Influence of Mooring Lines and Risers on the Trim, Heel and Displacement on FPUs

2015 ◽  
Author(s):  
Cecília Coelho ◽  
Bruna Nabuco
Keyword(s):  
Water Depth ◽  
Mooring System ◽  
Mooring Lines ◽  
Different Types ◽  
Zero Degree ◽  
Displacement Based ◽  
System Configurations ◽  
And Behavior ◽  
Seabed Bathymetry ◽  
Water Depths

By monitoring the variation of weights of floating production units (FPUs), the sum of total weight computed by load calculators on board very often does not match the actual displacement based on the current drafts. Differences can also be observed in the trim and heel of FPUs, which present values different from zero degree in the calculations, but in fact they are frequently kept near zero by ballast control. The mooring lines and risers tensions are one of the most uncertain weight items in loading conditions reported by the crew on board, therefore, this paper aims to assess the influence and behavior of these systems to a variety of situations in which FPUs operate. Analyses were performed for semi-submersibles and FPSOs considering two configurations of mooring system: catenary and taut-leg. The purpose is to evaluate how the magnitude of the resulting force varies — and hence how the trim and heel change — for a range of offsets caused by environmental conditions. The effect of mooring lines and risers is also discussed regarding the water depth by means of case studies considering a range of water depths. Actual lines properties and seabed bathymetry from mooring system models of platforms located offshore Brazil have been taken as reference. In short, the mooring lines and risers loads will be calculated for different types of floating production units, mooring system configurations and water depths in order to evaluate their influence on the trim, heel and displacement of FPUs.

Qualification and Certification of Polyester Rope for Seabed Contact

2017 ◽  
Author(s):  
Øystein Gabrielsen ◽  
Kjell Larsen
Keyword(s):  
Water Flow ◽  
Water Depth ◽  
Test Method ◽  
Mooring System ◽  
Qualification Test ◽  
Mooring Lines ◽  
Norwegian Sea ◽  
Flow Through ◽  
Full Scale Tests ◽  
Certification Requirements

The Aasta Hansteen spar in the Norwegian Sea is designed to be moored with a taut polyester rope mooring system. The water depth at the field is 1300 meters, and due to the short installation season the most efficient hookup is with pre-installed mooring lines, which require the mooring lines to be laid down on the seabed. DNV certification does not allow seabed contact for polyester ropes unless proven that no soil ingress and damage takes place. To be able to certify the ropes Statoil developed a test method including contact with soil, rope movement and forced water flow through the filter construction. Full scale tests were performed with actual rope and Aasta Hansteen soil, both in laboratory and at site. This paper discusses the certification requirements and presents adequate qualification test together with results from testing.

Lightweight Materials for Mooring Lines of Deepwater Tension Leg Platforms

1984 ◽  
Vol 21 (03) ◽  
pp. 234-241
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Carbon Fiber ◽  
Water Depth ◽  
Hybrid Composites ◽  
Medium Size ◽  
Mooring System ◽  
Basic Design ◽  
High Modulus ◽  
Mooring Lines ◽  
Lightweight Materials ◽  
Design Requirements

The design of a mooring system for tension leg platforms (TLPs) becomes more complicated as water depth increases. The use of steel mooring lines requires complicated tensioning, handling, and flotation systems. This paper discusses the basic design requirements for the TLP mooring system and identifies several advanced fiber-reinforced lightweight materials as alternatives to steel. High-modulus carbon fiber/KevlarcircleR fiber hybrid composites and Kevlar ropes appear to offer the optimum mooring systems for TLPs used in the development of large and medium-size reservoirs, respectively.

