Bentley 3300/20-01-01-02-01-00 Dual-channel Axial Displacement Monitor Detailed Product Description

I. Product Overview

The Bentley 3300/20-01-01-02-01-00 (Bently Nevada 3300/20) is a dual-channel axial displacement / thrust position monitoring module launched by Bently Nevada in the United States. It is a core component of the 3300 series mechanical protection monitoring system and complies with API 670 standards. It is widely used for continuous monitoring and protection of the axial displacement (thrust gap) of rotors in steam turbines, gas turbines, centrifugal compressors, large pump sets, etc. The model suffix "-01-01-02-01-00" encodes the hardware configuration, output / range / alarm / certification, etc. 

II. Core Functions

Dual-channel independent measurement: Receives input from two electrical eddy current probes (3300 series), real-time monitors the axial position of the rotor (thrust disk and thrust bearing gap), provides redundant measurement, can be configured with "AND logic" voting, reducing the risk of false tripping due to a single sensor failure.

Thrust bearing fault warning: Continuously tracks axial displacement changes, early identifies thrust bearing wear, axial load abnormalities, lubrication failure, etc., avoiding serious accidents such as shaft friction, rotor displacement.

Hierarchical alarm and tripping: Built-in 1 Alert relay + 2 Danger relays, supports two-level alarm + emergency tripping, action values can be set on-site.

Sensor circuit diagnosis: Real-time monitors the integrity of the probe, cable, and preamplifier, triggers "sensor failure" alarm when the circuit is open / short / beyond range, preventing erroneous measurement.

Analog output: Provides 4–20mA or 0–10VDC configurable transmitters, connects to DCS/PLC/SCADA systems, enabling remote monitoring and data recording.

Local display and configuration: Comes with LED digital display + keys, can locally view real-time displacement values, alarm / tripping status, circuit voltage, supports range, alarm values, output mapping, etc. parameters for on-site configuration.

III. Technical Specifications

Measurement channels: 2 independent electrical eddy current probe inputs (3300 series, -24VDC power supply).

Measurement range: Standard **±1.0mm (±40mil)**, can be adjusted through configuration (e.g., ±0.5mm, ±1.27mm).

Accuracy: At normal temperature, **±0.03mm (±1.1mil)**, full-scale error ≤ ±1%.

Resolution: 0.3662Å/bit.

Frequency response: DC–1kHz, suitable for static / low-speed axial displacement monitoring.

Input impedance: 10kΩ.

Relay output: 3 channels (1 Alert, 2 Danger), contact capacity 250VAC/3A, programmable normally open / normally closed.

Analog output: 1 channel (optional 4–20mA or 0–10VDC), isolated output, load capacity ≤ 500Ω.

Power supply: -24VDC ±10%, power consumption approximately 5.5W.

Operating temperature: 0℃–+60℃; storage temperature: -40℃–+85℃.

Environmental humidity: ≤95% (no condensation).

Dimensions (width × height × depth): 51mm×203mm×330mm (2.0"×8.0"×13.0"). Weight: approximately 1.4kg (3.0lbs).

Certification: CE, UL, CSA, complies with API 670. IV. Model Code Explanation (3300/20 - 01 - 01 - 02 - 01 - 00)

3300/20: Basic model, dual-channel shaft displacement monitor.

1st position (01): Input type, compatible with 3300 series eddy current probes.

2nd position (01): Measurement range, standard ±1.0mm.

3rd position (02): Output configuration, 4–20mA analog output.

4th position (01): Alarm / Trip logic, standard two-level alarm + trip.

5th position (00): Special functions / certifications, standard configuration.

V. Working Principle

Based on eddy current measurement principle: The probe (3300 series) is exposed to high-frequency alternating current, generating eddy currents with the metal shaft surface. The gap variation is converted into gap voltage (-24VDC linear range), and the signal is sent through the cable to 3300/20. The module converts the voltage signal into axial displacement value, compares it with the set alarm / trip values, triggers the corresponding relay action, and outputs an analog signal. The dual-channel design enables independent monitoring or redundant voting, enhancing system reliability.

VI. Installation and Configuration

Installation method: Standard 3300 series rack installation (19-inch cabinet, occupying 1 slot).

Probe installation: Axial alignment with the thrust disk, dual probes symmetrically arranged, gap set at the midpoint of the probe linear range (usually 0.5–1.0mm).

Configuration steps: Enter the configuration menu through panel buttons, set measurement range, alarm / trip values, analog output type, relay logic, channel voting mode, etc. Parameters are retained after power loss.

VII. Typical Applications

Steam Turbine / Gas Turbine: Monitoring rotor axial movement, protecting thrust bearings and shaft seals.

Centrifugal Compressor: Preventing excessive axial thrust causing rotor and stator friction.

Large Pump Sets / Fans: Monitoring axial position of the shaft system, avoiding mechanical failures.

Industrial Turbines / Expanders: Axial displacement protection, ensuring safe start-up, shutdown, and operation of the unit.

VIII. Advantages and Features

High reliability: Dual-channel redundancy + loop diagnosis, reducing false alarms / false trips.

High accuracy: Eddy current measurement + precise signal processing, meeting API 670 accuracy requirements.

Easy integration: Standard analog output + relay contacts, compatible with mainstream DCS/PLC systems.

Wide temperature range adaptation: Industrial-grade temperature range, suitable for harsh working conditions.

Local operation: Built-in display and buttons, allowing on-site configuration and fault troubleshooting without an upper computer.

IX. Supporting Components

Eddy Current Probe: 3300 series (e.g. 330101, 330102).

Preamplifier: 330180 series (-24VDC power supply).

High-frequency coaxial cable: 330130 series (extend signal transmission). 

Rack and Power Supply: 3300 series standard rack and -24VDC power module.