SIL Certification?

[malaveae]

Do we need Components SIL Certification? The standard IEC 61508 does not ask for this. I think the certification has to be at system level for the complete SIS for a specific SIF.

[Hix]

Hi, no you don't need a specific SIL level for components. As you said nor IEC-61508 or IEC-61511 (ISA 84) require this, using SIL rated component gives you an advantage as the calculation for the verification phase are easier. Remember the SIL level is for all the SIF, so you may have a SIL 3 logic solver and a SIL 3 transmitter, but if you have a SIL 1 Final Control Element you will have a SIL 1 SIF. The only way to improve the SIL rating would be putting ridiculous maintenance schemes. The other way of claiming a SIL level for a SIF with no SIL rated component would be using proven in use data, but you would have to be specific for the aplication, for example you can't claim proven in use for a pressure transmitter in the O&G industry if you have data for a food factory or so.