Case Study Validation of Common Torsional Rotordynamic Practices for Integrally Geared Compressors

2017 ◽  
Author(s):  
Dhruv Kumar ◽  
Michael Moeller
Keyword(s):  
Centrifugal Compressor ◽  
Torsional Stiffness ◽  
Electric Motors ◽  
Safe Operation ◽  
Plant Operations ◽  
Modelling Assumptions

Drivetrains for turbomachinery used in plant operations generally consist of a centrifugal compressor driven by turbines or electric motors, and may include intermediate speed reducing gearboxes. Each of these drivetrain components require accurate torsional modelling to ensure safe operation. Shaft modelling assumptions for these component sections can significantly alter the location of predicted torsional criticals and responses. One essential modelling assumption is the calculation of effective torsional stiffness in stepped shafts. Industry accepted methods include shaft penetration, the 45 degree rule and FEA approaches. A comparison of the three methods and the torsional impacts on a case study are presented.

Side effects of cultured bacteria addition in wastewater collection system on plant operations – a case study

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
Yanjin Liu ◽  
Giraldo Eugenio
Keyword(s):  
Energy Use ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Collection System ◽  
Oil And Grease ◽  
Odor Control ◽  
Plant Operations ◽  
Cultured Bacteria ◽  
Wastewater Collection

Cultured bacteria addition is one of the technologies used for odor control and FOG (fat, oil, and grease) removal in wastewater collection systems. This study investigated the efficiency of bacterial addition on wastewater odor control by conducting a set of full scale trials in a 60,000 cubic meter per day system for a period of two years. The objectives of this study were: (i) to identify factors that could impact wastewater treatment plant (WWTP) operations due to the effect of bacterial addition in the collection system, (ii) to estimate/understand the level of those impacts, and (iii) to present some interesting findings from the completed case study. The plant operation data before and during the bacterial addition were reviewed. The application of the cultured bacteria presented in the study was found to have significant impacts on the operation of the WWTP in terms of influent biological oxygen demand (BOD) and total suspended solids (TSS) loading, primary settling, sludge production, energy use, dissolved sulfides concentration, and methane production.

Comparison of Numerical Methods for Determining Torsion Stiffness of Automotive Chassis

2011 ◽  
Author(s):  
Steven Tebby ◽  
Ebrahim Esmailzadeh ◽  
Ahmad Barari
Keyword(s):  
Finite Element Analysis ◽  
Analytical Approach ◽  
Torsional Stiffness ◽  
Design Stage ◽  
Element Analysis ◽  
Detailed Design ◽  
Vertical Displacements ◽  
Comparison Of The Results ◽  
Torsion Stiffness

The torsion stiffness of an automotive chassis can be determined using an analytical approach based purely on geometry, using an experimental method, or alternatively by employing a Finite Element Analysis (FEA) process. These three methods are suitable at different design stages and combined together could prove to be practical methods of determining the torsion stiffness of a chassis. This paper describes and compares two distinct FEA processes to determine the torsion stiffness of an automotive chassis during the detailed design stage. The first process iteratively applies forces to the model and records displacements, while the second process gradually applies vertical displacements in place of force to determine the torsional stiffness threshold. Each method is explained and supported with a case study to provide a basis of comparison of the results.

Life cycle assessment of a large-scale centrifugal compressor: A case study in China

2016 ◽  
Vol 139 ◽  
pp. 810-820 ◽  
Author(s):  
Shitong Peng ◽  
Tao Li ◽  
Mengmeng Dong ◽  
Junli Shi ◽  
Hongchao Zhang
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Centrifugal Compressor ◽  
Large Scale

The Use of Interference Diagrams to Avoid Impeller Resonance: An Application to IGV Design

2009 ◽  
Author(s):  
Marco Ferioli
Keyword(s):  
Centrifugal Compressor ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Common Source ◽  
Operating Speed ◽  
Element Analysis ◽  
Exciting Frequency ◽  
Combine Information ◽  
The Impact

