SIL Requirements
A risk assessment determines whether a safety function requires SIL 2 or SIL 3.
For example, one machine has multiple safety functions with the maximum risk, which requires only SIL 2. In that case, a SIL 2-capable controller is acceptable. Another machine has multiple safety functions with at least one risk, which requires SIL 3. In that case, a SIL 3 capable controller is required.
ATTENTION:
The safety signature is required for the controller to operate at a SIL 2 or SIL 3 rating. Controller operation without a safety signature is only suitable during development.
IMPORTANT:
High-demand SIL 2 applications that follow the IEC 61511 standard require a Hardware Fault Tolerance of 1 and must use the guidance for SIL 3 requirements throughout this documentation.
High-demand SIL 2 applications that follow the IEC 62061 standard require a Hardware Fault Tolerance of 0 and must use at least the guidance for SIL 2 requirements throughout this documentation.
SIL 2 Requirements
The following applies to SIL 2 safety functions:
- A SIL 2GuardLogix®5580 controller requires only the primary controller.
- A SIL 2Compact GuardLogix®5380 controller requires a SIL 2-rated catalog number.
IMPORTANT:
If operating above 55 °C (131 °F) in a SIL 2 application, modules greater than 6.2 W must not be installed in slots that are next to a safety controller.
SIL 3 Requirements
To following applies to SIL 3 safety functions:
- A SIL 3GuardLogix®5580 controller requires both the primary controller and the safety partner.
- A SIL 3Compact GuardLogix®5380 controller requires a SIL 3-rated catalog number.
IMPORTANT:
The safety task can contain a number of safety functions. For a particular function to be SIL 3, the entire chain of devices and programming from the sensor to the actuator must be SIL 3. Be careful that you do not use a SIL 2 input signal for a safety function that requires SIL 3.
Provide Feedback