ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California / The ALMA Project is developing a 66 antenna radio astronomy array on a 5000 meter mountain in Chile. Radio astronomy depends on a radio frequency quiet area. The remote mountain top is ideal for such a radio astronomy array. However, RFI from equipment inside one type of antenna had a path loss of 13 dB to its feed area, when measured at 100 GHz. Carbon filled foam is being used to enhance shielding to reduce the negative effect of local radio frequency interference (RFI). This foam has been measured and verified to be effective from 1 to 100 GHz.

Electric arc welding is the most prevalent welding type in industry. It creates two main groups of health hazards for workers; fumes and gases, and radiant energy. Shielded Metal Arc (SMA) welding is the most widely used welding method in industrial plant welding shops. The main chemical health hazards associated with this type of welding are fumes. Fumes are particles formed when the electrode and base metal constituents are vaporized and condensed in the welding area. Potential health problems can be anticipated by measuring the concentration of fumes in the welding space and comparing these data to established exposure standards. If high concentrations of these fumes are present, control measures should be undertaken to reduce the potential toxic effect to workers. Most of the studies have been done on mild (carbon) steel welding where it is generally necessary to monitor only the total amount of fumes. Stainless steel welding differs from carbon steel welding in that it generates considerable fume concentrations of chromium and nickel, which are suspected human carcinogens. The first part of this study evaluated the health risks posed to workers exposed to chromium and nickel fumes from routine stainless steel welding procedures. All the welding was performed in an industrial plant welding shop by one experienced welder. The welded piece was a three-part stainless steel cylinder. The whole period of welding lasted almost three weeks, although the actual welding was done in eleven days during that period. All sampling was performed with filter cassettes connected to personal air pumps. Sampling was performed in welder's breathing zone, in the general area (background sample), and at conveniently located points outside the breathing zone for evaluation of ratios of chromium and nickel to total fumes. The results indicated that at this particular industrial plant, exposure levels did not exceed the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs) and the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). The results also indicated that it was not necessary to monitor the general area because of very low concentrations of chromium and nickel fumes. Rather, it is suggested that the monitoring focuses on the welder's breathing zone where it is important to sample hexavalent chromium (chromates) because of its proven carcinogenic effect and therefore very low TLV. Also, it was found that if TLV for chromates is not exceeded, then levels of total chromium and nickel are also likely to be below limits. The second part of the study sought to devise a simplified method of monitoring of welding operations. The results suggested that it is not always necessary to sample for all the components (total fumes, total chromium, chromates, and nickel) when estimating worker's exposure. Rather, it is possible to simplify the process by establishing the ratios of fume constituents during a period of heavy welding, thus enabling the industrial hygienist to make a reasonable estimate of exposure that occurs at other times. The estimate can be made by sampling either the main constituent (chromates) or total fumes, and predicting the exposure to remaining constituents of interest from these data. In addition, and in contrast to previous studies, it has been concluded that when fume concentrations are low, a welder's helmet does not provide any additional protection against fumes. Additional protection can be provided with the use of proper local ventilation, such as with a flexible hose, to reduce exposure well below suggested limits. / Graduation date: 1994

This Master’s project deals with general aspects and possible solution of effective shielded cover and cell/chamber shielding measurement for needs of electromagnetic compatibility EMC on the basis of available norms and standards. Electromagnetic shielding is one of the most anticlutter means of EMC. Its main task is reduction of disturbing emission at the side of sources of disturbing signals as well as electromagnetic resistance increase at the side of disturbing signal receivers. Shielding is considered to be an important structural means to reduce electromagnetic field referring to a defined space part. Technical means for achieving the given goals are called shielded covers or shielded cells/chambers. Shielding is one of highly effective methods related to electromagnetic protection, for instance against power/output disturbance. To express the shielding quality so called shielding effectiveness SE is used. It represents logarithmic rate of shielding coefficient that is defined by the intensity ratios of electric and magnetic fields in a certain point of the shielded space to electric or magnetic field intensity incident/impinging on the shielded screen or wall.

