Using a SIL 3 logic solver means that I have a SIL 3 system?

No. When using a SIL 3 logic solver, it is critical that the entire system is designed to conform to SIL 3 requirements. The PFD for the entire system is important.

If a user installs a SIL 3 logic solver but does not employ appropriate redundancy or does not incorporate components into the system with correct PFD calculations, then the entire system may not comply with a SIL 3 level. “A chain is only as strong as its weakest link.”