Description
1. Product Overview
Part Number: 3500/25, Item No. 125792-01
Manufacturer: Bently Nevada. It is a half-height dual-channel enhanced keyphasor dedicated module for the 3500 rotating machinery TSI protection and condition monitoring system. 125792-01 is the factory locked hardware revision.
Compatible Rack: Standard 19-inch 3500 series 14-slot rack, occupying only one single half-height slot. It seamlessly networks with 3500/42/45 displacement cards, 3500/50 relay cards, 3500/65 temperature cards and 3500/22M frame interface cards. Channel configuration, speed range and filter parameters are set via 3500 Rack Configuration Software. The keyphasor reference signal is distributed to all monitoring cards in the rack, and data is uploaded to System 1 asset management platform and plant-wide DCS/SCADA systems, complying with SIL2~SIL3 functional safety requirements.
Product Definition: Dual-channel keyphasor signal conditioning and conversion unit accepting eddy current probes or passive magnetic pickups. It converts analog trigger pulses from shaft keyways or gear teeth into standardized digital keyphasor timing signals, acting as the exclusive time reference for speed calculation and 1X vibration amplitude & phase demodulation of all vibration and displacement cards within the rack. Dual buffered keyphasor outputs are led out from front and rear sides for external fault diagnostic instruments, tachometers and protection interlock equipment to extract reference pulses, which is the fundamental signal source for rotating machinery dynamic balancing, fault spectrum analysis and overspeed protection.
2. Six Core Hardware Functional Units
2.1 Dual-Channel Isolated Sensor Power & Signal Conditioning Unit
Two fully isolated input loops supplying -24VDC max 40mA per channel for eddy current probes; passive magnetic pickups require no on-board power supply. Multi-stage EMI filtering, TVS surge clamping and differential amplification circuits eliminate ground loop interference from long cables and prevent pulse loss, speed fluctuation and phase drift. Two input voltage ranges are hardware limited automatically: +0.8~-21V for non-isolated I/O systems, +5~-11V for isolated I/O systems. Minimum input impedance per channel is 21.8kΩ for strong anti-noise performance.
2.2 Wide-Range Speed Counting & Digital Keyphasor Generation Unit
Input frequency covers 0.017~20kHz (1~1200000 CPM), supporting single-pulse per revolution and multi-tooth multi-pulse modes. Teeth quantity per revolution is configurable via software to calculate accurate rotating speed with output range 1~99999 CPM. An on-board hardware counter latches pulse edges to generate standard keyphasor trigger pulses for phase calculation of all rack monitoring modules. Passive magnetic pickups require shaft speed above 200rpm for stable signal recognition.
2.3 Front & Rear Dual Buffered Keyphasor Output Unit
Two BNC coaxial ports on the front panel and two isolated buffered keyphasor pulses via rear Euro terminals are provided synchronously, with maximum output impedance 504Ω. External oscilloscopes, dynamic balancers and portable acquisition devices can extract reference signals without occupying backplane bus resources for strong expandability.
2.4 Front Panel LED Self-Test Indication Unit
Three front-panel status LEDs: steady OK light indicates normal backplane power, hardware self-test and bus communication; flashing TX/RX light denotes data uploading of speed, faults and configuration to rack backplane; KEYPHASOR channel LED lights up upon valid pulse input, enabling on-site preliminary troubleshooting of probe open circuit, missing trigger pulse and loop short circuit without configuration software.
2.5 Backplane Bus Interaction & Fault Diagnosis Unit
Rear gold-finger edge connector interfaces with 3500 parallel backplane bus to upload dual-channel speed values, fault codes (probe open/short/low power) and module hardware alarms. Single-channel software bypass is supported; maintenance on one channel only disables the corresponding loop while the other keyphasor channel remains active without interrupting unit speed monitoring. It is compatible with single-card dual-channel and dual-module redundant keyphasor architectures for high-reliability critical unit design.
