Fundamentals of Fluid Film Thrust Bearing Operation and Modeling

TutorialsWidely used in turbomachinery, the fluid film thrust bearing is critical to the overall reliability of a machine. Their design complexity and application severity continue to increase, making it challenging for the plant engineer to evaluate their reliability. This tutorial first provides practical knowledge on their basic physics, including hydrodynamic pressure generation, temperature rise due to internal viscous shearing and elastic deformation, as well as how those aspects interact with each other during operation. Examples are given to demonstrate how common design and operational parameters affect a bearing’s key performance parameters, such as the minimum film thickness and pad temperature. Then, this tutorial reviews the analytical models used to simulate the various physical aspects. The state of the art techniques for modeling important aspects are presented, along with discussions on their capabilities and limitations. Also covered in this tutorial are subjects including flooded versus evacuated housing design and direct lubrication, as well as a brief discussion on dynamics

Lubrication: Fluid Film Bearings: Operation, Maintenance, Troubleshooting

Discussion GroupTurbomachinery bearings: Sleeve and tilting pad journal bearings, Thrust bearings, Babbitt bearing failures Bearing upgrades: Clearances, preload, offset, Installation, Oil Specific questions: Journal bearing fit – loose? Line on line? Or some crush?, Discuss API temperature sensor placement:Journal – how many per bearing? Axial locations? Thrust – how many? TPJ No. of pads & orientation – LOP or LBP? TPJ Pivot design Experience with pivot wear? Experience with Ball & Socket pivots? Locking issues? Alarm and shut down values Bearing temperature Rotor movement Varnish experiences? Solutions? Oil types – who is using synthetics and why

Fundamentals of Fluid Film Thrust Bearing Operation and Modeling

TutorialsWidely used in turbomachinery, the fluid film thrust bearing is critical to the overall reliability of a machine. Their design complexity and application severity continue to increase, making it challenging for the plant engineer to evaluate their reliability. This tutorial first provides practical knowledge on their basic physics, including hydrodynamic pressure generation, temperature rise due to internal viscous shearing and elastic deformation, as well as how those aspects interact with each other during operation. Examples are given to demonstrate how common design and operational parameters affect a bearing’s key performance parameters, such as the minimum film thickness and pad temperature. Then, this tutorial reviews the analytical models used to simulate the various physical aspects. The state of the art techniques for modeling important aspects are presented, along with discussions on their capabilities and limitations. Also covered in this tutorial are subjects including flooded versus evacuated housing design and direct lubrication, as well as a brief discussion on dynamics

Turbomachinery and Pump Vibrations

Discussion GroupThis group will discuss plant machinery vibration detection, monitoring, and diagnosis, from a Plant O&M point-of-view. All attendees will be encouraged (but not required) to participate in discussions, and contribute topics worthy of discussion. Likely topics presently suggested, which will be affirmed or rejected by attendee vote, include the following: • Condition monitoring vibration sensors and methods • Effectiveness of vibration condition monitoring on rotating equipment for detecting problems • “Diagnostics” versus “prognostics” • Value of, and ROI of, condition-based monitoring of vibration • Vertical pump monitoring, including below ground monitoring • Vibration standards for various pumps and turbomachinery types, sizes, and applications • Vibration test method options, and their proper selection and use • Standard locations for vibration measurement on machinery • Wireless devices: radio noise, effectiveness, experiences, security • Troubleshooting methods for typical vibration problems, and fix options • Operating Deflection Shapes and integration with condition-based monitoring • Finite element analysis application in support of machinery selection and troubleshooting • Rotordynamics analysis use in machinery selection and troubleshooting • Hydraulically-induced vibration: structural, system, rotor, acoustic • Measurement of presence, location, and severity of pump cavitation • Effect of high GVF (gas volume fraction) in centrifugal pumps • Mechanical installation (e.g. piping, foundation, alignment) issues affecting vibration • Seal and bearing effects on vibration, and vibration effects on bearings and seal

Fundamentals of Fluid Film Journal Bearing Operation and Modeling

TutorialWidely used in turbomachinery, the fluid film journal bearing is critical to a machine’s overall reliability level. Their design complexity and application severity continue to increase making it challenging for the plant machinery engineer to evaluate their reliability. This tutorial provides practical knowledge on their basic operation and what physical effects should be included in modeling a bearing to help ensure its reliable operation in the field. All the important theoretical aspects of journal bearing modeling, such as film pressure, film and pad temperatures, thermal and mechanical deformations and turbulent flow are reviewed. Through some examples, the tutorial explores how different effects influence key performance characteristics like minimum film thickness, Babbitt temperature as well as stiffness and damping coefficients. Due to their increasing popularity, the operation and analysis of advanced designs using directed lubrication principles, such as inlet grooves and associated starvation issues, are also examined with several examples including comparisons to manufacturers’ test data

Effect Of Starvation On The Dynamic Properties Of Tilting Pad Journal Bearings

LectureA new 46 MW steam turbine became unstable as the load on the turbine was increased. The turbine had a relatively long slender shaft and the subsynchronous frequency was near the first critical speed of 1800 rpm. In an effort to allow the machine to reach full load a bearing redesign was undertaken. The bearing design was changed from the original 5 pad tilting pad journal (TPJ) bearings, orientated with the load on the bottom pad (LOP), to three pad TPJ’s also in the LOP configuration. Analysis indicated that the additional asymmetry in the dynamic coefficients would significantly increase the system logarithmic decrement (log dec) and allow the machine to run at full load without going unstable. With the three pad bearings installed the machine was brought up in speed and experienced subsynchronous vibration before reaching full speed. A design review of the bearings indicated that the top two pads of the three pad bearing were operating in the fully starved condition; that is they were not receiving sufficient oil to develop a hydrodynamic oil film. As such the horizontal stiffness went to near zero. This paper will present the results of the analysis work performed, including the starved bearing analysis, and the resulting redesign of the three pad bearing to run flooded. Operation as a flooded bearing allowed the machine to run fully loaded with no indications of unstable operation

