This thesis reports a two part investigation of single- and two-stage ejector systems in which the primary fluid is steam and the secondary fluid is air. The first part is an experimental investigation. The vacuum created by the ejector is strongly affected by the distance between the steam nozzle outlet and the diffuser throat section. The relation between this distance, which is called in this thesis "the nozzle optimum distance (Lop)", and the geometrical and operating parameters of the nozzle and the diffuser were investigated and forms the object of this part of the thesis. The second part is a theoretical approach. The exit Mach number for the nozzle was found by using the one-dimensional gas dynamic equations together with the first law of thermodynamics. Also a two-dimensional approach using the Method of Characteristics was used to find the exit Mach number and the characteristic net of the flow from the throat to the outlet of the nozzle. Two computer programmes were written on the basis of these two different theoretical techniques and the comparison between the results for the exit Mach number found to be 95% in agreement over the pressure range of the experimental work. A computer programme was also written using the Method of Characteristics to find the shape i.e. the characteristic net and the constant density lines within the flow of the steam jet leaving the nozzle and entering the diffuser. It is believed that the jet diameter at the point where it meets the diffuser wall, which is called in this work "the optimum jet diameter (Dop)", is strongly related to the nozzle optimum distance (Lop). When the characteristic net for the jet is drawn, its point of interception with the diffuser wall can be found and then (Dop) can be measured. This diameter (Dop) was then related to the ejector dimensional parameters and the ejector operating conditions; an equation was found to predict the optimum jet diameter from this equation (Dop)e. Then the predicted optimum nozzles distance (Lop)e was determined by using this computer program where the characteristic net meets the diffuser wall at the calculated optimum jet diameter (Dop)e. Finally, the experimentally determined value of the nozzle optimum distance (Lop) was compared to the theoretically predicted value, and the average error was found to be 1.23%.

Thesis (M.S. - Electrical and Computer Engineering)--University of Arizona. / Includes bibliographical references (leaves 107-108).

Thesis--PlanB (M.S.)--University of Wisconsin--Stout, 1998. / Includes bibliographical references.

In the semiconductor industry, numerous potential occupational exposures exist as a result of the diversity of chemical and physical hazards unique to integrated circuit manufacturing. The hazards associated with maintenance tasks are challenging because the sporadic nature of the tasks make exposure monitoring difficult. In particular, vacuum pump maintenance is hazardous due to the close contact with chemical waste by-products. The purpose of this study was to characterize the chemical and physical occupational exposures associated with vacuum pump maintenance (VPM) in a semiconductor manufacturing environment. The study population consisted of 9 VPM technicians at a semiconductor manufacturing plant in Oregon. VPM tasks were observed and prioritized according to potential risk of exposure. For each task studied, an exposure monitoring strategy was developed to quantify both chemical and noise exposures. Personal and area air samples of potential waste gases were conducted during maintenance tasks. All air samples were below established governmental standards. Detectable levels were found for three tasks: 0.040 milligrams per cubic meter (mg/m��) of hydrochloric acid, 0.014 mg/m�� of chlorine, and 0.08 mg/m�� of fluoride containing gases during tasks associated with the metal etch tool, polynitride etch tool, and tungsten deposition tool, respectively. Several bulk samples of waste residues collected during the tasks where corrosive having low pH levels. Representative noise sampling was conducted during a 12 hour shift to characterize noise exposures. Noise samples revealed that 43% of the samples were above the 80 dBA action limit thus requiring the VPM technicians to be involved in a hearing conservation program. Field observations revealed that there were many chemical hazards associated with waste gases and residues, therefore it is likely that occupational exposures occur even though they were not detected at significant levels in this study. In addition, there were several ergonomic risk factors associated with dismantling the pump during the maintenance activities. Specific improvements in personal protective equipment, general work practices, ergonomics, and engineering controls will help to reduce the potential for occupational exposures unique to VPM. Results from this study indicate the need to conduct in depth hazard evaluations of high risk populations such as the VPM technicians. / Graduation date: 1997