Interference diagrams can be used to avoid the potential excitation of a particular mode of vibration for centrifugal compressor impellers, thus reducing the risk of fatigue failures. Such diagrams are an excellent tool to combine information on impeller natural frequencies and mode shapes, excitation sources and operating speed of the machine on the same graph. Once the impeller design has been finalized in terms of aerodynamic performance, structural assessments and therefore geometry, Finite Element Analysis can be used to predict its natural frequencies and mode shapes (i.e. nodal diameters). Results can therefore be shown on a chart, together with the operating speed range of the machine. The need to plot on a single diagram this whole set of data arises from the mathematical evidence to consider the frequency of vibration together with the mode shape and the shape of the exciting force, while analyzing resonances. Typical Campbell diagrams are unable to provide this information at a glance. A common source of excitation for the first impeller of centrifugal compressors is the IGV set. Inlet Guide Vanes produce an exciting frequency that is directly proportional to the number of vanes N, where N represents also the shape of the excitation. The interference diagram can therefore be used: • to design and optimize the IGV for a new machine; • to choose between two different designs; • to evaluate the impact of a new IGV for the impeller of an existing compressor. A case study will be introduced, in order to show the application of interference diagrams to avoid potentially dangerous resonances between an IGV set and the first impeller during the re-design phase for a centrifugal compressor already in operation.

Assessment of Weld Overlay Defects in a Hydrocracking Unit Reactor

2013 ◽  
Author(s):  
Mohammed S. Robai ◽  
Jarallah A. Al-Sudairy ◽  
Abdullah M. Al-Harbi ◽  
Joy Joseph
Keyword(s):  
Stainless Steel ◽  
Performance Management ◽  
Base Material ◽  
Material Degradation ◽  
Safe Operation ◽  
Weld Overlay ◽  
Temperature And Pressure ◽  
Operational Excellence ◽  
Very High

Asset Performance Management is a key element of operational excellence. It refers to the management systems, strategies and activities aimed at maintaining the integrity of plant assets for their desired life. The safe operation of the assets is to be ensured at any cost. The objective of this paper is to offer one of the most critical assets in a refinery, namely the Hydrocracking Unit (HCU) reactor, as a case study addressing assessment of defects found in the weld overlay. The reactor was built in 1978 according to ASME Sec. VIII Div. 2 and has been in operation since then. The reactor is constructed of Chromium-Molybdenum (Cr-Mo) base material (SA 336 F21) with thickness of 266 mm and corrosion resistant stainless steel (TP-347 with thickness of 3.2 mm) weld overlay. The very high operating temperature and pressure of the reactor in hydrogen rich hydrocarbon service and the resulting thermal stress and material degradation caused disbonding and cracks in the stainless steel weld overlay. This paper will address the approach that was used to alleviate such type of defects. Also, various considerations that go into the assessment are discussed and recommendations are suggested.

Adaptation of an Existing Impeller Design to Large Bore Requirements: Aerodynamic Considerations

2019 ◽  
Author(s):  
Vishal Jariwala ◽  
Louis Larosiliere
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Cost Effective ◽  
Aerodynamic Performance ◽  
Vector Diagram ◽  
Multistage Process ◽  
Rotor Stiffness

Abstract Multistage process centrifugal compressor applications with single shaft rotors supported by only two bearings are quite common. It is sometimes desirable to operate impellers at higher rotational speeds, resulting in relatively compact and cost-effective machines. Such high-speed rotors can, however, pose rotordynamic challenges, and therefore require larger shaft or impeller bore diameters to increase rotor stiffness and rotordynamic stability. This work explores aerodynamically favorable ways to adapt an existing standard bore impeller design to large bore requirements. First, the stage aerodynamic performance and flow range implications of increasing bore diameter are discussed using meanline modeling and vector diagram arguments. Some strategies for adapting a standard bore design to large bore variant are then presented. Attempts are made to identify and clarify technical limitations to the degree of adaptability of an existing impeller to large bore requirements. Finally, a CFD-backed case study on a large-bore adaptation of a particular stage is presented to clarify practical considerations.

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