Study on Design of Truncated Mooring Line with Static Similarity in Model Test Basins

The new scenario of oil exploration in ultra deep water moves forward to 3000 m, has been putting for the companies that accept this technological challenger significant, border of the techno-scientific knowledge. Therefore, nowadays in this case of ultra deep waters, where the forces above the mooring lines are increase and the use of the new material in Petrobras Floating Production Units, it is necessary the good numerical analyses and experimental test by the mooring line. It appears the need to look for a solution for the problems according to the changes of the polyester rope in the production platform without the bottom extension change and its foundation (fixed point). According to this challenge it was necessary to develop a remote connection and disconnection device. This device is the KS hook and its optimization has been created using the fracture mechanical conception optics and computers tools (FEM and mooring software). There are two conditions to develop this device: one condition is functional and the other is structural. For the functional condition, it’s necessary to create the facilities for handling and installations. For the structural conditions, it is necessary to use the special wrought steel material, treatment for steel characteristic and right geometry. Finite Elements Modeling analyze used the Ansys software, considered the hardness profile material for Minimum Break Load (MBL). The lifetime design is about 25 years for this case and the fatigue analysis considered the residual stress and plasticity for structural device. Previous simulation is especially important in predicting behavior and in the development of new design products before testing. The model was meshed with 3D first order tetrahedral elements solid45. The mesh was sufficiently fine to ensure minimal loss of accuracy in curved geometry. There isn’t a TN fatigue curve (reference API Fatigue curves) for this KS Hook device geometry, in this case become necessary to use the model test to obtain this curve with the extrapolation of the results. The Finite Elements Modeling analyze used with the Material SN Fatigue curve will be used for this validation. Previous simulation is especially important in predicting behavior and in the development of new design products before testing.

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Experimental Study on Mooring Manner and Safety Operation for 450,000DWT Supertanker

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.2124 ◽

2014 ◽

Vol 580-583 ◽

pp. 2124-2128

Author(s):

Bing Jiang ◽

Xuan Jun Huang ◽

Ying Xue Lv ◽

Xian Bo Zhang

Keyword(s):

Experimental Study ◽

Model Test ◽

Line Tension ◽

Mooring Line ◽

Physical Model Test ◽

Working Ability ◽

Steel Cable ◽

Wave Condition ◽

Oil Tank ◽

Safety Operation

At present, many oil tank wharfs of 300,000DWT which taken the maximum of 450,000DWT supertanker into account had been built in our country. In this paper, through the physical model test on 450,000DWT supertanker, the mooring line tension with different mooring arrangements, cable diameters and cable materials were studied and the wave condition for the supertanker safety operation was given. The results showed that: on the same wave condition, to increase the steel cable’s diameter could reduce the ship’s movements, which could enhance the ability to operation. In addition, using the combination cable on the same diameter instead of the steel cable could reduce the tension of mooring line and increase the working ability effectively. The research results can provide reference and guidance for the future of supertankers mooring operation.

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The Effect of Mooring Line Pre-Tension on FDPSO’s Motion

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54262 ◽

2016 ◽

Author(s):

Yanlong Sun ◽

Huilong Ren ◽

Zhendong Liu ◽

Liu Yan ◽

Zepeng Guo

Keyword(s):

Time Series ◽

Model Test ◽

Time Domain ◽

Prediction Method ◽

Line Tension ◽

Mooring Line ◽

Floating Platform ◽

Motion Response ◽

Drilling Unit ◽

Environment Condition

As a multifunction floating platform, Floating Drilling, Production, Storage and Offloading (FDPSO) combining the well-known Floating Production, Storage and Offloading (FPSO) with a drilling unit. For the environment condition of deep-water oilfield is very severe, the motion response and mooring line tension of FDPSO is a worthy topic of studying. In this study, the numerical time-domain coupled prediction method for the mooring line tension and motion response of FDPSO system is constructed by ANSYS AQWA software. Furthermore, the results of a model test conducted in Harbin Engimeering University are used to investigate the feasibility and validity of the commercial simulation. The effect of mooring line pre-tension on the response of FDPSO is studied by varying the pre-tension of mooring line during the calculation. The time series curve of the mooring line tension and motion response, and the comparison of motion spectrum and mooring line tension spectrum are provided in this article.

