Bently Nevada TACH100-01 / 174652-01 – Digital Tachometer | 3500 Series Machinery Protection
Engineering Background: The Bently Nevada 3500 Series is the industry benchmark for continuous online machinery protection in rotating equipment applications. Deployed across gas turbines, steam turbines, compressors, pumps, and generators, the 3500 rack architecture provides real-time vibration, position, and speed monitoring that feeds directly into plant safety instrumented systems (SIS) and DCS alarm hierarchies. Within this architecture, the TACH100-01 (catalog part number 174652-01) serves as the dedicated speed and phase reference module — converting raw proximity probe signals into clean digital tachometer outputs used for overspeed detection, phase-referenced vibration analysis, and Keyphasor® synchronization across the entire rack.
Product Positioning: The TACH100-01 is the standard single-channel tachometer input card for the 3500 Series. It is distinct from the dual-channel TACH200 variant and is specifically selected when a single Keyphasor® reference per machine train is sufficient. The module is not a standalone device — it operates exclusively within a 3500 rack with a valid rack interface module (RIM) and power supply. It is not interchangeable with 3300 or 3701 series tachometer inputs without firmware and rack reconfiguration.
Complete Technical Specifications
Electrical
- Input Signal Type: Proximity probe (eddy-current), magnetic pickup, or TTL-level pulse
- Input Voltage Range: –24 VDC nominal (proximity probe bias), 0–5 V TTL (digital input)
- Speed Measurement Range: 0 – 99,999 RPM
- Frequency Response: DC to 10 kHz
- Output Signal: Digital tachometer pulse, Keyphasor® reference output
- Power Consumption: <3 W (supplied via 3500 rack backplane)
- Isolation: Channel-to-channel and channel-to-rack isolation per 3500 Series standard
Mechanical
- Form Factor: Single-slot 3500 Series rack module
- Dimensions: Standard 3500 module (approx. 241 mm × 24 mm × 200 mm)
- Weight: 320 g (nominal)
- Connector: 25-pin D-sub field wiring connector (rear I/O)
- Part Numbers: TACH100-01 / 174652-01 (functionally equivalent)
Environmental
- Operating Temperature: 0°C to +65°C
- Storage Temperature: –40°C to +85°C
- Relative Humidity: 5% to 95% non-condensing
- Vibration Resistance: Per IEC 60068-2-6
- EMC: Designed to operate in Class A industrial electromagnetic environments
Certifications
- CE Marking: Electromagnetic Compatibility Directive
- SIL Capable: Suitable for use in SIL 1/2 safety loops when configured per Bently Nevada SIL documentation
- ATEX / IECEx: Not intrinsically safe — field wiring must comply with area classification requirements
Data source: Bently Nevada 3500 Series Product Specifications, GE Measurement & Control Solutions technical documentation. Specifications subject to revision; confirm with datasheet revision in effect at time of order.
Proven Application Environments
- Petrochemical / Ethylene Cracker: Cracked gas compressor trains — continuous overspeed monitoring during startup transients where speed ramp rates exceed 500 RPM/s
- Power Generation / Gas Turbine: Frame 7/9 gas turbines — Keyphasor® phase reference for 1× and 2× vibration vector trending during load cycling
- LNG Plant / Refrigeration Compressor: Multi-stage centrifugal compressors — speed signal integration with anti-surge control systems requiring <5 ms latency
- Water Treatment / High-Service Pumping Station: Vertical turbine pumps — tachometer feedback for variable-frequency drive (VFD) closed-loop speed verification
- Steel Mill / ID Fan: Induced draft fans on blast furnace gas systems — speed monitoring under high-vibration, high-temperature ambient conditions up to 55°C
- Offshore Platform / Gas Injection Compressor: Subsea-topside compression trains — rack-based monitoring where weight and footprint constraints favor single-slot tachometer modules
Engineering Advantages
- For overspeed trip applications, this tachometer module provides deterministic pulse counting with hardware-level latency below 5 ms, because the signal processing is executed on dedicated FPGA logic within the module rather than shared rack CPU cycles.
- For phase-referenced vibration analysis, this tachometer module delivers a stable Keyphasor® once-per-revolution marker, because the input conditioning circuit filters shaft runout and electrical noise without introducing phase shift errors that would corrupt 1× vector measurements.
- For multi-machine train installations, this tachometer module enables independent speed channels per machine, because each TACH100-01 slot operates autonomously on the 3500 backplane without cross-channel interference.
