Bentley 3300/45 Dual-Channel Differential Expansion Monitoring Module - General Product Description

I. Product Overview

The Bentley 3300/45 is a dual-channel differential expansion (differential expansion) monitoring module within the 3300 series TSI (Turbo-Supercharger Instrumentation) of Baker Hughes (formerly GE Bentley Nevada). It is used for critical rotating machinery such as large steam turbines, gas turbines, centrifugal compressors, etc., to monitor the axial relative thermal expansion between the rotor and the casing in real time. This prevents severe accidents such as dynamic friction, axial rubbing, and unit tripping due to excessive thermal expansion differences.

The module adopts a 19-inch standard rack-mounted, hot-swappable design. It can be installed together with modules such as vibration, shaft displacement, casing expansion, and rotational speed of the 3300 series, sharing the backplane - 24V DC power supply and system bus. It is compatible with Bentley 3300 XL series eddy current probes (8/11/14/25/35mm), providing dual-channel independent measurement, redundancy or dual-point monitoring, and built-in dual-stage alarm relays. It complies with API 670 standards and is suitable for applications in thermal power, nuclear power, petrochemicals, etc., in high-temperature, high-pressure, and strong electromagnetic interference environments. 

II. Model Coding Rules (3300/45-AA-DD-BB-CC)

3300: Bechtel 3300 modular TSI system, unified rack, centralized power supply, hot-swappable architecture.

45: Function code, dual-channel differential expansion monitoring module, monitoring the relative thermal expansion of rotor - casing.

AA (Range / Measurement Range):

01 = ±5mm; 02 = 0–10mm; 03 = ±12.7mm (±0.5in); 04 = 0–25.4mm (0–1in); 05 = ±25.4mm (±1in); 06 = 0–20mm.

DD (Probe Specification / Sensitivity):

01 = 11mm, 100mV/mil; 02 = 14mm, 100mV/mil; 03 = 25mm, 20mV/mil; 04 = 35mm, sealed four-core.

BB (Relay Configuration):

01 = Dual relays (ALERT + DANGER); 03 = Four relays (dual-channel independent ALERT + DANGER).

CC (Certification Level):

01 = General industrial certification (API 670/CE/UL); 05 = Multi-party certification; 00 = No special certification.

The last 00: No safety barrier (not applicable in non-explosion-proof areas).

III. Core Functions

1. Dual-channel independent signal acquisition and differential expansion calculation

Two-channel independent input from dual-channel electro-vortex probes (A/B), each channel is completely independent, can redundantly measure to enhance reliability, or monitor the differential expansion at both ends / different positions of the rotor.

Built-in signal conditioning circuit, compatible with 3300 XL series probes, input impedance 10kΩ, supports -24V DC probe power supply (can be switched by shorting -18V DC).

Directly measure the gap change between the rotor axis and the casing, output the differential expansion value (including positive and negative directions), without the need for a slope surface, installation is simple.

2. High-precision differential expansion measurement

Range: ±5mm to ±25.4mm (±1in), 0–10mm to 0–25.4mm, programmable scaling.

Accuracy: ≤±0.1% full scale (25℃), resolution 0.01mm.

Frequency response: DC–10Hz, suitable for slow changes in thermal expansion.

3. Dual-stage alarm relay output

Each channel independently configured **ALERT (warning) + DANGER (dangerous)** relays, epoxy resin sealed, moisture-proof and dust-proof.

Contact specifications: 250V AC/5A, 30V DC/5A, capable of driving audible and visual alarms, DCS/PLC or interlock circuits.

Threshold: independently set for positive and negative directions, delay 0–10 seconds adjustable, supports lock / non-lock mode.

4. Front panel display and on-site configuration

Display: LCD digital window + status LED, real-time display of A/B channel differential expansion values; OK/ALERT/DANGER/BYPASS four groups of LED, intuitive display of operation, alarm, bypass, fault status.

Configuration: key-based on-site programming, no need for a host computer to set range, alarm threshold, delay, probe calibration parameters, channel enable/disable.

5. Isolated buffered signal output

Two independent isolated analog outputs (4–20mA or 0–10V selectable), electrical isolation ≥2500V AC from power supply and input signals.

Can send differential expansion signals to recorders, DCS, oscilloscopes, for data recording, trend analysis and fault tracing.

6. Comprehensive self-diagnosis and fault identification

24-hour monitoring: probe open circuit / short circuit, signal over-limit, power abnormality, module hardware failure, calibration abnormality. Distinguish between true differential expansion anomalies and sensor/loop failures. The panel LEDs clearly indicate the type of failure.

7. Strong anti-interference and system integration

Metal shielding enclosure, input/output/power isolation ≥ 2500V AC, suitable for strong electromagnetic environments.

Compatible with 3300 series system bus (Type A), can be connected to the System 1 platform, enabling remote configuration, data storage, and trend analysis.

IV. Technical Parameters

Measurement Parameters

Monitoring Channels: Dual channels (A/B independent input, dual-channel differential expansion measurement).

Compatible Sensors: 3300 XL series eddy current probes (11/14/25/35mm).

Measurement Range: ±5mm to ±25.4mm, 0–10mm to 0–25.4mm.

Measurement Accuracy: ≤ ±0.1% full scale (25℃), resolution 0.01mm.

Frequency Response: DC–10Hz.

Input Impedance: 10kΩ, input voltage - 24V DC.

Electrical Parameters

Power Supply: -24V DC (±10%), backplane power supply; supports short-circuit switching - 18V DC.

Power Consumption: Typical 1.5W, maximum ≤ 3W.

Relay Output: 2 SPDT (per channel 1), 250V AC/5A, 30V DC/5A.

Buffer Output: 2 isolated analog signals (4–20mA/0–10V selectable).

