ABSTRACT
Proof testing has a fundamental importance for Safety Instrumented Systems (SIS). It is a periodic preventive maintenance activity that mainly intends to verify that the specified safety integrity level of the safety system is met and kept during the system lifecycle. Its direct objective is to detect dangerous unrevealed failures. However, testing can also convey some additional adverse effects. It is thus necessary to make an optimal planning of the testing activity throughout the overall system in-service life, balancing its benefits against its costs. This optimization problem is addressed herein.
