A Study on Reliability-Based Improvement of Reliquefaction System for LNG Carriers

2005 ◽  
Author(s):  
Daejun Chang ◽  
Taejin Lee ◽  
Kihoon Han ◽  
Kwangpil Chang ◽  
Kiho Moon ◽  
...  
Keyword(s):  
Natural Gas ◽  
Reliability Analysis ◽  
System Reliability ◽  
Cooling System ◽  
High Reliability ◽  
Block Diagram ◽  
Liquefied Natural Gas ◽  
Generation System ◽  
Reliability Improvement ◽  
Reliability And Availability

The objectives of the study are to quantify the reliability of a boil-off gas (BOG) reliquefaction system for liquefied natural gas (LNG) carriers and to verify design improvements based on the reliability analysis. The system is broken into subsystems and then further into components. Failure rates are collected from generic references, primarily from the OREDA handbook. The reliabilities of the subsystems are estimated, and a reliability block diagram for the whole system is established. The subsystems are classified into three ranks according to their reliability: the high reliability rank comprises the subsystems ‘BOG preparation system,’ ‘Seawater intake system,’ and ‘Buffer N2 reservoir system’, the medium reliability rank the subsystem ‘BOG liquefaction system’, and the low reliability rank the subsystems ‘BOG compression system,’ ‘N2 cooling system’, and ‘Buffer N2 generation system.’ The reliability and availability are estimated for various process configurations where some of the low reliability category have a standby. The ‘bare’ system without any redundancy fails to attain an availability higher than 0.96. Addition of redundancy to one of the least reliable three commonly results in an increase in reliability improvement, to around 0.97. If all of the three subsystems have standby units, the system reliability improves to 0.99. It is recommended that maintenance efforts should be concentrated on the rotating machines that caused the subsystems to have a low reliability.

Reliability analysis and state transfer scheduling optimization of degrading load-sharing system equipped with warm standby components

2021 ◽  
pp. 1748006X2110017
Author(s):  
Sheng-Jia Ruan ◽  
Yan-Hui Lin
Keyword(s):  
Reliability Analysis ◽  
System Reliability ◽  
High Reliability ◽  
Quadrature Rule ◽  
Load Sharing ◽  
Measurement Information ◽  
Model Parameters ◽  
Scheduling Optimization ◽  
State Transfer ◽  
Warm Standby

Standby redundancy can meet system safety requirements in industries with high reliability standards. To evaluate reliability of standby systems, failure dependency among components has to be considered especially when systems have load-sharing characteristics. In this paper, a reliability analysis and state transfer scheduling optimization framework is proposed for the load-sharing 1-out-of- N: G system equipped with M warm standby components and subject to continuous degradation process. First, the system reliability function considering multiple dependent components is derived in a recursive way. Then, a Monte Carlo method is developed and the closed Newton-Cotes quadrature rule is invoked for the system reliability quantification. Besides, likelihood functions are constructed based on the measurement information to estimate the model parameters of both active and standby components, whose degradation paths are modeled by the step-wise drifted Wiener processes. Finally, the system state transfer scheduling is optimized by the genetic algorithm to maximize the system reliability at mission time. The proposed methodology and its effectiveness are illustrated through a case study referring to a simplified aircraft hydraulic system.

scholarly journals An Overview of Various Importance Measures of Reliability System

2017 ◽  
Vol 2 (3) ◽  
pp. 150-171 ◽  
Author(s):  
Kalpesh P. Amrutkar ◽  
Kirtee K. Kamalja
Keyword(s):  
Reliability Analysis ◽  
System Reliability ◽  
System Failure ◽  
Numerical Rank ◽  
Reliability Improvement ◽  
System Reliability Analysis ◽  
Component Importance ◽  
Critical Components ◽  
The Impact ◽  
Reliability Systems

One of the purposes of system reliability analysis is to identify the weaknesses or the critical components in a system and to quantify the impact of component’s failures. Various importance measures are being introduced by many researchers since 1969. These component importance measures provide a numerical rank to determine which components are more important to system reliability improvement or more critical to system failure. In this paper, we overview various components importance measures and briefly discuss them with examples. We also discuss some other extended importance measures and review the developments in study of various importance measures with respect to some of the popular reliability systems.

Numerical study of steady natural convection in a liquefied natural gas cylindrical storage tank equipped with baffles

2019 ◽  
Vol 234 (5) ◽  
pp. 709-721 ◽  
Author(s):  
Mohamed Haddar ◽  
Moez Hammami ◽  
Mounir Baccar
Keyword(s):  
Rayleigh Number ◽  
Natural Gas ◽  
Lateral Surface ◽  
Storage Tank ◽  
Cooling System ◽  
Numerical Study ◽  
Gas Storage ◽  
Liquefied Natural Gas ◽  
Natural Gas Storage ◽  
Average Temperature

