Product No.: 3500/25-01-01-00 149369-01 - General Introduction
This product is a complete, pre-configured Keyphasor® Module Assembly for the Bently Nevada 3500 Machinery Protection System. It is not just the module but a designated assembly that includes the module with specific firmware and hardware options.
3500/25: This is the Keyphasor / Speed Monitor Module. Its primary function is to condition the signal from a Keyphasor probe (an eddy current or magnetic pickup sensor) to provide a once-per-revolution timing pulse and accurate rotational speed (RPM) measurement for an entire machinery train.
-01-01-00: These suffixes define the factory configuration. This typically specifies the firmware version, input type compatibility (e.g., -01 often denotes a standard eddy current probe input), and the number of channels or specific processing options.
149369-01: This is the specific Assembly Part Number or Service Kit Number. It confirms that this is a validated, ready-to-install unit with all necessary internal components (e.g., specific ICs, resistors, jumpers) set to a known configuration.
The module is critical for synchronizing vibration data (for order analysis) and providing reliable speed signals for alarm and protection logic.
Detailed Parameters
| Parameter Category | Specification | Details / Notes |
|---|---|---|
| Module Type | 3500/25 - Keyphasor / Speed Monitor | Dual-channel module that provides two independent Keyphasor signals. Essential for phase reference. |
| Physical Dimensions (Module) | Height: 318.0 mm (12.52 in) Width: 40.0 mm (1.57 in) - 2 Slots Depth: 193.0 mm (7.60 in) | The 3500/25 is a double-width module, occupying two adjacent slots in a 3500 rack. |
| Module Weight | Approx. 0.9 kg (2.0 lb) | Heavier than single-slot modules due to larger PCB and additional components. |
| Input Channels | Two (2) Independent Isolated Channels | Can accept signals from two separate Keyphasor probes (e.g., from opposite ends of a machine). |
| Input Type (Configured) | Eddy Current Probes (Preferred) | The "-01" configuration is typically set for -24 VDC powered, two-wire eddy current transducer inputs (e.g., 3300/46 proximity probes). Can also be configured for magnetic pickups (MPUs) or active digital sensors. |
| Input Signal Range | Pulse Input: -2 V to -26 V (for eddy current) Frequency: 0.1 Hz to 30,000 Hz (0.5 to 180,000 RPM) | Wide range suitable for from turning gear to overspeed conditions on most turbomachinery. |
| Power Requirement | Powered by the +24 VDC and ±15 VDC rails of the 3500 rack backplane. | |
| Primary Outputs | • Two isolated Keyphasor Pulse Outputs (to other 3500 vibration monitor modules) • Two 4-20 mA analog outputs (proportional to speed, one per channel) • Programmable Alarm Relays (Danger, Alert, OK - for speed deviations or signal loss) | Relays are Form C (SPDT). The KP pulses are the critical link for vibration phase data. |
| Key Accuracy | Speed Measurement: Typically ±1 RPM or 0.1% of reading (whichever is greater). | High accuracy for reliable overspeed protection and process control. |
| Display | Dual, 5-character LED displays (one per channel) on the front panel. | Displays speed (RPM) and channel status. |
| Configuration | Via 3500 Rack Configuration Software. Settings include: pulse per revolution, speed ranges, alarm setpoints, and input type. | The "-01-01-00" hardware suffix ensures the module matches its software configuration. |
| Operating Temperature | 0°C to +65°C (+32°F to +149°F) | Standard industrial range. |
| Key Feature | Point-to-Point (P2P) Communication: Broadcasts speed and Keyphasor data to all other monitoring modules in the rack simultaneously. | Enables all vibration and position channels to be synchronized to the same rotational phase. |
Primary Application Scenarios
The 3500/25 is the heartbeat and synchronizing clock for an entire machinery protection system.
Overspeed Protection for Turbines (Gas/Steam):
Critical Safety Function: Provides the primary or secondary speed signal for the turbine trip system. A Danger relay output is typically configured for the overspeed setpoint (e.g., 110% of rated speed) to initiate an emergency shutdown.
Vibration Phase Reference for Diagnostics:
Synchronization: Supplies the essential Keyphasor pulse to all connected 3500/42 (Vibration), 3500/45 (Axial Position), and other monitor modules. This allows vibration analysts to determine the phase angle of vibration, which is critical for diagnosing unbalance, misalignment, and cracked shafts.
Multi-Shaft & Gearbox Monitoring:
Dual-Channel Operation: Can monitor the speed of both the pinion and bull gear in a high-speed compressor train, or the HP and LP sections of a multi-shaft turbine, providing a complete speed picture on one module.
Control System Integration & Process Logic:
Speed-Based Control: The 4-20 mA speed output is fed to the plant Distributed Control System (DCS) or Turbine Control System (TCS) for speed governing, load control, and start-up/coast-down sequences.
Start-up Permissive: Provides a "Zero Speed" signal to confirm a machine is at rest before allowing maintenance or barring gear engagement.
Cascaded Alarm Logic:
Signal Validation: Can be programmed to generate an Alert if the Keyphasor signal is lost or becomes erratic, warning operators that vibration phase data is invalid, preventing false diagnoses.
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