Abstract
The availability of his plant is of prime interest to an operator; in general, this will be governed by the net effect of individual component reliabilities. As the number of components incorporated in a plant increases, there is a tendency for the availability to drop, and thus simplicity in design is frequently favoured. This paper will, however, be principally concerned with the complementary factor, namely the causes of failure or unreliability in individual components.
Components normally fail through some deficiency in the design of the plant or component, in the manufacture and erection stages, or due to operation. These ‘time’ bands, to which the root cause of an individual failure may be attributed, also indicate the general nature of the actions to be taken to prevent a recurrence of the fault.
The authors have drawn upon their experience as the operators of power plant and find that the ‘time’ bands can be further subdivided into various categories of failure cause. For example, design-stage faults may be due to environmental factors not taken into account, and perhaps unknown to the designer, or they may be due to the use of components unsuitable for the job specified. These various categories are considered and will be illustrated by examples taken from the authors' experiences.
The implications of the various categories of failure on plant maintenance and operation will also be discussed.
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