Description
Bently Nevada 3500/50-04-00 (136703-01)
Technical Specifications:
- Product Series: 3500 Machinery Protection System
- Module Type: 2-Channel Tachometer Monitor Module
- Part Number: 136703-01 (I/O module)
- Channel Count: 2 channels
- Sensor Input Range: +10.0V to -24.0V (signals outside this range are clamped internally)
Functional Features:
- Determines shaft rotational speed, rotor acceleration, or rotor direction from proximity probe or magnetic sensor inputs
- Configurable into four different channel types: speed monitoring with setpoint alarm and speed band alarm; speed monitoring with setpoint alarm and zero speed indication; speed monitoring with setpoint alarm and rotor acceleration alarm; speed monitoring with setpoint alarm and reverse rotation indication
- Can be configured to provide a keyphasor signal to the 3500 rack backplane for use by other monitors, eliminating the need for a separate keyphasor module
- Peak hold function stores the highest speed, highest reverse speed, or number of reversals reached by the machine; these peaks are user-resettable
- Alarm setpoints are software-configurable and adjustable within 0 to 100% of full scale
- Alarm delay is software-programmable: Alarm 1 from 1 to 60 seconds in 1-second intervals; Alarm 2 from 1 to 60 seconds in 0.1-second intervals
Application Scenarios:
- Rotational speed monitoring on steam turbines, gas turbines, compressors, and pumps
- Zero speed detection for turbine startup and shutdown sequences
- Reverse rotation detection for machinery protection
- Rotor acceleration monitoring during startup transients
- Keyphasor signal generation for phase-based vibration analysis
Performance Parameters:
- Channels: 2 independent tachometer channels
- Sensor Types: Eddy current proximity probes or magnetic pickup sensors
- Signal Range: +10.0V to -24.0V
- Alarm Setpoint Range: 0 to 100% of full scale
- Alarm Delay (Alarm 1): 1 to 60 seconds, 1-second increments
- Alarm Delay (Alarm 2): 1 to 60 seconds, 0.1-second increments
Material Composition:
- Industrial-grade PCB with signal processing and conditioning circuitry
- Standard 3500 rack module chassis
Structural Features:
- Full-height module form factor for 3500 rack
- Front panel with status LEDs (OK, TX/RX, Bypass)
- Buffered sensor output coaxial connectors on the front panel with short-circuit and ESD protection
- Rear I/O module (136703-01) provides terminal connections for field sensor cables
Working Principle: The tachometer module receives pulse signals from eddy current or magnetic sensors mounted near the rotating shaft. The module’s internal circuitry processes these pulses to calculate rotational speed, acceleration, or direction. The calculated values are compared against user-programmable alarm setpoints, and alarm outputs are generated when thresholds are exceeded. The module can also generate a keyphasor reference pulse from the once-per-revolution signal and distribute it through the backplane to other monitor modules.
Installation Requirements:
- Install in any available slot to the right of the rack interface module
- Sensor cables must be connected to the correct I/O module terminal positions
- The sensor gap must be properly set for eddy current probes
- Configuration must be downloaded using 3500 rack configuration software
Usage Precautions:
- The 3500/50 tachometer module is not to be used alone or as part of a speed control or overspeed protection system
- The module does not provide protection redundancy or response speed for speed control or overspeed protection systems
- Analog proportional outputs are for data collection, chart recording, or display only; speed warning setpoints are for notification purposes only
- Magnetic sensors are not recommended for zero speed options, as they do not provide clean edges at low rotational speeds
- Verify sensor signal quality before enabling speed monitoring
