In the chemical process industries, intrinsically safe operations must be the process engineer's goal, but, in reality, it is often not feasible, either technically or economically. In these cases, safety instrumented systems (SIS) are often used to detect and respond to process risk. SISs have many components that must work as designed in order to mitigate potential hazardous incidents. Over the years, many of these components have evolved from simple electro-mechanical devices to complex mechanical, electrical, and programmable devices. What makes these devices fail must be examined in order to understand how each component failure can propagate into fail-safe and fail-dangerous conditions.

This paper proposes the use of fault management analysis (FMA) for the assessment of proposed SIS designs. An FMA identifies not only the failure modes of each component, but also determines how to appropriately manage the identified failure. This paper demonstrates how proposed design, diagnostics, inspection, maintenance, and testing programs should be modified to improve the SIS performance.