Search

An adequate accommodation of sport horses implies the appliance of all construction, zootechnical and hygienic norms. Stables for horses should provide optimal microclimatic conditions for horses, social contact with other horses, unrestricted access to food and water, as well as to reduce the risk to injury to a minimum. Stables are essential for wellbeing of horses, because they spend a significant part of the day in them. Lights, temperature, humidity, air flow, concentration of gases and dust, hygiene and noise intensity in the areas where the animals are, must be within limits that are not harmful for horses. Satisfying optimal microclimatic conditions in the horse stables represent one of the most important items when projecting a facility. The aim of this paper is to highlight the significance of adequate accommodation for horses in accordance with the natural ethological characteristics of horses as well as to describe the most important ambient parameters in the closed type facilities.

Definisanje mehanizama uzajamnog dejstva metala sa vodonikom, koji uslovljavaju lokalnu promenu mikrostrukturnih karakteristika metala, promenu mehaničkih svojstava, a kao rezultat i pojavu različitih tipova vodoničnih oštećenja, uključujući i vodoničnu krtost, predstavlja izuzetno kompleksan problem. U zavisnosti od specifičnosti međusobnog dejstva uticajnih faktora odgovornih za inicijaciju i razvoj vodoničnih oštećenja, ispoljava se različit stepen makro pada plastičnosti metala, često praćen porastom mikro plastičnosti na lokalnom nivou koja je posledica dejstva različitih mehanizama vodonične krtosti koji su najčešće mikro lokalnog karaktera. Vodonična koroziona oštećenja, naročito kod isparivačkih cevi kotlova podkritičnih parametara, uprkos tome što su česta pojava, su istovremeno i najmanje istražena, posebno sa aspekta uslova za njihovu inicijaciju, kinetiku razvoja i mogućih uzročnika i mehanizama. U ovom radu dat je pregled savremenih saznanja iz oblasti mehanizama vodonične krtosti metala sa posebnim osvrtom na njihovo međusobno dejstvo.

Klasa čelika 1.25Cr1Mo0.3V se već dugo koristi za izradu elemenata TE postrojenja izloženih povišenoj temperaturi i unutrašnjem pritisku, tako da je i na našim postrojenjima već dugo u upotrebi. Ovaj čelik je mnogo bolje poznat kao: 15H1M1F (GOST), kao livena verzija 15H1M1FL (GOST), zatim livena verzija razvijena na zapadnom tržištu G17CrMoV510 (DIN EN) i relativno nova verzija od koje se izrađuju valjani proizvodi pod oznakom 15CrMoV510 (VdTUV). Iako je ruska varijanta ovog čelika dobro poznata i sa aspekta osobina i sa aspekta ponašanja u eksploataciji, zapadna varijanta pod oznakom 15CrMoV510 se praktično tretira kao potpuno nov materijal kod kojeg nije jasno pre svega njegovo ponašanje u eksploataciji, pa čak ni neke njegove osnovne karakteristike. S obzirom da se danas čelik 15CrMoV510 intenzivno ugrađuje u naš termoenergetski sistem u procesu revitalizacije parovoda, u ovom radu je dat pregled najznačajnijih karakteristika čelika ove klase. Određene osobine čelika 1.25Cr1Mo0.3V determinišu njegovo ponašanje u uslovima eksploatacije, a one mogu da imaju prihvatljive i neprihvatljive varijacije, koje se javljaju tokom njegove fabrikacije. U ovom radu je stavljen poseban akcenat na korelaciju ključnih osobina i eksploatacione upotrebljivosti, kako za osnovni materijal tako i za zavarene spojeve.

From the point of view of damage, mismatched welded joints often used in the production of the equipment, primarily pipes, are always critical sites in the system. Very often the problem is due to welding of different types of low-alloy and high-alloy steels. The selection of additional material presents a problem since the material can match only one of the steels in the mismatched joint, usually the low-alloy one. On the other hand, the selected material determines the properties of the welded joint by controlling the metallurgical processes that lead to the development of different phases with different characteristic properties. The existing experience with welding steel X10CrMoVNb91 in mismatched joints indicates that some of the phases that are formed can have negative effects on the exploitation capability of these joints. This work considers the development of different phases during formation of joints whose one component is steel X10CrMoVNb91 that is widely used in thermal power plant equipment.