Isolation Strength: Input/output/power isolation ≥ 2500V AC.

Environmental and Mechanical Parameters

Operating Temperature: 0℃ to +65℃ (standard type).

Storage Temperature: -40℃ to +85℃.

Relative Humidity: 5%–95% (no condensation).

Installation Method: 19-inch standard rack slot, supports hot swapping.

Dimensions: 203mm (height) × 330mm (depth) × 51mm (width).

Weight: Approximately 1kg.

Protection Grade: IP20 (installed in control cabinet).

Certification and Compliance

Industry Standards: Compliant with API 670 Rotating Machinery Monitoring and Protection Standards.

Electromagnetic Compatibility: CE Certification, complies with EN 61000–6–2/4.

Safety and Environmental Protection: UL Certification, RoHS Compliance.

V. Structural Design

Module: Integrated compact frame structure, divided into front panel, internal circuit, and rear terminal block. Front panel integrates LCD display window, multiple groups of LED indicators and local operation keys, allowing real-time viewing of differential expansion values, probe status, and alarm information, and completing parameter configuration. Internal circuit includes dual-channel signal conditioning unit, differential expansion calculation circuit, independent alarm comparison circuit, relay drive circuit, and self-diagnosis unit, with clear functional zones, metal shielding layer suppressing interference. Rear terminal block is clearly zoned and marked, covering dual probe input, dual relay output, dual buffer output, power and communication interfaces, and wiring is convenient. Module and frame use gold-plated connectors, reliable contact, wear-resistant, and anti-oxidation, and the electrical connection is stable during hot swapping process.

VI. System Compatibility

Hardware Compatibility

Frame and Power Supply: Compatible with 3300 series 19-inch frame, power module, system monitoring module, can be mixed with vibration, shaft displacement, shell expansion, speed, etc. modules.

Sensors: Fully compatible with original 3300 XL series eddy current probes (11/14/25/35mm), same specification can be directly interchangeable.

Output Connection: Relay contacts connected to audible and visual alarms, DCS/PLC, interlock circuits; buffer output connected to recorders, oscilloscopes, external instruments.

Software Compatibility Configuration software: Compatible with the 3300 series dedicated configuration software, supporting remote parameter configuration, alarm logic editing, and firmware upgrade.

Monitoring software: Connected to the System 1 platform, achieving real-time data, trend analysis, fault recording, report generation, and remote access.

VII. Typical Application Scenarios

Power Industry: Monitoring of rotor-shaft misalignment in thermal power / nuclear power steam turbines, dual-channel redundant measurement to enhance reliability, tracking of thermal expansion differences during start-up, shutdown, and load increase processes, dual-level alarm linkage and interlock, preventing dynamic friction and axial rubbing.

Petrochemical Industry: Monitoring of rotor misalignment in large-scale process turbines and centrifugal compressors, tracking of thermal deformation under high-temperature conditions, simultaneous monitoring of dual measurement points, misalignment over-limit alarm, preventing production interruptions caused by equipment deformation and misalignment failure.

Metallurgical Industry: Monitoring of residual pressure turbines and large transmission turbines in blast furnaces, dual-channel independent monitoring of different positions' misalignment, monitoring of thermal expansion trends during start-up, shutdown, and load increase processes, early warning and linkage alarms, reducing the risk of equipment failure and downtime.

VIII. Installation and Maintenance Specifications

Installation Requirements

Frame Installation: Push the frame into the vacant slot of the 3300 frame smoothly, ensure that the rear connectors are fully engaged, and tighten the panel screws.

Probe Wiring: Connect the dual-probe cables according to the A/B channel markings, single-ended grounding the shield layer, suppressing electromagnetic interference.

Alarm Wiring: Distinguish ALERT and DANGER contacts, connect them to the alarm/interlock circuit, confirm the logic is correct.

Power On Configuration: Confirm that the -24V DC power supply is normal, set the range, alarm threshold, delay, and probe calibration parameters through the panel or software and save.

Probe Installation: Fix the probe to the shell, align it with the axial end face of the rotor, strictly control the installation gap (4mm linear zone), secure it firmly, and protect the cable.

Daily Maintenance

Inspection: Observe the panel display and LED status, confirm that the misalignment value is normal and there are no fault alarms; check that the terminals are not loose, oxidized, or overheated.

Calibration: Calibrate the accuracy annually using a standard displacement generator, in accordance with API 670 standards; regularly check the probe linearity.

Cleaning: Regularly clean the modules and frame of accumulated dust to ensure ventilation and heat dissipation, avoiding dust accumulation causing short circuits and poor heat dissipation.

Replacement of Spare Parts: When the module, probe, or cable is damaged, it must be replaced with the original and compatible parts from Bently, ensuring compatibility and measurement accuracy.

IX. Usage Precautions

This model is non-explosion-proof. It is strictly prohibited to install and use it in flammable and explosive hazardous areas; for explosion-proof conditions, select models with an intrinsic safety safety barrier.

It must be paired with the original Bently 3300 XL series eddy current probes (matching DD code specifications), and different specifications of probes cannot be mixed.

The installation gap and coaxiality of the probe must be strictly set according to the manual, and installation deviations will lead to signal distortion and increased measurement errors.

It is strictly prohibited to disassemble the module, modify the internal circuitry, or modify the probe calibration parameters without authorization, as such actions will cause equipment damage and invalid warranty.

Before wiring, maintenance, or replacing the module, cut off the power supply of the frame to prevent short circuits and electric shock accidents.

Alarm threshold and delay must be set in combination with the unit's process settings; improper parameters will result in frequent false alarms or warning failures.

The installation location should be far away from power frequency converters, transformers, high-voltage cabinets, etc., to reduce signal interference and ensure stable monitoring.