I am working on a SIL2 system using Control Logix. I have gone through the TUV course and am working on my first project.

I have read through the control Logix manual and understand the requirement for SIL2 system design using control logix.
- All Inputs analog and/or discrete to be wired to 2 devices.
- Outputs don't need to be read back as inputs if diagnostic modules are used.

What i am wondering about are the relays, EStops, On/Off Switches, Reset Buttons, etc. Do they also need to be SIL 2 rated ?

Maybe someone can help me get started on this. I have collected all the transmitter and valve SFF's and details to layout calculations.

 

The SIL rating does not apply to a single element - it applies to the integrity of the overall safety function. So you can have unrated components as part of the system if they are connected in a configuration so that you can be sure the PFD of the entire system is acceptable.

Conversely, you can have "SIL4" rated components in a system and still end up with a SIL 1 rating. If you need an SIL 2 rating you may have some SIL 3 rated elements and some SIL1 or unrated components - but the latter will need to use redundancy, frequent testing or the like to meet the SIL requirement for the overall system.