Based on the analysis of the exploitation behavior of domestic thermal power plants it was concluded that the failures on the boiler tubing systems is due to erosion by flying ashes and that it is the main cause for the boiler tube failure especially in the evaporator and economiser surfaces. Current boiler tube erosion protection methods can be classified into three basic categories: a) welding overlay; b) thermal spraying (metallization) and c) mechanical protection. Welding overlay and thermal spraying procedures are successfully implemented on the clean boiler tubings prior to installation, although the same procedure with qualitative preparation (cleaning) can effectively be used even with the boiler tubings that were in the operation for a period of time. On modern thermal power plants in the world, thermal spraying method is widely used for the protection against erosion, abrasion and corrosion. Despite being inexpensive, mechanical protection methods are generally not used in the modern systems because of limited lifetime, difficulties during dismantling and reduced heat transfer on the protected tubings. In order to reduce the number of outages (direct material saving) and thus improve the operational reliability, availability and competitiveness, the use of modern erosion protection methods is of high priority.

The problem of boiler tube erosion is a very complex problem and present in practically all fossil fuel power plants burning low heating value coals irrespective of their particular design and operating characteristics. Predicting the rate of material degradation processes due to operating conditions is the essential feature for assessing the remaining lifetime. This clearly includes the knowledge of the type and kinetics of erosion phenomenon. In order to follow the erosion process and provide a reliable prediction of erosion rate and thus tube time to failure, models taking into account all relevant effects have to be developed. In this paper the is presented results of testing carried out on the evaporator hopper tubes of 350MW unit exposed to erosion and were used to assess their remaining life.

Oštećenja kotlovskih cevi usled erozije letećim pepelom predstavljaju jedan od najčešćih uzročnika pucanja cevi, otkaza grejne površine i neplaniranih zaustavljanja termoenergetskih postrojenja. Eroziono oštećivanje cevi kotlova na ugalj u svetskim razmerama predstavlja jedan od glavnih uzročnika otkaza termoenergetskih postrojenja sa dužinom trajanja zastoja koja iznosi 50-70% od ukupnog vremena zastoja postrojenja. Posebno ugrožene kotlovske grejne površine su zagrejači vode, isparivači, pregrejači pare i međupregrejači pare. Mehanički tip zaštite, i pored toga što je relativno jeftin, uglavnom se više ne primenjuje kod savremenih postrojenja već se zamenjuje savremenim vidovima zaštite. U cilju pripremanja podloga za sistematsko uvođenje savremenih tehnologija zaštite od erozije ugroženih kotlovskih cevi na domaćim termoelektranama izvršena su opsežna istraživanja i ispitivanja. U ovom radu prikazani su rezultati ispitivanja koja su sprovedena u cilju karakterizacije probnih uzoraka kotlovskih cevi sa zaštitnim prevlakama nanesenim postupkom hladne metalizacije, ugrađenih na jedno termoenergetsko postrojenje. Rezultati ispitivanja su jasno ukazali na tehno-ekonomsku opravdanost uvođenja postupka hladne metalizacije na erozijom ugroženim cevima kotlovskih grejnih površina., Erosion of boiler tubes is one of the main causes of damage of the boiler tubing system in thermal power plants operating with a low-quality abrasive coal often with a very low thermal efficiency. As a result, long-term and expensive shutdowns can occur. This is the problem faced by all thermal power plants worldwide irrespective of the coal quality used. Particularly endangered components of boiler tubing system are economizer, evaporator, superheater and reheater. Mechanical type of boiler tube protection by shield plates, despite of its simplicity and low cost, are not widely used on contemporary power plants, and often substituted with some kind of advanced protection technology. In the aim of preparation of background for implementation of modern boiler tube erosion protection technology in domestic thermal power plants comprehensive research and testings were carried out. In this paper were presented results of testings and characterization of boiler tube specimens with cold spray coating, taken from domestic thermal power plant. Results clearly indicate on techno-economical benefit of application of cold spray erosion protection coatings on boiler tubing system of thermal power plants.

