Structural Integrity Assessment of Welded Pipeline Designed with Reduced Safety

The main goal of this paper was to assess the integrity of welded joints in the main pipeline of the reversible hydropower plant "Bajina Bašta". Japanese steel Sumiten 80P (SM 80P) was used as the parent material. European recommendation for pipeline safety factor is equal to 1.7 and this value was used for calculations of the RHPP "Bajina Bašta", whereas the value recommended by Japanese standards is 2.1. A relatively small safety factor, which is different from the Japanese recommendation (since the material itself is Japanese), represented one of the main reasons for a detailed investigation of the pipeline structural integrity and safety, using the prototype. In the case of pressure vessels, the welded joint is a location of stress concentration, which can act in the same way as residual stresses. Assessment of prototype test results is possible to perform based on stress and strain calculations of vessels with ideal geometry. For this reason, the solution for thin-walled vessels is given, both in elastic and elastic-plastic areas. Numerous tests were performed in order to obtain a reliability assessment necessary for the construction of the pipeline, since the consequences of potential failure would be disastrous in this case. A numerical simulation, based on the experimentally determined mechanical properties of the material used, was also performed in order to obtain the stress/strain distribution. These results were then compared to the experimentally obtained ones, and it was concluded that there is a good level of compliance between numerical and experimental results

Integrity assessment of ammonia storage tank by non-destructive testing

Ammonia is a very dangerous fluid, and it is so important that its storage tanks are safe. Fusion welded joints (in further text: welded joints) are the 'weakest' location in some structures, in this case - tanks, and the detection of defects in welded joints during manufacture is also very important, since defects may cause failure with catastrophic events. NDT techniques that have been performed on welded joints show insight into the quality of the performed welding technique, and results imply whether tanks are safe to be put into exploitation. Three different methods are used for testing: visual, penetrant, and ultrasonic (in this case a new method is used). The first two methods show no irregularities, but third NDT method shows the necessity for tank repair. All of these tests are performed in accordance with relevant standards that are discussed, as well as the used NDT methods in general, with their ability and restrictions

Manufacturing and integrity of ammonia storage tanks

Manufacturing ammonia storage tanks represents a very demanding and responsible task. The paper presents the methodology for manufacturing two ammonia storage tanks in Russia, along with all the necessary steps. The base material used for tank manufacture is steel P355NL2. Instructions and requirements in EN 14620 standard need to be followed. This standard dictates all previously mentioned steps, hence the standard itself is shown here. The welding technology of two steel tank shells is also shown. Integrity assessment of the tanks is necessary to carry out immediately before the tanks are put into service. NDT results for welded joints and results of adequate tests performed on the tanks themselves provided insight into the quality of the performed work, and have shown that the selected welding technologies have met all requirements in terms of strength, thus confirming that the tank integrity is satisfactory

Manufacturing and integrity of ammonia storage tanks

Manufacturing ammonia storage tanks represents a very demanding and responsible task. The paper presents the methodology for manufacturing two ammonia storage tanks in Russia, along with all the necessary steps. The base material used for tank manufacture is steel P355NL2. Instructions and requirements in EN 14620 standard need to be followed. This standard dictates all previously mentioned steps, hence the standard itself is shown here. The welding technology of two steel tank shells is also shown. Integrity assessment of the tanks is necessary to carry out immediately before the tanks are put into service. NDT results for welded joints and results of adequate tests performed on the tanks themselves provided insight into the quality of the performed work, and have shown that the selected welding technologies have met all requirements in terms of strength, thus confirming that the tank integrity is satisfactory

Integrity assessment of ammonia storage tank by non-destructive testing

Ammonia is a very dangerous fluid, and it is so important that its storage tanks are safe. Fusion welded joints (in further text: welded joints) are the 'weakest' location in some structures, in this case - tanks, and the detection of defects in welded joints during manufacture is also very important, since defects may cause failure with catastrophic events. NDT techniques that have been performed on welded joints show insight into the quality of the performed welding technique, and results imply whether tanks are safe to be put into exploitation. Three different methods are used for testing: visual, penetrant, and ultrasonic (in this case a new method is used). The first two methods show no irregularities, but third NDT method shows the necessity for tank repair. All of these tests are performed in accordance with relevant standards that are discussed, as well as the used NDT methods in general, with their ability and restrictions

Structural Integrity Assessment of Welded Pipeline Designed with Reduced Safety

The main goal of this paper was to assess the integrity of welded joints in the main pipeline of the reversible hydropower plant "Bajina Bata". Japanese steel Sumiten 80P (SM 80P) was used as the parent material. European recommendation for pipeline safety factor is equal to 1.7 and this value was used for calculations of the RHPP "Bajina Bata", whereas the value recommended by Japanese standards is 2.1. A relatively small safety factor, which is different from the Japanese recommendation (since the material itself is Japanese), represented one of the main reasons for a detailed investigation of the pipeline structural integrity and safety, using the prototype. In the case of pressure vessels, the welded joint is a location of stress concentration, which can act in the same way as residual stresses. Assessment of prototype test results is possible to perform based on stress and strain calculations of vessels with ideal geometry. For this reason, the solution for thin-walled vessels is given, both in elastic and elastic-plastic areas. Numerous tests were performed in order to obtain a reliability assessment necessary for the construction of the pipeline, since the consequences of potential failure would be disastrous in this case. A numerical simulation, based on the experimentally determined mechanical properties of the material used, was also performed in order to obtain the stress/strain distribution. These results were then compared to the experimentally obtained ones, and it was concluded that there is a good level of compliance between numerical and experimental results

