Bently Nevada 330878-90-05 3300 XL 50 mm Differential Expansion Sensor

Bently Nevada 330878-90-05 3300 XL 50 mm Proximitor Sensor

The Bently Nevada 330878-90-05 is a high-performance 3300 XL 50 mm Proximitor Sensor specifically designed for precise, non-contact measurement of differential expansion and axial rotor position in large turbomachinery. Engineered directly for critical steam turbine generator sets within Turbine Supervisory Instrumentation (TSI) systems, this module operates seamlessly in conjunction with a matching 50 mm eddy-current probe and extension cable. Furthermore, by incorporating an extended linear range, the signal conditioner processes radio-frequency (RF) field changes into a proportional analog voltage output to reliably safeguard heavy rotating assets against dangerous rotor-to-stator mechanical contact.

Suffix Breakdown & Model Matrix

Hardware Specifications

Field Signal Condition and Rotor Dynamics

Fundamentally, the 330878-90-05 conditions dynamic impedance shifts generated at the 50 mm probe tip into a stable, continuous DC/AC voltage output. Because thermal expansion rates between heavy turbine casings and high-speed rotors diverge significantly during startup and load transients, precise continuous tracking is essential. Consequently, the 50 mm sensor provides a 27.9 mm (1100 mils) linear range—the longest in the Bently Nevada eddy-current product line—allowing plant operators to continuously monitor collar or ramp displacement near the thrust bearing. In addition, when installed in a complementary dual-transducer configuration, the system monitors total relative growth up to 56 mm (2.2 inches). As a result, it effectively suppresses cross-talk and phase distortion to deliver accurate input signals directly to downstream 3300 or 3500 rack monitoring channels.

Frequently Asked Questions

Q: What installation configuration allows the 330878-90-05 to double its standard linear measurement range?

A: By mounting two 50 mm probes in a complementary (opposite facing) arrangement targeting a single thrust collar or slanted ramp, the combined Proximitor outputs effectively measure up to 56 mm (2.2 inches) of total relative differential expansion.

Q: Can the 330878-90-05 be matched with a 5-meter or 1-meter probe assembly?

A: No, because the 330878-90-05 option code explicitly designates a 9.0-meter system. Therefore, it must be paired exclusively with a matching 50 mm probe and extension cable configured for a total electrical system length of 9.0 meters to maintain calibrated scale factor accuracy.

Q: Why is a 50 mm Proximitor Sensor required instead of a standard 8 mm or 11 mm sensor for turbine differential expansion?

A: Standard 8 mm and 11 mm probes lack the physical coil diameter to project an eddy-current field capable of linearly tracking large axial thermal shifts over several centimeters. As a consequence, smaller probes suffer from early signal saturation.