ABB Motors and Generators manufacture large AC machines with oil lubricated plainbearings. The machines have occasional problems with oil leakage from the bearings. aproblem that ABB wants to be solved.In this thesis the cause of this leakage were investigated, with focus on the bearingseals.The purpose of this work was also to suggest amndments for preventing thisproblem. , and to suggest improvements that can prevent this. The first step was todo a literature survey of earlier work on this problem, study the theory ofhydrodynamic bearings and different types of seals and their properties. Severalexperiments and pressure measurements were performed on machines in operation.The results were then analyzed to identify the causes of leakage and to confirm/oreliminate the hypotheses that had been stablished in the earlier stage of this work.Finally, recommendations for problem management was proposed. New designs werealso developed based on the experimental findings, interviews with the technicians inthe company, and observations on the manufacturing and repairing procedures madeduring this work.The experimental and analytical results suggests that the current design of the bearingsystmem is sensitive to oil leakage. It has been discovered that pressure is the mostrelevant parameter, while several other parameters also contribute to the problem.

Stora Enso Kvarnsveden är ett pappersbruk lokaliserat vid Dalälven i Kvarnsveden. Bruket har för tillfället två producerande maskiner och detta arbete behandlar en av dem, vilken är PM12. På PM12 har man problem med oljeläckage i maskinens torkparti. Läckagen uppstår genom de lagerhus som finns för att bära upp torkpartiets valsar. I detta arbete har man undersökt vad läckagen beror på med fokus på dess lagertätningar. Syftet och målet med detta arbete har varit att utreda varför läckagen uppstår samt att generera koncept för att minska eller helt eliminera läckagen. Arbetet har innefattat diverse mätningar och utredningar för att komma till rätta med problemet. En litteraturstudie har genomförts för att identifiera felorsaker samt lösningar. Koncept har genererats utifrån studien samt de mätningar som utförts. Man har inte under arbetets gång helt kommit fram till vad läckagen beror på men man har kommit en bra bit på vägen. Förslag till fortsatt arbete har getts där det rekommenderas mer specifikt vilka typer av mätningar som bör genomföras samt de koncept man som bör bygga vidare på. / Stora Enso Kvarnsveden is a paper mill located at Dalälven in Kvarnsveden. The utility currently has two producing machines, and this study deals with one of them, which is PM12. At PM12 there is a problem with oil leaks in the machine's drying section. Leakage occurs through the bearing houses who are there to support the dryer's rollers. In this study, it has been investigated what the leakage is due to focusing on its bearing seals. The purpose of this study has been to investigate why leakage occurs and to generate concepts to reduce or eliminate leaks. The study has included various measurements and investigations to address the problem. A literature study has been conducted to identify causes and solutions. Concepts have been generated from the literature study as well as the measurements that have been taken. After this study it´s not fully realized why the leakage occurs, but it had come a long bit on the way. Proposals for continued work have been given, where it is recommended more specifically what kind of measurements that should be done and the concepts that should be further developed.

The majority of the vessels in the commercial fleet utilize oil lubricated stern tubes. Unfortunately, this brings about a risk of oil leaking from the stern tube into the marine environment if the stern tube seal would become worn or damaged by foreign materials. Previous studies concluded that, on average, 2.6 litres of oil per day leak out from the stern tube of ships. This essay has investigated the causes that could increase the leakage rate from the stern tube by reviewing literature, interviewing experts, and sending out surveys with questions regarding the subject. The answers that were received painted a clear picture that it is impossible to get a perfect seal on a stern tube. The causes that could influence the leakage rate were design related, such as vibrations, the rotational speed of the propeller shaft, radial and axial movements of the propeller shaft, as well as external causes such as the quality of water and foreign materials, for example, fishing lines and nets. The question whether water lubricated stern tubes were a viable alternative compared to oil lubricated stern tubes was also investigated. The result was that the bearing on a water lubricated stern tube did not have as long lifespan as an oil lubricated bearing. / Majoriteten av fartygen i handelsflottan använder oljesmorda propellerhylsor för att smörja propelleraxeln. Tyvärr medför det en risk att olja kan läcka ut från hylsan om tätningarna skulle bli utslitna eller skadas av främmande föremål. Tidigare forskning har visat att cirka 2,6 liter olja per dag läcker ut genomsnittligen från fartyg i handelsflottan. Denna uppsats har utrett vad som kan påverka läckagemängden från en propellerhylsa genom att utnyttja intervjuer och enkätsvar. Svaren som framkom var att det är mer eller mindre omöjligt att få en perfekt tätning på en propellerhylsa. Saker som kan påverka läckagemängden var designfenomen som vibrationer, axiella- och radiella rörelser och varvtal på propelleraxeln, samt yttre påverkan som vattenkvalité och främmande föremål som fiskelinor och nät. I uppsatsen jämförs även vattensmorda propellerhylsor med fokus på livstid, kostnad och underhåll, med en oljesmord propellerhylsa. En slutsats är att det vattensmorda lagret inte har samma livstid som det oljesmorda.