Bently Nevada 3500/42 125672-02 Proximitor/Seismic Monitor – 4-Channel Machinery Protection Module

Brand Bently Nevada

Model Bently 3500/42 125672-02

Product Overview

The Bently Nevada 3500/42 125672-02 is a four-channel Proximitor/Seismic Monitor that serves as one of the core measurement cards inside the Bently Nevada 3500 Machinery Protection System. Designed and manufactured by Bently Nevada, a Baker Hughes business, it accepts input from eddy-current proximity probes as well as seismic transducers such as velocity sensors and accelerometers, conditions those raw transducer signals into calibrated engineering units, and continuously compares the resulting values against user-programmable alarm setpoints. The 125672-02 suffix identifies the printed wiring assembly (PWA) revision of the monitor main board, so the designation Bently Nevada 3500/42 125672-02 refers to a genuine 3500/42 monitor card built on that board revision and engineered for direct plug-in installation into a standard 3500 rack slot.

Functionally, the Bently Nevada 3500/42 125672-02 is configured through the 3500 Rack Configuration Software, and its four input channels are arranged in two independently programmable pairs. Channels 1 and 2 execute one measurement function while channels 3 and 4 execute another, allowing a single card to supervise two different machine parameters simultaneously. Supported functions include radial vibration, thrust (axial) position, differential expansion, eccentricity, REBAM rolling-element bearing analysis, acceleration, velocity, shaft absolute measurement and circular acceptance region evaluation, each supported by independent Alert and Danger setpoints.

The real value of the Bently Nevada 3500/42 125672-02 lies in its dual role as a protection device and a diagnostics data source. Machinery protection is executed by deterministic, hardware-level alarm comparison that drives 3500 relay modules independently of any host software, while diagnostic value is delivered through front-panel buffered transducer outputs and proportional 4–20 mA recorder signals that feed DCS, PLC, SCADA and System 1 condition-monitoring platforms. Fully aligned with API 670 requirements and suitable for SIL 2 protection architectures, the Bently Nevada 3500/42 125672-02 is a long-term, drop-in spare for turbine, compressor, pump, fan and generator trains where unplanned downtime is simply not an option.

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Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	3500/42 125672-02 (PWA 125672-02)
Manufacturer	Bently Nevada (Baker Hughes)
Product Type	4-Channel Proximitor/Seismic Monitor Module
Product Series	Bently Nevada 3500 Machinery Protection System
Input Channels	4, configured in two pairs (Ch.1–2 and Ch.3–4)
Compatible Transducers	Eddy-current proximity probes, velocity transducers, accelerometers, Velomitor sensors
Input Impedance	10 kΩ standard I/O (Proximitor and acceleration inputs)
Transducer Supply	-24 V DC
Sensitivity	Radial vibration, thrust, eccentricity: 3.94 mV/µm (100 mV/mil) or 7.87 mV/µm (200 mV/mil); differential expansion: 0.394 mV/µm or 0.787 mV/µm; acceleration: 10 mV/(m/s²); velocity: 20 mV/(mm/s) pk
Frequency Response	Direct filter user-programmable 4–4,000 Hz or 1–600 Hz; gap filter -3 dB at 0.09 Hz; 1X/2X vector filter, constant Q, -57.7 dB minimum stopband rejection
Recorder Output	+4 to +20 mA per channel, 550 Ω output impedance, 0–600 Ω load, 0 to +12 V DC compliance, 0.3662 µA/bit resolution
Buffered Outputs	One short-circuit-protected coaxial connector per channel
Power Consumption	7.7 W typical (supplied by 3500 rack backplane)
Alarm Accuracy	Within 0.13% of the desired value; Alert on every measured value, Danger on any two
Data Update Rate	100 ms or less
Operating Temperature	-30 °C to +65 °C
Storage Temperature	-40 °C to +85 °C
Humidity	Up to 95%, non-condensing
Dimensions (H x W x D)	241.3 mm x 24.4 mm x 241.8 mm (9.50 in x 0.96 in x 9.52 in)
Weight	0.91 kg (2.0 lb)
Rack Space	1 full-height front slot (monitor) plus 1 full-height rear slot (I/O module)
Compliance	API 670, CE, EMC EN 61000-6-2 / EN 61000-6-4, EN 61010-1, SIL 2 capable configurations

Main Features and Advantages

Universal four-channel input architecture:

The Bently Nevada 3500/42 125672-02 accepts proximity, velocity and acceleration signals on the same platform, which means one spare part number can protect a shaft-relative vibration point on a compressor bearing and a casing-absolute velocity point on a motor in the same rack. This universality dramatically reduces the spare-parts inventory a plant must carry, and it lets engineers re-purpose an installed channel simply by re-configuring it instead of buying a different card.

Paired-channel flexibility and measurement depth:

Because channels are programmed in pairs, the Bently Nevada 3500/42 125672-02 can run two different protection functions at once, for example radial vibration on channels 1–2 and axial thrust position on channels 3–4. Each active measurement supports its own Alert setpoint, while any two can carry Danger setpoints, giving protection engineers exactly the alarm depth that API 670 machinery trains demand without over-specifying the hardware.

Deterministic protection independent of host software:

Alarm evaluation happens on the card itself and is passed over the 3500 backplane to dedicated relay modules, so a trip decision never waits on a SCADA poll, an OPC server or an operator workstation. This architectural independence is what allows the Bently Nevada 3500/42 125672-02 to be specified in SIL 2 protection loops where response time and failure independence are audited requirements.

Diagnostic transparency for maintenance teams:

Each channel provides a front-panel buffered transducer output through a short-circuit-protected coaxial connector, so a portable analyzer can be clipped on for orbit plots, spectrum analysis or bump testing without breaking the protection loop. In parallel, the proportional 4–20 mA recorder output feeds trend data to the DCS, which turns the Bently Nevada 3500/42 125672-02 into a continuous source of condition-monitoring intelligence rather than a silent trip device.

Serviceability without process interruption:

Hot-swappable in a compliant 3500 rack, the module can be replaced under power once the affected channels are placed in Bypass mode, and front-panel OK, TX/RX and Bypass LEDs give immediate visual confirmation of card health, backplane communication and suppression state. Combined with -30 °C to +65 °C operating range and 95% non-condensing humidity tolerance, the Bently Nevada 3500/42 125672-02 is built for control rooms and field enclosures that are far from ideal.