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Florian Sprenger - One of the best experts on this subject based on the ideXlab platform.
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COUPLING EFFECTS BETWEEN TANK SLOSHING AND MOTIONS OF A LNG Carrier
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 1, 2010Co-Authors: Günther F. Clauss, Daniel Testa, Florian SprengerAbstract:Free liquid surfaces inside the cargo tanks of seagoing ships not only reduce the initial stability but also influence the sea-keeping characteristics, in particular roll motions. Due to the increasing demand of liquefied natural gas (LNG), the concept of offshore processing or receiving terminals will gain in importance. Since pipelines are not economic for long distances, LNG is transported by shuttle Carriers from remote marine locations for onshore energy supply. The loading/unloading procedure of an average Carrier Vessel takes 18 to 24 hours — a time span where the tanks are partially filled and feature free liquid surfaces. Depending on the filling level, the wave incident angle as well as the phase shift of tank sloshing and body motions, the characteristics of the Vessel’s response amplitude operators (RAO), especially the roll motion, are altering. This is ascribed to coupling effects between the moving liquid and the hull motions. Hence, the seakeeping characteristics have to be reappraised for each case. A 138,000 m3 LNG Carrier with four membrane tanks is numerically analysed with a potential theory based software at different filling levels and wave incident angles in frequency domain. For experimental validation, the tanks are filled with water. Optical motion sensors and transient wave packages are used to determine the RAOs in six degrees of freedom. Additionally, the forces and moments induced by the sloshing liquid are measured by six-component force sensors. On this basis, further computations with LNG are conducted. The focus of the investigations lies on the influence of sloshing on the surge and roll motions of the exemplarily chosen LNG Carrier. Instead of one single resonance peak as for the solid filling case, the roll RAO of the dual-mass system features two peaks, whose magnitude and position depends on the filling level of the cargo tanks. But coupling effects due to resonant sloshing also affect longitudinal body motions. The knowledge of the altered seakeeping characteristics of LNG Carriers due to free liquid surfaces is essential for save offshore transfer operations.Copyright © 2010 by ASME
T. Krings - One of the best experts on this subject based on the ideXlab platform.
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Magnetic versus manual guidewire manipulation in neuroradiology: in vitro results
Neuroradiology, 2006Co-Authors: T. Krings, J. Finney, P. Niggemann, P. Reinacher, N. Lück, A. Drexler, J. Lovell, A. Meyer, R. Sehra, P. SchauerteAbstract:Introduction Standard microguidewires used in interventional neuroradiology have a predefined shape of the tip that cannot be changed while the guidewire is in the Vessel. We evaluated a novel magnetic navigation system (MNS) that generates a magnetic field to control the deflection of a microguidewire that can be used to reshape the guidewire tip in vivo without removing the wire from the body, thereby potentially facilitating navigation along tortuous paths or multiple acute curves. Method The MNS consists of two permanent magnets positioned on either side of the fluoroscopy table that create a constant precisely controlled magnetic field in the defined region of interest. This field enables omnidirectional rotation of a 0.014-inch magnetic microguidewire (MG). Speed of navigation, accuracy in a tortuous Vessel anatomy and the potential for navigating into in vitro aneurysms were tested by four investigators with differing experience in neurointervention and compared to navigation with a standard, manually controlled microguidewire (SG). Results Navigation using MG was faster ( P =0.0056) and more accurate (0.2 mistakes per trial vs. 2.6 mistakes per trial) only in less-experienced investigators. There were no statistically significant differences between the MG and the SG in the hands of experienced investigators. One aneurysm with an acute angulation from the Carrier Vessel could be navigated only with the MG while the SG failed, even after multiple reshaping manoeuvres. Conclusion Our findings suggest that magnetic navigation seems to be easier, more accurate and faster in the hands of less-experienced investigators. We consider that the features of the MNS may improve the efficacy and safety of challenging neurointerventional procedures.
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Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model
Acta Neurochirurgica, 2005Co-Authors: Franz J Hans, Albrecht Von Brunn, W. Möller-hartmann, T. Schmitz-rode, A. Thron, T. KringsAbstract:Objective. Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term Vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent Vessel wall are present after stentgraft placement using polyurethane as the covering material. Methods. Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the Vessel wall after one (n = 5) and three months (n = 5) observation. Results. Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative Carrier Vessel wall changes and no in-stent stenosis. Conclusions. In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the Vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent Vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, Vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.
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Experimental Study Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model
2005Co-Authors: Franz J Hans, Albrecht Von Brunn, T. Schmitz-rode, A. Thron, T. KringsAbstract:Summary Objective. Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term Vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent Vessel wall are present after stentgraft placement using polyurethane as the covering material. Methods. Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the Vessel wall after one (n ¼ 5) and three months (n ¼ 5) observation. Results. Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative Carrier Vessel wall changes and no in-stent stenosis. Conclusions. In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the Vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent Vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, Vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.
