The BENTLY NEVADA 24765-02-01 is a DC LVDT casing expansion sensor assembly. Serving as a core displacement measuring device for turbine TSI monitoring systems, it is specially designed to acquire thermal expansion displacement data reflecting the relative movement between the turbine casing and its foundation during start-up, shutdown and steady-state operation of large generating units.

This device adopts a dual-sensor monitoring configuration, which enables real-time detection of potential hazards such as jamming of casing sliding supports and mismatched thermal expansion rates between the casing and rotor. It thereby prevents unit damage caused by rubbing between stationary and rotating components as well as casing deformation.

Integrated with a linear variable differential transformer (LVDT) measuring unit and fitted with a waterproof protective housing, the sensor is applicable to industrial sites under normal temperature conditions. It outputs standardized DC voltage signals to 3300 and 3500 series monitor racks for over-limit alarming and data logging.

The suffix "02" of the model denotes a linear measuring range of ±25.4 mm, while "01" stands for a built-in spring return mechanism, making the sensor suitable for measurement scenarios requiring continuous contact without sustained external force.

Electrical Specifications

Power Supply Input: 24 VDC, minimum operating current: 30 mA; Sensitivity: 0.404 V/mm (10.25 V/in); Linear Measurement Range: ±25.4 mm; -3dB Cutoff Frequency: 15 Hz; Output Impedance: 7 kΩ, minimum load resistance: 100 kΩ; Ripple: less than 1% full scale (FS); Linearity: ±0.5% FS; Long-term Stability: 0.125% FS; Sensitivity Temperature Coefficient: 0.07%/°C.

Environmental Specifications

Operating Temperature Range: -18°C ~ +71°C; Storage Temperature: -54°C ~ +93°C; Shock Resistance: 250 g / 11 ms; Vibration Resistance: 10 g (0 ~ 2 kHz); Protective housing complies with NEMA 3 enclosure standard.

Mechanical Specifications

Housing Material: 400-series magnetic stainless steel; Coil Material: laminated glass epoxy; Overall dimensions: height 88.9 mm, width 117 mm, total length 241 mm; Weight: 2.3 kg; Core diameter: 6.4 mm; Threads at two ends: 6-40 UNF-2B and 1/4-20 UNC-2A respectively; Standard accessory: 31 cm PTFE-insulated copper lead wires.

Complete Model Code Explanation

Product Coding Rule: 24765-AA-BB

24765: Series code for standard ambient-temperature casing expansion LVDT sensor.

AA Segment (Range Code)

01: ±12.7 mm measuring range

02: ±25.4 mm measuring range

03: ±51 mm measuring range

BB Segment (Spring Configuration Code)

00: No spring return

01: Equipped with spring return structure

Breakdown of Model 24765-02-01

24765: Standard ambient-temperature series; 02 corresponds to ±25.4 mm linear stroke; 01 denotes spring return plunger, which automatically fits the casing measuring point during measurement.

Core Features

High-precision linear measurement

Full-scale linear error is controlled within ±0.5%, with low temperature drift. No obvious data offset occurs during long-term continuous operation, meeting monitoring requirements for tiny thermal expansion differences during unit startup and shutdown.

Standardized DC output

No additional signal conditioning module is required; the sensor can be directly connected to all position monitor cards of Bently Nevada. The transmitted signal features strong immunity to power frequency interference.

Dual measuring point compatible design

Supports paired installation to monitor displacement differences of left and right casing sliding supports. The system will automatically trigger independent alarms when jamming occurs on a single sliding support.

Robust industrial protective structure

Integrated hermetically-sealed metal housing provides dustproof and waterproof performance, capable of withstanding continuous on-site vibration and shock conditions. The cables are covered with oil-resistant PTFE insulation.

Wide load adaptability

Minimum load resistance of 100 kΩ supports long-distance field wiring without signal attenuation or distortion in long-cable transmission.

Comprehensive compliance certifications

Complies with FCC regulations, EN 61000 EMC standards and RoHS environmental directives, and bears CE marking. It satisfies compliance requirements for thermal power and chemical projects at home and abroad.

Application Fields

TSI Monitoring of Large Steam Turbines in Thermal Power & Nuclear Power Plants

It measures the overall thermal expansion of the turbine cylinder and compares the thermal expansion rate of the rotor, so as to avoid rubbing between stationary and rotating blades during unit startup and shutdown.

Condition Monitoring for Gas Turbine Units

It collects axial thermal displacement of the turbine casing to evaluate the operating condition of sliding support pedestals.

Large Axial Flow Compressors & Blowers

Monitors casing thermal expansion to prevent shaft alignment deviation caused by casing deformation.

Industrial Steam Turbines & Waste Heat Power Generation Turbines

Enables continuous full-process thermal expansion monitoring throughout unit startup and shutdown, providing trigger reference for interlock protection.

Large Rotating Power Equipment in Petrochemical Industry

Supports long-term online monitoring of high-temperature casing displacement and facilitates predictive maintenance of equipment.

Compatible Matching Products

Monitoring Rack Modules

3500/45 Position Monitor Module (Part No. 176449-04)

This dual-channel displacement acquisition module supports dual-parameter alarming for case expansion and differential expansion, and is fully compatible with all sensors of the 24765 series.

3300 Series Position Monitor Cards

Matched for legacy TSI systems, supporting single-channel case expansion signal acquisition.

Special Installation Accessories

135941 Series Extended Measuring Plungers

Plungers of different lengths can be replaced on demand to adapt to varying measuring point distances.

285741 Ferrite Beads

Mandatory accessory for CE-certified projects, used to suppress radio frequency signal interference.

1/4-20 UNC Fixing Bolts, Flat Washers & Spring Washers

Standard mounting fasteners supplied with the equipment.

Upper Monitoring Software

System 1™ Machinery Condition Analysis Software

Collects case expansion data transmitted from the 3500 rack, generates long-term trend curves, and supports equipment failure prediction and diagnosis.