1.The last two metres of a safety loop
Every SIS terminates at a valve, motor or horn. Between the CPU and the field device are only two metres of copper—and a relay. If the relay hesitates, the highest SIL 3 logic is worthless. The HIMA F3423 was created to eliminate those two metres of uncertainty.

2.One-sentence summary
8 NO contacts, galvanically isolated, 24 V DC ↔ 230 V AC, 2 A per channel, < 10 ms pick-up, built-in coil/contact diagnostics, certified to IEC 61508 SIL 3, TÜV and CE, MTBF 212 years, keyed for H41q/H51q racks. Simple—and therefore trusted.

3.Why electromechanical still matters
Solid-state outputs are fast but hot; triacs leak and hate inductive loads. Electromechanical relays give a true air gap, zero off-state leakage and unconditional 2 A switching. In safety, “off must be off” is still a binary command.

4.Closed-loop diagnostics, > 99 % coverage
Each channel returns two bits: “coil energized” and “contact actually moved”. If they disagree with the CPU command for > 3 ms the module flags a fault, forces the redundant relay and uploads a 1 ms time-stamped event—no external feedback contact, no proof-test switch. The data can be fed straight into the SIL 3 PFD calculation.

5.Hot-swap without a cold-work permit
Traditional cabinets need a permit to change a relay. F3423 supports live withdrawal from –40 °C to +70 °C, 5 g vibration, touch-safe terminals and arc-free break. Average replacement time: 45 seconds; average production loss: zero.

6.Field facts
• 2024 South-China refinery: 96 F3423 replaced in 90 minutes during live FCC regenerator sequence; zero spurious trips.
• North-Sea platform: eleven-year-old contacts still < 30 mΩ after 1.8 million cycles—40 % below the maintenance limit.
• Middle-East LNG: diagnostic coverage 99 %, proof-test interval extended from 12 to 24 months, saving 4 800 man-hours per cycle.

7.Engineering check-list
✓ Use ELOP II V8.9 or later—diagnostic bits are auto-generated.
✓ Set “Force OFF” timer ≥ 20 ms to allow contact bounce to settle.
✓ For inductive loads > 0.5 A add RC-snubber or MOV to maintain 2 A / 100 000 operations.
✓ Keep 10 mm side clearance for 230 V AC; creepage is SIL-rated, heat is not.

8.Life-cycle guarantee
HIMA guarantees a 15-year production cycle and 20-year spare-part availability for all safety I/O. Amikon holds rotating stock of new and certified-refurb F3423 with same-day dispatch and 12-month functional warranty plus firmware conformity report—ready for insurance or audit spot checks.

9.Total cost of safe ownership
USD 1 200 per channel looks premium; factor in eliminated proof-test switches, smaller cabinets, zero downtime and a 24-month test interval and the 10-year TCO drops below USD 0.08 per safe switching cycle—half that of a conventional relay-plus-feedback solution.

10.Take-away
Safety is not a certificate on the wall; it is the click of a relay after the logic solver commands—and a message that says “I moved”. F3423 turns that click into a time-stamped, SIL 3-auditable event. Next time a HAZOP asks “How do we know the output really moved?” point to the F3423 diagnostics and move on.

Need a channel today?
sales5@amikon.cn | +86 181 0690 9650