What the ratings mean for a safety loop
The 6ES7138-4CF02-0AB0: The description spells out two separate safety levels: SIL 2 for the bus switching (used to drop power to a safe zone) and SIL 3 for the two fail-safe digital outputs (used for direct actuator control like stopping a motor). That means one module can handle both the power isolation and the final switching in a single slot. The module is also rated for installations with ungrounded reference potential – handy if your panel is running an IT system and you don't want to introduce a ground fault.