Product Short Description

18745-03 is a high-precision eddy-current proximity transducer system manufactured by Bently Nevada (Baker Hughes). It is designed for non-contact measurement of static and dynamic distances between the probe tip and conductive targets, primarily used for shaft position, radial vibration, and axial displacement monitoring in rotating machinery. The system comprises a proximity probe with integral coaxial cable, an extension cable, and the 18745-03 proximitor unit. It delivers a DC voltage output proportional to the gap, supporting both static position and dynamic vibration measurements, and fully complies with the API 670 Machinery Protection Standard.

Description

Core Measurement Specifications

  • Standard Measuring Ranges: 5 mm & 8 mm gap options
  • Linear Measurement Range: Up to 80 mils (2 mm) within the working gap
  • Scale Factor: 200 mV/mil (7.87 V/mm)
  • Output Signal: DC voltage proportional to gap, typical -18 VDC to -24 VDC full scale
  • Frequency Response: 0 Hz (DC) to 10 kHz (+0/-3 dB)
  • Measurement Principle: Eddy-current proximity sensing, non-contacting gap-to-voltage conversion

Electrical Specifications

  • Power Supply: -18 VDC to -24 VDC (loop-powered or dedicated supply)
  • Input Impedance: > 10 MΩ per lead
  • Output Isolation: Galvanic isolation between input and output circuits
  • Short-Circuit Protection: Integrated overcurrent protection
  • Noise Immunity: Meets industrial EMC standards for harsh environments

Mechanical & Physical Specifications

  • Probe Thread: Standard 1/4-28 UNF thread mounting
  • Probe Tip Material: High-grade stainless steel for corrosion and wear resistance
  • Probe Diameter: 5 mm & 8 mm variants (probe tip size)
  • Probe Length: Customizable (integral cable length matched with extension cable)
  • Overall Dimensions (Proximitor Unit): 132 mm × 114 mm × 102 mm (H × W × D)
  • Net Weight (Proximitor Unit): 0.23 kg
  • Shipping Weight: 1.3 kg

Environmental Specifications

  • Operating Temperature: -51 °C to +100 °C
  • Storage Temperature: -55 °C to +120 °C
  • Relative Humidity: 100% non-condensing
  • Protection Rating: IP67 (probe) / IP65 (proximitor unit)
  • Vibration Resistance: 10–2000 Hz, 10 g acceleration

Certifications & Compliance

  • API 670 Machinery Protection Standard Compliance
  • CE Conformity
  • CSA NRTL/C Certification
  • RoHS Compliant (lead-free materials)

Core Functional Features

  1. Non-Contact High-Precision Measurement

    No physical contact with the target, eliminating wear and tear. Delivers ±0.1% full scale accuracy for both static position and dynamic vibration measurements, ensuring long-term stability.

  2. Dual-Range Compatibility (5 mm & 8 mm)

    Supports two standard gap ranges to accommodate different machinery installation spaces and measurement requirements, providing flexibility for various applications.

  3. Wide Temperature Operation

    Operates reliably in extreme temperatures from -51 °C to +100 °C, making it suitable for harsh industrial environments such as power plants, petrochemical plants, and aerospace equipment.

  4. High-Frequency Response

    0 Hz to 10 kHz frequency response accurately captures high-frequency vibration signals, enabling early fault detection and comprehensive machinery health monitoring.

  5. API 670 Compliance

    Fully meets the international API 670 standard for machinery protection, ensuring compatibility with major monitoring and control systems (e.g., Bently 3500/3300 systems) and meeting project acceptance requirements.

  6. Modular System Design

    Consists of a probe, extension cable, and proximitor unit, allowing for easy replacement and maintenance. Probes and cables of the same length are fully interchangeable, reducing inventory costs.

  7. Robust Environmental Resistance

    The probe features a stainless steel construction with IP67 protection, resistant to dust, water, and corrosive gases. The proximitor unit is sealed and potted for enhanced EMI/EMC performance.

  8. Integrated Signal Conditioning

    The proximitor unit integrates high-frequency excitation, signal amplification, linearization, and filtering, simplifying system integration and reducing external component requirements.


Main Application Scenarios

18745-03 is widely used for condition monitoring and protection of critical rotating machinery in various industries:
  • Power Generation: Steam turbines, gas turbines, generators, and auxiliary equipment
  • Petrochemical Industry: Centrifugal compressors, pumps, fans, and process machinery
  • Oil & Gas: Offshore platforms, wellhead equipment, and pipeline compressors
  • Aerospace & Aviation: Jet engines, gas turbines, and aerospace test equipment
  • Marine Engineering: Ship propulsion systems, generators, and thrusters
  • General Manufacturing: Large motors, fans, blowers, and reciprocating machinery

System Composition & Installation Notes

Standard System Components

  1. Proximity Probe: Integral coaxial cable (custom length)
  2. Extension Cable: Matches probe cable length (5 m / 7 m / 9 m options)
  3. Proximitor Unit (18745-03): Signal processing and output unit

Key Installation Requirements

  • Target Material: AISI 4140 steel or equivalent conductive material (calibrated for steel targets)
  • Gap Setting: Maintain a working gap within the linear range (0.5–2.0 mm for 5 mm range, 1.0–3.0 mm for 8 mm range)
  • Mounting Thread: Use standard 1/4-28 UNF thread for probe installation
  • Cable Routing: Avoid sharp bends and strong electromagnetic interference sources
  • Grounding: Ensure reliable grounding to improve measurement stability

Model Definition Explanation

  • 18745-03: Official part number for the 7200 Series 5 mm & 8 mm Proximity Probe Transducer System
  • 7200 Series: Bently Nevada’s product line for high-precision proximity transducers
  • 5 mm / 8 mm: Nominal measuring range (gap) options for the system

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