System reliability improvement - an Australian experience

Author(s):  
J.N. Allen
Author(s):  
Kalpesh P. Amrutkar ◽  
Kirtee K. Kamalja

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.


Author(s):  
Daejun Chang ◽  
Taejin Lee ◽  
Kihoon Han ◽  
Kwangpil Chang ◽  
Kiho Moon ◽  
...  

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.


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