Lateral Rotordynamics of Petrochemical Equipment - Review, Examples and Problems

Short Cours

Shop Rotordynamic Testing - Options, Objectives, Benefits and Practices

TutorialUnderstanding the lateral rotordynamic behavior is critical in determining the reliability/operability of rotating equipment. Whether examining a centrifugal pump or compressor, steam or gas turbine, motor or generator, rotating machinery share the same need to accurately predict and measure dynamic behavior. Industrial specifications determining fit for purpose rely on the accuracy of rotordynamic predictions where direct measurement is impractical or otherwise impossible in an industrial setting. Testing to confirm rotordynamic prediction and behavior provides both the purchaser and vendor the confidence that the design will meet project expectations. Rotordynamic shop testing has several options available to the project during acceptance tests at the vendor’s shop. These options include mechanical run, string and full load/Type 1 testing as well as verification testing to validate unbalance response and stability predictions. Such testing has numerous advantages; the most important being the avoidance of production disruptions involved with testing at the job site. Each test option has associated costs as well as limitations as to what lateral vibration characteristics are revealed. Understanding these factors is vital to efficiently mitigate the risks associated with the purchased equipment. Applying best practices and an understanding of the industrial (API) test requirements are needed to derive the maximum benefit of each test option. The best practices not only involve the test procedure but also the associated analytical methods used to post process the measurement information. Whether performing a simple mechanical run test or more complex stability verification during ASME Type I testing, ensuring that a logical, repeatable and proven methodology is followed produces reliable evidence to confirm the rotordynamic model and lateral vibration performance. The rationale behind the API test requirements provides an understanding of why that test is being performed and its correct application to the dynamic behavior. Test options can be separated into two categories; tests that reveal portions of the dynamic behavior of the equipment to specific operating conditions and those used to verify the analytical predictions of that behavior. API mechanical, string and Type I (or full load) tests reveal the rotordynamic behavior of the equipment to a given set of conditions. These are used specifically to determine acceptability of the design. Unbalance and stability verification testing is used to confirm (or provide confidence in) the rotordynamic model. Confidence in the model permits extrapolation of the design (vendor) and operation (purchaser) beyond the machine’s asbuilt and specific shop test conditions

Predicting, Understanding and Avoiding the Ekofisk Rotor Instability Forty Years Later

LectureThis famous machine is re-examined to assess how well (or not) current design and analytical methods have evolved to avoid shaft whip instability. In addition to reviewing the compressors history and design evolution, the rotordynamic performance of a newly configured machine, based on todays technology, is compared against the original design

Lateral Rotordynamics of Petrochemical Equipment - Review, Examples and Problems

Short Cours

Predicting, Understanding and Avoiding the Ekofisk Rotor Instability Forty Years Later

LectureThis famous machine is re-examined to assess how well (or not) current design and analytical methods have evolved to avoid shaft whip instability. In addition to reviewing the compressors history and design evolution, the rotordynamic performance of a newly configured machine, based on todays technology, is compared against the original design

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

Simplified Modal Analysis for the Plant Machinery Engineer

TutorialTutorial 6: Experimental modal analysis and operating deflection shapes (ODS) are powerful tools in vibration analysis and machinery troubleshooting. However, the machinery plant engineer often doesn’t believe such techniques are available given a lack of advanced measurement equipment. This tutorial presents best practices with simplified experimental modal analysis and ODS techniques that can be used by a plant machinery engineer with the limited vibration analysis equipment usually available at a plant site. Minimum requirements and analyzer settings are discussed for a variety of commonly available measurement equipment. For different machinery problems, common measurement pitfalls and limitations are reviewed and, where appropriate, alternative methods are presented. During the presentation, demonstrations of modal testing measurements will be conducted using a portable generic data acquisition system

Simplified Modal Analysis For The Plant Machinery Engineer

TutorialExperimental modal analysis and operating deflection shapes (ODS) are powerful tools in vibration analysis and machinery troubleshooting. However, the machinery plant engineer often doesn’t believe such techniques are available given a lack of advanced measurement equipment. This tutorial presents best practices with simplified experimental modal analysis and ODS techniques that can be used by a plant machinery engineer with the limited vibration analysis equipment usually available at a plant site. Minimum requirements and analyzer settings are discussed for a variety of commonly available measurement equipment. For different machinery problems, common measurement pitfalls and limitations are reviewed and, where appropriate, alternative methods are presented. During the presentation, demonstrations of modal testing measurements will be conducted using a portable generic data acquisition system

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

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