Technical Paper
An Analysis Technique for Optimising Reliability in System Design

John A Hother, Proneta Ltd; SPE 56436; 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, 3-6 October 1999.

Abstract

This paper describes an analysis technique, developed for improving systems reliability in the aerospace and defence industry, that can be used in the oil & gas industry for engineering projects demanding high reliability, such as subsea production systems and deepwater remotely operated vehicles (ROVs).

The method, called Reversionary Mode Analysis, is based on the same principles as the well-known Failure Modes Effects & Criticality Analysis (FMECA). It is used to determine the effects, on the operational performance of the system, of failures in the constituent parts and thence to optimise the system’s resilience to failures. Its output is similar to that of FMECA in essence, but it does not depend on statistical data, and so can be used in circumstances where FMECA is not appropriate in its traditional form, such as when quantitative, statistical input data is not available.

Reversionary Mode Analysis has delivered important benefits in, for example, air defence systems -

	Highlighting areas of the system design that need priority attention to improve fault-tolerance;
	Confirming that design changes really do improve the fault-tolerance;
	Reassuring the customer that the proposed system will deliver the desired degree of fault-tolerance.

The paper explains how the technique was developed to meet customer demand for demonstrable fault tolerance in new systems at the design stage. The technique is then described in the form of six steps. The issues of who is best equipped to use the method, and when is the best time to apply it, are explored. Finally, the paper recommends how the technique can be applied to oil & gas projects, to deliver the benefits.