Ekološki značaj primene elektro-inovativnog uređaja u procesu suzbijanja Ambrosia artemisiifolia L

Large amounts of aerosols that linger in the atmosphere are becoming carriers of pollen. Ambrosia artemisiifolia L has the ability to produce large amounts of pollen. Given the high adaptability of Ambrosia artemisiifolia L for the dissemination of the big problem is its suppression. In practice, the most common method of combating Ambrosia is the use of different groups of herbicides which adversely affects the environment. Therefore, the aim of the paper is set to investigate the efficacy of the treatment plant Ambrosia artemisiifolia L supply via innovative devices in the stage of development of vegetative growth of the plants after harvest of wheat. The first results were visible after only 20 minutes, and the total number of plants in the treatment was destroyed after 5 days.Velike količine aerosola koje se zadržavaju u atmosferi postaju nosači polena. Ambrosia artemisiifolia L ima sposobnost produkcije velike količine polena. S obzirom na veliku adaptibilnost Ambrosia artemisiifolia L pri širenju veliki problem je njeno suzbijanje. U praksi najčešća metoda suzbijanja ambrozije je korišćenje različitih grupa herbicida čime se negativno utiče na životnu sredinu. Zato je za cilj rada postavljeno da se istraži efikasnost tretmana biljaka Ambrosia artemisiifolia L naponom preko inovativnog uređaja u fenofazi vegetativnog porasta biljaka posle žetve pšenice. Prvi rezultati su bili vidljivi posle samo 20 minuta, a ukupan broj biljaka u tretmanu bio je uništen posle 5 dana

Statistical correlation between vibration characteristics, surface temperatures and service life of rolling bearings - artificially contaminated by open pit coal mine debris particles

Nowadays, two most often used methods for rolling bearings condition monitoring are thermographic inspection and vibrodiagno stic. However, analysis of the relevant literature has shown that so far there is no established correlation between rolling bearings surface temperatures and measured radial vibration intensities. These variables also strongly depend on rolling bearing's service life and it's environmental operating conditions, especially in case of open pit coal mine conveyor idler's rolling bearings; where high concentration of debris particles (such as surface dust, dirt and excavated coal) is present. Taking into account previously listed facts; the main goal of the presented research results was to establish statistically significant correlation between listed variables: rolling bearings surface temperatures, radial vibration intensities, service life and concentration level of debris particles in bearing grease. In order to achieve this goal, specific experimental methodology was developed and implemented. Obtained results were then processed using standardized statistical software and appropriate correlation was generated and later verified in praxis. At this moment, developed experimental methodology is applied only to open pit coal mine conveyor idler's rolling bearings, but its principles are universal, so with minor modifications it could be used for prediction of any of listed variables for different kinds of rolling bearings, operating in different environments

Probability of failure of thermal power plant boiler tubing system due to corrosion

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

Probability of failure of thermal power plant boiler tubing system due to corrosion

