SIRIUS 3SK1122-1CB44 — Safety Relay for Guarding Circuits
The Siemens 3SK1122-1CB44 is a SIRIUS safety relay with solid-state enabling circuits, rated for 24 V DC supply. It carries SIL 3 per IEC 61508 and IEC 62061, and PL e per ISO 13849-1, with a safe failure fraction of 99% — the highest integrity tier for machine guarding and safety shutdown paths. The 22.5 mm width and screw-and-snap-on mounting mean it fits a standard DIN-rail enclosure without extra bracketing. Depth is 121.6 mm, height 100 mm — check clearance against the cabinet door or adjacent busbars.
SIL 3 / PL e means this relay is designed for safety functions up to the highest performance level in ISO 13849-1 — suitable for Category 4 architectures with redundant channels and cross-monitoring. The 99% SFF indicates that over 99% of dangerous failures are detected by diagnostics, a requirement for SIL 3 subsystems. The 24 V DC supply is the control voltage; the relay also accepts a start input and a feedback input, which are typical for monitored start/restart and external contactor feedback in a safety circuit. Two instantaneous contacts and two delayed switching contacts (60 ms minimum sensor input) give flexibility for both immediate and timed shutdown paths. Screw-type terminals accept 1x (20–14 AWG) solid or 1x (0.5–2.5 mm²) with ferrule.
Mounts in any position via the DIN-rail snap-on or screw fixing. Shock resistance is 10 g for 11 ms — suitable for panel mounting on machinery subject to vibration. Cascading is supported (design of cascading: yes), so multiple 3SK1122 units can be linked for expanded zone control without additional safety logic modules.