Safety Integrity Level
The term SIL is referred to a lot within the functional safety world, but it is often miss-understood. It is the safety integrity level of an overall safety function. Since Mutech design equipment that form part of a safety function, the task is to produce equipment that is capable of meeting the overall safety function. Since there are two types of failure, that essentially requires meeting two criteria:
………. 1. Systematic capability (SC). This is employing suitable techniques and measures suitable for the target SIL, and this is classified such that (for example) SC2 is normally suitable for SIL2.
………. 2. Hardware failure rates. The SIL will define a required failure rate for the overall safety function, and generally a percentage of that is allocated to the element. Quite often when designing elements, the rest of the safety system is not known and hence a reasonable proportion is assigned.