Bently 3300/20-02-01-02-00-00 Dual Channel Thrust Position Monitor (Product Description)

I. Product Overview

The Bently 3300/20-02-01-02-00 is a dual-channel thrust position monitoring module within the 3300 series mechanical protection system of Bently Nevada (now part of GE). It is used for continuous monitoring of the axial displacement (thrust gap) of rotating machinery rotors, providing early warnings for major faults such as thrust bearing failure, axial movement, and dynamic friction, and is widely applied in key units such as steam turbines, centrifugal compressors, gas turbines, and large pump sets for protection and condition monitoring.

Code meanings of the model:

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

02: Range ±30 mil (±0.762 mm);

01: Compatible with 3300/7200 series eddy current preamplifiers, sensitivity 200 mV/mil;

02: Alarm relay is sealed type;

00: No hazardous relay output (only retains warning, no hard contact for tripping);

00: No safety barrier (non-ia type, used in non-explosion-proof areas).

II. Working Principle

Based on the eddy current measurement principle, it is equipped with 3300/7200 series eddy current probes and preamplifiers: The probe is aligned with the thrust disk of the rotor, converting the axial displacement variation into high-frequency impedance changes, and the preamplifier linearly converts them into 0–24 VDC gap voltage signals and sends them to the monitor. The module independently samples, filters, and calculates the dual-channel signals, and outputs the axial displacement value in real time; compared with the user-defined alarm threshold, if it exceeds the limit, it drives the alarm relay to act; this model has no hazardous trip relay, only providing warning without directly triggering shutdown. The dual channels support redundant installation and can be configured with "AND/OR" logic to reduce false alarm risks, in line with API 670 standards.

III. Core Functions

Dual-channel independent monitoring: 2 completely independent axial displacement measurement channels, which can be separately configured with ranges and alarm thresholds; a single-channel failure does not affect the normal operation of the other channel, improving the monitoring continuity.

Precise measurement and real-time display: The measurement accuracy reaches ±0.33% of the full scale (typical), with a maximum error of ≤±1% of the full scale; frequency response DC–1 kHz, covering low-speed to high-speed rotating machinery; the front panel displays the displacement value (mil/mm) and channel status in real time.

Single-level warning protection: Equipped with a sealed-type warning relay (Alert), no hazardous (Danger) relay; customizable alarm thresholds; when the displacement exceeds the limit, it triggers the relay output, used for DCS/PLC alarms or audible and visual prompts, without directly tripping.

Standard signal output: Provides 4–20 mA analog output (optional 0–10 VDC), linearly corresponding to the full range of displacement, suitable for various recorders, DCS/PLC systems, for remote monitoring and data collection.

Comprehensive self-diagnosis: Real-time monitoring of probe circuit breakage / short circuit, preamplifier signal abnormalities, module power supply and internal circuit faults; when a fault occurs, it locks the output and lights the front panel fault indicator, avoiding false alarms.

IV. Technical Parameters

Model: 3300/20-02-01-02-00-00

Type: Dual-channel thrust position monitor

Measurement parameters: Rotor axial displacement (thrust position)

Range: ±30 mil (±0.762 mm, code 02)

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

Measurement accuracy: ±0.33% of the full scale (typical), ±1% of the full scale (maximum) Frequency response: DC–1 kHz

Number of channels: 2 independent inputs

Alarm configuration: 1 sealed warning relay (code 02), no hazardous relay (code 00)

Analog output: 4–20 mA (default)/0–10 VDC (optional), accuracy ±0.1%

Probe power supply: -24 VDC (provided by the module internally)

Operating power: 110/220 VAC, 50/60 Hz

Power consumption: ≤5.5 W (typical)

Operating temperature: 0℃～+60℃

Storage temperature: -40℃～+85℃

Humidity: 5%–95% (no condensation)

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

Weight: Approximately 1.1 kg

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

Installation method: Standard 19-inch rack slot installation of the 3300 series

V. Model Configuration Description

3300/20: Dual-channel thrust position monitor (core function)

02: Full-scale ±30 mil (±0.762 mm)

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

02: Alarm relay is epoxy resin sealed type (dustproof, moistureproof, vibration-resistant)

00: No hazardous relay (only warning, no trip output)

00: No safety barrier (non-explosion-proof design, for general industrial environments)

VI. Application Scenarios

Power industry: Thermal power / nuclear power turbine, generator rotor axial displacement warning monitoring;

Petroleum industry: Centrifugal compressor, ethylene / propylene unit, large pump set 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' non-tripping protection.

VII. Installation and Maintenance Tips

Installation: Standard 3300 rack vertical slot installation, ensure good heat dissipation; probe installed above the thrust disk, initial gap controlled at 0.5–2.5 mm, avoid oil and water vapor erosion.

Connection: Connect the preamplifier and the monitor with high-frequency coaxial cable, length ≤5 m; Analog output uses shielded twisted pair, single-ended grounding, keep away from power cables to reduce electromagnetic interference.

Calibration: At least calibrate once a year, use a standard displacement simulator to verify the range, accuracy and alarm threshold, ensure error ≤±1% of full scale.

Maintenance: Regularly check probe gap, cable insulation and relay contacts; prioritize troubleshooting the probe circuit, preamplifier power supply and signal status when self-diagnostic alarms occur.

VIII. Advantages and Features

High reliability: Sealed relay, wide temperature design, anti-electromagnetic interference, suitable for harsh industrial environments;

Safe warning design: No hard trip contacts, only provide warning signals, avoid machine stoppage affecting continuous production;

Easy integration: Standard 4–20 mA signal output, compatible with mainstream DCS/PLC, quick access to existing systems;

Redundant safety: Dual-channel independent monitoring + self-diagnosis, effectively reduce false alarms / missed alarms risk;

Long life: Industrial-grade components, no wear parts, normal maintenance life ≥10 years.