PRZEGLĄD ELEKTROTECHNICZNY (Electrical Review), ISSN 0033-2097, R. 87 NR 12a/2011 21 Çetin GENÇER 1 , Serkan GÜRKAN 2 University of Firat (1), Turkish army Non-commissioned Officer Vocational Collage (2) The Application of a Microcontroller based Electrofusion Welding Machine Abstract- The application of a microcontroller based electrofusion welding machine has been carried out in this paper. The purpose of this paper is to check the voltage rate which the welding element needs, in a required interval. In order to make safer and better quality welding, features such as bar code reading, welding process parameters memory, the measurement of ambient temperature and internal device temperature. True RMS measurement and real time clock have been added to the system. Electrofusion welding machine, which has been designed after various tests, is thought to be cheaper than the ones on the market, to have high output voltage stability and to operate efficiently in welding electrofusion fittings. Streszczenie. Przedstawiono koncepcję elektrodyfuzyjnej maszyny spawalniczej sterowanej mikrokontrolerem. Rolą sterowania jest zapewnienie dostarczania impulsów napięciowych o odpowiednim kształcie i interwale z uwzględnieniem temperatury zewnętrznej. (Zastosowanie mikrokontrolera do sterowania elektrodyfuzyjną maszyną spawalniczą) Keywords: Electrofusion welding, Polyethylene, Microcontroller, True RMS. Słowa kluczowe: spawanie elektrodyfuzyjne, polietylen, mikrokontroler. Introduction The pipes used for transmitting liquid and gas in installation technology are required to be durable and long lasting. Plastic and metal transmission lines are used widely in gas and water transmission lines. Nevertheless with the invention of polyethylene (PE) material in 1933, thermoplastic materials began to replace these plastic and metal transmission lines [1,2]. In the modern technology, pipes made from polyethylene (PE) are used in a wide range of fields such as transmission and distribution of natural gas; drinking and potable water networks; waste water and sewage systems; agricultural irrigation; drainage projects; temporary water distribution pipelines; sports ground irrigation; fire fighting systems; telecommunication cabling systems; hazardous waste transmission; maritime and fishery; marinas; power plants; petrochemical industry; cement industry; chemical industry [3]. Installation technology is one of the most prominent fields in which PE is used. The features making transmission lines made from PE advantageous are physical life, impermeability, controlled and easy joining process, wearing, chemical resistance, fatigue, flexibility, seismic resistance, easy production, durability, hydraulic efficiency, thermal resistance. Electrofusion (EF) fittings made from PE material are also used to join PE transmission lines (Fig. 1.a). As it can be seen in the Fig. 1.b, an EF fitting consists of PE outer surface, coil and PE inner surface. When voltage determined by the manufacturer is applied to the fitting for a time period determined by the manufacturer, PE material in the inner surface melts and fills the gaps between the pipe ends. After the cooling period determined again by the manufacturing firm, joining is realized. Three welding methods are widely used in welding PE pipes. These are: hot plate butt welding (Butt fusion welding), hot plate coupling welding (Socket fusion welding) and EF welding [4-7]. In hot plate butt welding, the welding process is carried out with mechanical equipments prepared specifically for this process. Surfaces to be joined are pressed against the hot plate and are heated to the welding temperature at low pressure. After the hot plate is removed, pressure to the surfaces to be joined is increased and in this way joining is accomplished. When the pipes are connected to the welding apparatus welding surfaces should be parallel to each other. In hot plate butt welding, only the butt surface is machined with the help of equipment. After the pipes are machined and cleaned the welding surfaces are checked out to be parallel. Joining pressure is maintained until the welding area cools down completely [8]. a) (b) Fig. 1. a) Electrofusion fitting b) An electrofusion cross section [4]. In hot plate coupling welding, parts, the end of the pipe and the coupler are heated in a hot plate and the pipe is pushed into the coupler. After sufficient cooling, welding is completed. Particularly fittings in small diameter are used. Nowadays in in-house heating installations and clean water installations, joining process is carried out with the help of socket fusion welding technique [2;8]. Because human factor is at minimum level in joining process, electrofusion welding is a safe method with a minimum margin of error. In electrofusion welding, first of all the polyethylene pipes are cleaned up and prepared for welding, for a perfect welding process. Then joining of the pipe or pipes is carried out with EF fitting element and welding process begins by applying the energy determined by the firm. This method is the mostly preferred one because it minimizes human errors [8]. b)