This project examined the feasibility of using flux modification to reduce the as-deposited hydrogen content of basic-type shielded metal arc welds. Additions of oxidizing ingredients (micaceous iron oxides) to the reference flux formulation lowered the diffusible weld hydrogen content by up to 70%. Increasing amounts of silica caused a slight reduction in hydrogen content, probably as a result of the reaction between SiO2 and CaF2, which produces SiF4 and CaO as reaction products. Flux formulations containing additions of fluorine-containing compounds and calcite displayed lower hydrogen levels, with the diffusible weld metal hydrogen content reaching a minimum with increasing additions. Higher levels caused an increase in the weld hydrogen content. Thermodynamic slag modelling attributes the existence of these minima to a decrease in slag water capacity with an increase in slag fluorine content (at constant basicity), brought about by higher concentrations of fluorine-containing compounds in the flux formulation. The effect of flux additions on the weld mechanical properties and the electrode operating characteristics was not evaluated during the course of this investigation. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2007. / Materials Science and Metallurgical Engineering / unrestricted

As bobinas ativamente blindadas (actively shielded) melhoram a performance das bobinas de gradiente ao cancelar o campo magnético na parte externa da bobina primária, evitando a degradação do campo no seu interior devido às correntes induzidas (eddy currents). O presente trabalho resultou na construção de um conjunto de bobinas de gradientes ativamente blindadas (Gx, Gy e Gz ), de geometria cilíndrica e acesso axial, com diâmetro de volume útil de 10cm para imagens (field of view), com campos de gradiente de aproximadamente 8.0 G/cm para r=0, com uma máxima distorção de campo de 5% neste volume, onde foi observado um efetivo cancelamento do campo externo, o que evita correntes induzidas nas partes metálicas internas do magneto OXFORD de 2.0 Tesla horizontal de 30cm de diâmetro, no qual serão empregadas. Alguns resultados prévios foram obtidos com um protótipo transversal, em apenas uma direção, e também com um conjunto de bobinas de gradiente para utilização em obtenção de imagens microscópicas de ESR pulsado. As bobinas foram projetadas utilizando-se a técnica de densidade de corrente, que se baseia na abordagem de campo alvo (target field) e também foi empregado o método de \"simulated annealing\" para otimização do desenho. Este sistema de gradientes apresenta também uma baixa indutância, o que permitirá chaveamentos rápidos (~0.1 ms). Na análise do campo de gradiente gerado foi utilizado o método de diferença de fase, confirmando a eficiência da técnica de densidade de corrente utilizada nos cálculos para a construção destas bobinas de gradiente / Actively shielded coils are designed to improve the performance of a gradient coil set by canceling the magnetic field in the region outside the body of the coil, avoiding degradation of the field in its interior due to eddy currents induced in the electric vicinity. The present work resulted on the construction of a shielded gradient coil set (Gx, Gy e Gz) with cylindrical geometry and axial access, with volume diameter of 1 O cm (imaging FOV) and gradient field intensity of 8.0 Gauss/cm in r=0. The maximum gradient distortion aim was 5% inside that volume, along with an effective cancellation of the field close to the inner metallic parts of the OXFORD 2.0 Tesla 31 cm bore horizontal magnet. Preliminary results were obtained with a prototype, which included only one transverse channel, and a miniature set with the same geometry was specially designed to perform micro imaging experiments using pulsed Electron Paramagnetic Resonance. Coils were designed using the current density technique, which is based on the target field approach and simulated annealing for optimization. The gradient systems described here present also a low inductance necessary to perform fast switching (~0.1 ms). For the analysis of the performance of the gradients we used the method of phase reference, confirming the efficiency of the current density technique used on the design of the gradient sets

