Bently Nevada 3300/48

Bently Nevada 3300/48

Product Overview The 3300/48 is a dual-channel case expansion monitor designed to measure the thermal growth of machine casings relative to a fixed foundation reference point. This monitor uses DC Linear Variable Differential Transformers (LVDTs) to detect casing expansion caused by thermal gradients during machine startup, operation, and shutdown. Case expansion monitoring is critical for large heat-generating equipment such as steam turbines and reciprocating compressors, where unrestricted casing growth is essential for maintaining internal clearances and preventing binding or distortion.

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Description

Bently Nevada 3300/48

Technical Specifications

Parameter Specification
Channels Two independent case expansion channels
Input DC LVDT transducers
Measurement Range 0 to 25 mm (typical configuration)
Input Voltage 18–36 VDC
Output Signal 4–20 mA
Display Vertical bargraph LCD, 63 segments per channel, 83 mm height
Display Resolution ±1.6% of full-scale
Operating Temperature -20°C to +65°C
Storage Temperature -40°C to +85°C
Dimensions Standard 3300 rack module format
Weight Standard module weight
Origin USA

Functional Features

  • Measures casing thermal growth relative to foundation using LVDTs
  • Provides two independent channels for multi-point monitoring
  • Features high-resolution LCD display for expansion reading
  • Offers 4–20 mA recorder output for trending systems
  • Includes programmable alarm setpoints for over-expansion conditions
  • Provides LED status indicators for OK, Alert, and Danger conditions
  • Performs continuous transducer OK checking
  • Supports rack-mount installation in standard 3300 chassis

Structural Characteristics The case expansion monitor is housed in a standard 3300 series module enclosure with a front panel containing a vertical bargraph LCD display, LED indicators, and programming switches. The unit accepts input from DC LVDTs mounted between the machine casing and a fixed foundation reference. The internal circuitry includes LVDT excitation, signal demodulation, filtering, and microprocessor-based measurement and alarm logic.

Working Principle DC LVDTs are mounted with one end attached to the machine casing and the other end anchored to a fixed foundation point. As the machine heats during operation, the casing expands, causing relative movement between the LVDT core and coil. The LVDT converts this mechanical displacement into a proportional electrical signal. The monitor excites the LVDT, demodulates the return signal, filters noise, and converts the result into a linear displacement reading. When casing expansion exceeds programmed limits, the monitor activates alarm relays to warn operators of potential binding or clearance issues.

Installation Requirements

  • Mount LVDTs between machine casing and rigid foundation reference
  • Ensure LVDT mounting brackets are thermally stable and rigid
  • Use shielded cable for LVDT signal connections
  • Route cables away from high-energy power conductors
  • Program full-scale range to match expected casing growth
  • Set alarm thresholds based on manufacturer casing expansion limits
  • Verify measurement accuracy during thermal transient conditions
  • Ensure proper LVDT core-to-coil alignment for linear operation

Application Scenarios

  • Steam turbine case expansion monitoring
  • Generator stator thermal growth measurement
  • Large compressor casing expansion supervision
  • Reciprocating engine frame expansion monitoring
  • Refinery heat exchanger thermal growth assessment
  • Power plant foundation movement detection
  • Industrial boiler and vessel expansion monitoring

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