Dynamic Stability Identification of a Full-Scale Tainter-Gate and Extension of Gate-Opening Range for Operation

2015 ◽  
Author(s):  
Keiko Anami ◽  
Noriaki Ishii ◽  
Charles W. Knisely
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Stability ◽  
Operating Conditions ◽  
Specific Test ◽  
Term Operation ◽  
Gate Opening ◽  
Long Duration ◽  
Ambient Excitation

To assure the complete stability and long-term safe operation of the large number of Tainter gates used worldwide, an effective method of distinguishing those gates susceptible to instability from unsusceptible gates is essential. This paper presents a case study of the dynamic stability identification of an operational Tainter gate in Japan, based on field vibration testing using steel-rod breaking excitation. First, an overview of the field vibration test and the in-water natural vibration characteristics of the gate is presented. The dynamic stability of the gate was identified from the test results in conjunction with our previously developed theoretical analysis. From the specific test data for a limited number of operating conditions, our theoretical analysis permits assessment of the dynamic stability of the gate for all operating conditions. In particular, the dynamic stability of the gate for small gate openings was confirmed, and subsequently validated by long-duration ambient excitation tests with very small gate openings. This study was the first attempt at operating the gate at openings smaller than the conventional minimum recommended opening. As a result, not only did the field test validate the gate’s reliability for long-term operation, but it also permitted an extension of the gate-opening range for operation.

scholarly journals A Combined Approach for Model-Based PV Power Plant Failure Detection and Diagnostic

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1261
Author(s):  
Christopher Gradwohl ◽  
Vesna Dimitrievska ◽  
Federico Pittino ◽  
Wolfgang Muehleisen ◽  
András Montvay ◽  
...  
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Failure Detection ◽  
Energy Yield ◽  
Combined Approach ◽  
Levelized Cost Of Electricity ◽  
Term Operation ◽  
Model Based

Photovoltaic (PV) technology allows large-scale investments in a renewable power-generating system at a competitive levelized cost of electricity (LCOE) and with a low environmental impact. Large-scale PV installations operate in a highly competitive market environment where even small performance losses have a high impact on profit margins. Therefore, operation at maximum performance is the key for long-term profitability. This can be achieved by advanced performance monitoring and instant or gradual failure detection methodologies. We present in this paper a combined approach on model-based fault detection by means of physical and statistical models and failure diagnosis based on physics of failure. Both approaches contribute to optimized PV plant operation and maintenance based on typically available supervisory control and data acquisition (SCADA) data. The failure detection and diagnosis capabilities were demonstrated in a case study based on six years of SCADA data from a PV plant in Slovenia. In this case study, underperforming values of the inverters of the PV plant were reliably detected and possible root causes were identified. Our work has led us to conclude that the combined approach can contribute to an efficient and long-term operation of photovoltaic power plants with a maximum energy yield and can be applied to the monitoring of photovoltaic plants.

Investigation of long-term operation and biomass activity in a membrane bioreactor system

2011 ◽  
Vol 63 (9) ◽  
pp. 1906-1912 ◽  
Author(s):  
Simos Malamis ◽  
Andreas Andreadakis ◽  
Daniel Mamais ◽  
Constantinos Noutsopoulos
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Extracellular Polymeric Substances ◽  
Operating Conditions ◽  
Term Operation ◽  
Solids Retention ◽  
Biomass Activity ◽  
Long Term Performance ◽  
Term Performance

The aim of this work was to evaluate the long-term performance of a Membrane Bioreactor (MBR) that operated continuously for 2.5 years and to assess membrane fouling and biomass activity under various operating conditions. Furthermore, a method for the characterisation of influent wastewater was developed based on its separation into various fractions. The MBR system operated at the solids retention times (SRT) of 10, 15, 20 and 33 days. The increase of SRT resulted in a decrease of the fouling rate associated with the reduction of extracellular polymeric substances. Moreover, the SRT increase resulted in a significant reduction of the Oxygen Uptake Rate (OUR) due to the lower availability of substrate and in a notable decrease of the maximum OUR since high SRT allowed the development of slower growing microorganisms. Biomass consisted of small flocs due to extensive deflocculation caused by intense aeration. Finally, the method developed for wastewater characterisation is straightforward and less time consuming than the usual method that is employed.

