N. Stosic, I. K. Smith, A. Kovacevic Screw compressor: A strong link in the development chain TEHNIKI VJESNIK 9 (2002)(3,4)41-46 41 ISSN 1330-3651 UDC/UDK SCREW COMPRESSOR: A STRONG LINK IN THE DEVELOPMENT CHAIN Nikola Stosic, Ian K. Smith, Ahmed Kovacevic Professional paper In any development, screw compressor has several prominent roles. One is its unavoidable application in infrastructure building of the road and railway networks, as well as in major housing developments. Other roles are introduction of new compressor manufacturing facilities and a consequential improvement of the existing compressor industry in which the screw compressor has a vital part as an effective, efficient and robust machine. Old compressor industry, which has experience in manufacturing of traditional compressors, is a valuable basis for direct application of new developments in area of screw compressors achieved in recent years. A role of screw compressors as a potential means in the local and world trade also must be seriously considered. Key words: screw compressor, design, development, efficient use of energy Vijani kompresor: Snana veza u razvojnom lancu Struni lanak U svakom razvojnom projektu, vijani kompresor ima nekoliko istaknutih uloga. Jedna od njih je njegova neizbjena primjena u izgradnji infrastrukture cestovnih i eljeznikih mrea i velikih stambenih projekata. Druge uloge su uvoenje novih naina za proizvodnju kompresora te slijedom toga unapreenje postojee industrije kompresora u kojoj je vijani kompresor bitan kao uinkovit, efikasan i robustan stroj. Stara industrija kompresora, koja ima iskustva u proizvodnji tradicionalnih kompresora, predstavlja vanu polaznu toku za direktnu primjenu novih razvojnih dostignua u podruju vijanih kompresora zadnjih godina. Uloga vijanih kompresora u lokalnoj i svjetskoj trgovini se takoer mora ozbiljno razmotriti. Kljune rijei: vijani kompresor, konstrukcija, razvoj, djelotvorno koritenje energije  Uvod Introduction Industrial and domestic compressors consume staggering 7 % of the world power production. Their majority today is reciprocating compressors. However, many other types have their substantial share. Among them, screw compressors play a significant role because of their popularity and relatively large size and consequently large power consumption. Screw compressor is a rotational machine of volumetric action, which transforms mechanical work of the electromotor, turbine or IC engine into potential energy of the working medium of higher pressure. They operate on gases, vapour or multi-phase mixtures with phase changes taking place within the machine with or without internal lubrication. The main users of compressed gases supplied by screw compressors are today building engineering, food, process and pharmaceutical industry, metallurgy and pneumatic transport. For optimum performance from such machines, a specific design and operating mode is needed for each application. They are simple machines capable of high-speed operation over a wide range of operating pressures and flow rates with high efficiencies. Favourable features of the screw compressor process and its design details give certain advantage compared with all other compression machines. Before others, these are a pure rotational movement of the compressor elements, which allows higher speeds and higher efficiency per compressor unit mass, less wear and longer life of the machine. Therefore, screw compressors are up to five times lighter than their reciprocating counterparts of the same capacity and their longevity can be almost ten times higher. Since they are both reliable and compact, consequently they comprise a large portion of all positive displacement compressors sold and currently in operation. However, volumetric and adiabatic efficiency of screw compressors is highly dependent upon the precision of manufacturing of their rotors as well as other component parts, housings and bearings. Such a precision can be achieved only by use of specialized machine tools. The present world production rate of positive displacement compressors is in excess of 50 million units per year, the bulk of them being required for compressed air and refrigeration systems. During the past thirty years, for many applications, traditional reciprocating compressors have been replaced by those of the twin-screw type. The main reasons for this change are the development of improved rotor profiles, which have drastically reduced internal leakage, and machine tools, which can manufacture the most complex shapes to tolerances of the order of 5 m at an affordable cost. Although advances have also been made in analytical methods, which are gradually being adopted by designers to predict compressor performance more reliably, their scope and accuracy lag behind that of modern NC machine tools and assembly procedures. Consequently improved methods of analysis can create, as yet unrealised, opportunities for improving the performance and reducing the cost of screw compressors and, thereby further extending the