Dropped Polyester Mooring Line Qualification for Reuse

2021 ◽  
Author(s):  
Craig R Gage ◽  
Pierre F Liagre ◽  
Caspar N Heyl ◽  
Cesar Del Vecchio
Keyword(s):  
Gulf Of Mexico ◽  
Water Depth ◽  
Cost Savings ◽  
Mooring Line ◽  
Mooring System ◽  
Potential Cost ◽  
Mooring Lines ◽  
Minimal Damage ◽  
Recovery Effort ◽  
The Impact

The Perdido platform is a spar located in a water depth of 7,825 feet in the Alaminos Canyon Block 857in the Gulf of Mexico. The mooring system consists of nine mooring lines in three groups of three, spacedapproximately 120 degrees apart between each group. Each mooring line is composed of a platform chain,a multi-segment polyester rope including a 120 feet long test insert at the top, a ground chain, a pile chainand other associated connectors. The mooring lines are connected to suction piles. The Minimum BreakStrength for the Perdido polyester mooring line is 4,000 kips. Installation of the spar hull was completed inSeptember 2008 and the topsides was set in March 2009. The spar and its mooring system were originallydesigned for a twenty (20) year life. On May 4, 2019, mooring line # 6 (ML6) was contacted by a marine vessel down line and was severed.Contact occurred along the polyester test insert. A recovery effort was planned, and the mooring line wasreplaced in early June. The original ML6 was recovered from the seafloor on June 4, 2019 as a part of thatcampaign and submitted to an initial inspection. This paper is not intended to go into either the cause of the incident or the replacement of ML6 but willlook to the inspection of the recovered mooring line and explore its suitability for reuse. Initial inspection ofthe lines suggested minimal damage to the polyester rope segments and raised questions to the impacts of 10years of use. Testing was envisioned as a learning opportunity for the impact of service on polyester mooringand was reinforced by the potential cost savings that could be attained though reuse. A methodology wasdeveloped, supported by initial inspections and a suite of testing was performed. The results of these testsare presented in the following, along with a proposed process for assessing and considering reuse of a linefollowing a drop. Additionally, conclusions will be shared for the process, the results, and the potentialramifications for the industry.

Experimental and Numerical Study on Large Truncation of Deepwater Mooring Line

2009 ◽  
Author(s):  
Yihua Su ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Gang Chen
Keyword(s):  
Dynamic Response ◽  
Water Depth ◽  
Numerical Study ◽  
Unit Length ◽  
Low Frequency ◽  
Model Tests ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Wave Basin

Modeling the deepwater mooring system in present available basin using standard Froude scaling at an acceptable scale presents new challenges. A prospective method is to truncate the full-depth mooring lines and find an equivalent truncated mooring system that can reproduce both static and dynamic response of the full-depth mooring system, but large truncation arise if the water depth where the deepwater platform located is very deep or the available water depth of the basin is shallow. A Cell-Truss Spar operated in 1500m water depth is calibrated in a wave basin with 4m water depth. Large truncation arises even though a small model scale 1:100 is chosen. A series of truncated mooring lines are designed and investigated through numerical simulations, single line model tests and coupled wave basin model tests. It is found that dynamic response of the truncated mooring line can be enlarged by using larger diameter and mass per unit length in air. Although the truncated mooring line with clump presents a “taut” shape, its dynamic characteristics is dominated by the geometry stiffness and it underestimates dynamic response of the full-depth mooring line, even induces high-frequency dynamic response. There are still two obstacles in realizing dynamic similarity for the largely truncated mooring system: lower mean value of the top tension of upstream mooring lines, and smaller low-frequency mooring-induced damping.

scholarly journals Water Depth Variation Influence on the Mooring Line Design for FOWT within Shallow Water Region

2021 ◽  
Vol 9 (4) ◽  
pp. 409
Author(s):  
Wei-Hua Huang ◽  
Ray-Yeng Yang
Keyword(s):  
Wind Turbine ◽  
Water Depth ◽  
Return Period ◽  
Limit State ◽  
The Other ◽  
Ultimate Limit State ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines ◽  
Line Design ◽  
Water Depths