Socioeconomic status may affect association of vegetable intake with risk of ischemic cardio-cerebral vascular disease: a Mendelian randomization study

BackgroundPrevious studies found that increasing vegetable intake benefits are reduced after adjustment for socioeconomic factors. Using genetic variation as an instrumental variable for vegetable intake and socioeconomic status, we investigated the relationship between vegetable intake and ischemic cardio-cerebral vascular diseases and focused on whether socioeconomic status was a possible confounder.MethodsFrom three independent genome-wide association studies, we extracted instrumental variables reflecting raw and cooked vegetable intake, which were used to perform Mendelian randomization analysis. To evaluate the effects of socioeconomic factors on vegetable intake, univariate and multivariate Mendelian randomization analyses were performed using single nucleotide polymorphisms representing education attainment and household income reported in the literature. We also performed outlier assessment and a series of sensitivity analyses to confirm the results.ResultsGenetically predicted raw and cooked vegetable intake were not associated with any ischemic cardio-cerebral vascular diseases and lipid components after Bonferroni correction. Univariate Mendelian randomized analysis revealed that raw vegetable intake was positively correlated with education attainment (β = 0.04, p = 0.029) and household income (β = 0.07, p < 0.001). Multivariate Mendelian randomized model showed a positive correlation between household income and raw vegetable intake (β = 0.06, p = 0.004). Socioeconomic status was closely associated with eating habits and lifestyle related to the risk of cardiovascular diseases.ConclusionGenetically determined raw and cooked vegetable intake was not associated with significant benefits in terms of ischemic cardio-cerebral vascular diseases while genetically determined socioeconomic status may have an impact on vegetable intake. Socioeconomic status, which was closely associated with other eating habits and lifestyle, may affect the association between vegetable intake and ischemic cardio-cerebral vascular diseases

Fundamentals of Fluid Film Journal Bearing Operation and Modeling

TutorialTutorial 14: Widely used in turbomachinery, the fluid film journal bearing is critical to a machine’s overall reliability level. Their design complexity and application severity continue to increase making it challenging for the plant machinery engineer to evaluate their reliability. This tutorial provides practical knowledge on their basic operation and what physical effects should be included in modeling a bearing to help ensure its reliable operation in the field. All the important theoretical aspects of journal bearing modeling, such as film pressure, film and pad temperatures, thermal and mechanical deformations and turbulent flow are reviewed. Through some examples, the tutorial explores how different effects influence key performance characteristics like minimum film thickness, Babbitt temperature as well as stiffness and damping coefficients. Due to their increasing popularity, the operation and analysis of advanced designs using directed lubrication principles, such as inlet grooves and associated starvation issues, are also examined with several examples including comparisons to manufacturers’ test data

Turbomachinery and Pump Vibrations

Discussion GroupThis group will discuss plant machinery vibration detection, monitoring, and diagnosis, from a Plant O&M point-of-view. All attendees will be encouraged (but not required) to participate in discussions, and contribute topics worthy of discussion. Likely topics presently suggested, which will be affirmed or rejected by attendee vote, include the following: • Condition monitoring vibration sensors and methods • Effectiveness of vibration condition monitoring on rotating equipment for detecting problems • “Diagnostics” versus “prognostics” • Value of, and ROI of, condition-based monitoring of vibration • Vertical pump monitoring, including below ground monitoring • Vibration standards for various pumps and turbomachinery types, sizes, and applications • Vibration test method options, and their proper selection and use • Standard locations for vibration measurement on machinery • Wireless devices: radio noise, effectiveness, experiences, security • Troubleshooting methods for typical vibration problems, and fix options • Operating Deflection Shapes and integration with condition-based monitoring • Finite element analysis application in support of machinery selection and troubleshooting • Rotordynamics analysis use in machinery selection and troubleshooting • Hydraulically-induced vibration: structural, system, rotor, acoustic • Measurement of presence, location, and severity of pump cavitation • Effect of high GVF (gas volume fraction) in centrifugal pumps • Mechanical installation (e.g. piping, foundation, alignment) issues affecting vibration • Seal and bearing effects on vibration, and vibration effects on bearings and seal

Steady State Performance Prediction Of Directly Lubricated Fluid Film Journal Bearings

LecturePredicting the performance of directly lubricated bearings is a challenge facing bearing manufacturers and end users alike. In this study, thermoelastohydrodynamic (TEHD) theories are applied to analyze three directly lubricated bearings that have been experimentally investigated by the Turbomachinery Laboratory at Texas A&M University, including two inlet groove bearings and one spray bar bearing. The main aspects of the TEHD models are presented, including an extensive discussion on groove mixing. Comparisons are made between the theoretical and experimental results for the pad temperatures and shaft centerline locations. The results, which show generally good agreement, indicate that the TEHD theories are capable of predicting the steady state performance of these directly lubricated bearings with reasonable accuracy. Limitations of the simple groove mixing model and the elastic model were also identified