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Parameter Calculation of Viscous Damper Applied in the Truncated Model Test Design of a Deepwater Semi-Submersible Platform

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.1480 ◽

2010 ◽

Vol 168-170 ◽

pp. 1480-1485

Author(s):

Dong Sheng Qiao ◽

Jin Ping Ou

Keyword(s):

Model Test ◽

Dissipated Energy ◽

Mooring Line ◽

Inertia Force ◽

Test Design ◽

Viscous Damper ◽

Floating Platform ◽

Fluid Drag ◽

Seabed Interaction ◽

The Time Domain

In the equivalent water depth truncated model test design of a deepwater semi-submersible platform, the viscous damper is designed to simulate the contribution of mooring damping to total damping of floating platform. The dissipated energy by a mooring line from the floating platform as a result of its oscillation is applied to calculate the mooring-induced damping. The mooring line and seabed interaction is based on the hypothesis of rigid seabed. The fluid drag force and inertia force on the mooring line are calculated according to the Morrison formula. The non-liner dynamic analysis of mooring line is executed in the time domain based on the finite element method. The mooring induced damping is obtained from the results. The value difference of mooring induced damping between the truncated and full-depth mooring line is linearized to provide parameter for the design of viscous damper.

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Experimental and Numerical Investigation on Planar Motion Responses of a Single Point Moored Shuttle Tanker in Waves

Volume 7A: Ocean Engineering ◽

10.1115/omae2019-95251 ◽

2019 ◽

Author(s):

Ning He ◽

Cheng Zhang ◽

Zhuang Kang ◽

Youwei Kang ◽

Changhong Wang

Keyword(s):

Model Test ◽

Deep Water ◽

Oil And Gas ◽

Single Point ◽

Diffraction Theory ◽

Line Length ◽

Plane Motion ◽

Mooring Line ◽

Motion Responses ◽

Motion Characteristics

Abstract In order to ensure the safety of the single point moored shuttle tanker in waves, the numerical model of a shuttle tanker moored with a fixed point was established on the basis of radiation / diffraction theory and pressure integral method in this paper, which was further checked by a series of model tests. Then the plane motion characteristics of the tanker like fishtailing oscillation were analyzed by applying the combined approach of numerical simulation and model test. On this basis, the effects of wave and ballast conditions as well as mooring line length and stiffness on the plane motion of the single point moored tanker were investigated by means of model test. Overall, the research can provide a reference for the design and safety assessment of deep-water offloading system, and give the technical support for the engineering development of deep-water oil and gas projects.

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Experimental Study on Development of Mooring Simulator for Multi Floating Cranes

Journal of Marine Science and Engineering ◽

10.3390/jmse9030344 ◽

2021 ◽

Vol 9 (3) ◽

pp. 344

Author(s):

Junhyeok Bae ◽

Juhwan Cha ◽

Min-Guk Seo ◽

Kangsu Lee ◽

Jaeyong Lee ◽

...

Keyword(s):

Model Test ◽

Equations Of Motion ◽

Mooring Line ◽

Analysis Program ◽

The Finite Element Method ◽

Mooring Lines ◽

Calculation Results ◽

Floating Crane ◽

Pile Model ◽

Equations Of Motions

In this study, the coupled motion of a mooring system and multifloating cranes were analyzed. For the motion analysis, the combined equations of motions of the mooring line and multifloating cranes were introduced. The multibody equations for floating cranes were derived from the equations of motion. The finite element method (FEM) was used to derive equations to solve the stretchable catenary problem of the mooring line. To verify the function of mooring simulator, calculation results were compared with commercial mooring software. To validate the analysis results, we conducted an experimental test for offshore operation using two floating crane models scaled to 1:40. Two floating crane models and a pile model were established for operation of uprighting flare towers. During the model test, the motion of the floating cranes and tensions of the mooring lines were measured. Through the model test, the accuracy of the mooring analysis program developed in this study was verified. Therefore, if this mooring analysis program is used, it will be possible to perform a mooring analysis simulation at the same time as a maritime work simulation.

