Description

The Bently Nevada 3500/20 is a high-precision Proximitor® Interface Module within the industry-leading 3500 Machinery Protection System, designed for continuous monitoring of radial vibration, axial position, and speed in critical rotating equipment. This dual-channel module conditions signals from eddy current proximity probes (e.g., 3300 XL 8mm), converting raw sensor data into calibrated vibration/position values while providing dynamic waveform outputs for diagnostics. Engineered for SIL 2 (IEC 61508) safety applications, the 3500/20 integrates with 3500 racks to deliver real-time machinery health data to DCS/PLC systems via 4–20mA outputs. Its patented Auto-Calibration™ technology ensures accuracy within ±1% across -35°C to +85°C environments, making it indispensable for gas turbines, compressors, and steam turbines in power generation and oil & gas sectors.

As the foundational input layer of the 3500 platform, the Bently Nevada 3500/20 supports ISO 10816/7919 standards compliance with configurable alarm thresholds, gap voltage monitoring, and built-in sensor diagnostics. Each channel operates independently with galvanic isolation, preventing cross-channel interference during fault conditions. The module’s non-volatile EEPROM retains calibration data during power loss, while its compatibility with System 1® software enables predictive maintenance analytics. For asset-intensive facilities requiring zero-false trips, the 3500/20 delivers uncompromised reliability in preventing catastrophic machinery failures.

Bently 3500/20

Technical Specifications

Parameter Name	Parameter Value
Product Model	3500/20
Manufacturer	Bently Nevada (Baker Hughes)
Product Type	Proximity Transducer Interface Module
Channels	2 (fully isolated)
Input Signal	Eddy Current Probes (5–24 VDC, -2 to -18 VDC gap voltage)
Output Signals	4–20mA (vibration/position), ±5V (dynamic waveform)
Accuracy	±1% full scale
Update Rate	1 ms per channel
Frequency Response	0.5 Hz to 12 kHz (±3 dB)
Operating Temperature	-35°C to +85°C (-31°F to 185°F)
Power Requirement	+15 VDC @ 70 mA, -15 VDC @ 70 mA (per channel)
Certifications	SIL 2, ATEX/IECEx Ex ia IIC T4 Gc, API 670
Mounting	3500 Series Rack (1 slot)

Main Features and Advantages

Intelligent Sensor Management: The 3500/20 continuously monitors probe health (gap voltage, coil resistance) and cable integrity. Its Auto-Calibration™ feature compensates for temperature drift without manual intervention, maintaining ±1% accuracy in extreme environments like compressor skids.

Advanced Diagnostics: Dual-level alarms with user-defined setpoints trigger on mechanical faults (unbalance, misalignment). Dynamic waveform outputs enable FFT analysis in System 1® software for early detection of bearing defects or blade-pass vibrations.

Safety-Certified Architecture: Each channel meets SIL 2 requirements with hardware-based fault detection. Redundant power inputs (available via 3500/15 PSU) ensure continuous operation during power transients.

Seamless Integration: Direct 4–20mA output to DCS simplifies loop integration. The module’s “OK-to-Monitor” relay logic prevents false trips during startup/shutdown. Front-panel LEDs provide instant channel status (Normal/Alarm/Bypass).

Application Field

The Bently Nevada 3500/20 is deployed where machinery failure carries severe consequences. In power generation, it monitors steam turbine shaft eccentricity during barring and detects generator stator rubs via axial position tracking. Offshore platforms rely on the 3500/20 for centrifugal compressor surge prevention, integrating with anti-surge valves through SIL 2 logic solvers.

For petrochemical plants, the module safeguards catalytic cracker expanders by tracking radial vibration trends predictive of fouling. Pipeline operators use it on electric motor-driven pumps to detect coupling misalignment before seal failure. In hydroelectric facilities, the Bently Nevada 3500/20 monitors Francis turbine guide bearing wear with custom linearization curves. Its hazardous-area certification (ATEX/IECEx) allows deployment in Zone 2 gas compressor packages.

Bently 3500/20

Related Products

3500/25: Gap Voltage Monitor Module for probe health validation.

3500/15: Redundant Power Supply for critical rack systems.

3500/42M: Relay Module for trip/shutdown logic.

3500/92: Communication Gateway for Modbus TCP/IP integration.

3300 XL 8mm Proximity Probes: Industry-standard sensors for 3500/20 inputs.

3500/22M: TMR Version for SIL 3 applications.

3500/32: 4-Channel Vibration Monitor (economical alternative).

System 1® Software: Predictive analytics platform for 3500/20 data.

Installation and Maintenance

Pre-installation preparation: Verify rack slot compatibility (3500/01 or /02 frame). Discharge static before handling. Set DIP switches for probe type (5mm/8mm) and scaling (mV/µm or mV/mil). Ensure probe gap voltage is within -2 to -18 VDC range prior to power-up.

Maintenance recommendations: Perform quarterly “Sensor OK” validation via System 1®. Calibrate using TK-3E Proximitor® Tester every 24 months. Check terminal tightness (0.5 N·m torque) annually. Replace modules only with identical firmware revisions. For firmware updates, use 3500 Rack Interface Module (3500/90). Monitor “Dynamic Peak-Peak” values for trend deviations indicating mechanical degradation.