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The double-cone ring gasket used as a static seal for high pressure operates on the principle of unsupported area by which the pressure applied to the gasket produces a large pressure at the seating surfaces thus maintaining a tight joint. An analysis based on elastic behaviour and simplifying assumptions is developed for predicting the sealing forces and the strains in the gasket. An apparatus was built for testing the effectiveness of the gasket for sealing pressures to 10,000 psi. Gaskets of several different proportions were tested and all were found to seal satisfactorily. Strain measurements made during the tests showed satisfactory agreement with predicted values for the assembly condition, but there were discrepancies between the predicted and observed values for the gaskets under pressure. These discrepancies indicate that the simple assumptions used in the analysis are not sufficiently accurate. The general conclusions are that the double-cone ring gasket is satisfactory for high pressure static seals and that the proportions of the ring cross section are not critical to the effectiveness of the seal. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Proton Exchange Membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the hydrogen and air/oxygen within their respective regions. The stability of the gaskets is critical to the operating life as well as the electrochemical performance of the fuel cell. Chemical degradation of five elastomeric gasket materials in a simulated and an aggressive accelerated fuel cell solution at PEM operating temperature for up to 63 weeks was investigated in this work. The five materials are Copolymeric Resin (CR), Liquid Silicone Rubber (LSR), Fluorosilicone Rubber (FSR), Ethylene Propylene Diene Monomer Rubber (EPDM), and Fluoroelastomer Copolymer (FKM). In order to assess the durability of the materials, observation of chemical degradation level, dynamic mechanical analysis, and micro-indentation test were adopted in this study. This experimental result showed that the influence of the chemical reaction could affect the material surface condition. Also, the chemical reaction could affect material¡¦s mechanical properties had been changed over the soaking time. By considering the level of chemical degradation and mechanical properties, the experimental results showed that EPDM is recommended as the best choice of sealing material for using in a PEMFC.

The historic use of asbestos-containing materials during the manufacturing of automobiles has resulted in a perception of an increased risk of asbestos-related pulmonary diseases within mechanics. This study was conducted to assess the potential asbestos exposures mechanics encounter while servicing vehicles assembled with parts containing asbestos, in addition to compare the cumulative lifetime asbestos exposures for different maintenance activities against theorical threshold exposures for asbestosis, lung cancer and mesothelioma. Exposure data were assembled from four independent exposure assessments performed to elucidate the airborne asbestos levels generated during the removal and replacement of brakes, gaskets, clutches and seam sealants containing asbestos. The phase contrast microscopy (PCM) and phase contrast microscopy equivalent (PCME) fiber concentrations for personal samples and air sampled identified to contain asbestos fibers through Transmission Electron Microscopy (TEM) analysis were applied to calculate the cumulative lifetime asbestos exposures. This index of exposure was compared to no-effect exposure thresholds identified through an extensive literature review for the selected pulmonary diseases. The results of this study indicate that mechanics encounter PCM fiber concentrations approximately 10 to 100 times lower than the current Occupational Safety Health Administration (OSHA) Permissible Limit Exposure (PEL) of 0.1 fibers per cubic centimeter (f/cc). Additionally, the cumulative lifetime asbestos exposures ranged from <1 fiber-year/cubic centimeter of air (f-yr/cc) to 2.0 f-yr/cc, and did not exceed the no-effect exposure thresholds for asbestosis, lung cancer and mesothelioma. The findings of this study provide additional support to previously published epidemiologic investigations and exposure assessments against an increased risk of asbestos-related disease within mechanics historically employed to service vehicles containing asbestos fibers.

As bombas centrífugas com vedações à base de gaxetas possuem uma boa eficiência, porém impõem ao sistema de bombeamento, perdas do produto recalcado. Estas são variáveis que norteiam fatores relacionados às condições físicas do equipamento, como por exemplo, o desgaste excessivo das buchas, falta da regulagem adequada e até mesmo o porte das bombas. O objetivo principal desta pesquisa foi identificar e quantificar os vazamentos provenientes das vedações das bombas centrífugas que operam em regime permanente e propor a substituição do sistema de vedação com gaxetas por sêlos mecânicos com maior eficiência, na Estação Elevatória de Água Tratada de Itaquera pertencente à empresa SABESP Companhia de Saneamento Básico do Estado de São Paulo, localizada na Avenida Virgínia Ferne, n 1036 - Itaquera, na cidade de São Paulo. Pôde-se observar com os resultados, que o investimento é totalmente amortizado a partir do 4 ano de operação do selo mecânico, bem como a economia com os vazamentos de água e energia elétrica. O novo dispositivo mostrou-se eficaz na questão de implantação e manutenção, sendo que cabe um investimento inicial a ser disponibilizado pela empresa interessada. / The centrifugal pumps with sealing based on gaskets have a good efficiency, but, impose to the pumping system, losses of product to be pumped. These ones, are variables that guide related factors to physical condition of equipments, for example, exceeding wearing of the sleeves (wad), and a lack of a proper adjustment and even the pumps size. The main objective of this research was to identify and quantify the leakages originated from the sealing of centrifugal pumps which operates in permanent regime, at Lifting Station treated Water of Itaquera, belonging to the company SABESP - Companhia de Saneamento Básico do Estado de São Paulo, located at Avenida Virgínia Ferne, n 1036 - Itaquera, city of São Paulo. We could find out with the results, that the investment is totally amortized from the 4th year of mechanical sealing operation, as well as the economy with the leakages of water and electrical energy. The new device has shown efficiency in implementation and maintenance, and an investment should be made by an interested company due to its efficiency.