Service reliability and maintenance of the major pipeline systems is still not consider to be important issue in the country. The explicit methodology have been developed that can answer more or less accurately the crucial question of how long certain part of the pipeline can be in reliable service. This methodology is generalized approach, and can be fully applicable to the system of interest only if all specific characteristics of the examined system are taken into account, including type of fluid, specific track, expected service life, etc. In this paper, the example of how methodology for reliability assessment of the pipeline is demonstrated for the case of the magistral pipeline in fossil fuel plant, together with the example of how obtained results of the applied methodology in addition to some other measures can be used to enhance maintenance.

U cilju izvođenja validne procene integriteta komponenti ugrađenih u industrijska energetska postrojenja neophodno je primeniti metodološki pristup koji obuhvata prikupljanje, sistematizaciju i analizu podataka iz eksploatacione istorije, propisivanje programa ispitivanja stanja materijala metodama sa i bez razaranja, kao i odgovarajućih kriterijuma prihvatljivosti. U radu je dat primer procene integriteta cevnog sistema vrelovodnog kotla jednog domaćeg postrojenja izloženog koroziji na osnovu podataka iz eksploatacione istorije, rezultata ranijih ispitivanja, kao i na osnovu poređenja dobijenih rezultata ispitivanja sa usvojenim kriterijumima prihvatljivosti. Procena integriteta kritičnih komponenti predstavlja podlogu za definisanje predloga o parcijalnoj zameni kotlovskih cevi, kao i niza korektivno - preventivnih koje imaju za cilj prevenciju pojave razaranja kao i obezbeđivanje visoke pouzdanosti u radu., In the aim of valid assessment of components integrity built-in industrial plants it was necessary to apply methodological approach, which includes: plant service history data acquisition, assortment and analysis, defining a programme for non-destructive and destructive inspection of material, and formulating of acceptance criteria. This paper present an example of integrity assessment of hot-water boiler tubing system exposed to corrosion based on boiler service history, previous test results and comparison of new results to adopted acceptance criteria. Integrity assessment of critical components represent background for defining of boiler tube partial replacement proposal, and also for defining of corrective and preventive maintenance measures. .

Vodonična oštećenja metala, kao opšti pojam, podrazumevaju mehanička oštećenja, degradaciju mehaničkih svojstava i mikrostrukturne promene izazvane prisustvom i efektima vodonika u metalu, najčešće uz istovremeno dejstvo zaostalih i/ili eksploatacionih zateznih napona. Nezavisno od izvora vodonika, vodonična koroziona oštećenja kotlovskih cevi, učestalo se javljaju čak i kod termoenergetskih postrojenja najrazvijenijih zemalja. Na osnovu rezultata eksperimentalnih ispitivanja uzoraka isparivačkih cevi termoelektrane, koje su tokom eksploatacije pretrpele vodonična oštećenja kao i teorijskih saznanja, u ovom radu je izvršeno multidisciplinarno sagledavanje mogućih mehanizama interakcije metala sa vodonikom i to sa aspekta uslova za nukleaciju oštećenja i poremećaja u hidrodinamici radnog fluida., Hydrogen damage of metal as a general concept implies mechanical damage degradation of mechanical properties and microstructural changes caused by the presence and effects of hydrogen in the metal, mostly accompanied by simultaneous action of residual and/or exploitational tensile stresses. Independent of the hydrogen source, the hydrogen corrosion damages in boiler tubes occur frequently even in power plant installations of the most developed countries. Based on experimental results of tested water wall tube samples that sustained hydrogen damage in exploitation, and based on theoretical knowledge, a multidisciplinary survey is given on possible interacting mechanisms of metal and hydrogen from a point of view of prerequisites for damage nucleations and perturbations in hydrodynamics of the operating fluid.

