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Energy security as a concept
Published in David Bernell, Christopher A. Simon, The Energy Security Dilemma, 2016
David Bernell, Christopher A. Simon
For example, in order to increase the abundance of oil, deepwater drilling in the Gulf of Mexico is pursued, but oil spills such as the Deepwater Horizon accident have diminished the environmental health of the region and caused many individuals the loss of their livelihoods. While solar and wind are seen as good alternative energy sources with respect to human health and environmental impacts (though not direct substitutes for oil), their availability—both the volume of production and the fact that solar and wind power are intermittent resources—means that they cannot provide (at least not at this time) a sufficient supply of electricity to meet the nation’s demands. Moreover, solar and wind are generally not quite cost-competitive with coal and natural gas power plants at this stage of their development in most markets. (However, this price differential is rapidly shrinking, and “grid-parity” seems to be an attainable goal in the not-too-distant future.)
Oil Spill Topic Map
Published in Yejun Wu, Oil Spill Impacts, 2016
Yejun Wu, Amanda Lehman, David J. Dunaway
Drill in Water about 5,000 feet (1,525 meters) in Gulf of Mexico “The rig was drilling in about 5,000ft (1,525m) of water, pushing the boundaries of deepwater drilling technology” (Sylvester, 2011).
Deep reinforcement learning in dynamic positioning control: by rewarding small response of riser angles
Published in Ships and Offshore Structures, 2022
Fang Wang, Yong Bai, Jie Bai, Liang Zhao
To verify the effectiveness of the proposed method, the ‘Haiyangshiyou 981’ deepwater drilling rig is used for simulation. This rig has 8 azimuthing thrusters, each of which has a maximum thrust of 800 kN; the thruster configuration is shown in Figure 6. The length of the drilling riser is 1500 m, the outer diameter of the riser is 0.25 m, the thickness of the pipe wall is 0.025 m, the young's modulus E = 2.1105 MPa, and the top tension is 2500 kn. The environmental load acting on the drilling riser is the current load. The current is non-rotational and non-fluctuating, with a velocity = 0.93 m/s and a direction .
Systematic reliability analysis of the Dynamic Positioning (DP) control system for a deepwater drilling rig
Published in Ships and Offshore Structures, 2021
Fang Wang, Yong Bai, Jian Wang
Today, thousands of vessels around the world rely on DP functionality to do their jobs, where control system beats at the heart of this functionality. The safety and reliability of DP control system has been a great issue for ocean engineering. The unavailability or breakdown of a DP system may lead to serious consequence. In this paper, we proposed some qualitative and quantitative methods to assess the reliability of DPS-3 control system. FMEA method is applied to qualitatively assess the main components of DP control system. From the FMEA analysis, we can conclude that single failed component does not have any effect on vessel positioning capacity because of its redundant configuration; however, components with higher RPNs should be concerned in the vessel and DP system design stage, and if it is necessary, they should be taken into account in the quantitative reliability assessment.Markov model is used to quantitatively assess the reliability of DPS-3 DP control system for ‘haiyang shiyou 981’ deepwater drilling rig. Based on the results of FMEA analysis and some assumptions we have made, a simplified control system structure, which include main DP and back-up DP, is built to the reliability assessment. The whole system reliability was obtained by the Markov state transition.Finally, it should be mentioned that DP operation involves human factors. For example, the manual switch located in back-up DP control station is responsible for taking control command from the main DP control to backup DP is done by human action, which is critical for DP system. And the human operations on OS are also involving human factors, which will be addressed in the later research.
Survey on reliability analysis of dynamic positioning systems
Published in Ships and Offshore Structures, 2023
Fang Wang, Liang Zhao, Yong Bai
The Markov model is a much more flexible model that can be used for reliability evaluation of control system, because various security measures (such as reliability, availability, mean time to failure (MTTF), etc.) can be calculated from the Markov model. For a given system, the Markov model consists of a list of possible states, the possible transition paths between these states, and the rate parameters (failure rate and repair rate) of these transitions. In the context of DP systems, Markov methods can be employed to model the system’s reliability, availability, and performance by considering different operational states and the probabilities of transitioning between them. Wang et al. (2018) used Markov modelling method to quantitatively analyse the main DP control system of the class 3 DP system for a deepwater drilling rig, The main DP control system of Class 3 is divided into six major components: three independent control computes and three identical Operator Stations (OSs). The dual network which connects the OS and control computers is assumed to be faultless. As the complexity and size of DP system increases, the states and components of interest rapidly becomes large leading to difficulty in constructing and solving the reliability model. To simplify the Markov process, Wang et al. (2016) decomposed the target Class 3 DP system into two independent subsystems and the whole system is modelled using Markov models of sub-systems. For subsystems, both the main DP subsystem and back-up DP system are composed of identical components with constant failure rates. The reliability or failure rate of the whole system can be obtained from the Markov models of the main DP subsystem and back-up DP system. Different component failure rates together with subsystem failure rates are incorporated to the Markov model to predict the reliability of the whole class 3 DP control system. Paralleled Markov models are built to model the main and back-up control system, respectively, the state transition is shown in Figure 7. The States of the main and back-up DP control stations are shown Tables 2 and 3. Fault Tree