Reliability Analysis on the Effect of Subsea Buoy to the Tension of Spread Mooring System
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Abstract:
A lot of research has been carried out regarding variations in mooring systems, one of which is the addition of buoys to the mooring system. In analyzing variations in mooring system designs, what needs to be considered is the reliability of the mooring lines. Therefore, in this research will analyze reliability on the effect of subsea buoy to the tension of mooring line with a variation position of subsea buoy. The variations on the position of one subsea buoy is arranged at the distance of the anchor 605 m, 577.5 m, 550 m, 522.5 and two subsea buoys at the distance from the anchor 605 m and 467.5 m. The analysis was performed for stand alone and offloading conditions with wave directions of 0 °, 45 °, 90 °, 135 °, 180 °. In this study to find the reliability of mooring lines, the author uses the Mean Value First Order Second Moment (MVFOSM) method. The results from this study, the probability of failure in the offloading condition without subsea buoy is 4.897E-17 and with subsea buoy (522.5 m) is 4.018E-17. Probability of failure in the stand alone condition without subsea buoy is 2.763E-16 and with subsea buoy (522.5 m) is 1.881E-16. From the probability of failure, the reliability of mooring lines in the offloading condition and stand alone condition without subsea buoy and with subsea buoy (522.5 m) is 1.00. The reliability calculation determined by DNV-OS E301, the results obtained meet the specified reliability criteria.Keywords:
Subsea
Buoy
Mooring
Tension (geology)
A lot of research has been carried out regarding variations in mooring systems, one of which is the addition of buoys to the mooring system. In analyzing variations in mooring system designs, what needs to be considered is the reliability of the mooring lines. Therefore, in this research will analyze reliability on the effect of subsea buoy to the tension of mooring line with a variation position of subsea buoy. The variations on the position of one subsea buoy is arranged at the distance of the anchor 605 m, 577.5 m, 550 m, 522.5 and two subsea buoys at the distance from the anchor 605 m and 467.5 m. The analysis was performed for stand alone and offloading conditions with wave directions of 0 °, 45 °, 90 °, 135 °, 180 °. In this study to find the reliability of mooring lines, the author uses the Mean Value First Order Second Moment (MVFOSM) method. The results from this study, the probability of failure in the offloading condition without subsea buoy is 4.897E-17 and with subsea buoy (522.5 m) is 4.018E-17. Probability of failure in the stand alone condition without subsea buoy is 2.763E-16 and with subsea buoy (522.5 m) is 1.881E-16. From the probability of failure, the reliability of mooring lines in the offloading condition and stand alone condition without subsea buoy and with subsea buoy (522.5 m) is 1.00. The reliability calculation determined by DNV-OS E301, the results obtained meet the specified reliability criteria.
Subsea
Buoy
Mooring
Tension (geology)
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A buoy/mooring designed to measure waves with a surface-following buoy was instrumented with an ADCP and water property sensors. Compliant elastic elements at the top of the mooring allow the buoy to move freely with the waves without having to accelerate the mooring and heavy instrumentation. About 710 N (160 lbf.) of midwater flotation at the bottom of the elastic elements help keep the lower part of the mooring taut. The elastic elements provided about 1.3 kN (300 lbf.) of mooring pretension, and, depending on the horizontal current and the wave activity, the tension at the buoy could rise to about 3.5 kN (800 lbf.). Computer modeling of the mooring showed no vertical and minimal horizontal motion in the lower part of the mooring and reasonable tensions that would allow the buoy to follow the waves. Data from the accelerometer in the buoy (telemetered to shore in real-time), the SeaCats in-line and ADCP near the bottom were of high quality. The mooring was recovered by releasing a float from mid-depth that brought a line to the surface from below the elastic elements to allow the mooring (with sensors) and anchor to be retrieved. Validation of the accelerometer wave observations with a near-surface moored waves ADCP showed good agreement and indicates that the waves ADCP technology may be used for deeper water waves observations from subsurface moorings.
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Mooring
Instrumentation
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This paper presents the design and analysis of a mooring buoy and its mooring systems to moor a floating platform mounting an arrayed Wave Energy Converters (WECs). The mooring buoy allows the WEC platform to weathervane around the mooring buoy freely by the prevailing environment directions, which enables consistent power generation. The WEC platform is connected to the buoy with synthetic hawsers, while station-keeping of the buoy is maintained with catenary mooring lines of chains tied to the buoy keel. The buoy also accommodates a power cable to transfer the electricity from the WEC platform to the shore. The WEC platform is designed to produce a total of 1.0 MW with multiple WECs installed in an array. Fully coupled time-domain analyses are conducted under the site sea states, including extreme 50 y and survival 100 y conditions. The buoy motions, mooring tensions and other design parameters are evaluated. Strength and fatigue designs of the mooring systems are validated with requirements according to industry standards. Global and local structural designs of the mooring buoy are carried out and confirm the design compliances.
