Description
Product Description
The BENTLY 131151-01 is a specialized signal conditioning and driver module for the Bently Nevada 3500 system, specifically identified as a 3500/25 Keyphasor Module. This module is a fundamental component for the timing and phase reference of rotating machinery. Its primary function is to condition the raw signal from a Keyphasor transducer—typically an eddy current proximity probe observing a once-per-revolution mark on a shaft—and convert it into a clean, digital timing pulse. This Keyphasor pulse is then distributed to other monitoring modules within the 3500 rack, such as vibration monitors, to provide a phase-locked reference. This enables critical measurements like phase angle for balancing, order tracking for resonance analysis, and synchronous time-averaging for noise reduction in vibration data. The reliable operation of the Bently Nevada 131151-01 is essential for accurate diagnostic measurements and for certain protection algorithms on turbines, compressors, and other large rotating equipment.
Product Parameters
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Module Type: Keyphasor Signal Conditioner / Timing Module
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Compatible System: Bently Nevada 3500 Rack System
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Primary Function: Conditions the Keyphasor transducer signal and generates a phase-reference pulse for the monitoring system.
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Input Signal: Accepts signal from an eddy current proximity probe (or other Keyphasor sensor) observing a once-per-revoltion event (keyway, notch, tooth).
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Signal Conditioning: Includes adjustable trigger level (threshold), filtering, and hysteresis to generate a clean, jitter-free pulse even from noisy or varying amplitude signals.
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Output Signal: Provides a digital TTL-compatible pulse (Keyphasor pulse) to the 3500 rack backplane for use by other modules.
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Pulse Characteristics: Fixed width and voltage level suitable for the 3500 system’s internal timing bus.
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Status Indicators: LEDs for Power, OK, and often an LED that flashes with the Keyphasor pulse.
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Configuration: Programmable via the 3500 Configuration Software for trigger level and filtering settings.
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Mounting: Occupies a single slot in a 3500 system rack.
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Operating Temperature: 0°C to +65°C.
Advantages and Features
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Critical for Advanced Diagnostics: The BENTLY 131151-01 is indispensable for any vibration analysis requiring phase data, such as determining unbalance direction, identifying cracked shafts, or performing operational deflection shape analysis.
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High Signal Integrity: Advanced conditioning circuits ensure a reliable, noise-immune timing pulse is generated even if the raw transducer signal is degraded due to dirt, minor surface defects, or electrical interference.
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System-Wide Synchronization: A single 131151-01 module can provide the Keyphasor pulse to all other monitoring modules in the rack (e.g., 3500/42M, 3500/45), ensuring all vibration and position measurements are perfectly synchronized to shaft rotation.
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Configuration Flexibility: Adjustable trigger levels allow it to work reliably with different Keyphasor mark geometries and probe gaps, accommodating various machine designs.
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Proven Reliability: As a core component of the 3500 protection system, it is engineered for continuous, fail-safe operation in the critical timing path of machinery monitoring.
Application Cases in Various Fields
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Gas & Steam Turbine Balancing: The Bently Nevada 131151-01 provides the essential phase reference during startup and operation to determine the location and amount of balance weight required on turbine rotors.
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Compressor Train Monitoring: In a string of compressors driven by a single motor or turbine, a Keyphasor pulse from the 131151-01 on the high-speed shaft enables order-tracking analysis to diagnose issues like blade-pass frequency or gear mesh problems.
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Hydroelectric Unit Alignment: Used to measure the phase relationship between vibration points on a large hydroturbine generator, aiding in the detection of misalignment or stator/rotor interactions.
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Critical Pump and Fan Trains: Provides timing data to distinguish between running speed vibration and other forcing frequencies, enabling more precise fault diagnosis on induced draft fans or boiler feed pumps.
Comparisons with Competing Products
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Integrated vs. Dedicated Timing: Some competing monitoring systems (e.g., from other vendors) integrate Keyphasor conditioning into their main vibration monitor cards. The advantage of the dedicated BENTLY 131151-01 is that it provides a centralized, high-quality timing source for the entire rack, freeing up processing power on individual monitors and ensuring consistency.
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System-Centric vs. External Analyzers: Compared to using the Keyphasor input on a portable vibration analyzer, the 131151-01 provides a permanent, calibrated, and continuously available timing signal integrated directly into the online protection and condition monitoring system.
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Performance and Reliability: Generic pulse conditioners or PLC high-speed counters lack the specialized filtering, adjustable hysteresis, and seamless integration with vibration data acquisition that the 131151-01 offers as part of a certified machinery protection system.
Selection Suggestions and Precautions
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One Per Shaft Line: Typically, only one BENTLY 131151-01 module is required per independent rotor (shaft line) being monitored. It is a system-level resource, not a per-probe module.
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Proper Transducer Selection and Installation: The performance of the 131151-01 is entirely dependent on a clean, reliable signal from the Keyphasor probe. Ensure the probe is correctly installed, the keyway or mark is well-defined, and the signal meets minimum amplitude requirements.
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Critical Configuration: The trigger level setting in the configuration software is crucial. It must be set between the peak voltage of the Keyphasor “blip” and the baseline vibration signal to avoid double-pulsing or missed pulses. Incorrect setup will render all phase data useless.
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Verify Pulse with LED: During commissioning and troubleshooting, use the module’s pulse indicator LED to visually confirm it is firing once per revolution. This is a basic but vital health check.
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Redundancy Consideration: For machines where phase-related protection or diagnostics are critical, some sites install a redundant Keyphasor probe and a second 131151-01 module configured on a separate channel. The primary module’s failure would not completely disable phase-based monitoring.

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