Why are there different types of compressor? Our “Compressor FAQ” answers these and other frequently asked questions, aiming to shed some light on the subject of compressors.<\/p>\n If you need individual advice beyond this, it is best to contact our experts<\/a>. Simply by email, phone or contact form<\/a>. We look forward to your questions!<\/p>\n<\/div><\/div><\/div> This question is more complex than it sounds, as every compressor has several distinguishing features at once. Overlaps are inevitable. Below you will find some typical criteria we use to distinguish between different types of compressor.<\/p>\n Compression by displacement is a common method of generating compressed air. The principle is easy to understand if you think of a bellows being opened and squeezed together again. Or an accordion.<\/p>\n Positive displacement compressors work in a similar way: they draw ambient air into a closed housing and compress it there by reducing the available space. This reduces the volume of the air, which results in an increase in temperature, pressure and density. You can picture how the movement of the reciprocating piston presses a certain amount of air against the housing wall. And it keeps doing so until the desired pressure is reached. Screw and scroll compressors work in a similar way. Here, however, it is not pistons but rotors that keep squeezing the air together. By design, positive displacement compressors can deliver particularly high pressures.<\/p>\n<\/div><\/div><\/div><\/div><\/div> Many people know these compressors as turbo compressors. The centrifugal force that gives them their name is created by an impeller that rotates extremely fast and forces the air through the compression chamber. This is why it is also referred to as dynamic compression. Turbo compressors are not displacement machines but turbomachines. They always compress oil-free and are extremely powerful. They are therefore mainly used where large gas volumes are involved. These include pipelines, refineries and blast furnaces.<\/p>\n<\/div><\/div><\/div><\/div><\/div> As the name suggests, dry-running compressors require neither water nor lubricating oil and can therefore produce oil-free compressed air. However, users should bear in mind that the ambient air drawn in may already be contaminated with oil vapours or dust particles. So compressed air treatment is still necessary, also with regard to the moisture contained in the air.<\/p>\n<\/div><\/div><\/div><\/div><\/div> A two-stage compressor is a high-performance compressor for generating high pressures<\/strong>. If it is a piston compressor, it works with two successive cylinders: in the first cylinder, the ambient air is pre-compressed to a low pressure, then cooled and compressed to the final pressure in a second cylinder. This two-stage process allows greater compression, so that the compressor can generate a higher pressure level overall. Two-stage or multi-stage air compressors are often used in industrial manufacturing to drive pneumatic tools and machines.<\/p>\n The same applies to two-stage screw compressors, which use two compression stages connected in series. The first unit generates a certain pressure before the air is cooled and then flows into the second unit. Two-stage screw compressors are a good choice when the application continuously requires high pressure.<\/p>\n<\/div><\/div><\/div><\/div><\/div> Compared with single-stage compression, a two-stage compression process uses less electricity, as the final pressure is reached with less energy input <\/strong>. The reason for this is intercooling<\/strong>: after the first compression stage, the hot compressed air is cooled before it enters the second stage. We know from physics that cool air is “easier” to compress than hot air. So we achieve the same result with less energy.<\/p>\n Pre-cooled air also helps to keep the temperature during the second compression as low as possible. This in turn protects the components and extends the service life of the compressor.<\/p>\n<\/div><\/div><\/div><\/div><\/div> The main difference between a belt-driven compressor and a direct-drive compressor lies in the way the motor’s power is transmitted to the compressor stage. Either this is done via a V-belt or the motor is connected directly to the compressor. In this case, both run at the same speed.<\/p>\n So which is better? Here, too, the answer lies in the eye of the beholder, or rather in the customer’s application:<\/p>\n The range of compressed air applications is huge, and there are also industry-specific or individual requirements. It is therefore not surprising that different types of compressor are used in the various trade and industrial businesses. Nevertheless, we can identify three groups<\/strong> that account for the largest share:<\/p>\n<\/div><\/div><\/div> Piston compressors<\/strong><\/p>\n<\/div> Screw compressors<\/strong><\/p>\n<\/div> Scroll compressors<\/strong><\/p>\n<\/div> As our overview shows, scroll compressors have now become just as indispensable as screw and piston compressors. However, especially with the first two groups, it should be noted that various sizes and performance classes are available. There are also control and drive variants, cooling, air quality, receivers and many other specifications that allow you to adapt a compressor to your needs. A comparison like this therefore does not come close to reflecting what is available in practice.<\/p>\n<\/div><\/div><\/div><\/div><\/div> As a rule, the approved inspection body (e.g. T\u00dcV) checks a compressed air station for compliance with applicable safety standards before it is first put into service. If a compressor has a type examination<\/strong>, this means that a corresponding product sample has already been successfully approved at the manufacturer’s premises. The result of this examination is indicated by a marking on the compressor or in the accompanying documentation. A T\u00dcV appointment at the customer’s site is therefore no longer necessary. Instead, commissioning can be carried out by a “competent person”<\/strong>.<\/p>\n The same applies to the periodic pressure vessel inspection, which may also be carried out by a certified specialist on a T\u00dcV\/Z\u00dcS-exempt compressor. The training required to become a “competent person for pressure vessels and pipework” is offered throughout Germany by T\u00dcV and DEKRA, among others.<\/p>\n<\/div><\/div><\/div><\/div><\/div>
\nWhat does 2-stage compression mean?
\nAre all scroll compressors oil-free? <\/strong><\/span><\/p>\n<\/div>![\"The](\"https:\/\/www.eputec.de\/wp-content\/uploads\/2017\/02\/kompressor-smart-behaelter-trockner.jpg\" "\\"Oil-injected")
<\/span><\/div><\/div><\/div><\/div><\/div>What types of compressor are there?<\/strong><\/h3>\n<\/div>
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What is a positive displacement compressor? <\/strong><\/h3>\n<\/div>
What is a centrifugal compressor? <\/strong><\/h3>\n<\/div>
What is a dry-running compressor? <\/strong><\/h3>\n<\/div>
What is a two-stage compressor? <\/strong><\/h3>\n<\/div>
What are the advantages of two-stage compression? <\/strong><\/h3>\n<\/div>
What is the difference between belt-driven and direct-drive compressors?<\/h3>\n<\/div>
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Which compressors are suitable for trade and industrial businesses? <\/strong><\/h3>\n<\/div>
![\"RIK](\"https:\/\/www.eputec.de\/wp-content\/uploads\/2023\/02\/Renner-RIK-Kompressoren.jpg\" "\\"RIK")
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![\"The](\"https:\/\/www.eputec.de\/wp-content\/uploads\/2017\/02\/aquarius-oelfreier-wasser-kompressor.jpg\" "\\"aquarius-oil-free-water-compressor\\"")
<\/span><\/div>\n
![\"The](\"https:\/\/www.eputec.de\/wp-content\/uploads\/2017\/02\/scrolli-oelfrei-kompressor-schraube-e1663352917612.jpg\" "\\"Oil-free")
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What is a “T\u00dcV\/Z\u00dcS-exempt” compressor? And what does “type-tested” mean?<\/h3>\n<\/div>