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Mooring
Catenary
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Elastic mooring of a rubber rope is an international novel mooring system.We devised an elastic mooring system for a wave buoy and improved its attachment device.Marine experiments show that the detected data from such elastic mooring buoy system is more approximate to the authentic value.
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Mooring
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The Sea Commander is a subsea oil and gas production control buoy providing electrohydraulic power and chemical injection to remote locations in the downhole tubing string and mudline structures such as christmas trees and manifolds. This paper will describe the evolution of the various buoy-bases subsea production facilities and how this technology was applied and utilized by operators to recover gas from two different remote locations in approximately 300-ft of water.
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Oil Production
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The 100,000 dwt mooring buoy in Meizhou Bay Anchorage is the largest one at the coast area of Fujian Province. The paper mainly introduces the mooring buoy, forces on mooring chain, deadman design, calculation of the force ofground breaking by deadman, as well as the construction process of mooring buoy.
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Abstract : The computer simulation was performed on a rubber band mooring to estimate the extent to which that mooring method can reduce the watch circle of a navigational buoy. The 8X26 navigational buoy and an 8-foot diameter OSI buoy were used in the mooring simulation. The 8X26 buoy is used because it is presently in the aids-to-navigation system; the 8-foot diameter OSI buoy is used because it is a low-drag lightweight plastic buoy that might be used in place of the 8X26 buoy. The rubber band mooring is compared to a one-inch diameter nylon mooring. The rubber band mooring can reduce the watch circle of the 8X26 and OSI buoys when compared to that of the nylon slack mooring. The reduction in the watch circle is most apparent at low currents (approximately 1 knot) and becomes less pronounced as the current approaches 3 knots. The 8-foot diameter OSI buoy shows a smaller watch circle on a rubber band mooring than the 8X26 buoy because of the reduced drag of the OSI buoy. While the rubber band mooring increases the mooring tension, it does not appear to increase the sinker weight over that specified for a conventional chain mooring. Using the results of the simulation, a method was developed for measuring the watch circle of the 8X26 buoy by measuring the angle at the top and bottom of the mooring. Increasing pretension in the mooring (tension in the mooring at zero current) reduces the watch circle.
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Tension (geology)
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The National Data Buoy Center (NDBC) has a global operating theater that encompasses marine weather buoys, Tropical Atmosphere Ocean (TAO) buoys and Deep-Ocean Assessment and Reporting of Tsunami (DART®) buoys. NDBC operates and maintains 117 weather buoys, 55 TAO buoys and 38 DART buoys. These systems are deployed into harsh marine environments and are under constant attack from biological, environmental and human forces. NDBC realized that tackling the mooring issues associated with these deep-ocean moored buoy systems was going to be difficult and long term. In dealing with the short-term issues NDBC decided to host a two-day mooring workshop with the intention to improve the operational reliability of their moored systems. In order to better facilitate this mooring workshop, NDBC requested the NDBC Technical Services Contractor (NTSC) to bring together an internal mooring working group to address the mooring issues and problems. This paper presents the NDBC mooring configurations, the mooring working group and their finding, the actual 2010 NDBC mooring workshop and its findings and recommendations, and finally the actions and on-going efforts generated by the mooring workshop.
Buoy
Mooring
Ocean observations
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To investigate the dynamic behavior of a mooring buoy installed in an open shore, a simplified simulation model is developed, which consists of the surging and heaving motions of a mooring buoy.
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Planning for Mooring Buoy Coordinate Point Placement as a Barge Anchor Facility in the Port of Tegal Area
Mooring bouy is a facility to the ships in the anchorage to prevent shifts caused by waves, currents and wind; and as a tool for rotating the ship. The main components are mooring buoys, concrete blocks or anchors and chains or ropes with a max length of 1.5 x the depth of waters between the anchor and the buoy. Research aims deployed the mooring buoy as a means of barge anchor in the port area of the Tegal area. In this research the authors used a qualitative descriptive method in discussing the problems encountered during conducting research. Regarding the planned mooring buoy placement, 11 mooring buoy units will be installed in the Port of Tegal Area. The installation of the mooring buoy is carried out in two stages. The first is pre-installation, ie activities where mooring buoy material is assembled, installed and marked. Next is the installation where the mooring buoy begins to be installed at point 10 Installing the Floating Mooring Tool - Mooring Buoy point that has been determined, and is followed by taking the coordinates of the position of the installed mooring buoy. besides using being a mooring buoy ship mooring also used as a helper underwater ecosystem. So, Mooring bouy is an alternative in mooring ships so that ships need't to throw anchors that can damage corals and other underwater ecosystems.
Keywords: Mooring buoy, Block Concrete, Coordinate Point, Ecosystem, Port of Tegal Area
Buoy
Mooring
BARGE
Port (circuit theory)
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