J. Abrahamsen, Frank Tore Sæther, S. Haugen, Stian Bentsen, Yngve Villanger, O. Økland
Critical rotating machinery topside is monitored by sensors providing detailed information on the mechanical condition. Early signs of abnormalities can be detected and corrected. This is contrary to subsea pumps where only a very small percentage of the installed base is monitored. This is due to the lack of availability of qualified proximity probes for subsea pumps, although this has started to be addressed for recent applications. Furthermore, sensors inside the machine add complexity, failure modes and cost, while benefits are limited as repair requires the machine to be recovered to the surface. Consequently, a run to failure philosophy is applied. With sensors being omitted because of cost and risk, the operator often operates in an uncomfortable "blind" mode. With no information on remaining life time and the risk of a creeping failure underway, the only mitigation is to accept the cost for a spare pump and IMR vessel ready for a replacement at minimum notice. By applying an array of sensing elements, the presented condition monitoring system measures and analyses the acoustic and electric field generated by a subsea pump. The sensor system operates completely independently, can be installed and replaced without interfering with the pump and will also provide monitoring of components adjacent to the pump. The level of precision provided is not designed for detailing a repair plan (e.g. defining the position of balance weights), however it is fully adequate for early detection of a fault under development and will help guide the operator to maximize remaining lifetime by tuning the process parameters. Using data acquired over a 10 year period, we will demonstrate how the system has successfully been used to monitor the health status of two different subsea pumps. Both pumps were eventually damaged, and we will investigate how the system provided the operator with a warning 6-8 weeks before the pump had to be stopped.
{"title":"Non-Intrusive Monitoring of Subsea Boosting Systems","authors":"J. Abrahamsen, Frank Tore Sæther, S. Haugen, Stian Bentsen, Yngve Villanger, O. Økland","doi":"10.4043/29216-MS","DOIUrl":"https://doi.org/10.4043/29216-MS","url":null,"abstract":"\u0000 Critical rotating machinery topside is monitored by sensors providing detailed information on the mechanical condition. Early signs of abnormalities can be detected and corrected. This is contrary to subsea pumps where only a very small percentage of the installed base is monitored. This is due to the lack of availability of qualified proximity probes for subsea pumps, although this has started to be addressed for recent applications. Furthermore, sensors inside the machine add complexity, failure modes and cost, while benefits are limited as repair requires the machine to be recovered to the surface. Consequently, a run to failure philosophy is applied.\u0000 With sensors being omitted because of cost and risk, the operator often operates in an uncomfortable \"blind\" mode. With no information on remaining life time and the risk of a creeping failure underway, the only mitigation is to accept the cost for a spare pump and IMR vessel ready for a replacement at minimum notice.\u0000 By applying an array of sensing elements, the presented condition monitoring system measures and analyses the acoustic and electric field generated by a subsea pump. The sensor system operates completely independently, can be installed and replaced without interfering with the pump and will also provide monitoring of components adjacent to the pump. The level of precision provided is not designed for detailing a repair plan (e.g. defining the position of balance weights), however it is fully adequate for early detection of a fault under development and will help guide the operator to maximize remaining lifetime by tuning the process parameters.\u0000 Using data acquired over a 10 year period, we will demonstrate how the system has successfully been used to monitor the health status of two different subsea pumps. Both pumps were eventually damaged, and we will investigate how the system provided the operator with a warning 6-8 weeks before the pump had to be stopped.","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83188301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tao Wang, Yongyan Wu, Rolf Loken, N. Haug, Rolf Eide
Wind represents a driving factor for floating system designs, not only for stability, but also for platform global performance including offset, heel and airgap, and thus for mooring, riser/umbilical, structure, topsides equipment and personnel habitability. Wind load evolves as metocean criteria, topsides layouts, design requirements, and estimation methods, and can be in continuous development from concept, design, execution to operation phases. The impact needs to be considered from operability to survivability of floating systems. A case study of semi-submersibles in worldwide regions will be considered. It is first developed a semi-submersible in the Gulf of Mexico for hurricanes up to 1,000-year return period. Wind speeds in other representative locations worldwide, i.e., the North Sea, and offshore Northwest Australia, are then applied to reconfigure the semi-submersible hull and mooring. The impacts of wind loads are evaluated by changing the wind speed and associated wind profile, but maintaining the other design parameters. The North Sea case is for relatively less severe winds of up to 10,000-year storms, while the offshore Northwest Australia case is for strong tropical winds of up to 10,000-year cyclones. The hull configuration, including main dimension, displacement, GM, and mooring sizing, are compared for the worldwide cases. For the Gulf of Mexico case, wind load is not only crucial for stability in 100-year environment, but also for survivability in 1,000-year hurricane. Comparably, wind load governs the North Sea case for stability although its 100-year wind speed is less severe, while 10,000-year cyclone wind is critical to survivability for the offshore Northwest Australia case. For mooring system, wind contributes to the majority of environmental loads, especially for the offshore Northwest Australia case. It is presented as a result of wind speed, and can be used to interpret uncertainty in wind load estimation from empirical method, model testing, CFD and design requirements. This paper evaluates the impact of wind loads for floating system designs from operating, extreme to survival conditions, identifies the governing factor in worldwide regions, and provides a view of systematic approach to the integrated system.