The Case for Combining Pump Maintenance and Systematic Upgrading

2008 ◽  
Author(s):  
Heinz P. Bloch ◽  
Robert Bluse ◽  
James Steiger
Keyword(s):  
System Performance ◽  
Current System ◽  
Highly Qualified ◽  
Centrifugal Pumps ◽  
Term Operation ◽  
Performance Requirements ◽  
Periodic Maintenance ◽  
Work Supports

Virtually, all industrial machinery requires periodic maintenance for dependable long-term operation. In fact, the very term “maintenance” is defined as keeping machines in the as-designed or as-purchased and manufactured condition. At issue is whether the equipment owner’s profitability objectives are best served by “maintaining only”, or by judiciously combining maintenance and upgrading tasks. Assuming the answer favors combining maintenance and upgrading, the question arises whether an intelligent and well thought-out combination of maintenance and upgrading should be entrusted only to the original equipment manufacturer (OEM), or if qualified non-OEMs should be considered also. The co-authors would like to offer their answer to the question. Experience shows that a highly qualified independent rebuild shop with demonstrated capabilities and experienced personnel can offer high-quality upgrades that improve both uptime and efficiency. Such a shop can do so consistent with current system performance requirements. With the considerable consolidations in the pump industry, the distinct possibility exists that the OEM is not able to offer the same engineering competence he previously had and that independent shops should be considered. This presentation deals with a case study and details where such upgrading was being planned, implemented, and verified to have had the desired results. It further explains the role played by competent pump rebuild shops (we chose to call them “CPRS”) in these important endeavors. Our work supports the premise that rebuilding a vintage process pump to original OEM specifications makes no sense, given current pump rebuilding technology and changes to the system performance that occur over time. We find compelling reasons to systematically upgrade the efficiency and potential run length of large centrifugal pumps. Of course, this upgrading must be pre-planned and then carried out during a future maintenance outage.

Numerical Modelling of a District Scale Groundwater Heat Pump Operation: Case Study from Colchester, UK

2021 ◽  
Author(s):  
Taha Sezer ◽  
Abubakar Kawuwa Sani ◽  
Rao Martand Singh ◽  
David P. Boon
Keyword(s):  
Large Scale ◽  
District Level ◽  
Thermal Plume ◽  
Injection Wells ◽  
Term Operation ◽  
Heating And Cooling ◽  
Groundwater Heat Pump ◽  
The Impact

<p>Groundwater heat pumps (GWHP) are an environmentally friendly and highly efficient low carbon heating technology that can benefit from low-temperature groundwater sources lying in the shallow depths to provide heating and cooling to buildings. However, the utilisation of groundwater for heating and cooling, especially in large scale (district level), can create a thermal plume around injection wells. If a plume reaches the production well this may result in a decrease in the system performance or even failure in the long-term operation. This research aims to investigate the impact of GWHP usage in district-level heating by using a numerical approach and considering a GWHP system being constructed in Colchester, UK as a case study, which will be the largest GWHP system in the UK. Transient 3D simulations have been performed pre-construction to investigate the long-term effect of injecting water at 5°C, into a chalk bedrock aquifer. Modelling suggests a thermal plume develops but does not reach the production wells after 10 years of operation. The model result can be attributed to the low hydraulic gradient, assumed lack of interconnecting fractures, and large (>500m) spacing between the production and injection wells. Model validation may be possible after a period operational monitoring.</p>

scholarly journals Identifying Efficient Operating Rules for Hydropower Reservoirs Using System Dynamics Approach—A Case Study of Three Gorges Reservoir, China

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2448 ◽  
Author(s):  
Jianzhong Zhou ◽  
Benjun Jia ◽  
Xiao Chen ◽  
Hui Qin ◽  
Zhongzheng He ◽  
...  
Keyword(s):  
System Dynamics ◽  
Three Gorges Reservoir ◽  
Central China ◽  
Optimal Decision ◽  
Three Gorges ◽  
Term Operation ◽  
Operating Rules ◽  
Hydropower Reservoirs