Procena eksploatacijske raspoloživosti i integriteta materijala termoenergetske opreme zahteva primenu metodološkog pristupa koji obuhvata prikupljanje i analizu podataka iz eksploatacije, definisanje programa ispitivanja stanja materijala metodama bez razaranja i razaranjem i propisivanje kriterijuma prihvatljivosti. Na osnovu podataka iz eksploatacije kotlovskog postrojenja, rezultata ranijih ispitivanja, kao i na osnovu poređenja novih rezultata ispitivanja sa kriterijumima prihvatljivosti izvršena je procenu integriteta vrelovodnog kotla u toplani "Mirijevo" u sastavu JKP "Beogradske elektrane". Nakon procene integriteta ugroženih delova cevnog sistema kotla definisan je predlog o parcijalnoj zameni ekranskih cevi, kao i niz preporuka za eksploataciju radi prevencije otkaza ekranskih cevi., Assessment of service availability and integrity of power plant component materials requires the use of methodological approach, that includes service history data acquisition and analysis; defining a programme for material state nondestructive and destructive testing; and formulating acceptance criteria. Data based on boiler service history and on previous test results comparing the new results to adopted acceptance criteria served as a basis for integrity assessment of hot-water boiler at plant "Mirijevo", belonging to JKP "Beogradske elektrane". Following the integrity assessment of critical boiler piping system parts, a proposal is defined for partial replacement of boiler wall tubes and a sequence of service recommendations how to prevent appearance of wall tubing damage is also given.

Korozija predstavlja nepovratni proces degradacije materijala. Zbog nepovoljanog uticaja koji ima na radne osobine materijal, posebno materijala cevnog sistema kotla, ona predstavlja predstavlja neizostavni deo rada termoenergetskih postrojenja i glavni uzrok mnogih otkaza. Pored uobičajenih metoda za procenu preostalog radnog veka korisno je primeniti i metode za procenu pouzdanosti kotlovskih cevi termoenergetskih postrojenja koje su oštećene korozijom. Korelacijom rezultata koji se dobijaju primenom ove dve različite metode moguće je dobiti bolja saznanja o trenutnom stanju materijala cevi uz istovremeno izvođenje tačnije procene njihovog ponašanja tokom dalje eksploatacije. Stoga je u ovom radu na primeru cevi ulazne zone paketa naknadnog pregrejača prikazan integralni pristup procene preostalog radnog veka i pouzdanosti. Razmatranja ove vrste su veoma značajna za pristupe u održavanju koji su zasnovani na riziku., Corrosion is irreversible process of material degradation. Due to detrimental effects exerted on the operating material characteristics, especially in the boiler tube system, it is of one the most important issues in the operation of thermal plants and is considered to be the root cause of many outages. Besides common remaining life assessment methods, it is useful to apply a method of reliability evaluation of the thermal power plant boiler tubes with corrosion damages. Correlation of results obtained by these two methods makes possible to obtain a better knowledge of current tubes material state as well as a more accurate assessment of their behavior during future exploitation. Therefore, an integrated approach of remaining life assessment and reliability evaluation, on the first stage reheater tubes system example, is presented in this paper. Considerations of this kind are very important for the risk-based maintenance programs.

Filler material choice for repair welding of stop valve spindle of thermal power plant by-pass pipeline was presented in this paper. Repair welding of the stop valve spindle was necessary because of plant operating problems due to very frequent localized damage appearance in the form of erosive wear on it. For this purpose it was necessary to choice appropriate filler material with high wear resistance characteristic. Experimental investigation and testing (hardness measurement, chemical composition analysis and microstructural investigation) of prepared specimens after welding simulation with different kind of filler material was performed. On the basis of obtained results it was recommended procedure for application of the filler material with generally preferable characteristic.