Franz J Hans - One of the best experts on this subject based on the ideXlab platform.
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Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model
Acta Neurochirurgica, 2005Co-Authors: Franz J Hans, Albrecht Von Brunn, W. Möller-hartmann, T. Schmitz-rode, A. Thron, T. KringsAbstract:Objective. Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term Vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent Vessel wall are present after stentgraft placement using polyurethane as the covering material. Methods. Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the Vessel wall after one (n = 5) and three months (n = 5) observation. Results. Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative Carrier Vessel wall changes and no in-stent stenosis. Conclusions. In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the Vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent Vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, Vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.
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treatment of experimentally induced aneurysms with stents
Neurosurgery, 2005Co-Authors: Timo Krings, Franz J Hans, Peter Verken, Heiko Dreeskamp, Ruth Thiex, Albrecht Von Brunn, K Scherer, W Mollerhartmann, Thomas Schmitzrode, Klaus P SteinAbstract:OBJECTIVE: Although Guglielmi detachable coil systems have been widely accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents, stent grafts, or implantation of coils after stent placement constitute emerging techniques in endovascular treatment. The aim of the present study was to use an animal model to investigate these different approaches to treat cerebral aneurysms with regard to the rate of closure and the histopathological changes within the aneurysm cavity and the parent Vessel after stent placement. METHODS: We created aneurysms in 30 rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. Ten animals were treated with porous stents alone, 10 animals with stent grafts (covered stents), and 10 animals with stents and additional coiling via the interstices of the stent, which enabled dense packing of the coils. Five animals in each group were observed for 1 month and the other animals for 3 months. Histological analyses were performed, including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration. RESULTS: Covered stents led to a complete and stable aneurysm occlusion with only minimal proliferative Carrier Vessel wall changes. One covered stent was completely occluded with old thrombus, and the other 9 remained patent. Porous stents occluded two of five aneurysms in the 1-month follow-up group and four of five after 3 months. However, progressive sprouting of neointima inside the Carrier Vessel that resulted in a stenosis of up to 40% was present. In the Stent + Coil group, one aneurysm showed recanalization after 1 month, and three of five aneurysms were recanalized after 3 months after coil compaction. Moreover, in-stent stenosis of up to 30% was present. CONCLUSION: This study demonstrates the possible shortcomings and problems of emerging stent techniques to treat intracerebral aneurysms, shows where technical advances have to be made, and describes in which cases of aneurysm morphology caution has to be exercised when considering an endovascular approach using stents.
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Experimental Study Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model
2005Co-Authors: Franz J Hans, Albrecht Von Brunn, T. Schmitz-rode, A. Thron, T. KringsAbstract:Summary Objective. Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term Vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent Vessel wall are present after stentgraft placement using polyurethane as the covering material. Methods. Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the Vessel wall after one (n ¼ 5) and three months (n ¼ 5) observation. Results. Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative Carrier Vessel wall changes and no in-stent stenosis. Conclusions. In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the Vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent Vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, Vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.
Günther F. Clauss - One of the best experts on this subject based on the ideXlab platform.
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COUPLING EFFECTS BETWEEN TANK SLOSHING AND MOTIONS OF A LNG Carrier
29th International Conference on Ocean Offshore and Arctic Engineering: Volume 1, 2010Co-Authors: Günther F. Clauss, Daniel Testa, Florian SprengerAbstract:Free liquid surfaces inside the cargo tanks of seagoing ships not only reduce the initial stability but also influence the sea-keeping characteristics, in particular roll motions. Due to the increasing demand of liquefied natural gas (LNG), the concept of offshore processing or receiving terminals will gain in importance. Since pipelines are not economic for long distances, LNG is transported by shuttle Carriers from remote marine locations for onshore energy supply. The loading/unloading procedure of an average Carrier Vessel takes 18 to 24 hours — a time span where the tanks are partially filled and feature free liquid surfaces. Depending on the filling level, the wave incident angle as well as the phase shift of tank sloshing and body motions, the characteristics of the Vessel’s response amplitude operators (RAO), especially the roll motion, are altering. This is ascribed to coupling effects between the moving liquid and the hull motions. Hence, the seakeeping characteristics have to be reappraised for each case. A 138,000 m3 LNG Carrier with four membrane tanks is numerically analysed with a potential theory based software at different filling levels and wave incident angles in frequency domain. For experimental validation, the tanks are filled with water. Optical motion sensors and transient wave packages are used to determine the RAOs in six degrees of freedom. Additionally, the forces and moments induced by the sloshing liquid are measured by six-component force sensors. On this basis, further computations with LNG are conducted. The focus of the investigations lies on the influence of sloshing on the surge and roll motions of the exemplarily chosen LNG Carrier. Instead of one single resonance peak as for the solid filling case, the roll RAO of the dual-mass system features two peaks, whose magnitude and position depends on the filling level of the cargo tanks. But coupling effects due to resonant sloshing also affect longitudinal body motions. The knowledge of the altered seakeeping characteristics of LNG Carriers due to free liquid surfaces is essential for save offshore transfer operations.Copyright © 2010 by ASME
Masahiko Ozaki - One of the best experts on this subject based on the ideXlab platform.