{"title":"Importance of Wind Loads for Floating System Designs","authors":"Tao Wang, Yongyan Wu, Rolf Loken, N. Haug, Rolf Eide","doi":"10.4043/29526-MS","DOIUrl":"https://doi.org/10.4043/29526-MS","url":null,"abstract":"\u0000 Wind represents a driving factor for floating system designs, not only for stability, but also for platform global performance including offset, heel and airgap, and thus for mooring, riser/umbilical, structure, topsides equipment and personnel habitability. Wind load evolves as metocean criteria, topsides layouts, design requirements, and estimation methods, and can be in continuous development from concept, design, execution to operation phases. The impact needs to be considered from operability to survivability of floating systems.\u0000 A case study of semi-submersibles in worldwide regions will be considered. It is first developed a semi-submersible in the Gulf of Mexico for hurricanes up to 1,000-year return period. Wind speeds in other representative locations worldwide, i.e., the North Sea, and offshore Northwest Australia, are then applied to reconfigure the semi-submersible hull and mooring. The impacts of wind loads are evaluated by changing the wind speed and associated wind profile, but maintaining the other design parameters. The North Sea case is for relatively less severe winds of up to 10,000-year storms, while the offshore Northwest Australia case is for strong tropical winds of up to 10,000-year cyclones.\u0000 The hull configuration, including main dimension, displacement, GM, and mooring sizing, are compared for the worldwide cases. For the Gulf of Mexico case, wind load is not only crucial for stability in 100-year environment, but also for survivability in 1,000-year hurricane. Comparably, wind load governs the North Sea case for stability although its 100-year wind speed is less severe, while 10,000-year cyclone wind is critical to survivability for the offshore Northwest Australia case. For mooring system, wind contributes to the majority of environmental loads, especially for the offshore Northwest Australia case. It is presented as a result of wind speed, and can be used to interpret uncertainty in wind load estimation from empirical method, model testing, CFD and design requirements.\u0000 This paper evaluates the impact of wind loads for floating system designs from operating, extreme to survival conditions, identifies the governing factor in worldwide regions, and provides a view of systematic approach to the integrated system.","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85506315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Vanneste, F. Løvholt, D. Issler, Zhongqiang Liu, N. Boylan, Jihwan Kim
Submarine landslides can pose a significant threat to offshore installations and coastal communities. They can strike installations far from their origin and generate destructive tsunamis. To assess and quantify this hazard, it is necessary to be able to model their dynamics in complex submarine environments with realistic rheological input parameters. Many submarine landslides involve cohesive visco-plastic soils, which can be described mathematically by rheological models such as the non-linear Herschel–Bulkley model. To model these events, accounting for complex bathymetry and rheological behavior, NGI has developed BingClaw. It incorporates buoyancy, hydrodynamic resistance and remolding, which are crucial for underwater landslide dynamics. BingClaw has been used to study the dynamics and tsunami generation of some of the largest and most complex submarine landslides in the world such as the Storegga Slide about 8000 years ago and the 1929 Grand Banks landslide and tsunami. In both cases, BingClaw provided a far more realistic description of both the landslide dynamics and the induced tsunami than other models. The link to the tsunami generation was used to better constrain the landslide dynamics. Here, we demonstrate how BingClaw is used for geohazard applications, including attempts to hindcast past landslides directly relevant to these applications, as often rheological data are sparse or not available from a given site. We first present benchmark results comparing the landslide model with results from laboratory experiments. Then, we show comparisons between simulations and observed landslide run-out for both offshore and onshore applications. The onshore application provides additional well-controlled field studies for validation, in soils with high sensitivity. We also used BingClaw in an offshore/nearshore geohazard project, namely the Bjørnafjorden project offshore western Norway. There, we linked the run-out analysis directly to static and seismic slope stability evaluations, and the predicted run-out scenarios were used in the assessment of competing bridge concepts and their foundations in the deep fjord (around 560 m water depth). These studies illustrate that this novel method, applicable for onshore and offshore geohazard assessments, can reliably reproduce field observations using realistic rheological parameters, which is important when estimating the risk posed by submarine mass movements, particularly with respect to the potential impact on infrastructure.