Effect of plasma hardfacing and carbides presence on the occurrence of cracks and microcracks

Presented is the effect of plasma hardfacing (or just hardfacing) and carbides presence on the occurrence of cracks and microcracks in the welded layer. The reasons behind this phenomenon are analysed and explained. In addition, the plasma welding technology with all the necessary data such as welding parameters is shown for the case of undamaged tooth of a machine used for the milling of marble. The welded layer with a significant amount of tungsten-carbide is applied onto new, undamaged tooth in order to improve the characteristics of the surface layer of the base material by increasing its hardness which leads to increasing of wear resistance and impact toughness. After welding, the tooth is cut using electrical discharge machining (EDM) for examining the applied surface layer in different locations throughout the welded joint. Macro and microstructural analysis aided in determining the characteristics of the surface layer. The nature and causes of cracks and microcracks are analysed in order to provide a better solution to avoid crack occurrence, as well as in determining their potential effect on the integrity of the tooth as a whole

Towards continuous and real-time attention monitoring at work: reaction time versus brain response

Continuous and objective measurement of the user attention state still represents a major challenge in the ergonomics research. Recently available wearable electroencephalography (EEG) opens new opportunities for objective and continuous evaluation of operators' attention, which may provide a new paradigm in ergonomics. In this study, wearable EEG was recorded during simulated assembly operation, with the aim to analyse P300 event-related potential component, which provides reliable information on attention processing. In parallel, reaction times (RTs) were recorded and the correlation between these two attention-related modalities was investigated. Negative correlation between P300 amplitudes and RTs has been observed on the group level (p lt .001). However, on the individual level, the obtained correlations were not consistent. As a result, we propose the P300 amplitude for accurate attention monitoring in ergonomics research. On the other hand, no significant correlation between RTs and P300 latency was found on group, neither on individual level. Practitioner Summary: Ergonomic studies of assembly operations mainly investigated physical aspects, while mental states of the assemblers were not sufficiently addressed. Presented study aims at attention tracking, using realistic workplace replica. It is shown that drops in attention could be successfully traced only by direct brainwave observation, using wireless electroencephalographic measurements.This is the peer-reviewed version of the article: Mijović, P.; Ković, V.; De Vos, M.; Macuzić, I.; Todorović, P.; Jeremić, B.; Gligorijević, I. Towards Continuous and Real-Time Attention Monitoring at Work: Reaction Time versus Brain Response. Ergonomics 2017, 60 (2), 241–254. [https://doi.org/10.1080/00140139.2016.1142121

Nove mogućnosti lečenja poremećaja puerperijuma visoko mlečnih krava

Delivery in cows especially difficult calving leads to disorders of normal uterine involution, lengthening of service period, increased insemination index and in certain number of cases (from 6 to 12 %) can lead to temporary or permanent infertility. Often findings in these cows are repeated heats without clear clinical symptoms of cause. Pathologic puerperium in the first 9 and especially in following 12 days or in the first 3 weeks after calving (because of retained placentas or puerperal infection) leads to extended service period and increased insemination index. This can be prevented by use of novel approach to therapy with widely used cures for local treatment of uterus and often better with use of hypertonic solutions of NaCl in 3 continuous days in hot - cold pattern in first 3 weeks after calving. In our work 1177 cows were included, we achieved shorter service period, lower insemination index and improved fertility of cows. .Teška teljenja krava dovode do poremećaja normalne involucije uterusa, produžetka servis perioda, povećanja indeksa osemenjavanja, a u određenom broju slučajeva (od 6 do 12 % krava) i do privremenog ili trajnog steriliteta. Česti nalazi kod takvih krava su porađanja, bez jasnih i uočljivih kliničkih simptoma. Patološki puerperijum u prvih 9 dana a pogotovu u narednih 12 dana posle teljenja, tj. u prve tri nedelje, (zbog retentio secundinarum ili puerperalne infekcije) produžava servis period i povećava indeks osemenjavanja krava. To može da se spreči novijim metodama lečenja krava, sa sredstvima za lokalno lečenje uterusa, ali isto tako i još bolje sa hipertoničnim rastvorima natrijum hlorida, tri dana uzastopno, primenom toplo hladnih rastvora u prve tri nedelje posle teljenja. Naš rad je bio lečenje krava, na jednoj farmi, gde smo postigli skraćenje servis perioda, smanjenje indeksa osemenjavanja, poboljšanje koncepcije i povećanje plodnosti krava.