Cette thèse présente une méthode de pronostic basée sur des règles symboliques extraites par fouille de données. Une application de cette méthode au cas du grippage de pompes à vide est aussi détaillée. Plus précisément, à partir d'un historique de données vibratoires, nous modélisons le comportement des pompes par extraction d'un type particulier de règles d'épisode appelé « First Local Maximum episode rules » (FLM-règles). L'algorithme utilisé pour extraire ces FLM-règles extrait aussi de manière automatique leur fenêtre optimale respective, i.e. la fenêtre dans laquelle la probabilité d'observer la prémisse et la conclusion de la règle est maximale. Un sous-ensemble de ces FLM-règles est ensuite sélectionné pour prédire les grippages à partir d'un flux de données vibratoires. Notre contribution porte sur la sélection des FLM-règles les plus fiables, la recherche de ces FLM-règles dans un flux continu de données vibratoires et la construction d'un intervalle de pronostic de grippage à partir des fenêtres optimales des FLM-règles retrouvées. / This thesis presents a symbolic rule-based method that addresses system prognosis. It also details a successful application to complex vacuum pumping systems. More precisely, using historical vibratory data, we first model the behavior of the pumps by extracting a given type of episode rules, namely the First Local Maximum episode rules (FLM-rules). The algorithm that extracts FLM-rules also determines automatically their respective optimal temporal window, i.e. the temporal window in which the probability of observing the premiss and the conclusion of a rule is maximum. A subset of the extracted FLM-rules is then selected in order to further predict pumping system failures in a vibratory data stream context. Our contribution consists in selecting the most reliable FLM-rules, continuously matching them in a data stream of vibratory data and building a forecast time interval using the optimal temporal windows of the FLM-rules that have been matched.

No description available.

El presente estudio tiene como finalidad evaluar la viabilidad técnica, económica, financiera y de mercado para la implementación de una planta para la fabricación de bombas de vacío. / This study aims to assess the technical, economic, financial and market feasibility for the implementation of a plant for the manufacture of vacuum pumps. / Trabajo de investigación