L'impact des émissions fugitives sur l'environnement est un enjeu capital pour les industries. Ainsi, de nombreuses réglementations et normes sont établies afin de prévenir des risques et limiter leurs impacts. L'une des sources majeures de ces émissions provient de la robinetterie industrielle. Dans ce domaine, l'un des systèmes les plus communs est le presse-garniture. Dans le secteur de l'Energie, l'étanchéité peut être garantie sur les éléments mobiles par un empilement de bagues en Graphite Expansé Matricé (GEM); matériau relativement souple, plébiscité pour ses caractéristiques et ayant une structure macroscopique particulière. Ces travaux de thèse s'intéressent à la compréhension du comportement mécanique complexe des solutions d'étanchéité de type GEM. L'objectif est de déterminer le comportement mécanique de ces garnitures afin de prédire leur étanchéité. Dans le but de caractériser ce comportement, diverses campagnes d'essais sont menées sur des joints en situation. Ainsi, sur la base d'un montage existant et d'un dispositif développé spécifiquement pour cette étude, la caractérisation de ce type de joints est effectuée via des essais de compression charge-décharge et cyclique. La base de données qui en résulte permet le développement d'un modèle numérique apte à décrire le comportement complexe de ces systèmes presse-garnitures. Ce modèle phénoménologique de type Hyperélasto-Hystérésis (HH) correspond à une loi additive en contrainte avec une contribution hyperélastique et une contribution hystérétique. La comparaison des réponses expérimentales et numériques du joint, dans le cadre de l'étude d'un seul joint mais également pour des empilements, est discutée. / The impact of fugitive emissions leakage rate on the environment is an essential issue for industries. Therefore, many regulations and standards are created to prevent risks and to limit their impacts. One of these major sources of fugitive emissions comes from industrial valves. In the Valve Industrie, the tightness of stem are often ensured by stuffing box seal. In the energy sector, the tightness could be ensure with compression packing which is manufactured in exfoliated graphite; which is a relatively flexible material, endorsed for its characteristics and having a particular macroscopic structure. The aim of this study is to improve the knowledge of the complex mechanical behaviour of compression packing in exfoliated graphite. The aim is to determinate the mechanical behaviour of these packings in order to predict their tightness. To characterize this behaviour, various test campaigns are conducted on seals in situation. Thus, based on an existing apparatus and a device developed specifically for this study, the characterization of this kind of packing is performed through loading-unloading and cyclic compression tests. A numerical model which is able to describe a complexe mechanical behaviour of compression packing, is performed thanks to resulting database. This Hyperelasto-Hysteresis phenomenological model corresponds to an additive decomposition in stress with an hyperelastic contribution and an hysteretic contribution. The comparison of the experimental and numerical responses of the seal, as part of the study a single seal but also of a packing, is discussed.

I det här arbetet har tätningsmetoder för aluminiumhus undersökts. Arbetet avgränsades mot fordonsindustrin och statiska packningar. Examensarbetet tar upp flänskonstruktionens inver-kan på tätheten och packningen, packningstyper, ytjämnhetens inverkan på packningsmateri-al, porositet, relativ materialkostnad och fästelement.Arbetet grundar sig på en litteraturstudie och intervjuer med berörda personer på företaget. Även praktiska prover genomfördes på ett urval av material från leverantörer där material exponerades för olika kemikalier och därefter dragprovades.Materialet som insamlats genom intervjuer och litteraturstudien vittnar om att många paramet-rar påverkar vilka tätningsmetoder som är möjliga att använda. Det är inte bara materialval som det behövs tas hänsyn till. Faktorer som flänskonstruktioner, materialkostnader, ytdefek-ter, fästelement samt porositet har en stor påverkan. De praktiska proverna vittnar om att olika kemikalier har olika stor inverkan på materialens mekaniska egenskaper och svullnad.Slutligen föreslås ett par packningsmaterial som är lämpliga för företaget att använda i deras produkter. / In this work sealing methods for aluminum housing have been investigated. The work was delimited to the automotive industry and static gaskets. The thesis brings up how the flange impacts on the sealing capability and the gasket, sealing types, the surface impact on gasket materials, porosity, relative material cost and fasteners.The work is based on a literature study and interviews with concerned people at the company. Practical samples were carried out on a number of materials from suppliers and the materials where exposed to different chemicals and then tensile tested.The materials that were collected through interviews and the literature study testify that many parameters influence the possible sealing methods. It’s not just the material itself that needs to be taken into account. Factors like flange design, material cost, surface defects, fasteners and porosity have a great impact. The practical sample testifies that different chemicals have dif-ferent impact on the mechanical properties and swelling of the material.Finally, a couple of sealing materials are suggested that are suitable for the company to use in their products.