Citation

Nieuwhof GWE. Reliab. Eng. 1985; 11(2): 121-129.

Copyright

(Copyright © 1985, Elsevier Publishing)

DOI

10.1016/0143-8174(85)90051-4

PMID

unavailable

Abstract

In general the failure data of equipment are given in failure rate values. If we know the failure rate time function of a system, λs(t), we can determine its reliability over the considered time interval (t1→t2) by using the general equation for reliability, namely: Rs(t1→t2)=exp −∫t1t2λs(t)dt

Taking the natural logarithm of both sides of this equation and multiplying both sides by (−1) gives: −InRs(t1→t2)=∫t1t2λs(t)dt which represents the area under the graph of λs(t) over the time interval (t1→t2). This area determines the reliability of the system over the considered time interval.

An example illustrates that the failure rate time function reveals more about the operational performance assurance of the system at a point in time than the reliability value over a time interval.