A comprehensive study was conducted on the collapse mechanism of rings cut off from line pipe specimens. It was theoretically established that a ring without end restraints should have a lower collapse pressure value than an equivalent full-scale joint. However, similar collapse pressure test results were obtained for both rings and joints. Ring tests differ from joint tests in end restraint, but both capture collapse resistance integrally, while coupon tests (production tests) only capture the influence of material properties. The ‘length effect’ and the ‘end cap effect’ increase the collapse resistance of a joint, while radial end restraints increase the collapse resistance of a ring. These effects are found to be of same order of magnitude for the investigated combination of parameters (thermally aged SAWL 450 and D/t of approximately 20). Further, influence of the out-of-roundness shape and material properties on the collapse behaviour of rings was assessed.
The present study aims at characterizing the carbide precipitation behavior of model high Mn steels by developing a time-temperature-precipitation (TTP) and continuous-cooling-precipitation (CCP) diagram. Samples were isothermally heat treated at 1150 °C for 1 hr to dissolve pre-existing carbides, quenched to temperature range from 500 to 1000°C and held for time range from 30 to 2400s. The initiation of carbides precipitation was found as early as 30s. Higher carbon content in the model steels resulted in fast carbide precipitation.
Motion response of hinged multi-body system is studied in frequency domain based on the linear potential flow theory. Hydrodynamic coefficients and exciting forces are obtained by solving the boundary integral equations, which are implemented by higher order element. The global equilibrium equations of this multi-body system are established by the adoption of constrained matrix, which is derived by the displacement continuous condition. A multi-body system composed of five hinged barges is considered, and the influence of water depth and local seabed on motion response and hinged force is investigated.
China’s first demonstration offshore wind turbine (OWT), which independently designed, constructed and installed by China Offshore Oil Engineering Company in 2007, was introduced in the paper. An inactive single-point mooring system jacket foundation in Suizhong oil field was used as supporting structure for 1.5 MW OWT. The OWT was pre-assembled with a jacket cap module together onshore, and then be transported vertically onboard of a derrick barge for around 170 nautical miles. The OWT was installed with only one lift. To ensure a safe operation manner, overall stability, motion response, and the strength and stability of the tower and wind turbine structure were analyzed. Moreover, optimal ballast scheme were designed, and model test was carried out to compare with the numerical findings. In addition, a real-time monitoring system was mounted on the turbine body to verify the numerical findings.
Carbon Capture & Storage ( CCS ) technology was developed to reduce anthropogenic emission of carbon dioxide ( CO2 ) into atmosphere. As the energy sector accounts for around two-thirds of Green House Gases emissions ( GHG ), coming from fossil fuels utilization; the first logical application for CCS was in power generation; for many decades to come, forecasts of global energy demand indicate this fossil fuel dependence will continue. However in the last years, also in other industrial sectors the CCS technology is growing as an option to get emissions cuts at low cost without revamping production technologies.
The estimated growth of the CO2 transportation network, to meet the climate challenge with CCS, is very large compared to the actual carbon dioxide pipelines network having an overall length ( around 6000 km ). Recently, some new stimuli have came up as for application of CCS in refineries, cement plants, gasification uses, cement and iron industries, or fertilizers, chemical feedstock. Furthermore offshore pipeline could enhance the industrial deployment of CCS by avoiding the NIMBY effect of onshore storage sites selection.
Tidal current is the flow of sea water due to tidal phenomenon. Therefore it is possible to predict generated output of the tidal current power generation system, which is more advantageous than other renewable energy sources, when the tidal current power generation system is connected to the power system and operated. This paper examines the gear ratio and generator capacity which maximize generated energy, when the tidal current power generation system is operated using the maximum power-point tracking (MPPT) control method. This paper shows that the MPPT control method increases generated energy, capacity factor and energy conversion efficiency in comparison with the fixed speed method.
Melis, Giorgio (Centro Sviluppo Materiali) | Fonzo, Andrea (Centro Sviluppo Materiali) | Ferino, Jan (Centro Sviluppo Materiali) | Darcis, Philippe (Tenaris) | Quintanilla, Hector (Tenaris Tamsa) | Marines-Garcia, Israel (Tenaris Tamsa) | Marchesani, Furio (Saipem) | Vitali, Luigino (Saipem)
Tenaris, Centro Sviluppo Materiali and Saipem launched a cooperation program aimed at evaluating the in-service flaw tolerability of girth welded seamless pipes for offshore applications. Full-scale testing has been conducted considering severe bi-axial loading scenarios replicating actual offshore in-service conditions. Tearing by an occasional high axial strain has also been accounted in order to consider the suitability for strain-based conditions.
Different notch sizes and sampling positions have been taken into account, this improving the experimental database which may assist the designer to evaluate the pipeline residual resistance when it is subjected to specific installation and in-service loading conditions.
Oh, Semyun (Samsung Heavy Industries, Ltd.) | Lee, Jinsuk (Samsung Heavy Industries, Ltd.) | Paik, Kwang-Jun (Samsung Heavy Industries, Ltd.) | Choi, Soonho (Samsung Heavy Industries, Ltd.) | Park, Hyoung-Gil (Samsung Heavy Industries, Ltd.) | Hoshino, Tetsuji (Samsung Heavy Industries, Ltd.)
Recently, interest in the development of the ships with higher energy efficiency is rapidly increasing in many shipping and shipbuilding companies, as the regulations on reduction of the greenhouse gas emission are reinforced. In this study, a number of model tests were carried out for a selected model ship with CRP (Contra-Rotating Propeller) system at the towing tank of Samsung Ship Model Basin (SSMB). In order to investigate the hydrodynamic characteristics of CRP, propeller open water, self-propulsion, and propeller position variation tests were performed. Based on the experimental results, the ITTC (International Towing Tank Conference) performance prediction method is applied for ships with CRP in three different ways. CRP system is regarded as a single propulsion unit or a combination of two propellers. The extrapolation method of CRP performance as a combination of two propellers can be analyzed by comparing open water test results with CRP set-up and individual open water test results.
Based on the replacement of CH4 with CO2 + N2 (also called “swapping”), we demonstrated the direct recovery of methane from artificially synthetic methane hydrate sediments. The injection of CO2 + N2 existing as a gaseous state at deep-sea conditions of high pressure and low temperature makes the favorable diffusion and high methane recovery compared with pure CO2 injection. For simulation of actual deep-sea MH sediments, we first attempted to explore the replacement of CH4 with CO2+ N2 gas in the macroscopic scale under natural MH reservoir condition and thus designed and set up the 1-dimensional high-pressure reactor with around 10m length. Natural MH can be converted into CO2 hydrate, potentially carrying out both energy resource supply and CO2 sequestration. In particular, the fluid movement under continuous gas injection is described along with actual replacement efficiency according to several gas movement velocities. We clearly confirmed that the replacement efficiency is inversely proportional to the injection rate of CO2 + N2 gas mixture that is directly related with the contact time. From the analysis on compositional profiles at each port, the length is required more than 5.6 m to have noticeable recovery rate for natural gas hydrate production. For future off-shore field tests, we should establish the optimized MH production process with careful consideration of various influencing variables.
This study presents the effects of geometric characteristics on the structural responses of three target risers (simple riser, flat coupled riser, and circular coupled riser). For the purpose, a coupled analysis was carried out to initially calculate the pressure fields on the target structures in water flow fields and then obtain structural responses such as the maximum displacements and equivalent stresses. From the results, it is shown that the responses increase as the riser thickness decreases or radius of curvature increases. Therefore, it is found to be better to increase the riser thickness for all the risers and to decrease the radius of curvature for the circular coupled riser in the design stage.