Bentley 3300/20 Dual-Channel Axial Displacement (Thrust Position) Monitor Detailed Product Description

I. Product Overview

The Bentley 3300/20 is a dual-channel thrust/axial displacement monitoring module within the Bently Nevada 3300 series of rotating machinery protection system. It is specifically designed for continuous monitoring and protection of the rotor's axial position in critical rotating equipment, fully adhering to the API 670 industrial standard. The equipment adopts a standard 19-inch rack-mounted modular structure, with a single slot for installation, and can be directly integrated into the 3300 series dedicated rack, seamlessly matching with the series' electromagnetic eddy current probes, preamplifiers, extension cables, and power supply components. It is widely used in steam turbines, gas turbines, centrifugal compressors, large pump sets, industrial turbines, expanders, and other equipment in the power, petrochemical, metallurgical, oil and gas, etc. industries. Its core function is to monitor the axial movement of the rotor and the thrust bearing clearance in real time, achieving fault warning, safety interlock, and shutdown protection, making it the core device for shaft system safety protection of the unit.

II. Model Coding System

3300/20 is the main product model, defining the equipment type as a dual-channel axial displacement/thrust position monitor. The suffix consists of 6 two-digit/letter segments, sequentially defining the input specification, range, analog output, alarm logic, additional functions, and hardware version. Different coding combinations correspond to customized configurations, suitable for different on-site conditions and system integration requirements.

1st digit: Input type, compatible with the 3300 series standard electromagnetic eddy current sensor system (including probe, preamplifier, extension cable);

2nd digit: Measurement range, standard is ±1.0mm, configurable to ±2.0mm to ±5.0mm;

3rd digit: Analog output, selectable 0-10VDC, 1-5VDC, or 4-20mA;

4th digit: Alarm logic, defines warning, danger, and trip relay configuration and channel voting rules;

5th digit: Additional functions, including sensor circuit diagnosis, fault modes, communication interfaces, etc.;

6th digit: Hardware version and certification, such as CE, UL, CSA certification configurations.

III. Core Functions

1. Dual-channel Independent Monitoring

Equipped with two completely independent measurement channels, capable of simultaneously connecting two sets of electromagnetic eddy current sensors, synchronously collecting axial displacement data of the rotor, supporting redundant monitoring and channel voting logic. A single channel failure does not affect the overall protection function, significantly reducing false alarms and false trips.

2. Precise Axial Displacement Monitoring

Real-time capture of rotor axial movement, thrust bearing wear, axial load abnormalities, lubrication failure, rotor force imbalance, etc., providing early warnings of rotor friction, shaft system damage, unplanned shutdown, etc., ensuring the safety of the unit operation.

3. Hierarchical Alarm and Interlock Protection

Integrated with 1 Alert relay (Alert) + 2 Danger trip relays (Danger), the warning value, danger value, and trip value can be configured locally. The relay contacts have a rated 250VAC/3A, supporting normally open / normally closed settings, meeting the requirements of unit hierarchical protection and emergency shutdown logic.

4. Sensor Circuit Self-Diagnosis

Real-time inspection of the sensing circuit composed of the probe, extension cable, and preamplifier, automatically identifying open circuits, short circuits, signal over-range, probe failure, etc., triggering dedicated fault alarms to avoid invalid monitoring and false interlocks, enhancing system reliability.

5. On-site Configuration and Status Display

Front panel equipped with an LED digital display and operation keys, allowing on-site viewing of real-time displacement values, loop voltage, alarm/fault status; Supports full parameter configuration including measurement range, alarm threshold, output parameters, relay mode, voting logic, etc., with automatic storage and no data loss upon power failure.

6. Standard analog output

Each channel provides independent isolated analog output, selectable from 0-10VDC, 1-5VDC (voltage) or 4-20mA (current), corresponding to the linear measurement range, directly connectable to DCS, PLC, SCADA, etc., for remote data acquisition, trend recording and centralized monitoring.

IV. Working Principle

Based on the non-contact eddy current measurement principle, 3300 series eddy current probes are connected with high-frequency alternating current. When the probe approaches the metal thrust disk, the metal surface induces eddy currents, and the gap change between the probe and the thrust disk directly alters the eddy current intensity and the equivalent impedance of the probe. The weak signal corresponding to the gap is transmitted through the extension cable to the preamplifier, which completes signal amplification, shaping, and temperature compensation, and outputs a linear DC voltage signal to the 3300/20 module. The internal circuit of the module converts the voltage signal into precise axial displacement values. On one hand, it compares with the preset threshold to drive the relay to output alarm / trip interlock signals; on the other hand, it converts the displacement value into a standard analog signal for external output. The two channels operate independently and cooperate with the voting logic to achieve redundant monitoring and reliable protection.