In this paper, a study of cooling system for a liquefied natural gas storage tank is conducted. Our objective is to remedy the heat ingress to the liquefied natural gas from the environment using baffles toward limiting temperature elevation in the tank, and then the Boil-off Gas (BOG) formation. A specific code based on the finite volume method is developed to supply a fine knowledge of the hydrodynamic and thermal liquefied natural gas characteristics in the cylindrical tank heated from bottom and lateral surfaces. The effect of the number, position and dimension of baffles, on the flow structure and thermal behavior, has been analyzed. According to our simulation results, the baffles should be placed at the top of tank nearby the lateral wall as the liquefied natural gas dimensionless average temperature can be reduced by 36%. The installation of four rectangular baffles, equally spaced around the perimeter of the tank, gives better homogenization of the temperature field and decreases the average temperature by about 44% in order to limit BOG formation. Finally, two correlations of the Nusselt number are established for the flat rectangular baffle plates and the lateral surface of the cylindrical liquefied natural gas storage tank as a function of the Rayleigh number, as well as the baffle number. Scaling of these correlations with the Rayleigh number gives exponents of 0.25 and 0.18 for lateral surface and baffle, respectively, which are in good agreement with literature.

Reliability Analysis and Engineering Application on Chemical Process Equipment System

2012 ◽  
Vol 522 ◽  
pp. 529-534
Author(s):  
Ya Xin Zhang ◽  
Hai Li Pan ◽  
Tao Yang
Keyword(s):  
Reliability Analysis ◽  
Chemical Process ◽  
Block Diagram ◽  
Engineering Application ◽  
Production Equipment ◽  
Process Equipment ◽  
Chemical Production ◽  
Chemical Process Equipment ◽  
Equipment System ◽  
Reliability And Availability

Reliability and availability are important symbols which weigh the reliability of product. Chemical production equipment system is consisted of many single devices. Due to special dangerous, the reliability analysis to whole equipment system is very important to keeping the safety of production process. In this article, to chemical process equipment system, the reliability calculation method, basic principles, basic assumptions and calculation program are described. To a aromatic semi-renewable dehydration process system, by using the reliability calculated method above, the fault tree and reliability block diagram are derived, the system reliability and availability are accounted, the corresponding reliability and availability curves are obtained and the main factors influencing the reliability of the system are analyzed.

Reliability Analysis of Shiplift Gear Based on System-Level Load-Strength Interference Model

2010 ◽  
Vol 118-120 ◽  
pp. 354-358
Author(s):  
Ying Wu ◽  
Li Yang Xie ◽  
De Cheng Wang ◽  
Ji Zhang Gao
Keyword(s):  
Reliability Analysis ◽  
Order Statistic ◽  
System Reliability ◽  
Bending Strength ◽  
High Reliability ◽  
Interference Model ◽  
System Level ◽  
Maximum Order ◽  
Minimum Order ◽  
Analysis System

A reliability analysis method for the shiplift gear according to the system-level load-strength interference model is presented. The gear is regarded as a series system with dependent failure and multiple failure models. Its reliability is obtained by calculating the probability that the minimum order statistic of the strengths exceeds the maximum order statistic of repeated random loads. The load probability distribution of gear is then obtained using Monte Carlo on the basis of load information. The contact strength and bending strength are calculated. On the basis of system-level load-strength interference analysis, system reliability of a gear is straightforward built up. Finally, system reliability of a gear is worked out, which shows a high reliability.

LNG Vaporization Using a Novel Co-Generation System

2008 ◽  
Author(s):  
H. Griepentrog ◽  
G. Tsatsaronis ◽  
T. Morosuk
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Electricity Generation ◽  
Primary Energy ◽  
Liquefied Natural Gas ◽  
Energy Sources ◽  
Generation System ◽  
Large Share ◽  
Total Cost ◽  
Liquefaction Process

Natural gas is one of the most important primary energy sources. It is expected to account for about 30% of total electricity generation by 2020 compared with 17% in 2000. Liquefied natural gas (LNG) is expected to have a large share in this expansion of use of natural gas. In the last years the total cost of LNG technology has decreased mainly due to improvements in the liquefaction process. The paper discusses some novel, gas-turbine-based concepts for combining LNG regasification with electricity generation. A comparative exergetic evaluation of the concepts is presented.

scholarly journals Reliability-based Optimization of Maintenance Scheduling of Mechanical Components with the Method of Accelerated Tests

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Reliability Analysis ◽  
System Reliability ◽  
Block Diagram ◽  
Practical Method ◽  
Accelerated Tests ◽  
Planning And Control ◽  
System Reliability Analysis ◽  
Short Period ◽  
In Series ◽  
Reliability Based Optimization

To have effective production planning and control, it is necessary to calculate the reliability and maintenance of a production system as a whole. Therefore, with today’s highly reliable components, we are often unable to obtain a reasonable amount of test data under normal use condition. For this reason, accelerated tests method is the reasonable procedure to be applied. It is used to determine the reliability of a product in a short period of time by accelerating the use environment. Application of the method of accelerated tests can save cost that we used to pay for overcoming the dilemma of not being able to estimate failure rates by testing directly at use conditions. In this paper, we propose a practical method for system reliability analysis. Among the existing methods for system reliability analysis, reliability graph theory is particularly attractive due to its intuitiveness, which is an extension of the conventional reliability graph. A function library was developed and designed to calculate the reliability-maintainability and availability of parallel series complex systems, whose functional description is translated into a block diagram that combines in series and parallel components studied. An Extensive analytical modeling study has been performed also to verify the effectiveness of the proposed technique.

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