Made available in DSpace on 2014-06-11T19:22:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-27Bitstream added on 2014-06-13T20:49:15Z : No. of bitstreams: 1 sartin_acp_me_bauru.pdf: 2377399 bytes, checksum: d4b29001d0dcb0173350d8175fba63b3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho possui como foco principal a apresentação de proposições técnicas para a avaliação da suscetibilidade eletromagnética de cabos metálicos isolados, blindados ou não, para atender aos sistemas de supervisão, proteção, comunicação e controle de subestações de alta tensão frente às interferências eletromagnéticas provocadas pelas descargas atmosféricas, manobras de chaveamento, campo magnético na frequência de 60Hz e do efeito corona. Para a realização destas proposições foram analisados e estudados diversos cabos usados em uma subestação de 440kV. A diretriz metodológica adotada nesta pesquisa incorporou simulações de modelo computacional, ensaios laboratoriais recomendados pelas normas e publicações técnicas correlatas com a finalidade de identificar os efeitos provocados pelas interferências eletromagnéticas nesses cabos. Os resultados obtidos conduziram a uma análise da interferência eletromagnética nos diversos cabos avaliados fornecendo, assim, um valor de imunidade de cada cabo estudado. Constatou-se que os cabos sem blindagem devem ser usados com reservas e podem ser instalados em sistemas poucos sujeitos a interferências eletromagnéticas ou promover uma blindagem adicional. Os cabos blindados, menos suscetível a interferências eletromagnéticas, podem ser instalados em pátios de subestações, entretanto devem-se tomar os devidos cuidados com o aterramento da blindagem. Desta forma, a pesquisa realizada contribuiu para o desenvolvimento de um procedimento técnico para o uso adequado de cabos em questão visando minimizar os efeitos provocados pelas interferências eletromagnéticas nos sistemas de supervisão, proteção, comunicação e controle presentes em subestações de alta tensão. / The main focus of this work is the presentation of technical propositions to assessing the electromagnetic susceptibility of isolated metallic cable, shielded or not, in order to comply with the supervision, protection, communication and control systems of high voltage substations in the presence of electromagnetic interferences caused by lightning discharge, switching maneuver, electromagnetic field at 60Hz and corona effect. Several cables used in 440 kV substation were analyzed and studied for accomplishing these propositions. The methodological guideline adopted in this research has included simulations of computational models, laboratorial tests recommended by standards and technical publications correlated in order to identifying the effects provoked by electromagnetic interferences to these cables. The obtained results led to an analysis of the electromagnetic interference in the several cables assessed, thus providing a value of immunity for each cable studied. It was verified that cable without shielding must be employed with restrictions and can be installed in systems which are little subject to electromagnetic interference or to promote an additional shielding. The shielding cables less susceptible to the electromagnetic interference can be installed in substation courtyard; however, it is important to pay special attention to the grounding of the shielding. Thus, this research contributed to the development of a technical proceeding for employing the mentioned cables suitably, aiming at minimizing the effects provoked by the electromagnetic interferences in the supervision, protection, communication and control systems which are present at the high voltage substations.

Orientador: José Alfredo Covolan Ulson / Banca: Paulo Roberto de Aguiar / Banca: José Carlos de Melo Vieira Junior / Resumo: O presente trabalho possui como foco principal a apresentação de proposições técnicas para a avaliação da suscetibilidade eletromagnética de cabos metálicos isolados, blindados ou não, para atender aos sistemas de supervisão, proteção, comunicação e controle de subestações de alta tensão frente às interferências eletromagnéticas provocadas pelas descargas atmosféricas, manobras de chaveamento, campo magnético na frequência de 60Hz e do efeito corona. Para a realização destas proposições foram analisados e estudados diversos cabos usados em uma subestação de 440kV. A diretriz metodológica adotada nesta pesquisa incorporou simulações de modelo computacional, ensaios laboratoriais recomendados pelas normas e publicações técnicas correlatas com a finalidade de identificar os efeitos provocados pelas interferências eletromagnéticas nesses cabos. Os resultados obtidos conduziram a uma análise da interferência eletromagnética nos diversos cabos avaliados fornecendo, assim, um valor de imunidade de cada cabo estudado. Constatou-se que os cabos sem blindagem devem ser usados com reservas e podem ser instalados em sistemas poucos sujeitos a interferências eletromagnéticas ou promover uma blindagem adicional. Os cabos blindados, menos suscetível a interferências eletromagnéticas, podem ser instalados em pátios de subestações, entretanto devem-se tomar os devidos cuidados com o aterramento da blindagem. Desta forma, a pesquisa realizada contribuiu para o desenvolvimento de um procedimento técnico para o uso adequado de cabos em questão visando minimizar os efeitos provocados pelas interferências eletromagnéticas nos sistemas de supervisão, proteção, comunicação e controle presentes em subestações de alta tensão. / Abstract: The main focus of this work is the presentation of technical propositions to assessing the electromagnetic susceptibility of isolated metallic cable, shielded or not, in order to comply with the supervision, protection, communication and control systems of high voltage substations in the presence of electromagnetic interferences caused by lightning discharge, switching maneuver, electromagnetic field at 60Hz and corona effect. Several cables used in 440 kV substation were analyzed and studied for accomplishing these propositions. The methodological guideline adopted in this research has included simulations of computational models, laboratorial tests recommended by standards and technical publications correlated in order to identifying the effects provoked by electromagnetic interferences to these cables. The obtained results led to an analysis of the electromagnetic interference in the several cables assessed, thus providing a value of immunity for each cable studied. It was verified that cable without shielding must be employed with restrictions and can be installed in systems which are little subject to electromagnetic interference or to promote an additional shielding. The shielding cables less susceptible to the electromagnetic interference can be installed in substation courtyard; however, it is important to pay special attention to the grounding of the shielding. Thus, this research contributed to the development of a technical proceeding for employing the mentioned cables suitably, aiming at minimizing the effects provoked by the electromagnetic interferences in the supervision, protection, communication and control systems which are present at the high voltage substations. / Mestre