2.6 Industrial Reinforced Conformal Coating Unit
The full gold-plated FR-4 PCB is coated with moisture, salt fog and corrosion resistant conformal coating. Fanless passive heat dissipation relies on rack airflow. No adjustable potentiometers or consumable fuses are equipped to withstand high temperature & dust accumulation inside sealed cabinets, long-term low-frequency vibration of unit base and humid coastal environment, enabling 24/7 unattended maintenance-free continuous operation.
3. Key Technical Specifications
3.1 Basic Hardware Specifications
| Item | Specification |
|---|---|
| Model | 3500/25 Item No.125792-01 Half-Height Dual-Channel Enhanced Keyphasor Module |
| Rack Slot Occupation | 1 half-height slot of 3500 rack |
| Input Channels | 2 mutually isolated independent keyphasor inputs |
| Supported Transducers | Eddy current proximity probe, passive magnetic pickup |
| Per-Channel Probe Power | -24VDC, max 40mA output |
| Typical Power Consumption | 3.2W |
| Net Weight | Approx. 0.38kg |
| Origin | Original USA Bently Nevada Manufacture |
3.2 Signal & Measurement Parameters
- Input Frequency Range: 0.017Hz ~ 20kHz (1 ~ 1200000 RPM)
- Speed Output Accuracy: ≤±1 CPM (low frequency), ≤±8 CPM (mid frequency), ≤±1% of reading (high frequency)
- Buffered Output: 2×BNC on front + 2×Euro terminals on rear, output impedance ≤504Ω
- Alarm Logic: Independent fault detection per channel for open circuit, short circuit, power loss and no pulse signal
- Backplane Communication: Native 3500 parallel backplane bus; speed and fault data can be transmitted to upper system via Modbus through frame interface card
3.3 Environmental & Safety Compliance
- Operating Temperature: -30℃ ~ +65℃
- Storage & Transport Temperature: -40℃ ~ +85℃
- Humidity: 5%~95%RH non-condensing, no corrosive acid/alkali gas or salt fog deposition
- Ingress Protection: IP20, for indoor cabinet installation only
4. Core Product Advantages
- Compact half-height form factor with dual channels per single card greatly reduces rack slot occupation, facilitating rack expansion and redundant wiring layout.
- Software-only configuration switches between eddy current probe and magnetic pickup modes without hardware modification or rewiring for maximum on-site adaptability.
- Synchronous buffered outputs on both front and rear eliminate the need for external signal splitters for cabinet internal system access and field portable device debugging.
- Fine-grained single-channel bypass and precise fault localization allow maintenance on one measuring point without unit load reduction or shutdown.
- Native full compatibility with entire 3500 ecosystem; drop-in replacement is automatically recognized by the rack with direct configuration import to minimize outage duration during emergency repair.
- Wide frequency range and high-precision speed measurement maintain stable phase reference across cranking speed up to full rated load, serving as a reliable benchmark for vibration analysis, fault diagnosis and overspeed protection.
5. Typical Application Scenarios
1. Combined-Cycle Thermal Power Gas & Steam Turbine 3500 TSI System
Core module for main shaft speed acquisition and vibration phase locking, paired with shaft and bearing vibration cards to monitor 1X vibration amplitude and phase, standardized for GE & Siemens gas turbine TSI systems.
2. Petrochemical Large Process Compressor Monitoring System
Shaft speed and keyphasor reference collection for cracking gas and recycle hydrogen compressors to enable rotor vibration spectrum analysis, anti-surge early warning and unit interlock trip logic for continuous chemical production safety.
3. Large & Medium Hydropower Unit Governor & Shaft Monitoring
Water turbine main shaft speed and runner phase signal acquisition to coordinate with governor for grid synchronization, load regulation and overspeed protection, adapted to humid hydropower plant environment.
4. Metallurgy Blast Furnace Main Fans & Large Pump Station Equipment
Online fan shaft speed monitoring to predict rotor unbalance and blade fracture faults via keyphasor-referenced vibration diagnosis and prevent severe shaft seizure damage.