In the long-term operation of hydropower reservoirs, operating rules have been used widely to decide reservoir operation because they can help operators make an approximately optimal decision with limited runoff information. However, the problems faced by reservoir managers is how to make and select an efficient operating rule properly. This study focuses on identifying efficient and reliable operating rules for the long-term operation of hydropower reservoirs using system dynamics (SD) approach. A stochastic hydrological model of reservoir inflow time series was established and used to generate a large number of inflow scenarios. A deterministic optimization operation model of hydropower reservoirs was constructed and then resolved using dynamic programming (DP) algorithm. Simultaneously, within implicit stochastic optimization (ISO) framework, different operating rules were derived using linear fitting methods. Finally, the most efficient one of the existing operating rules was identified based on SD simulation coupled with the operating rules. The Three Gorges Reservoir (TGR) in central China was used as a case study. The results show that the SD simulation is an efficient way to simulate a complicated reservoir system using feedback and causal loops. Moreover, it can directly and efficiently guide reservoir managers to make and identify efficient operating rules for the long-term operation of hydropower reservoirs.

Fatigue Cracking Processes of a Thick-Walled Component of a Chemical Pipeline

2013 ◽  
Vol 586 ◽  
pp. 104-107 ◽  
Author(s):  
Marek Cieśla ◽  
Kazimierz Mutwil
Keyword(s):  
Mechanical Properties ◽  
Degradation Mechanism ◽  
Fatigue Cracking ◽  
Operating Conditions ◽  
Material Structure ◽  
Mechanical Loads ◽  
Factors Affecting ◽  
Term Operation ◽  
Materials Used

At present, there are no generally accepted and widely recognized procedures to determine condition of material of devices subject to complex long-term thermo-mechanical loads. Condition of pipeline material usually changes when subjected to the conditions of long-term operation. Its structure changes and, consequently, so do its mechanical properties, including fatigue characteristics and crack resistance. Therefore, the durability of a component operating under thermal and mechanical loads cannot be discussed separately from its current material properties. This applies in particular to changes that take place in the material micro-structure and to their connection with mechanical properties. This paper covers analyses of stress in the material of a selected pipeline component – pipe tee that is used in chemical plants. Thermo-mechanical interactions determining stress distribution in the component have been taken into account in the calculations. Morphology and location of the cracks indicated that a fatigue-like nature of impacts was the cause of material destruction. Loads of this type occur mainly in conditions of start-up and shut-down. For these reasons, condition of the material in the above-mentioned unstable conditions was subjected to numerical stress analysis. Due to geometric complexity of the pipeline, the distribution of stress in the T-pipe was calculated in two stages: the object was modeled from a global and local perspective. The resulting stress distributions helped to determine factors affecting durability of the tested object. Metallurgy tests were also conducted in order to ascertain factors determining the degradation of material structure and processes of crack formation and development. As a result of research one ascertained that the process of T-pipe cracking under operating conditions was a combined effect of thermo-mechanical and chemical actions determined by the course of intercrystalline corrosion. Synergic interaction of corrosion processes and variable thermal and mechanical loads caused nucleation and propagation of cracks. The crack systems in T-pipe areas subject to the highest stress showed courses characteristic for thermal fatigue of material. The results obtained will identify degradation mechanism of materials used in chemical installations.