V. Main Technical Parameters

1. Measurement System

Channels: 2 independent eddy current signal inputs;

Compatible sensors: 3300/7200/3300 XL series eddy current probes (8mm/11mm etc.);

Input impedance: 10kΩ;

Sensitivity: Programmable 8V/mm (200mV/mil) or 4V/mm (100mV/mil).

2. Measurement Performance

Standard range: ±1.0mm (configurable ±2.0mm to ±5.0mm);

Accuracy: Full-scale error at normal temperature ≤ ±1%, single-point accuracy ±0.03mm;

Frequency response: DC to 1kHz;

Resolution: Satisfies high-precision industrial monitoring requirements.

3. Output Characteristics

Analog output: Each channel independently selectable, 0-10VDC, 1-5VDC (isolated, output impedance 100Ω) or 4-20mA (isolated);

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

4. Electrical and Environmental

Power supply: -24VDC (±10%);

Power consumption: Typical 5.5W;

Operating temperature: 0℃ to 60℃;

Storage temperature: -40℃ to 85℃;

Relative humidity: ≤95% (no condensation);

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

5. Mechanical Characteristics

Structure: Standard 19-inch rack, single slot;

Weight: Approximately 1.4kg;

Protection: Industrial-grade anti-vibration, anti-EMI design, suitable for complex working conditions.

VI. Installation and System Configuration

1. Rack Installation

Directly mount on the 3300 series dedicated rack, single slot fixed, convenient installation and disassembly, compatible with industrial control room standard cabinet layout, neat wiring.

2. Sensor Installation

Two eddy current probes are axially aligned with the rotor thrust disk, symmetrically arranged, the initial gap is set at the midpoint of the sensor's linear range to ensure effective measurement throughout.

3. On-site Configuration

After power-on, enter the configuration menu through the panel buttons, sequentially set the measurement range, warning / danger / trip threshold, analog output correspondence, relay contact type, channel voting logic, fault alarm mode, etc. Parameters are automatically saved, no upper-level software required to complete on-site debugging.

4. Wiring Specifications It is divided into power connection (-24VDC), sensor signal connection (probe / preamplifier), relay interlock connection, analog output connection. The polarity and signal type should be strictly distinguished according to the body markings to ensure reliable connection.

VII. Typical Application Scenarios

Power industry: Steam turbine generator sets, gas turbine generator sets, monitor the axial movement of the rotor, protect thrust bearings, shaft seals and flow components;

Petrochemical industry: Centrifugal compressors, process turbines, expanders, prevent excessive axial thrust causing rotor - stator scraping and blade damage;

Metallurgical industry: Large fans, booster fans, industrial pump sets, monitor the axial position of the shaft system, avoid bearing burnout and shaft system instability;

Other fields: High-speed pumps, turbomachinery, cover the entire process of axial displacement protection for unit start-stop, load regulation, and steady operation.

VIII. Product Advantages

1. High-reliability redundant design

Dual-channel independent monitoring + loop self-diagnosis, hardware redundancy + software fault-tolerance, significantly reduce the false action caused by single-point failure, ensure continuous operation of the unit.

2. High precision and long-term stability

Electro-vortex non-contact measurement without mechanical wear, combined with high-precision signal processing circuit, precise measurement, small long-term drift, suitable for industrial high-precision monitoring requirements.

3. Flexible system integration

Multiple types of analog output + multiple-channel relay interface, strong versatility, seamless connection with mainstream industrial control systems, low integration difficulty.

4. Industrial-grade environmental adaptability

Wide temperature and humidity range, anti-vibration, anti-EMI design, can operate stably in harsh working conditions such as power plants, chemical plants, and metallurgy for a long time.

5. Convenient operation and maintenance

Full-function local display and configuration, on-site can quickly view status, judge faults, modify parameters, daily maintenance is efficient; modular design facilitates spare parts replacement, shortens downtime.

IX. Supporting Components

It needs to work in coordination with the following components to form a complete monitoring system:

Electro-vortex probe: 3300 series (such as 8mm/11mm specifications), select according to installation space and range;

Preamplifier: 330180 series, supplies power to the probe and pre-processes the signal;

Extension cable: 330130 series high-frequency coaxial cable, extends the signal transmission distance;

System frame: 3300 series standard frame, provides installation support;

Power module: -24VDC dedicated power supply, supplies power to the monitor and sensing system.