The degree project was done at Södra Cell Värö with the purpose to investigate how the use of energy for pulp drying in a pulp dryer could be made more effective to decrease the energy consumption or increase the capacity. The pulp dryer is one of the machines that consumes the most energy at SCV. The air that dryes the pulp is heated by low pressure steam, and since the amount low pressure steam was limited, the purpose with the project was to investigate how the low pressure steam best could be used. If the drying capacity could be improved it could enable for an increase in production or a decrease low pressure steam consumption. The task was divided into: 1. Analysis of steam and condensate flows connected to the pulp dryer. Can they be adjusted to improve the drying capacity? 2. Investigation of possible sectors of application for hot air flows from vacuum pumps. 3. Investigation of the condensate system. Can condensate and flash steam be used in a better way to provide more steam to the pulp dryer? For task 1, air and energy balances were made ove the pulp dryer, then temperature, flow and moisture content were measured for all air flows in and out. To investigate how the consumption low pressure steam in the pulp dryer depends on the air flows in to the pulp dryer, tests were made where the rotation speed for the fans and the temperature for the air were varied. The result of measuring the air balance over the pulp dryer was that the same amount air was going in and out, which means that all the air was going in to the dryer preheated. The energy balance over the thermal recycling system showed that 40 % of the energy in outgoing air was being reused. Increasing the rotation speed from 750 rpm to 1000 rpm was favourable when the production was high. Increasing the temperature of the air in to the pulp dryer showed that the consumption low pressure steam decreased. Recommended rotation speeds: December – february: 1000 rpm, all levels of production mars – november: 1000 rpm for high production (over 3 bar low pressure steam to pulp dryer) 750 rpm for low production (below 3 bar low pressure steam to pulp dryer) For task 2, temperature, flow and moisture content were measured for all air flows out from the vacuum pumps. The air flows out from the vacuum pumps had a temperature of 40-50 °C, which was too low to be used for preheating of air to pulp dryer. For task 3, a mapping of the condensate system including all steam and condensate flows connected to the pulp dryer was made. The mapping was made in AutoCAD. Since the experiment with increased temperature of the air in to the pulp dryer showed that an increase in temperature caused the consumption low pressure steam to decrease, calculations of how much more the consumption low pressure steam could be decreased by switching to steam of a higher pressure for preaheating the drying air. By using only steam of higher pressure for air preheating, the amount available low pressure steam to the pulp dryer could be increased with 6 tonnes/h. / Examensarbetet utfördes på Södra Cell Värö med syfte att undersöka hur energianvändningen för massatorkning på torkmaskinen (TM) kunde effektiviseras för att ge lägre energiförbrukning eller högre kapacitet. TM är en av de mest energiförbrukande avdelningarna på bruket. Massan torkas där med luft som värms av processånga vilken utgörs av lågtrycksånga, och eftersom tillgången av lågtrycksånga var begränsad var det önskvärt att undersöka hur den kunde användas på mest effektiva sätt. Om torkkapaciteten kan förbättras kan det möjliggöra en ökning av produktionen alternativt en minskning av förbrukning av lågtrycksånga. Uppgiften delades upp i: 1. Analys av ång- och luftflöden kopplat till TM. Kan de justeras för att ge bättre torkkapacitet? 2. Undersökning av möjliga användningsområden för varma luftflöden från vakuumpumparna. 3. Undersökning av kondensatsystemet. Kan kondensat och flashånga utnyttjas på ett bättre sätt för att tillhandahålla mer ånga till TM? Till uppgift 1 ställdes luft- och energibalanser upp över TM, och sedan gjordes mätningar på temperatur, flöde och fukthalt på in- och utgående luftflöden. För att undersöka hur förbrukningen lågtrycksånga i torkskåpet påverkas av tilluften gjordes försök där varvtal på tilluftfläktar och temperatur på tilluft varierades. Resultatet av luftbalansmätningarna var att inget undertryck rådde över torkskåpet, vilket innebär att all tilluft gick förvärmd in till torkningen. Energibalans över värmeåtervinningssystemet visade att ca 40 % av energin i utgående våtluft återvinns. Försök med varvtal och temperatur på tilluft visade att en ökning av varvtal från 750 rpm till 1000 rpm var gynnsamt vid hög produktion, samt att en temperaturökning på tilluft minskade förbrukningen lågtrycksånga i torkskåpet. Rekommenderade körinställningar: December-februari: 1000 rpm, alla produktionsnivåer Mars-november: 1000 rpm vid hög produktion (över 3 bars tryck på lågtrycksångan till skåpet) 750 rpm vid låg produktion (under 3 bars tryck på lågtrycksångan till skåpet) Till uppgift 2 gjordes mätningar på temperatur, flöde och fukthalt på utgående luftflöden från vakuumpumpar. Luftflödena från vakuumpumpar höll en temperatur på 40-50 °C, vilket var för lågt för att kunna användas till att förvärma torkluft till TM. Till uppgift 3 gjordes en kartering av kondensatsystemet inkluderande alla ång- och kondensatflöden kopplade till massatorkningen. Karteringen utfördes i AutoCAD. Eftersom försöket med temperaturökning på tilluft visade att lågtrycksångförbrukningen i skåpet minskade med ökad temperatur på tilluft, beräknades hur stor en ytterligare besparing lågtrycksånga skulle kunna bli om all tilluft förvärmdes av mellantrycksånga. Genom att använda mellantrycksånga för att förvärma all tilluft till torkskåpet skulle mängden tillgänglig lågtrycksånga till torkskåpet kunna ökas med 6 ton/h.