Damage of boiler tubes is a very serious problem in many utilities worldwide, including even in the most advanced countries. Preserve of boiler tube integrity present major part in maintenance programs centered to achievement of high levels of availability and reliability of thermal power plants. This is due to a very specific and complex interconnection of design and operating characteristics of the boiler unit. Based on the results of numerous boiler tube damages investigation performed on domestic thermal power plants it is concluded that the initiation of different damage mechanism was strongly influenced by tube weld geometry defects. In this paper particular attention was dedicated to this not well documented problem. Structural integrity of the boiler tubes are greatly affected by the weld excessive root penetration (melt-through) on the tube inner surface. This type of weld geometry defect, which occured often on boiler tubing system, present local flow disrupter and also very strong stress riser. In the vicinity and donwnstream of excessive root penetration type disrupter initiation of different damage mechanisms (erosive and corrrosive wear, underdeposit corrosion, stress corrosion, corrosion fatigue) occured due to working fluid nucleate boiling destabilization (eveporator), or due to turbulent flow (superheater and reheater), followed by intensive suspended solids deposition.

U radu je dat prikaz oštećenja koja se javljaju kod poluga mlinova za ugalj termoenergetskih postrojenja u uslovima eksploatacije. Nastala oštećenja mogu da budu takvog karaktera da poluge mlinova za ugalj izgube svoju funkcionalnost, usled čega dolazi do otkaza postrojenja. Istraživanja koja su sprovedena su imala za cilj i određivanje napona kojima su poluge tokom eksploatacije izložene da bi na što korektniji način mogla da bude propisana procedura sanacije poluga., Different kinds of damages provoked on the fossil fuel power plant coal mill crank in exploitation condition are considered in this paper. Sometimes obtained damages could be so severe that coal mill crank completely lose their functionality and malfunction of coal mill is taking place. Comprehensive investigations that was carried out on the damaged cranks are also included the determination of different kind of stresses which acting on cranks during exploitation. All obtained results are used as the background for the crank rehabilitation procedure.

Structural integrity of power plant component is usually estimate by its residual service life. Input data for component residual life estimation exposed to high-temperature creep is the creep strength of material (time dependent strength), after particular service period. Creep strength is usually obtained by statistical treatment of experimental data, and it decreases during service time due to degradation of microstructure. Since the creep resistance decreases with time due to microstructure degradation, it is essential for practice to use microstructural parameters in order to define statistically the changes in the creep resistance, which in turn enables to follow the physical significance of these changes. Due to a considerable scatter in the creep data, treatment by statistical analysis of the physically significant parameters is a problem that, to date has not been satisfactorily solved. One of attempt to overcome the lack of all data, which were required for previous analyses and estimation of service resources/service life, is done in this paper. Kinetic process has to be defined by the rate of process or by time for which such process will cause the rupture, instead of creep strength. Thus, the time to fracture of the component subjected to a high-temperature creep is determined due the kinetic theory of strength (model Zurkov) and using the microstructural parameters as an input data.

Hydrogen-induced fractures of metallic components of thermal fossil fuel power plants (TPP) presents very serious exploitation problem and often exert considerable influence on the loss of power plant availability. Hydrogen damage is one of the most disturbing of boiler tube failure mechanism, and from the international experience, remains as one of the leading causes of frequent outages of boiler tubing system. To clarify root causes and complexity of problems associated with hydrogen damages, it is necessary to apply a multidisciplinary approach which comprises research in the field of material quality, boiler design, operation and maintenance. The work reported here is based on the theory and, particularly, on the experimental tests performed on boiler evaporator tube samples, taken from a domestic 210 MW power plant, that had experienced hydrogen damages during service. Possible mechanisms for metal - hydrogen interaction are considered from materials point of view, fluid hydrodynamics in evaporator tubes and the complexity of structural - exploitation plant characteristics. The aim of this paper is to contribute to the analysis of hydrogen damaging in boiler evaporator tubes and to propose failure mechanism model based on "micro-departure from nucleate boiling" (micro-DNB) of working fluid. In addition, this paper elucidates some definitions of major root cause influences by proposing model for systematization of influencing and corresponding operating factors responsible for hydrogen damages of boiler evaporator tubes.