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Offshore Operational Availability of Onboard Direct Injection of CO2 into Sub-seabed Geological Formations
Energy Procedia, 2013Co-Authors: Tsuyoshi Miyazaki, Hiroyuki Osawa, Masami Matsuura, Makoto Ohta, Masahiko OzakiAbstract:Abstract Offshore operational availability was investigated for the proposed handling system consisting of the Carrier Vessel equipped with dynamic positioning capability, on-board manual operation of picking-up the sea-surface float connected to the upstream end of the flexible riser pipe laid-dawn on sea floor. An offshore site was selected to collect the oceanographic off the southern part of Japan facing to the Pacific Ocean. The response amplitude operator of the proposed CO 2 Carrier Vessel was calculated based on 3-D Singularity Distribution Method. Based on the result of the interview survey with captains of research Vessels which showed that for offshore operations a Vessel's pitch motion and service deck wetness are dominant factors which define a Vessel's operational availability, the RAO of the pitch and relative wave elevation was evaluated. The hull motions and the relative wave elevation in unidirectional irregular waves and in multidirectional irregular waves were calculated by a conventional method based on the seakeeping theory using the RAOs, the wave spectrum and the directional wave spectrum. Under the assumption that the operational availability of the proposed CO 2 Carrier Vessel is constrained by the pitch motion and the service deck wetness, the allowable upper limit values of the significant wave height were calculated by a conventional method based on the sea keeping theorem using the 1/10 maximum expected response value of pitch motion and the relative wave elevation evaluated in the above-mentioned calculation. The threshold value of operation availability was set at the pitch of 3.0 degrees and the relative wave elevation at the freeboard to the service deck, based on the result of the interview survey with captains of research Vessels. Finally, the overall operational availability was estimated, on the assumption that the threshold value of operation availability was set at the pitch of 3.0 degrees and the relative wave elevation at the freeboard to the service deck. We concluded that the operational availability of the proposed CO 2 Carrier Vessel reaches a target value of nearly 90% for both full year and four seasons in the case that freeboard of service deck for offshore buoy picking-up operations set greater than 2.3 m as a service platform.
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Cargo Conditions of CO2 in Shuttle Transport by Ship
Energy Procedia, 2013Co-Authors: Noriyuki Kokubun, Masahiko OzakiAbstract:Abstract For shuttle transport of liquid CO2 in ship-based CCS, the cargo conditions were investigated in view of the pressure tank manufacturability, the cost of the tanks and the Carrier Vessel, the total energy efficiency of the CO2 flow, etc. In a CCS chain, since the critical path might be the injectivity of the well, the unit cargo of a Carrier Vessel is set to 3000 tonnes, which is equivalent to the Sleipner case, annual injection rate of ca. 1 million tonnes. The physical properties of CO2, specifically the vapor liquid equilibrium properties of CO2, are such that the design of a storage tank for the containment of liquid carbon dioxide is very similar to existing designs for intermediate pressure liquefied petroleum gas (LPG) containment systems. The design methodology for LPG cargo tanks is well understood and is regulated by international standards (specifically the “International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk”; IGC code) and Classification Societion Societies (such as DNV, BV and LRS) The disign methodology employed in this study, which is for the marine transport of LCO2 is exactly the same as described by the IGC code and subject to Classification Society rules. These design rules are well proven with literally hundreds of LPG Carriers operating worldwide in an industry that has an excellent safety record since the advent of LPG bulk marine transport in the early 1960s. The proposed ship design which installs two cargo tanks was as follows: - the volume of the tanks is about 1500 m3 and design pressure and temperature are 3.10 MPa and munus 10 degC, respectively. - The shape of the tanks is a cylindrical bilobe with single cylinder radius of 3.50 m and 26.96 m in length The necessary facilities for LCO2 loading from land-based storage tanks are also examined, including CO2 buffer storage tanks, the loading pumps, the loading arms, and so on. The offshore delivery and injection system are investigated and the resultant design proposal was as follows: the temperature of the cargo LCO2 is raised to 5 degC by on-board heat exchange system using the ambient seawater. The cost estimate of the proposed system will be also given in the presentation. The study is a part of the Preliminary Feasibility Study on CO2 Carrier for Ship-based CCS and its follow-up study sponsored by Global CCS Institute and conducted by Chiyoda Corporation. The other technical parts of the study are Ship-based offshore CCS featuring CO2 shuttle ships equipped with injection facilities by M Ozaki et al, “Offshore operational availability of onboard direct injection of CO2 into sub-seabed geological formations” by T Miyazaki et al, and “Onboard CO2 injection into subseabed geological formation via picked-up flexible pipe by N. Nakazawa et al.