The objective of this paper was to present the modeling and optimization of mooring lines for floating offshore wind turbines (FOWT) located in various water depths from 50 m to 100 m in Taiwan western offshore areas. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCwind platform with the National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine. The mooring lines proposed consist of a catenary mooring with studless chains. Three nominal sizes of the mooring chain links are taken into account with diameters of 95 mm, 115 mm and 135 mm. According to this configuration, a total of five mooring designs for different water depths (i.e., 50 m, 60 m, 70 m, 80 m, 100 m) are analyzed according to the rules and regulations of the two certification institutions, Det Norske Veritas (DNV) and American Petroleum Institute (API). Considering ultimate limit state (ULS), fatigue limit state (FLS) and maximum operating sea state (MOSS) based on a typhoon with a 50-year return period and current with a 10-year return period, 25-year design life, as well as 1-year return period, respectively, long-term predictions of breaking strength, fatigue and stability are performed. The software OrcaFlex version 10.3 d is used to simulate and design the mooring lines. The obtained results show that the shallow mooring design of 50 m water depth case presents the heaviest chains among the other water depths, increasing their mooring costs. On the other hand, the 100 m water design has much longer mooring lines, making this parameter the cost driving one. Thus, the minimum mooring cost range is from 60 m to 80 m water depth.

scholarly journals Gravity-Based Foundations in the Offshore Wind Sector

2019 ◽  
Vol 7 (3) ◽  
pp. 64 ◽  
Author(s):  
M. Esteban ◽  
José-Santos López-Gutiérrez ◽  
Vicente Negro
Keyword(s):  
Water Depth ◽  
High Water ◽  
Offshore Wind ◽  
Is Research ◽  
Current State ◽  
Different Types ◽  
Large Water ◽  
Water Depths ◽  
Offshore Wind Industry

In recent years, the offshore wind industry has seen an important boost that is expected to continue in the coming years. In order for the offshore wind industry to achieve adequate development, it is essential to solve some existing uncertainties, some of which relate to foundations. These foundations are important for this type of project. As foundations represent approximately 35% of the total cost of an offshore wind project, it is essential that they receive special attention. There are different types of foundations that are used in the offshore wind industry. The most common types are steel monopiles, gravity-based structures (GBS), tripods, and jackets. However, there are some other types, such as suction caissons, tripiles, etc. For high water depths, the alternative to the previously mentioned foundations is the use of floating supports. Some offshore wind installations currently in operation have GBS-type foundations (also known as GBF: Gravity-based foundation). Although this typology has not been widely used until now, there is research that has highlighted its advantages over other types of foundation for both small and large water depth sites. There are no doubts over the importance of GBS. In fact, the offshore wind industry is trying to introduce improvements so as to turn GBF into a competitive foundation alternative, suitable for the widest ranges of water depth. The present article deals with GBS foundations. The article begins with the current state of the field, including not only the concepts of GBS constructed so far, but also other concepts that are in a less mature state of development. Furthermore, we also present a classification of this type of structure based on the GBS of offshore wind facilities that are currently in operation, as well as some reflections on future GBS alternatives.

LNG Floating Regasification Unit (FRU) Side-by-Side Mooring Analysis

2005 ◽  
Author(s):  
Wei Ye ◽  
Yong Luo ◽  
Jack Pollack
Keyword(s):  
Hydrodynamic Interactions ◽  
Mooring System ◽  
Water Effect ◽  
Mooring Lines ◽  
Close Proximity ◽  
The Us ◽  
Modeling Techniques ◽  
Fully Coupled ◽  
Shallow Water Effect ◽  
Water Depths

This paper presents a newly developed Floating Regasification Unit (FRU) concept for LNG import in the US Golf of Mexico (GOM) region. The FRU can be converted from a Suezmax tanker and has a turret mooring system. One of the key technologies of the FRU concept is the Side-By-Side (SBS) mooring between the FRU and the LNG Carrier (LNGC) for offloading. The mooring lines and pneumatic fenders between the two vessels should be able to restrain the relative motions to ensure the safe transfer of LNG. Advanced hydrodynamics modeling techniques have been applied, which include full hydrodynamic interactions between the FRU and the LNGC with full QTFs considering the shallow water effect. The anchor legs are modeled as dynamically, fully coupled to the turret and the FRU. The feasibility of the FRU concept is established for LNG import in the GOM, with a variety of workable water depths ranging from 40 meters to more than 100 meters with an uptime exceeding 98%. Analysis results demonstrate the significance of hydrodynamic interactions between the two vessels in close proximity arrangement.

