Bently 3300/20-02-01-02-03-02 Dual-channel Axial Displacement Monitor (Product Description)

I. Product Overview

The Bently 3300/20-02-01-02-03-02 is a dual-channel thrust position monitoring module within the 3300 series mechanical protection system of Bently Nevada. It is primarily used for continuous monitoring of the axial displacement (thrust gap) of rotating machinery, providing early warnings for thrust bearing failures and axial movement, and is widely applied in key units such as steam turbines, centrifugal compressors, and large pump sets for protection and condition monitoring. The codes in the model number represent: 02 = range ±30mil (±0.762mm), 01 = compatible with 3300/7200 preamplifier (200mV/mil), 02 = seal relay, 03 = danger relay configuration, 02 = no safety barrier.

II. Working Principle

Based on the eddy current measurement principle, it is equipped with 3300 series eddy current probes and preamplifiers: The probe senses the surface of the rotor thrust disk, converting the gap changes into high-frequency voltage signals, which are then amplified and shaped by the preamplifier to a standard 0–24VDC signal and sent to this monitor; The module independently processes the dual-channel signals and calculates the axial displacement value in real time, comparing it with the preset alarm/trigger threshold, driving the relay to output a switch quantity protection signal, and simultaneously outputting an analog signal for DCS/PLC collection. The dual-channel design supports redundant probe installation, and combined with "AND/OR" logic, it can effectively avoid false actions and meet the API 670 standard protection requirements.

III. Core Functions

Dual-channel independent monitoring: Synchronously collects 2 axial displacement signals, can independently configure the range, alarm/trigger threshold, and supports independent operation of the other channel when one channel fails, improving monitoring reliability.

Precise measurement and display: Real-time displays the axial displacement value (unit mil/mm), with an accuracy of **±0.33% of full scale (typical)**, maximum error ≤ ±1% of full scale, frequency response DC–1kHz, suitable for low-speed to high-speed rotating machinery.

Multi-level alarm protection: Equipped with sealed relays, including 1 alert (Alert) and 2 danger (Danger) outputs, customizable thresholds, triggering alarms or unit tripping when the displacement exceeds the limit, preventing severe accidents such as thrust disk friction and bearing burnout.

Signal output and compatibility: Provides 4–20mA analog output (configurable 0–10VDC), compatible with various recorders, DCS/PLC systems; Supports seamless connection with 3300 series racks, power supplies, and preamplifiers, compatible with 3300/7200 series probes (8mm/11mm specifications).

Self-diagnosis and fault identification: Real-time monitors the probe circuit, preamplifier signals, and internal circuits of the module. When the probe is disconnected, short-circuited, or the signal exceeds the range, it automatically triggers a fault alarm and locks the output to avoid false protection.

IV. Technical Parameters

Model: 3300/20-02-01-02-03-02

Type: Dual-channel thrust position monitoring module

Range: ±30mil (±0.762mm, code 02)

Sensor compatibility: 3300/7200 eddy current preamplifier, sensitivity 200mV/mil (code 01)

Measurement accuracy: ±0.33% of full scale (typical), ±1% of full scale (maximum)

Frequency response: DC–1kHz

Channel quantity: 2 independent inputs

Alarm relays: Sealed type (code 02), 1 alert + 2 danger

Analog output: 4–20mA (default)/0–10VDC (optional) Power Supply: -24VDC (for probes / preamplifiers), 110/220VAC (for module operation)

Power Consumption: ≤ 5.5W (typical)

Operating Temperature: 0℃ - +60℃

Storage Temperature: -40℃ - +85℃

Humidity: 5% - 95% (no condensation)

Dimensions: 165mm × 114mm × 64mm (width × height × depth)

Weight: Approximately 1.1kg

Certifications: CE, UL, CSA, compliant with API 670 standard

Installation Method: Standard 3300 rack installation

VII. Model Configuration Description

3300/20: Basic model, dual-channel thrust position monitor

02: Full-scale ±30mil (±0.762mm)

01: Compatible with 3300/7200 preamplifier, 200mV/mil

02: Alarm relay is sealed type

03: Hazard relay configuration (2 channels)

02: No safety barrier (intrinsic safety type available)

VIII. Application Scenarios

Power Industry: Thermal power / nuclear power turbine, generator rotor axial displacement monitoring and protection

Petrochemical Industry: Centrifugal compressor, propylene machine, large pump group thrust bearing condition monitoring

Metallurgical Industry: Blast furnace blower, sintering main exhaust fan, etc. high-speed rotating equipment

General Machinery: Large motors, gas turbines, screw compressors, etc. key units

IX. Installation and Maintenance Tips

Installation: Standard 3300 rack slot installation, vertical placement; probe installed above the thrust disk, gap controlled within 0.5 - 2.5mm, avoid oil contamination, water vapor erosion.

Connection: Preamplifier and monitor connected by high-frequency coaxial cable, length ≤ 5m; analog output uses shielded twisted pair, reliable grounding, avoid electromagnetic interference.

Calibration: Calibrate once a year, use standard displacement simulator to verify range, accuracy and alarm threshold, ensure measurement error ≤ ±1%.

Maintenance: Regularly check probe gap, cable insulation and relay contacts, prioritize troubleshooting the probe circuit and preamplifier status when self-diagnostic alarm occurs.