Bently Nevada 3300/45

Bently Nevada 3300/45

Product Overview The 3300/45 is a dual-channel differential expansion monitor designed for continuous measurement of axial thermal growth between rotating machinery rotors and their casings. Differential expansion monitoring is essential for large steam turbines and generators where thermal expansion during startup and shutdown can create axial clearance changes that threaten internal components. This monitor provides two independent channels, each capable of measuring the magnitude and direction of differential expansion using proximity probe transducers observing rotor collars.

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Description

Bently Nevada 3300/45

Technical Specifications

Parameter Specification
Channels Two independent differential expansion channels
Input Proximity probe transducer signals
Full-Scale Range Options 0–5 mm, 0–10 mm, 0.25–0–0.25 in, 0–0.5 in, 10–0–10 mm, 0–20 mm, 0.5–0–0.5 in, 0–1.0 in
Transducer Input Options 25 mm, 35 mm, or 50 mm proximity probes
Input Impedance 10 kΩ
Alarm Setpoints Four per channel (two over, two under)
Input Voltage 24 VDC
Output Signal 4–20 mA recorder output
Operating Temperature 0°C to +65°C
Dimensions 16 cm × 16 cm × 12 cm
Weight 0.8 kg
Origin USA

Functional Features

  • Provides two channels of continuous differential expansion monitoring
  • Monitors both magnitude and direction of thermal expansion
  • Offers four alarm setpoints per channel (two over, two under)
  • Allows Channel B to be turned OFF for single-location measurements
  • Includes front-panel LCD display with magnitude and direction indication
  • Features LED indicators for OK, Alert, Danger, and Bypass status
  • Provides recorder outputs for trending and data acquisition
  • Supports programmable alarm delays and relay logic
  • Performs continuous transducer OK verification

Structural Characteristics The monitor is housed in a standard 3300 series module enclosure with a front panel containing an 83 mm vertical bargraph LCD, green OK LEDs, red Alert and Danger LEDs, and red Bypass LEDs. The rear panel provides terminal blocks for field wiring, coaxial connectors for buffered transducer outputs, and relay contact terminals. The internal circuitry includes signal conditioning, linearization, and microprocessor-based measurement and alarm logic.

Working Principle A proximity probe mounted on the machine casing observes an axial surface or collar on the rotor. As the machine heats during startup, the rotor and casing expand at different rates, causing relative axial movement. The proximity probe detects this movement as a change in gap distance. The monitor converts the probe voltage signal into a linear displacement reading, compensates for transducer nonlinearities, and displays the differential expansion value. When the expansion exceeds safe limits, the monitor activates alarm relays to alert operators or trigger automatic shutdown sequences.

Installation Requirements

  • Mount proximity probe to observe an axial collar or surface on the rotor
  • Ensure probe mounting is rigid and thermally stable
  • Use shielded coaxial cable for transducer connections
  • Maintain cable shield continuity to single-point ground
  • Program full-scale range to match expected differential expansion
  • Set alarm thresholds based on manufacturer axial clearance limits
  • Verify measurement accuracy during known thermal transients

Application Scenarios

  • Steam turbine differential expansion monitoring
  • Generator rotor-to-stator thermal growth measurement
  • Large compressor casing expansion supervision
  • Refinery turbine supervisory instrumentation
  • Power plant startup thermal monitoring
  • Industrial gas turbine expansion protection

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