of air treatment options and compressed air management systems that run on industrial PC platforms. These systems enable users to manage an energy efficient compressed air supply which is tailored to their specific needs, and they also maximize availability and cost transparency. ADA is a computer-based compressed air requirements analysis system which helps users plan and modernize their compressor stations. Users can generate a low-cost requirements profile and determine the most efficient supply option. The latest screw compressors, the SK 21 und 24, reflect the attempt to generate compressed air as efficiently as possible. On a footprint of only 0.67 m2, the standard versions generate 1.8/2.2 m3/min at 8 bar (11 kW/15 kW motor). They are environmentally friendly, and acoustic noise levels remain at a tolerable 64/65 dB(A). A durable, smooth running, self-adjusting V-ribbed belt is used to transfer drive force from the EFF1 class motor to the compressor block.
The Delta Screw series of screw compressors manufactured by Aerzener Maschinenfabrik has been designed to transport air and neutral gas. The compressors are primarily used to transport bulk goods, but they are also found in many other applications in the process and water management industries. Frequency-controlled machines are being used to an increasing extent in the pneumatic industry. The reasons for this are speed control which provides optimal response to variations in pressure and a resulting reduction in energy consumption. The disadvantage in the past has been the high cost of the control equipment, and the new AS 200 controller has been designed to alleviate this problem. It is specially programmed for the supplier’s compressors, and users save more than 50% compared to PLC solutions.
Speed control saves energy
Market studies show that on average compressors with a power rating exceeding 55 kW only run at about 50 to 70% of full load. The maximum available volume of air is only needed at peak times. With this in mind, Alup has developed SCD technology for its Allegro range of speed-controlled screw com-pressors, which deliver good performance when running at partial load. SCD stands for speed controlled and direct drive. The manufacturer claims that energy savings of up to 35% can be achieved at constant line pressure (continuously adjustable from 5 to 13 bar). They are very efficient, and they eliminate start up/changeover current peaks and expensive idle time.
Storage and transport of gas
Piston compressors are used for storage and wide area supply of gas. Compressor reliability is one reason why gas is generally regarded as an extremely dependable, low cost source of energy. Hoerbiger compressors, for example, are used in the gas supply network to maintain efficient operations with a minimum of faults. The company offers a full range of maintenance services for piston and screw compressors which are designed to maximize reliability. The service packages include a wide variety of elements. An analysis of compressor operations, selection of optimal components and control systems and compressor modifications increase and optimize compressor performance. For compressor monitoring, Hoerbiger uses periodic snapshot monitoring or HydroCOM-CCM, a continuous online-monitoring system.
Small compressors
Services also include repair, spare part supply, compressor inspection, maintenance and full stock management. Small compressors are also moving with the times. They are developing into complete compressed air stations with integrated conditioning features. Atlas Copco has upgraded and modernized its industrial piston compressors which have motors rated at up to 15 kW. Nearly all of the models are now available with an optional refrigerated air dryer (pressure dew point +3 °C) and high-performance or multi-purpose air filters. Users who need the performance of an absorption dryer (pressure dew point –20 °C) can choose a self-enclosed dryer/filter package which turns the compressor unit into a complete source of high quality air. This solution provides a source of air in applications where only a small volume of air is need and only limited space is available.