As bobinas ativamente blindadas (actively shielded) melhoram a performance das bobinas de gradiente ao cancelar o campo magnético na parte externa da bobina primária, evitando a degradação do campo no seu interior devido às correntes induzidas (eddy currents). O presente trabalho resultou na construção de um conjunto de bobinas de gradientes ativamente blindadas (Gx, Gy e Gz ), de geometria cilíndrica e acesso axial, com diâmetro de volume útil de 10cm para imagens (field of view), com campos de gradiente de aproximadamente 8.0 G/cm para r=0, com uma máxima distorção de campo de 5% neste volume, onde foi observado um efetivo cancelamento do campo externo, o que evita correntes induzidas nas partes metálicas internas do magneto OXFORD de 2.0 Tesla horizontal de 30cm de diâmetro, no qual serão empregadas. Alguns resultados prévios foram obtidos com um protótipo transversal, em apenas uma direção, e também com um conjunto de bobinas de gradiente para utilização em obtenção de imagens microscópicas de ESR pulsado. As bobinas foram projetadas utilizando-se a técnica de densidade de corrente, que se baseia na abordagem de campo alvo (target field) e também foi empregado o método de \"simulated annealing\" para otimização do desenho. Este sistema de gradientes apresenta também uma baixa indutância, o que permitirá chaveamentos rápidos (~0.1 ms). Na análise do campo de gradiente gerado foi utilizado o método de diferença de fase, confirmando a eficiência da técnica de densidade de corrente utilizada nos cálculos para a construção destas bobinas de gradiente / Actively shielded coils are designed to improve the performance of a gradient coil set by canceling the magnetic field in the region outside the body of the coil, avoiding degradation of the field in its interior due to eddy currents induced in the electric vicinity. The present work resulted on the construction of a shielded gradient coil set (Gx, Gy e Gz) with cylindrical geometry and axial access, with volume diameter of 1 O cm (imaging FOV) and gradient field intensity of 8.0 Gauss/cm in r=0. The maximum gradient distortion aim was 5% inside that volume, along with an effective cancellation of the field close to the inner metallic parts of the OXFORD 2.0 Tesla 31 cm bore horizontal magnet. Preliminary results were obtained with a prototype, which included only one transverse channel, and a miniature set with the same geometry was specially designed to perform micro imaging experiments using pulsed Electron Paramagnetic Resonance. Coils were designed using the current density technique, which is based on the target field approach and simulated annealing for optimization. The gradient systems described here present also a low inductance necessary to perform fast switching (~0.1 ms). For the analysis of the performance of the gradients we used the method of phase reference, confirming the efficiency of the current density technique used on the design of the gradient sets