Changes in abdominal muscles architecture induced by different types of breathing

2021 ◽  
pp. 1-7
Author(s):  
Iria Da Cuña-Carrera ◽  
Alejandra Alonso-Calvete ◽  
Yoana González-González ◽  
Mercedes Soto-González
Keyword(s):  
Effect Size ◽  
Health Care Professionals ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Abdominal Muscles ◽  
Healthy Population ◽  
Different Types ◽  
Architectural Characteristics ◽  
And Behavior ◽  
Internal Oblique

BACKGROUND: The underlying morphology and behavior of abdominal muscles during breathing are still lacking in knowledge in healthy population. OBJECTIVE: To analyze the effects of three different types of breathing on the architectural characteristics of abdominal muscles. METHODS: Ninety-eight healthy subjects were measured to assess the effects of breathing on the abdominal muscles, subjects performed three different types of breathing and the muscular thickness was measured with ultrasound imaging, analyzing also the differences between sexes. RESULTS: During the three different types of breathing and in comparison with the resting state, an increase of the thickness has been reported in the transversus abdominis (p< 0.001; effect size = 2.44, very large) and internal oblique (p< 0.001; effect size = 1.04, moderate) in both sexes, but with a higher increase in men. External oblique and rectus abdominis increased their thickness through breathing only while the lips were with pursed (p< 0.05) with trivial effect sizes and only differences between sexes were found in rectus abdominis. CONCLUSIONS: All breathings activated the deepest abdominal muscles, but the most superficial were only activated with lips pursed. Moreover, men appeared to activate more the deepest abdominal muscles but also the rectus abdominis. Findings in this study support the use of different types of breathing depending on the muscle to be activated or the sex, helping health care professionals to address their interventions on the abdominal muscles with a more focused approach.

scholarly journals Transient Responses Evaluation of FPSO with Different Failure Scenarios of Mooring Lines

2021 ◽  
Vol 9 (2) ◽  
pp. 103
Author(s):  
Dongsheng Qiao ◽  
Binbin Li ◽  
Jun Yan ◽  
Yu Qin ◽  
Haizhi Liang ◽  
...  
Keyword(s):  
Service Condition ◽  
Mooring Line ◽  
Mooring System ◽  
Transient Effects ◽  
Floating Platform ◽  
Transient Responses ◽  
Mooring Lines ◽  
Performance Deterioration ◽  
Steady State Responses ◽  
Influence Process

During the long-term service condition, the mooring line of the deep-water floating platform may fail due to various reasons, such as overloading caused by an accidental condition or performance deterioration. Therefore, the safety performance under the transient responses process should be evaluated in advance, during the design phase. A series of time-domain numerical simulations for evaluating the performance changes of a Floating Production Storage and Offloading (FPSO) with different broken modes of mooring lines was carried out. The broken conditions include the single mooring line or two mooring lines failure under ipsilateral, opposite, and adjacent sides. The resulting transient and following steady-state responses of the vessel and the mooring line tensions were analyzed, and the corresponding influence mechanism was investigated. The accidental failure of a single or two mooring lines changes the watch circle of the vessel and the tension redistribution of the remaining mooring lines. The results indicated that the failure of mooring lines mainly influences the responses of sway, surge, and yaw, and the change rule is closely related to the stiffness and symmetry of the mooring system. The simulation results could give a profound understanding of the transient-effects influence process of mooring line failure, and the suggestions are given to account for the transient effects in the design of the mooring system.

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