Screw compressors for demanding processes

The reliable generation of compressed air is essential in industry, power stations and many other sectors. AERZEN screw compressors have proven their worth worldwide in a wide range of applications and industries. They operate reliably across a wide range of temperature zones, both indoors and outdoors. Whether air, neutral gases or special gases: thanks to their high versatility, they are suitable for demanding conveying, compression and vacuum applications across a broad spectrum of industrial uses.

The oil-free and oil-injected screw compressors reliably convey and compress in numerous applications, such as pneumatic conveying, chemical and process engineering, or compressed air technology. Typical areas of application also include the aeration of sewage treatment tanks, keeping lakes and harbour facilities free of ice, the supply of oxidation air for power stations, and their use as jet starters for aircraft turbines.

Screw compressors are twin-shaft rotary piston machines. They operate on the displacement principle with internal compression and are known as positive-displacement compressors. This applies to all screw compressors. Their operation is based on two intermeshing rotors, which continuously draw in the medium, compress it and convey it to the discharge port.

What sets AERZEN apart is that we have made reliability, ease of maintenance, user-friendliness, flexibility and energy efficiency our guiding principles. The result is a range of unique design features. One example of this is the efficiency coefficients of the AERZEN 3+4 VML and 4+6 VM profiles. Compared to standard compressors, they save a considerable amount of energy. And what, in fact, is the ultimate in compressor technology? The ultimate is the new E-compressors from AERZEN. With an efficiency increase of up to 6 per cent, they unlock even more valuable potential.

How a screw compressor works:

• Displacement principle with internal compression
• Designed as a positive-displacement compressor
• Twin-shaft rotary piston machines
• Two intermeshing, helical rotors
• Continuous compression of the medium being conveyed

There are single- and double-rotor rotary compressors, but when we talk about screw compressors, we usually mean two rotors arranged in parallel with different screw profiles. These mesh together like gears and compress the gas situated between the profiles by displacement. Unless the machines are oil-free, oil is injected for cooling and sealing. This process, known as liquid cooling, is particularly necessary where there are high pressure differentials between the suction and discharge sides. Oil can also help to minimise wear and reduce temperatures. Top-class oil-free designs do not require this measure and, thanks to high-precision manufacturing processes and synchronised gears, operate with low friction. It is guaranteed that no lubricant enters the chamber at any time – which qualifies the new models as completely oil-free compressors. This is particularly advantageous in applications with high demands on purity and process reliability, such as in the food and pharmaceutical industries, as well as in chemical and process engineering.

Economic considerations are prompting many companies to switch to screw compressors. A key reason for this is their high compression efficiency, which has a positive impact on energy consumption. This is a decisive factor, particularly in times of high energy prices. Heat recovery is also becoming increasingly important in this context.

Due to their basic design, screw compressors are clearly superior to reciprocating compressors in terms of efficiency. This enables a noticeable reduction in energy costs and CO₂ emissions during operation. Whilst around one-tenth of the intake air is lost via the piston rings in piston compressors, the pressure loss in screw compressors is significantly lower and rarely exceeds 0.1 to 0.2 per cent.

The energy efficiency of screw compressors can be further improved by optimising the flow conditions during the compression process. Improvements to the air inlet into the compressor unit have proved particularly effective in this regard. In AERZEN’s latest 5plus generation of machines, all components are precisely coordinated to ensure optimum flow behaviour. The reduction in pressure losses and the optimisation of the inlet and outlet ports help to ensure that the desired delivery pressure is maintained in a stable and reliable manner. The additional sound insulation not only reduces noise levels during operation but also optimises flow behaviour.

Premium motors are available on request to meet the requirements of current energy efficiency classes. Future-proofing is particularly important for customers in this context, as longevity is also measured by whether or not future requirements regarding energy efficiency classes can be met.

Modern rotary compressors are easy to operate and maintain efficiently. Digitalisation simplifies processes, increases transparency and reduces additional running costs. Furthermore, screw compressors generally suffer less wear and tear. The result is robust, reliable and easy-to-maintain machines for a wide range of applications.

The smooth-running V-belt drive on Generation 5plus machines allows different pulleys to be fitted to achieve the desired transmission ratio. Changing the pulleys is also straightforward at a later date. The screw compressor remains flexible when the desired parameters change and does not need to be replaced by another model with inflexible settings. Maintenance requirements for the V-belt drive are extremely low, as the correct tension is ensured by its own weight. On many units, the speed can also be controlled electronically.

High precision and exact maintenance of the desired pressure are an absolute must in most applications. Control can then be carried out, for example, directly via an integrated control element on the housing. As the control elements are positioned on the front of the units, they can be arranged side by side to save space. With this design, it is even possible to check the oil level whilst the unit is in operation. Special AERZEN oils extend the oil change intervals to twice the prescribed intervals.

A major advantage of screw compressors is their quiet operation. Unlike piston compressors, there is no need to hold masses at their respective dead centres, which means that vibrations inside a rotary compressor are considerably lower. This quiet operation can be further optimised through design measures. At the same time, intelligent sound insulation offers further benefits for safety- and hygiene-critical applications.

The use of an innovative silencer design reduces the sound pressure level. It also acts as an effective spark arrestor. Machines fitted with this feature are also approved for use in explosion-protected areas. Thanks to the optimal sound-insulating properties, no additional materials are required for sound insulation. There is therefore no risk of contamination from damaged insulation materials or similar sources. The associated maintenance work is also eliminated.

Particularly in hygiene-critical areas of the food industry and in chemical plants, a key requirement – alongside the need for oil-free compressors – is effective sound insulation without any risk of contamination. Where necessary, a compressed air filter can be used to further purify the compressed air. In the medical sector, specialised filters for treating compressed air are just as common as separation systems for other residues. To ensure that no unwanted moisture is carried into the application area, aftercoolers and dryers provide effective dehumidification of the compressed air.