Extensive Dynamic Analyses to Achieve Stringent Noise and Vibration Levels for an Offshore Reciprocating Compressor System

2011 ◽  
Author(s):  
Andre´ Eijk ◽  
Hans Elferink
Keyword(s):  
Operating Conditions ◽  
Reciprocating Compressor ◽  
Gas Well ◽  
Noise And Vibration ◽  
Term Operation ◽  
The North ◽  
Final Design ◽  
The North Sea ◽  
System Requirements

During the lifetime of an existing gas well, located in the D15FA/FB field in the North Sea, the pressure has dropped and consequently production is reduced. A depletion compressor had to be added to this existing platform to increase the production. This sounds easy but has been very challenging due to physical, noise and vibration restrictions. For this platform it appeared that a reciprocating compressor was the best choice based on its flexibility with respect to the specified operating conditions, available power, and efficiency. However, despite of several advantages a disadvantage of a reciprocating compressor is that it generates additional vibrations and noise in the living quarters, which are located close to the compressor system. The specified requirements, not to exceed the allowable noise limits in the living quarters and the vibration limits of the complete compressor system, could in this specific case, not be met with straightforward solutions. This presentation will explain the dynamic analysis and the efforts taken in compressor, skid, motor, piping and deck design to meet the very stringent specified requirements and to ensure a safe and reliable system for the long term operation. Special attention will be given to the measures taken to reduce the excitations acting on the platform, and the mechanical and acoustical analysis that have led to the final design of this reciprocating compressor system. The solutions that have been developed can be regarded as non-standard and have resulted in new directions in solving very demanding system requirements.

scholarly journals Rail Track with Rail Compression

2021 ◽  
Vol 20 (3) ◽  
pp. 234-242
Author(s):  
V. N. Sukhodoev
Keyword(s):  
Effective Property ◽  
Operating Conditions ◽  
Design Parameters ◽  
Labor Costs ◽  
Term Operation ◽  
Rail Track ◽  
Loading And Unloading ◽  
The Stability ◽  
The Cost

The problem of damping the noise on the track, arising from the movement of the train, is solved sufficiently but it is simple, if the rail with spacers is laid inside the longitudinally located band sleeper-mechanism. The result is a layered rail thread, consisting of belts: a rail tape with elastic spacers on three sides, a tie-mechanism tape and a ballast layer. The unity of the layers is carried out due to their own mass. This is the static track without external load. Rail compression is an effective property of rail tracks. It is formed in the sleeper mechanism under the influence of vertical forces with displacements and their horizontal derivatives. When loading the track, the compression is carried out repeatedly with subsequent unloading.n this case, each previous changes in the conditions in work of the track are taken into account in the subsequent cycle of loading and unloading. A rail track with a rail compression is a kind of self-adapting linear system, which is necessary with frequent changes in load and operating conditions for silent performance of a functional purpose. The specificity of this path is that the movement of the wheel creates rail vibration and noise, which are immediately damped by compression with damping. The balance between the occurrence of noise and its suppression is achieved by the ratio of the lengths of half-sleeper shoulders as a lever. The condition for the appearance of a shift of the compression forces in the direction from vertical shoulder of the half-sleepers is the unequal settlements of the horizontal shoulder of the L-shaped half-sleepers and its eccentric loading. As a result of the research, the advantages of a rail track with rail compression have been revealed, which is a guarantor of the stability of the design parameters during long-term operation of the track. The cost of a rail track with rail reduction is halved as a result of steel savings, lower labor costs and operational needs.

Making the Case for Global Outsourcing

2019 ◽  
pp. 611-632
Author(s):  
Alan D. Smith ◽  
Sara Joy Krivacek
Keyword(s):  
Business Practices ◽  
Cultural Changes ◽  
Term Operation ◽  
Customer Expectations ◽  
Global Outsourcing ◽  
Quality Product ◽  
The Common ◽  
Best Business Practices

Social media and empowered customers have significantly raised customer expectations of quality. Although there are similarities and differences in the approaches taken by management, they share the common goal of delivering a high-quality product and satisfying their customers. The majority of the case study concentrates on how both companies monitor quality, evaluate performance, train employees, and promote continuous improvement in order to achieve best business practices. The review of the literature on global outsourcing and analysis of the case studies provide evidence that economic development creates both short-term operation advantages through increased levels of efficiency as well as long-term social and cultural changes. Operational and strategic managers can use this information when making decisions on where to locate various aspects of their business. In some cases, it may make sense to outsource a particular task, but in other cases an organization may want to offshore particular tasks in order to keep control of the process.

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