Impact of damper seal coefficients in rotor dynamics : uncertainties and optimization

Damper seals can have a significant impact on rotor dynamics, but the calculation of the stiffness and damping coefficients for this component can be challenging and has a high uncertainty. In the present work, a probabilistic model is proposed to model the seal coefficients, which are frequency-dependent. We develop a stochastic process (frequency indexed) so that the uncertainty in the model is taken into account. The impact of these uncertainties on the rotordynamic behavior of a compressor is analyzed. The deterministic coefficients of the seal are determined considering a bulk-flow model and values calculated by a compressor vendor based on the extrapolation of experimental data. The obtained results show that the uncertainty of these coefficients have a considerable impact on the compressor rotordynamic behavior, affecting the stability margin and the unbalance response. Based on this analysis, a procedure for the robust optimization of the compressor rotordynamic behavior is proposed. This procedure considers the seal geometric parameters as design variables. The results for the robust optimization show that the seal length and the cell hole depth can be modified to improve the unbalance response.Os selos amortecedores podem ter grande impacto na dinâmica de rotores, mas o cálculo dos valores dos coeficientes de rigidez e amortecimento para este componente é difícil e possui grande incerteza. No presente trabalho, um modelo probabilístico é proposto para modelar os coeficientes do selo, que são dependentes da frequência. Um processo estocástico (indexado na frequência) é construído de forma que o erro do modelo seja levado em consideração. O impacto dessas incertezas no comportamento rotodinâmico de um compressor é analisado. Os coeficientes determinísticos do selo são determinados considerando o modelo ‘bulk-flow’ e valores calculados por um fabricante de compressores baseado em uma extrapolação de dados experimentais. Os resultados obtidos mostram que a incerteza desses coeficientes tem um impacto considerável no comportamento rotodinâmico do compressor, afetando a margem de estabilidade e a resposta ao desbalanceamento. Baseado nesta análise, um procedimento para a otimização robusta do comportamento rotodinâmico do compressor é proposto. Este procedimento considera parâmetros geométricos do selo como variáveis de projeto. Os resultados da otimização robusta mostram que o comprimento do selo e a profundidade das células podem ser alterados com o objetivo de se obter uma melhor resposta ao desbalanceamento

Technical Assistance To The Manufacture, Construction, And Assembly Of Osorio-Canoas Oil Pipeline Flow Pumps

LectureThis paper reports the experiences acquired through the modifications and improvements implemented in the manufacture, construction and assembly of the oil flow centrifugal pumps. A Brazilian oil pipeline pumping capacity expansion, on Rio Grande do Sul – South Region of Brazil, was conceived aiming at refinery processing increase project from 20,000 m³/day to 30,000 m³/day, besides changing the product profile from processed product to national high viscosity national oils. Due to this reason, a new pump park and a new intermediate pump station have been erected. Thus, the oil received by a tanker and stored at the first pump park should be sending through a 97 km long and 560 mm diameter oil pipeline. In order to get such oil flow done, 03 new main pumps have been installed at the first pump park, one of them being a stand-by one, and other 03 pumps at second pump park, one of them being also a standby. During the startup of news pumps, high vibration levels were observed in the rotors and in the equipment structures. The values defined by the manufacturer for equipment alarm and shutdown were, respectively, 50.0 µm and 75.0 µm, measured on the pump rotors in the bearing region. However, the global vibration levels of the pumps reached 110.0 µm during the startup attended by the manufacturers. The equipment warranty period started after that, and a detailed activity planning was drawn up with the purpose of keeping the new pumps running at the lowest possible operational risk and avoiding a production reduction at Refinery. Simultaneously, various actions were taken in order to identify the vibration sources and reduce its intensity to the lowest possible values. After equipment modifications, median vibration values at 15.0 µm were obtained. The logistics adopted in this process and the activities carried out to eliminate the causes of the high pump vibrations prevented an approximately U$ 25 million loss for the Customer and ensured an expressive increase in the equipment operational continuity reliability