- For plants with mixed probe types, this tachometer module accepts proximity, magnetic pickup, and TTL inputs on the same hardware platform, because the input stage includes selectable signal conditioning modes configurable via 3500 System Configuration Utility (SCU).
- For long-term asset reliability programs, this tachometer module supports continuous online diagnostics, because the 3500 rack performs self-test routines that flag module faults to the DCS without interrupting the protection channel.
- For brownfield retrofit projects, this tachometer module slots directly into existing 3500 racks without rack replacement, because the backplane interface and firmware architecture have maintained backward compatibility across 3500 Series generations.
System Architecture & Signal Flow
Signal Flow: Proximity probe (field) → TACH100-01 input conditioning → digital pulse train → 3500 rack backplane → Rack Interface Module (RIM) → Modbus/TCP or 4–20 mA output → DCS / SIS / historian
Compatible Modules:
- 3500/20 Rack Interface Module — required for Modbus/TCP communication; provides the network gateway for all rack data
- 3500/15 Power Supply — rack power; dual-redundant configuration recommended for SIL applications
- 3500/25 Keyphasor® Module — alternative when Keyphasor® signal must be distributed to multiple downstream monitors simultaneously
- 3500/42M Proximitor®/Seismic Monitor — consumes the Keyphasor® reference from TACH100-01 for phase-referenced vibration calculations
Substitution Conditions: The TACH100-01 may be replaced by the 3500/25 Keyphasor® Module when the application requires Keyphasor® signal distribution to more than four downstream monitor modules. Direct substitution with non-Bently Nevada tachometer cards is not supported without full rack reconfiguration and re-validation of the protection system.
Sourcing & Quality Verification
Units offered through Konmask.com are sourced from decommissioned plant upgrades, authorized distributor overstock, and verified secondary market channels. Each unit undergoes the following verification process before dispatch:
- Visual & Mechanical Inspection: Connector pin integrity, PCB condition, label legibility, and absence of physical damage or corrosion
- Firmware Version Check: Module firmware revision recorded and disclosed; customer notified if firmware upgrade is required for target rack configuration
- Functional Bench Test: Module inserted into 3500 test rack; speed input simulated at 1,000 / 3,600 / 10,000 RPM; output pulse verified against reference counter
- Documentation Package: Serial number, test record, and condition report issued with each unit
Available Documentation: Test report, serial number certificate, original Bently Nevada datasheet (current revision), and packing list. Factory calibration certificate available on request for units with traceable test history.
Procurement Process
- Submit Inquiry: Provide target rack slot, existing firmware revision (if known), and required quantity via email to support@konmask.com or the on-page inquiry form
- Receive Quote & Availability Confirmation: A technical response is issued within 24 hours, including unit condition grade, firmware version, lead time, and pricing in your preferred currency
- Order & Dispatch: Payment confirmed → unit re-inspected → ESD-safe packaging → shipped with full documentation package; DHL/FedEx express available for urgent plant requirements
Technical Support: Pre-sale support covers rack compatibility verification, firmware revision guidance, and wiring diagram review. Post-sale support covers installation confirmation and basic commissioning questions. For full system integration engineering, referral to a certified Bently Nevada service partner is available on request.
Technical FAQ
- Q: Is the TACH100-01 compatible with both 3500/20 and 3500/20E Rack Interface Modules?
- A: Yes. The TACH100-01 is compatible with all 3500/20 RIM variants including the 3500/20E Ethernet version. The tachometer module communicates via the rack backplane and is not affected by the RIM communication protocol selection.
- Q: Can the TACH100-01 replace a 3500/25 Keyphasor® Module in an existing rack?
- A: Partial substitution is possible for single-machine applications where Keyphasor® distribution to downstream monitors is not required. If the existing configuration uses the 3500/25 to distribute the Keyphasor® reference to four or more monitor modules, the TACH100-01 is not a direct drop-in replacement and rack reconfiguration via SCU is required. Confirm the existing rack configuration file before ordering.
- Q: Is the TACH100-01 certified for use in SIL 2 safety instrumented functions?
- A: The 3500 Series platform, including the TACH100-01, is designed to support SIL 1 and SIL 2 safety functions when the complete installation — including rack configuration, proof test interval, and field wiring — complies with the Bently Nevada 3500 Series Safety Manual. SIL certification applies to the system architecture, not the module in isolation. The applicable safety manual revision must be confirmed for the target firmware version.
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