Constant demands for quality improvement of high-speed steels have contributed to the prolonged importance of tests, such as test in structural changes and properties derived from the applied heat treatment. Generally, tools from high-speed steel are treated by multiple tempering after quenching in order to reduce amount of retained austenite and value of internal stresses to the lowest level. A review of literature shows that processes taking place during the first tempering have been studied comprehensively and in great detail while very little attention has been paid to testing structural changes in the succeeding tempering cycles. Having this in mind, the differential dilatometric method has been used to test the influences of quenching temperature (1170-1230°C), tempering temperature (540-605°C), and the number (1 to 5) and tempering time, on the process of destabilization of retained austenite at circumstances of multiple continuous tempering of quenched W-Mo-V high-speed steel. The acquired results have contributed to the conviction that the customary regime of tempering for this type of high-speed steel could be rationally modified. We emphasize that the change in tendency of the dilatometric cooling curve in the austenitic-martensitic transformation region is the result of self-tempering of secondary martensite. The explanation proposed in literature for this dilatometric effect is from our point of view totally incorrect.

Korozija, kao nepovratan oblik razaranja materijala, predstavlja veliki problem kod postrojenja procesne industrije, kako sa aspekta obezbeđivanja njihove pouzdane eksploatacije, tako i sa ekonomskog aspekta. U ovom radu je prikazana metodologija proučavanja korozionih fenomena i date su smernice za primenu analitičke dijagnostike – multidisciplinarne metode za analizu i utvrđivanje uzroka korozionih oštećenja., Corrosion, as a process of irreversible destruction or deterioration of material, is a serious problem in process industry plants exploitation both from the economical and reliable exploitation points of view. In the present paper methodology to study corrosion phenomena, including analytical diagnostic – multidisciplinary method for root causes determination and analyses, are presented.

U radu je dat prikaz grešaka tipa prslina koje mogu da se jave kod zavarenih spojeva vitalnih komponenti termoenergetskih postrojenja. Posebno su obrađene greške zavarivanja koje se javljaju kod toplotno postojanih Cr-Mo-V i Cr-Mo čelika za parovode, koje pod određenim uslovima pogoduju stvaranju prslina tokom eksploatacije., Possible crack-like failures in the vicinity of the welds of fossil fuel power plant components are presented in this paper. Welding flaws of Cr-Mo-V and Cr-Mo pipeline heat resistant steels are especially discussed. These flaws are very unbeneficial because they could provoked crack initiation and their propagation during service.

U raduje prikazan značaj makrofraktografije kao dijagnostičke metode u održavanju industrijskih objekata. Istaknuta je neophodnost saznanja uzroka razaranja/loma bilo koje strukture kao neželjenog događaja sa različitim brojnim posledicama, Dat je pregled klasifikacije lomova i njihove osobenosti, kao i faze same makroskopske fraktografije., Importance of macrofractography as a diagnostic method in industrial maintenance is presented in this paper. The necessity off allure/fracture causes determination as a unplaned event with numerous different consequences is also emphasized. Short review of fracture classifications their characteristics, as well as the macrofractography phases are shown too.

