Siemens 3TK2923-0BB4 Timing Relay – Obsolete SIRIUS Safety Series Spare Part

Technical Dossier

Product Details And Specifications

Siemens 3TK2923-0BB4 Timing Relay – Obsolete SIRIUS Safety Series Spare Part

When a delay module fails inside a legacy safety relay circuit, the consequences extend far beyond a single component. The 3TK2923-0BB4 is a timing expansion module belonging to Siemens' SIRIUS 3TK29 safety relay series — a product line that has reached end-of-life status. Facilities still operating on this platform face a hard reality: sourcing a direct replacement is no longer a matter of placing a standard purchase order. It requires locating verified old stock from specialist distributors.

The cost of ignoring this is not abstract. A production line built around a SIRIUS 3TK28/3TK29 safety architecture — common in press control, conveyor guarding, and robotic cell interlocking — cannot simply swap in a modern successor module without engineering re-validation, updated wiring diagrams, and in many jurisdictions, re-certification of the safety function. That process routinely runs into tens of thousands of dollars in engineering hours alone, before accounting for production downtime. A single verified spare part at the right moment eliminates that entire exposure.

DriveKNMS maintains allocated stock of the 3TK2923-0BB4 sourced through controlled supply channels. Inventory is finite and not replenishable on demand.

Technical Specifications

Note: Electrical parameters (supply voltage, contact ratings, timing range) are not published here to avoid inaccuracy on an EOL component. Please contact us directly for datasheet confirmation against your specific installation.

Solving the Discontinued Hardware Crisis

The SIRIUS 3TK28/3TK29 safety relay platform was widely deployed across European and Asian manufacturing facilities throughout the 2000s and 2010s. Its modular architecture — base relay plus expansion modules including the 3TK2923-0BB4 timing unit — made it a standard choice for machine builders designing to EN ISO 13849 and IEC 62061 safety standards.

Siemens has since transitioned its safety relay portfolio toward the 3SK1 and 3SK2 series. These successors are not pin-compatible with 3TK29 expansion modules. A facility that loses a 3TK2923-0BB4 and cannot source a like-for-like replacement faces one of two paths: locate old stock, or undertake a full safety relay panel redesign.

The redesign path carries costs that are rarely fully anticipated at the outset. Beyond the hardware itself, the safety function must be re-validated. If the machine is CE-marked or subject to local safety authority oversight, the updated design may require third-party assessment. Production is halted throughout. For a mid-size automotive stamping line or a food packaging system running three shifts, even a two-week shutdown represents revenue loss that dwarfs the cost of maintaining a strategic spare parts inventory.

Facilities managing aging SIRIUS-based safety systems should treat the 3TK2923-0BB4 — and equivalent expansion modules — as critical long-lead items requiring proactive stock management, not reactive emergency sourcing.

Extending Automation Asset Life by 5–10 Years: A Practical Framework

For plant managers and maintenance engineers operating equipment built on legacy Siemens SIRIUS safety relay infrastructure, the following approach has proven effective in deferring costly system overhauls:

1. Conduct a full module census. Identify every 3TK28 base unit and 3TK29 expansion module installed across all machines and panels. Cross-reference against Siemens EOL notifications to flag which part numbers are no longer available through standard distribution.

2. Establish minimum stock levels based on failure history. Timing and delay modules in safety relay circuits are subject to contact wear and capacitor degradation over time. If your facility has experienced even one failure of a 3TK2923-0BB4 in the past five years, that is sufficient justification for holding at least two verified spares per machine type.

3. Prioritize machines where downtime cost is highest. Not every line carries equal financial exposure. Allocate spare parts budget toward the equipment where a safety relay failure would halt the highest-value production or trigger the most complex restart procedure.

4. Source from verifiable channels only. The market for obsolete Siemens components includes a significant volume of counterfeit and substandard product. For safety-rated components, this is not a quality inconvenience — it is a liability issue. Require documentation of sourcing chain and condition assessment from any supplier.

5. Schedule periodic functional testing. Even stored spare modules should be tested against known-good reference units before being placed into service. A module that has been in uncontrolled storage for several years may have degraded without visible indication.

This framework does not require capital expenditure. It requires structured attention to parts criticality — and it routinely extends the viable service life of legacy safety systems by five to ten years beyond what facilities would otherwise achieve through reactive maintenance alone.

Condition & Reliability Assurance

DriveKNMS applies a five-stage assessment protocol to all obsolete and legacy components before they are offered for sale:

Step 1 – Electrolytic Capacitor Inspection: Capacitor aging is the primary failure mode in timing relay modules. Each unit is inspected for bulging, leakage, and ESR deviation from specification.

Step 2 – Firmware and Configuration Verification: Where applicable, firmware version and DIP switch / parameter settings are verified and documented against the original factory configuration.

Step 3 – Contact and Pin Corrosion Assessment: All connector pins and relay contacts are inspected under magnification for oxidation, pitting, and mechanical deformation. Affected units are not offered for sale.

Step 4 – Functional Bench Test: Units are powered and cycled through their timing function under controlled conditions. Timing accuracy is logged.

Step 5 – Packaging and Storage: Cleared units are repackaged in anti-static materials with desiccant and stored in a controlled environment until dispatch.

Key Features for System Maintenance

• Drop-in replacement: The 3TK2923-0BB4 installs directly into existing 3TK28 base unit slots with no wiring modification required.
• No reprogramming required: Timing parameters are set via onboard controls, consistent with the original module. No PLC or safety controller reconfiguration is needed.
• Avoids engineering redesign costs: A verified like-for-like replacement eliminates the need for panel redesign, re-validation, and re-certification of the safety function.
• Maintains existing safety integrity level: Replacing with the original part number preserves the documented safety architecture without requiring re-assessment of the safety function's PL or SIL rating.

FAQ

Q: What warranty applies to an obsolete part like the 3TK2923-0BB4?
A: We offer a 90-day functional warranty on all units that have passed our five-stage assessment. This covers failure under normal operating conditions. Contact us before purchase to confirm the specific warranty terms for your order.

Q: How do I know the unit is genuine and not counterfeit?
A: We provide documentation of the sourcing chain for each unit. Physical authenticity markers — label printing, housing markings, PCB construction — are verified against known-genuine reference units as part of our intake process.

Q: Should I buy more than one unit?
A: For any machine where a 3TK2923-0BB4 failure would halt production, holding at least one additional spare is a defensible maintenance decision. Given that this part is no longer manufactured, current available stock represents a finite global supply. Prices for remaining units will not decrease over time.

Q: Can you source additional units if I need more than you have in stock?
A: We maintain active sourcing relationships for legacy Siemens components. Contact us with your quantity requirement and we will advise on availability and lead time.

© 2026 DriveKNMS. All trademarks belong to their respective owners. Specifications are for reference only and subject to change without notice. Verify all parameters against official documentation before installation.