Bently Nevada 3500/45 176449-04 Position Monitor

3500/45 Position Monitor is a four-channel position monitoring module under the 3500 Machinery Protection System, serving as a critical component of the 3500 series. It is specifically designed to accept signals from various position sensors, including proximity transducers, rotary position transducers (RPTs), DC linear variable differential transformers (DC LVDTs), AC linear variable differential transformers (AC LVDTs), and rotary potentiometers. Through high-precision signal conditioning and processing, the monitor enables real-time monitoring of key machine position parameters and provides multi-level alarm functions to ensure safe and reliable operation of the unit.

The 3500/45 consists of a fixed front card (176449-04) and four types of I/O rear cards (see the Ordering page for details). The front card can operate with any of the rear cards.

The 3500/45 monitor offers highly flexible configuration capabilities. Users can independently program each channel via the 3500 Rack Configuration Software, making it suitable for various industrial applications, including power generation, oil and gas, chemical processing, marine propulsion, and more.

Key Features
The 3500/45 monitor supports the following position monitoring functions:

• Axial (Thrust) Position

• Differential Expansion

• Standard Single Ramp Differential Expansion

• Non-standard Single Ramp Differential Expansion

• Dual Ramp Differential Expansion

• Complementary Input Differential Expansion (CIDE)

• Case Expansion

• Valve Position

The four channels of the monitor operate in pairs, allowing two different monitoring functions to be performed simultaneously. For example, channels 1 and 2 can monitor axial position, while channels 3 and 4 can monitor differential expansion or valve position.
The monitor also supports multiple sets of alarm parameters. Users can configure Alert and Danger setpoints and delay times for each channel to meet protection requirements under different operating modes.

Working Principle
The core workflow of the 3500/45 monitor includes four stages: signal input, conditioning, parameter calculation, and alarm judgment.

1. Signal Input
   The monitor accepts analog signals from various sensors. Input impedance varies depending on the sensor type and I/O module:

   The power supply method also varies by sensor type:

• Proximity Transducer/RPT: -24 Vdc

• DC LVDT: +15 Vdc

• AC LVDT: 2.3 Vrms, 3400 Hz sine wave

• Rotary Potentiometer: -12.38 Vdc

• Proximity Transducer or RPT: 10 kΩ

• DC LVDT: 1 MΩ

• AC LVDT: 137 kΩ

• Rotary Potentiometer: 200 kΩ

2. Signal Conditioning
   Input signals are processed through amplification, filtering, etc., and converted into engineering values (e.g., μm, mm, degrees). The system provides multiple filtering methods:

   Signal conditioning also includes sensitivity adjustments, such as:

• Thrust Position: 3.94 mV/μm or 7.87 mV/μm

• Differential Expansion: 0.394 mV/μm or 0.787 mV/μm

• Valve Position (Rotary Potentiometer): 41 mV/degree or 140/70/50 mV/degree

• Direct Filter: -3 dB cutoff frequency at 1.2 Hz

• Gap Filter: -3 dB cutoff frequency at 0.41 Hz

3. Parameter Calculation
   Based on the configured monitoring type, the module calculates the following Measured Variables:

• Thrust Position: Direct, Gap

• Differential Expansion: Direct, Gap

• Ramp Differential Expansion: Composite, Direct, Gap

• Complementary Input Differential Expansion (CIDE): Composite, Direct, Gap

• Case Expansion: Composite, Direct, Position

• Valve Position: Direct, Position

4. Alarm Judgment
   Each measured variable can be set with Alert and Danger alarm points. Alarm delays are configurable:

• Alert Delay: 1–60 seconds (in 1-second intervals)

• Danger Delay: 0.1 seconds or 1–60 seconds (in 0.1-second intervals)
  Alarm accuracy is as high as ±0.13% of the set value, ensuring timely and reliable response.

Outputs & Communication

• Front Panel Indicators: Equipped with OK (operational status) and TX/RX (communication status) LEDs.

• Buffered Transducer Outputs: One coaxial connector per channel, with short-circuit protection.

• Recorder Outputs: 4–20 mA current signal, proportional to full scale, independent output per channel (except for Ramp Differential Expansion and CIDE). Short circuits do not affect operation.

• Communication Interface: Communicates with other modules in the 3500 rack via the backplane, supporting remote monitoring and data integration.

Technical Characteristics

• High-Precision Measurement: Typical accuracy is ±0.33% of full scale, with a maximum of ±1%.

• Multi-Sensor Compatibility: Supports various sensors, including proximity transducers, RPTs, DC/AC LVDTs, and rotary potentiometers.

• Flexible Configuration: Each channel pair can be independently configured, supporting multiple sets of alarm parameters.

• Advanced Signal Conditioning: Includes direct and gap filtering to adapt to different dynamic response requirements.

• Environmental Adaptability: Operating temperature range from -30°C to +65°C, suitable for harsh industrial environments.

• Safety Certifications: Complies with FCC, EMC, LV Directive, RoHS, ATEX, IECEx, CSA, and other international standards for use in hazardous areas.

Physical Characteristics

• Monitor Module (Main Board):
  Dimensions: 241.3 mm × 24.4 mm × 241.8 mm
  Weight: 0.91 kg

• I/O Modules:
  Dimensions: 241.3 mm × 24.4 mm × 99.1 mm
  Weight: 0.20 kg

• Rack Space Requirements: Occupies 1 front slot (monitor module) and 1 rear slot (I/O module).

Applications
The 3500/45 Position Monitor is widely used for critical mechanical equipment in the following industrial fields:

• Power Plants: Axial position and differential expansion monitoring for steam turbines and gas turbines

• Oil & Gas: Shaft displacement and valve position monitoring for compressors and pumps

• Chemical Processing: Mechanical protection for reactors and centrifuges

• Marine Propulsion: Propulsion shaft line position monitoring

• Industrial Drives: Axial displacement and expansion monitoring for large motors