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

Life estimation of first stage high pressure gas turbine blades

Posle pojave prevremenih lomova koji su se javili kod lopatica prvog stepena turbine visokog pritiska određenog tipa turboreaktora u jednoj lokalnoj avio kompaniji, usledila su istraživanja u cilju određivanja njihovog sigurnog (pouzdanog) radnog veka. Lopatice prvog stepena turbine visokog pritiska su tokom rada izložene simultanom delovanju pritiska gasa iz komore za sagorevanje, centrifugalne sile u slučaju rotorskih lopatica, velikim temperaturnim promenama, kao i agresivnoj radnoj sredini. Kombinacija svih navedenih činilaca izaziva vrlo kompleksno naponsko stanje lopatica kao i mogućnost pojave višestrukih mehanizama oštećivanja: zamora izazvanog fluktuacijama u mehaničkom naponu, termo-mehaničkog zamora usled temperaturnih promena i korozije naponski opterećenih delova. Da bi se odredio radni vek u navedenim uslovima, neophodno je proceniti napone kojima su lopatice izložene uzimajući u obzir nekoliko promenljivih koje se u radu tretiraju deterministički. Razmatran je prenos toplote između sagorelih gasova i metala lopatica turbine. Izračunat je ukupni napon na dve vrste lopatica imajući u vidu termičke efekte i mehaničko opterećenje. Naponski ciklus je zatim izračunat za različite faze rada turboreaktora uz varijacije termičkih i mehaničkih osobina. Procena sigurnog radnog veka je izvršena primenom dva pristupa: inicijalnog modela i pristupa sa tolerancijom oštećenja uzimajući u obzir mehanički rast oštećenja i rast korozionog pita. Proračun je primenjen i na statorske i na rotorske lopatice turbine visokog pritiska turboreaktora koje su izrađene od čelika NI 738. Nađeno je da su ovo komponente visokog rizika, tako da je procenjen i rizik sa aspekta potencijalnih posledica od loma. Dobijeni rezultati su razmatrani u cilju rešavanja problema i donošenja sigurne odluke sa aspekta procedure održavanja ali i konstrukcijskog rešenja.Based on very early occurring ruptures found in the first stage high pressure turbine blades of a turbo reactor in a local aviation company, this study has the aim to determine their safe life. The first stage blades are subjected to simultaneous action of gas pressure coming from the combustion chamber, centrifugal forces in the case of the rotor blades and to important temperatures transients, which progress in a very aggressive environment due to hot gases. These combined parameters cause a high state of stress involving several complex mechanisms of damage, such as: fatigue caused by mechanical stress fluctuations, thermo-mechanical fatigue caused by temperature variations and corrosion caused on the stressed elements. Life cycle determination asks for stress evaluation of blades regarding several variables which are approached deterministically in the study. Heat exchange between combustion gases and metal blades is considered. The total stress on two kinds of blades is calculated by the addition of the thermal effect and the mechanical loading. The stress cycle is then calculated for different steps of the engine function during the operation by considering the variation of the thermal and the mechanical properties of the system. Safe life determination is done by two different approaches: the safe life approach by the initiation model and the damage tolerance approach considering the defect growth mechanics and considering the pitting corrosion effect. The calculation is applied for stator and rotor blades of an aero engine high pressure turbine made of NI 738. Since these parts are high risk components from the point of view of potential failure consequences, the risk is assessed as well. The results obtained are studied to determine the solution to the problem, and to propose a safe decision to be taken about the design or maintenance procedures.

Hydrogen embrittlement of low carbon structural steel

Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20- St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials

