Functional safety - SIL

Functional safety - SIL

Functional safety and SIL are terms frequently used in combination with safety of technical systems - promoted by the issue of new international standards.


AUMA actuators are frequently used in safety critical applications and therefore contribute to safe operation of technical systems. For this reason, functional safety is an important issue for us.


AC .2 controls are ideal for sophisticated modulating tasks if communication via fi eldbus is required or if the actuator must provide diagnostic information for operating parameter optimisation.


AUMA have developed a special SIL module for the AC .2 to utilise these functions in SIL 2 and SIL 3 applications.


The SIL module

The SIL module consists in an additional electronic unit, responsible for executing the safety functions. This SIL module is installed in integral AC .2 controls.


If a safety function is requested in the event of an emergency, the standard logic of AC .2 is by-passed and the safety function is performed via the SIL module.


The SIL modules integrate comparatively simple components such as transistors, resistors and capacitors for which the failure rates are completely known. Determined safety fi gures allow implementation in SIL 2 applications and, in redundant version (1oo2 - one out of two), in SIL 3 applications.


Priority of the safety function

Systems equipped with AC .2 in SIL version combine the functions of two controls. On the one hand, standard AC .2 functions can be used for "normal operation". On the other hand, the integral SIL module is used to perform the safety functions which always overrule normal operation This is ensured due to the fact that the standard controls logic is by-passed when a safety function is requested.