Conceptual Comparison of two Commonly Used Safeguarding Principles

Abstract

Many of today’s processes are safeguarded. The objective is to reduce the risk of an out-of-control process to an acceptable level with regard to human safety, environmental safety and economic benefits. Safeguarding systems are applied to obtain the required risk reduction. These systems are “fail safe” or “fault tolerant for safety” (i.e. one failure will not affect the system safety function). System-internal voting determines the overall system action. Two safe guarding architectures are applied in practice.

A comparison study has been done with regard to these architectures and, in particular, to their voting principles.

This study does not include influences of common causes. This paper shows that, for certain parameter values, there is a clear difference in safety performance between these voting principles.