Prediction and prevention of boiler tubing systems erosion in thermal plant

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

Life estimation of first stage high pressure gas turbine blades

Posle pojave prevremenih lomova koji su se javili kod lopatica prvog stepena turbine visokog pritiska određenog tipa turboreaktora u jednoj lokalnoj avio kompaniji, usledila su istraživanja u cilju određivanja njihovog sigurnog (pouzdanog) radnog veka. Lopatice prvog stepena turbine visokog pritiska su tokom rada izložene simultanom delovanju pritiska gasa iz komore za sagorevanje, centrifugalne sile u slučaju rotorskih lopatica, velikim temperaturnim promenama, kao i agresivnoj radnoj sredini. Kombinacija svih navedenih činilaca izaziva vrlo kompleksno naponsko stanje lopatica kao i mogućnost pojave višestrukih mehanizama oštećivanja: zamora izazvanog fluktuacijama u mehaničkom naponu, termo-mehaničkog zamora usled temperaturnih promena i korozije naponski opterećenih delova. Da bi se odredio radni vek u navedenim uslovima, neophodno je proceniti napone kojima su lopatice izložene uzimajući u obzir nekoliko promenljivih koje se u radu tretiraju deterministički. Razmatran je prenos toplote između sagorelih gasova i metala lopatica turbine. Izračunat je ukupni napon na dve vrste lopatica imajući u vidu termičke efekte i mehaničko opterećenje. Naponski ciklus je zatim izračunat za različite faze rada turboreaktora uz varijacije termičkih i mehaničkih osobina. Procena sigurnog radnog veka je izvršena primenom dva pristupa: inicijalnog modela i pristupa sa tolerancijom oštećenja uzimajući u obzir mehanički rast oštećenja i rast korozionog pita. Proračun je primenjen i na statorske i na rotorske lopatice turbine visokog pritiska turboreaktora koje su izrađene od čelika NI 738. Nađeno je da su ovo komponente visokog rizika, tako da je procenjen i rizik sa aspekta potencijalnih posledica od loma. Dobijeni rezultati su razmatrani u cilju rešavanja problema i donošenja sigurne odluke sa aspekta procedure održavanja ali i konstrukcijskog rešenja.Based on very early occurring ruptures found in the first stage high pressure turbine blades of a turbo reactor in a local aviation company, this study has the aim to determine their safe life. The first stage blades are subjected to simultaneous action of gas pressure coming from the combustion chamber, centrifugal forces in the case of the rotor blades and to important temperatures transients, which progress in a very aggressive environment due to hot gases. These combined parameters cause a high state of stress involving several complex mechanisms of damage, such as: fatigue caused by mechanical stress fluctuations, thermo-mechanical fatigue caused by temperature variations and corrosion caused on the stressed elements. Life cycle determination asks for stress evaluation of blades regarding several variables which are approached deterministically in the study. Heat exchange between combustion gases and metal blades is considered. The total stress on two kinds of blades is calculated by the addition of the thermal effect and the mechanical loading. The stress cycle is then calculated for different steps of the engine function during the operation by considering the variation of the thermal and the mechanical properties of the system. Safe life determination is done by two different approaches: the safe life approach by the initiation model and the damage tolerance approach considering the defect growth mechanics and considering the pitting corrosion effect. The calculation is applied for stator and rotor blades of an aero engine high pressure turbine made of NI 738. Since these parts are high risk components from the point of view of potential failure consequences, the risk is assessed as well. The results obtained are studied to determine the solution to the problem, and to propose a safe decision to be taken about the design or maintenance procedures.

Hydrogen embrittlement of low carbon structural steel

Hydrogen embrittlement (HE) of steels is extremely interesting topic in many industrial applications, while a predictive physical model still does not exist. A number of studies carried out in the world are unambiguous confirmation of that statement. Bearing in mind multiple effects of hydrogen in certain metals, the specific mechanism of hydrogen embrittlement is manifested, depending on the experimental conditions. In this paper structural, low carbon steel, for pressure purposes, grade 20- St.20 (GOST 1050-88) was investigated. Numerous tested samples were cut out from the boiler tubes of fossil fuel power plant, damaged due to high temperature hydrogen attack and HE during service, as a result of the development of hydrogen-induced corrosion process. Samples were prepared for the chemical composition analysis, hardness measurement, impact strength testing (on instrumented Charpy machine) and microstructural characterization by optical and scanning electron microscopy - SEM/EDX. Based on multi-scale special approach, applied in experimental investigations, the results, presented in this paper, indicate the simultaneous action of the hydrogen-enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) mechanisms of HE, depending on the local concentration of hydrogen in investigated steel. These results are consistent with some models proposed in literature, about a possible simultaneous action of the HELP and HEDE mechanisms in metallic materials

Managing water pressure for water savings in developing countries

Many water utilities, particularly in the developing countries, continue to operate inefficient water distribution systems (WDSs) with a significant amount of water and revenue losses. Various factors, manageable to different extents, contribute to water losses, such as poor infrastructure, high pressures, illegal water use, etc. Whilst the problem of water losses in WDSs is global in scale, solutions need to be tailored to local circumstances due to the various causes of water loss and the mechanisms available to manage them. This paper investigates the potentials of the available pressure management methodologies and their implementation in developing countries, using a case study of a district metering area (DMA) in Kotez-Serbia. The minimal night flow method was applied for assessment of real losses. A particular focus is on assessment of water savings due to reduction of pressures. A total of three methods for estimation of water savings are described and tested against data measured in the DMA under initial and reduced pressures: (i) the method based on Leakage Index (LI) calculations, (ii) the PRESMAC model and (iii) a newly-developed method which is based on the assumption that both leakage and consumption are pressure dependent. The results indicate that the third method leads to the most accurate prediction of the total amount of water savings under reduced pressures, with only 6% difference between measured and estimated volume of saved water