{"title":"A Novel Quasi-3D Landslide Dynamics Model: From Theory to Applications and Risk Assessment","authors":"M. Vanneste, F. Løvholt, D. Issler, Zhongqiang Liu, N. Boylan, Jihwan Kim","doi":"10.4043/29363-MS","DOIUrl":"https://doi.org/10.4043/29363-MS","url":null,"abstract":"\u0000 Submarine landslides can pose a significant threat to offshore installations and coastal communities. They can strike installations far from their origin and generate destructive tsunamis. To assess and quantify this hazard, it is necessary to be able to model their dynamics in complex submarine environments with realistic rheological input parameters.\u0000 Many submarine landslides involve cohesive visco-plastic soils, which can be described mathematically by rheological models such as the non-linear Herschel–Bulkley model. To model these events, accounting for complex bathymetry and rheological behavior, NGI has developed BingClaw. It incorporates buoyancy, hydrodynamic resistance and remolding, which are crucial for underwater landslide dynamics. BingClaw has been used to study the dynamics and tsunami generation of some of the largest and most complex submarine landslides in the world such as the Storegga Slide about 8000 years ago and the 1929 Grand Banks landslide and tsunami. In both cases, BingClaw provided a far more realistic description of both the landslide dynamics and the induced tsunami than other models. The link to the tsunami generation was used to better constrain the landslide dynamics.\u0000 Here, we demonstrate how BingClaw is used for geohazard applications, including attempts to hindcast past landslides directly relevant to these applications, as often rheological data are sparse or not available from a given site. We first present benchmark results comparing the landslide model with results from laboratory experiments. Then, we show comparisons between simulations and observed landslide run-out for both offshore and onshore applications. The onshore application provides additional well-controlled field studies for validation, in soils with high sensitivity. We also used BingClaw in an offshore/nearshore geohazard project, namely the Bjørnafjorden project offshore western Norway. There, we linked the run-out analysis directly to static and seismic slope stability evaluations, and the predicted run-out scenarios were used in the assessment of competing bridge concepts and their foundations in the deep fjord (around 560 m water depth).\u0000 These studies illustrate that this novel method, applicable for onshore and offshore geohazard assessments, can reliably reproduce field observations using realistic rheological parameters, which is important when estimating the risk posed by submarine mass movements, particularly with respect to the potential impact on infrastructure.","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82174358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jinbo Chen, J. Newlin, Heping Zhang, Shuang Hu, Meng Luo
Dynamic analyses of steel catenary risers (SCRs) suspended from a floating platform usually show that the vicinity of the zone where the riser touches down on the seabed is important to fatigue assessments, and can be critical in realizing an economical SCR design or in assessing SCR design life extension. The motivations of the paper are to advance the understanding of the complex mechanism of SCR-soil interactions in a comprehensive yet efficient way, to supplement the extensive model test-based SCR-soil interaction studies in the literature, and to offer a numerical tool to predict the SCR-soil interaction in different clay types. The objective is to investigate the fundamental mechanism of SCR-soil interactions using advanced finite element (FE) analyses. The FE analysis is conducted in Abaqus using the coupled Euler-Lagrangian (CEL) technique to capture the local large deformation surrounding a riser. A strain-softening soil model for deepwater soft clays subject to cyclic degradation is developed based on cyclic direct simple shear (DSS) tests to avoid cycle-by-cycle simulations. The stress-displacement relations are proposed in the FE analysis to avoid the size effect associated with strain-softening soils. The FE analysis results are compared to the test data from the independently conducted model tests and the established results from the literature. Good agreements among different studies are observed.
