Safety Relays

Choosing Safety Relays components

Safety relays must match the safety function, performance level (PL or SIL), and circuit architecture of the original — substituting a different model is not just an electrical swap, it is a re-validation of the safety function. Always replace by exact OEM part number where possible, and re-document the safety function after any change.

Specs to confirm before ordering:

Exact OEM part number including all option suffixes
Number of safety outputs (often called "safety contacts" or "redundant outputs")
Number of auxiliary outputs (non-safety, for status to PLC)
Supply voltage: 24 VDC, 24 VAC, 115 VAC, 230 VAC
Input type: single-channel, dual-channel, dual-channel with cross-monitoring, OSSD inputs from light curtain
Reset behavior: manual, monitored manual, automatic
Performance level rating (PL d / PL e per ISO 13849, SIL CL2 / CL3 per IEC 62061)
Mounting: DIN-rail width (17.5 mm, 22.5 mm, 45 mm)

Common gotchas: a PNOZ X3 and PNOZ X3P look similar but have different reset behavior. The 440R-N23126 has 3 safety outputs; the -N23132 has 2 plus 2 timed. Mixing them changes the wiring diagram and the safety analysis. Configurable safety relays (Pilz PNOZmulti, MSR210P) require the original configuration file or a freshly engineered one — the unit alone is not a complete replacement.

Typical applications: emergency-stop monitoring on machine tools, light-curtain monitoring on press brakes and stamping presses, gate-interlock monitoring with guard locking, and safe stop / safe limited speed coordination with safety-rated drives. On legacy machines, the original safety relay was selected and documented as part of the machine's risk assessment; an exact replacement preserves that documentation chain.

For obsolete or discontinued safety relays, request a quote with the OEM part number.

Can I substitute a different safety relay if the OEM model is discontinued?

Sometimes, but it changes the safety function and requires re-validation per ISO 13849. The lower-effort path is sourcing the exact OEM part from surplus stock, which keeps the existing safety documentation valid.

Are these safety-certified to PL d / PL e?

The original OEM rating is preserved — surplus units retain their factory certification. We do not re-certify and we do not modify the device. The 12-month warranty covers functional failure, not the system safety case.

Do you stock obsolete Pilz PNOZ and Allen-Bradley 440R?

Yes. Legacy X-series and older 440R variants are sourced regularly. Send the full OEM number.

Will an AC-supply relay work on DC?

No. Safety relays are designed for a specific supply voltage and type. Mismatched supply will at best stop functioning and at worst damage the unit.

What is the lead time?

In-stock units ship same or next business day from St. Louis. Sourced units typically quote in 1–2 business days.

What is the warranty?

12-month functional warranty on the device. Safety-function validation in the application is the integrator's responsibility, independent of the device warranty.

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