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Shallow Water STL Mooring and Riser System

Volume 1: Offshore Technology ◽

10.1115/omae2009-79511 ◽

2009 ◽

Author(s):

Qinzheng Yang ◽

Muthu Chezhian ◽

Geir Olav Hovde

Keyword(s):

Shallow Water ◽

Wave Height ◽

Model Test ◽

Water Depth ◽

Significant Wave Height ◽

Mooring Line ◽

Test Results ◽

Sea State ◽

Significant Wave ◽

The Impact

A shallow water disconnectable STL turret mooring and riser system has been developed for water depth between 30 and 50 m. This technology is based on APL’s disconnectable STL (Submerged Turret Loading) and STP (Submerged Turret Production) technologies which had been widely applied for water depth between 70 m to 2600 m for FPSOs and LNG offshore terminals. The advantage of disconnectable system is that the mooring and riser system can be designed to a preferred sea state. When the sea state is higher than design sea state (like hurricane), the vessel can be disconnected and sail away. The shallow water STL system consists of STL buoy, mooring lines, riser system and landing pad. The interface with vessel is the same as traditional STL system. The mooring and riser system are connected to the vessel through STL buoy and can be pulled into vessel by using ship winch. Unlike traditional STP and STL buoys, the shallow STL buoy has a net weight and will stay on the landing pad when disconnected from vessel. The landing pad is designed to support the impact load from STL buoy and supply enough friction for the STL buoy to stay in position during 100-year storm. The mooring system design has taken the advantage of directionality of weather when close to the shore by using different mooring line length in different directions. Further an innovative Hold-Back-Wave riser configuration has been developed for shallow water system. The riser configuration has a larger flexibility compared to traditional wave configuration and has proved to be feasible for significant wave height at least 7 m when connected to the vessel and 10+ m when disconnected from the vessel. Model test for the disconnectable shallow water turret mooring and riser system had been performed in MARINTEK, Trondheim with a LNG re-gasification vessel model at 30 m water depth. For connected system, significant wave height Hs = 6 m and 8 m has been tested. The mooring and riser system perform well, as predicted. For disconnected system (when the buoy sitting on the landing pad), significant wave height Hs = 10 m has been tested. The STL buoy is sitting on the landing pad without significant movement and the riser system performs well. SIMO program has been used to calibrate the model test results with numerical simulations. By adjusting surge, sway, yaw damping and 2nd order wave drift force, the calibrated SIMO model agrees well with model test results and can be used for similar development.

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Experimental Validation of a Numerical Model for a Dry-Tree Semisubmersible in Benign Environments

Volume 1B: Offshore Technology ◽

10.1115/omae2014-24185 ◽

2014 ◽

Author(s):

Bruce Martin ◽

Oriol Rijken ◽

Kent Davies

Keyword(s):

Model Test ◽

Nonlinear Behavior ◽

Primary Objective ◽

Mooring Line ◽

Mooring System ◽

Mooring Lines ◽

Test Configuration ◽

Numerical Tools ◽

Offshore Industry ◽

Heave Motion

The offshore industry has spent the last several years developing semisubmersible platforms capable of supporting both drilling and production activities. The production trees are located on top of the top tensioned risers (TTRs) on a Dry Tree Semisubmersible. A key challenge in the design of these vessels is to reduce the heave motion as much as possible to enable the use of state-of-the-art riser tensioners. A model test campaign was executed as part of the developmental program. The primary objective of this campaign was to improve the accuracy of the numerical tools to be used in the design process. Riser tensioners are typically hydro-pneumatic devices, with a nonlinear tension-stroke relationship. A riser tensioner was developed at model scale which had a similar nonlinear behavior to the prototype. Examining the effect of this tensioner on the global motions was an additional objective of this test campaign. The techniques used to model this nonlinear spring is described, and its effect on global motions investigated. A key challenge in model testing platforms intended for ultra-deep water (e.g. greater than 7000 ft) is the modeling of the mooring and riser system. The premise for the design of the model mooring system is 1.) maintain as best as possible the force-offset relationship of the mooring lines and 2.) be able to describe the model test configuration in the numerical tools to be used for global design. The near taut behavior of the prototype mooring system is modeled using heavy chain and a high-catenary mooring line.

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A Novel Adjustment Method of Mooring Line Pre-Tension in Model Test

10.1115/1.0001152v ◽

2021 ◽

Author(s):

Junfeng Du ◽

Hongchao Wang ◽

Anteng Chang ◽

Mingyuan Sun ◽

Junrong Wang ◽

...

Keyword(s):

Model Test ◽

Mooring Line ◽

Adjustment Method

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