[pt] O presente estudo faz parte de um projeto relacionado ao estudo de aplicação de tubos de aço API 5L Grau X80 fabricados no Brasil e destinados para a montagem de tubulações para o transporte de gás. Objetiva-se avaliar os parâmetros de soldagem empregados na execução da soldagem circunferencial combinando os processos de eletrodo revestido, para a execução do passe de raiz e passe quente, e arame tubular autoprotegido para a execução dos passes de enchimento e acabamento. Os resultados obtidos indicam que embora o material utilizado, tanto metal de solda como metal de base estejam atendendo aos requisitos básicos de tenacidade e resistência, em acordo com as normas, a qualificação do procedimento é dependente do desempenho dos soldadores. Existe portanto, a necessidade de habilitação técnica mais ampla quanto a formação de profissionais nesta área, excedendo assim o escopo do presente estudo cujo objetivo foi estudar e caracterizar a solda circunferencial. As propriedades mecânicas foram avaliadas mediante ensaios de dureza, tração, dobramento, ensaios nick-break e tenacidade mediante ensaios de impacto Charpy. A caracterização da junta soldada foi realizada, utilizando-se microscopia ótica e microscopia eletrônica de varredura. Embora o procedimento empregado não tenha sido qualificado pela norma API 1104, em função da execução do procedimento, os valores de resistência mecânica obtidos foram aceitáveis e a caracterização microestrutural e mecânica da junta comprova a não ocorrência de microestruturas frágeis, seja no metal de solda ou na ZTA. / [en] The current work is part of a larger project to study the application of API 5L X80 steel tubes, produced in Brazil, in gas pipeline fabrication. The objective of this work is to evaluate the effects of the process parameters used when performing a circumferential welding technique which combines the utilization of coated electrodes for the root and hot passes, while exploiting self-shielded flux cored arc welding for the filling and finishing passes. The results obtained indicate that, though the material studied, both filler metal and the base alloy, meet the basic toughness and strength specifications of the relevant standards, the final overall quality of the joint is very dependent on the skill of the welders. Although there is a necessity to guarantee an adequate level of training for these professionals for such tasks, that would be beyond the scope of then present work, as it aims to emphasize the characterization of the circumferential weld itself. The mechanical properties were evaluated using hardness measurements, bend testing, nick-break tests and toughness was evaluated by Charpy notchimpact tests. The metallographic characterization of the girth weld joint was undertaken by means of optical and scanning electron microscopy. Though the specific methodology applied has not been qualified by the API 1104 Standard, as such, the strength values obtained were of acceptable levels and an analysis of the joint`s microstructure and overall mechanical properties confirm that no typical fragile structures or phases were present either in the weld metal or the heat affected zone.

Na indústria de petróleo e gás as tubulações são formas eficientes de transportar esses produtos ou seus derivados das regiões de exploração para as refinarias e em alguns casos até o consumidor. O principal tipo de aço utilizado na fabricação dessas tubulações são os aços ARBL que devido à boa relação entre resistência à tração e tenacidade a baixas temperaturas geram uma boa relação custo/benefício na utilização e na montagem de tubulações. Neste trabalho é apresentado um estudo sobre a soldabilidade do tubo API 5L X80 construído com aço ARBL. Os corpos-de-prova utilizados foram anéis de 508 mm de diâmetro externo com espessura de parede de 19,0 mm. A soldagem foi executada com o processo eletrodo revestida no experimento 1, em um par de anéis, e o outro par de anéis foi soldado, na raiz, com o processo de soldagem MAG-TC e nos passes de enchimento e acabamento foi utilizado o processo arame tubular auto-protegido. Os resultados dos ensaios de resistência à tração, dobramento lateral e de Nick-Break demonstram que ambos os procedimentos de soldagem são qualificados pela norma API 1104. Associando o resultado do ensaio de Charpy V a 0°C e associando-o a quantificação das frações volumétricas de microconstituintes MA e a caracterização microestrutural é possível observar que os valores de energia absorvida na ZAC tem maior relação com o mecanismo de refino de grão, que melhora os valores obtidos, do que com a quantidade de fração volumétrica do microconstituinte MA. / In the oil and gas industries, pipelines are efficient ways of transporting these products, or its derivatives, from exploration regions to refineries and, in some cases, up to the final consumer. The main type of steel used in manufacturing these pipelines are HSLA steels that, due to the good relationship between tensile strength and toughness at low temperatures, create a cost/benefit ratio in the use and installation of these pipelines. This paper presents a study on the weldability of API 5L X80 HSLA pipe steel. The samples used were pipe rings with 508 mm outside diameter and a wall thickness of 19.0 mm. The root welding process was performed using SMAW in Experiment 1 with filing and finishing passes with SMAW. In the second experiment, the root pass were welded with GMAW-CT, and filling and finishing passes with FCAW-SS. Tensile test results, lateral bending tests and \'Nick-Break\' tests showed that both welding procedures were qualified according to API 1104 Standard. Associating these results with Charpy V test at 0°C and with quantification of volume fractions of MA microconstituent is possible to observe that the values of absorbed energy in the HAZ are more closely related to the mechanism of grain refinement, which improves the values obtained with the volume fraction of the amount of microconstituent MA.