Korozija metala kotlovskih cevi uslovljava ne samo povišenje troškova održavanja, već u velikoj meri utiče i na pad pouzdanosti i raspoloživosti celog termoenergetskog postrojenja. Blagovremena detekcija korozionih oštećenja i naslaga sa unutrašnje strane cevnog sistema kotla obezbeđuje uslove za sprovođenje preventivnog kao i održavanja usmerenog ka pouzdanosti. Imajući u vidu nedostatke dosadašnjih konvencionalnih metoda ispitivanja, na Mašinskom fakultetu u Beogradu u saradnji sa firmom ELZO razvijen je i sertifikovan nov i u našoj zemlji jedinstven uređaj, EMF3-MI, za otkrivanje korozionih oštećenja i naslaga sa unutrašnje strane cevnog sistema. U ovom radu je dat predlog modela preventivnog održavanja kotlovskih cevi, generalni prikaz problematike korozije metala i naslaga sa vodene strane kotlovskih cevi, kao i iskustva u primeni uređaja EMF3-MI na cevnom sistemu jednog domaćeg kotlovskog postrojenja., Metal corrosion of steam power plant tubing system provoke not only advancement of maintenance cost but also have a great influence on reduction of power plant reliability and availability. Timely detection of inner side corrosion of boiler tubes provide condition for implementation of RCM methodology as well as preventive maintenance. Taking into account all limitation of conventional detection methods, research group from Faculty of Mechanical Engineering, Belgrade in cooperation with ELZO company was developed a new NDT corrosion detection device EMF3-MI. This paper gives a proposal for boiler tube preventive maintenance methodology, general review of boiler tubes metal corrosion, tubes inner side scaling problems as well as EMF3-MI devices application experience on tubing system of domestic fossil fuel steam power plant.

Značajan broj otkaza termoenergetskih postrojenja, prema statističkim podacima, je posledica neodgovarajućeg kvaliteta materijala od koga je neka komponenta izrađena. Interesantno je pitanje kako materijal može da bude neodgovarajući, kada se s jedne strane, pri projektovanju izabiraju materijali koji, po svojim standardizovanim osobinama, zadovoljavaju mogućnost eksploatacije pri povišenim parametrima za određeni radni vek, dok se s druge strane uz specifikaciju isporučenih materijala dostavljaju i atesti kao nepobitni dokazi o kvalitetu materijala. Međutim, mnogobrojna ispitivanja, koja su na našim postrojenjima usledila nakon havarijskih ispada, su kao rezultat imala jednoznačan zaključak: polazni materijal nije bio zadovoljavajućeg kvaliteta. Namera u ovom radu je da predloži klasifikaciju mogućih grešaka kod komponenti termoenergetskih postrojenja čime bi bila pojednostavljena i olakšana procedura svih vidova kontrola ali i otkrivanje uzroka pojave oštećenja i razaranja. Takođe su prikazani neki od konkretnih slučajeva razaranja komponenti termoenergetskih postrojenja koja su usledila zbog nezadovoljavajućeg polaznog kvaliteta materijala, ne ulazeći u tehno-ekonomsku analizu štete koja bi bila kruna svakog ovakvog nalaza., According to statistics, a substantial number of shutdowns occurring in power plant components, have resulted from inadequate material quality. It is interesting to know how this particular material proves to be inappropriate when it satisfies conditions of high temperature and service life, and is delivered with an asserted quality specification as proof of its quality. Numerous tests performed on domestic components after breakdowns all lead to a common conclusion: the initial material quality was poor. The aim of this paper is to present a proposal of possible flaws classification of power plant components which can ensure easier control of material during inspection as well as reveal possible causes of flaws/damages and failures. Some specific cases of component damages provoked by inadequate material quality are also presented.

Estimating the influence of texture on the resistance and wear of bimetal is of great interest in metallurgical and industrial applications. Hot rolled sheets of low carbon steel were joined to brass Cu76Zn24 and Cu78Zn22, separately. The specimens were deformed in rolling regimes RI and RII. The specimens defined by such parameters were exposed to ruby laser in Q switch regimes with 0.7-2.7 J of energy. The dependence of the damage’s degree versus phkl is investigated.

U ovom radu predstavljene su primene mikrolegiranih čelika u modernom tehničkom svetu. Ukazano je na razvoj mikrolegiranih čelika: smanjenje sadržaja ugljenika, umirivanje čelika aluminijumom i formiranje taložnih čestica koje su odgovorne za sprečavanje rasta austenitnog zrna. Mehanizmi ojačavanja mikrolegiranih čelika kao i uticaj čestica karbida i nitrida vanadijuma, niobijuma i titanijuma na mehaničke karakteristike navedenih materijala su takođe prikazani.