{"title":"Large Deformation Finite Element Analysis of Riser-Soil Interactions with Strain-Softening Soils","authors":"Jinbo Chen, J. Newlin, Heping Zhang, Shuang Hu, Meng Luo","doi":"10.4043/29376-MS","DOIUrl":"https://doi.org/10.4043/29376-MS","url":null,"abstract":"\u0000 Dynamic analyses of steel catenary risers (SCRs) suspended from a floating platform usually show that the vicinity of the zone where the riser touches down on the seabed is important to fatigue assessments, and can be critical in realizing an economical SCR design or in assessing SCR design life extension. The motivations of the paper are to advance the understanding of the complex mechanism of SCR-soil interactions in a comprehensive yet efficient way, to supplement the extensive model test-based SCR-soil interaction studies in the literature, and to offer a numerical tool to predict the SCR-soil interaction in different clay types. The objective is to investigate the fundamental mechanism of SCR-soil interactions using advanced finite element (FE) analyses. The FE analysis is conducted in Abaqus using the coupled Euler-Lagrangian (CEL) technique to capture the local large deformation surrounding a riser. A strain-softening soil model for deepwater soft clays subject to cyclic degradation is developed based on cyclic direct simple shear (DSS) tests to avoid cycle-by-cycle simulations. The stress-displacement relations are proposed in the FE analysis to avoid the size effect associated with strain-softening soils. The FE analysis results are compared to the test data from the independently conducted model tests and the established results from the literature. Good agreements among different studies are observed.","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89397215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-038
S. K. Savvinikh
{"title":"Optical Properties of the Impurity Intervalley Multiplet in Ge-Type Semiconductors in Uniform Constant Electric Field","authors":"S. K. Savvinikh","doi":"10.1515/9783112495308-038","DOIUrl":"https://doi.org/10.1515/9783112495308-038","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84280176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-015
A. S. T. Pibes
{"title":"A Discussion about the N-Pole Approximation to the Continued-Fraction Expansion","authors":"A. S. T. Pibes","doi":"10.1515/9783112495308-015","DOIUrl":"https://doi.org/10.1515/9783112495308-015","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"159 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76974830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-009
E. Anastassakis, M. Cardona
{"title":"Effects of Strains on the Dynamic Effective Charge of III -V Semiconductors","authors":"E. Anastassakis, M. Cardona","doi":"10.1515/9783112495308-009","DOIUrl":"https://doi.org/10.1515/9783112495308-009","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81701438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-002
S. Sugai
{"title":"Lattice Vibrations in the Charge-Density-Wave States of Layered Transition Metal Dichalcogenides","authors":"S. Sugai","doi":"10.1515/9783112495308-002","DOIUrl":"https://doi.org/10.1515/9783112495308-002","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90811500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-056
I. Savić, L. Maurer
{"title":"On the Ground-State Properties of Two-Dimensional q-State Potts Antiferromagnets","authors":"I. Savić, L. Maurer","doi":"10.1515/9783112495308-056","DOIUrl":"https://doi.org/10.1515/9783112495308-056","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87769135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1985-12-31DOI: 10.1515/9783112495308-060
F. W. O. Da Silva, A. Pires
{"title":"A Linear Chain Approximation to the Ising Model with Alternate Next-Nearest-Neighbor Interactions2","authors":"F. W. O. Da Silva, A. Pires","doi":"10.1515/9783112495308-060","DOIUrl":"https://doi.org/10.1515/9783112495308-060","url":null,"abstract":"","PeriodicalId":11149,"journal":{"name":"Day 1 Mon, May 06, 2019","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"1985-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75911546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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