6. Our advice

6.1 Prefer to show a barrier in its entirety, rather than presenting its component parts separately.

In the case presented below, we consider on the one hand the dreaded event Gas leak on a pipeline with a frequency of occurrence of 10 - ² /year, and on the other hand a Safety Instrumented System (SIS) composed of :

• a gas detector with a PFD equal to 10 - ¹ /sollicitation;

• a treatment plant with a PFD equal to 10 - ² /sollicitation;

• an automatic isolation valve with a PFD equal to 10 - ¹ ...