Product Overview

The Bently Nevada 330750-20 is a specialized piezo-velocity transducer system engineered for absolute vibration monitoring in extreme thermal environments. Unlike integrated velocity sensors, the 330750-20 utilizes a segregated architecture that separates the sensing head from the signal conditioning electronics. This design allows the sensing element to be mounted directly on machinery surfaces reaching up to 400°C (752°F), while the sensitive electronic components are situated in a cooler, remote location via an integral hardline cable. This system is a critical component of Turbine Supervisory Instrumentation (TSI), providing a standard velocity output that simplifies integration with existing monitoring racks and control systems.

Hardware Parameters and Key Technical Characteristics

The 330750-20 system is designed to eliminate common failure points in high-heat applications, such as connector degradation and electronic thermal drift. By removing connectors between the probe head and the converter, the system ensures maximum signal integrity.

• Model Number 330750-20

• Transducer Type Piezo-velocity (Remote Electronics)

• Maximum Sensing Temperature 400°C (752°F)

• Sensitivity 5.7 mV/mm/s (145 mV/in/s) ±5%

• Frequency Response 15 Hz to 2,000 Hz (900 to 120,000 cpm) ±3.0 dB

• Amplitude Linearity ±2% up to 152 mm/s (6 in/s) peak

• Integral Cable Length 2.0 Meters (Option -20)

• Output Bias Voltage -12 ± 2.0 VDC

• Excitation Current 2 mA to 10 mA (Constant Current)

• Housing Material 304L Stainless Steel (Sensing Head)

• Weight 0.2 kg (System total)

Industrial Applications and Operational Use Cases

The High Temperature Velomitor System is the industry standard for monitoring the casing vibration of assets where standard sensors would fail due to heat soak.

• Gas Turbine Casing Monitoring Measuring absolute vibration on the hot sections of gas turbines to detect unbalance and aerodynamic instabilities.

• Steam Turbine Valve Gear Providing vibration data for main steam valves and high-pressure casing points.

• Exhaust Fan Assemblies Monitoring large industrial fans handling high-temperature process gases in smelting or chemical refining.

• Heat Exchanger Vibration Tracking flow-induced vibration in high-temperature heat exchange units.

• Predictive Maintenance Interfacing with Bently Nevada 3500/42M or 1900/65A monitors to provide real-time vibration velocity data for automated machinery protection.

By moving the signal conditioning circuitry away from the heat source, the 330750-20 extends the mean time between failures (MTBF) and ensures that critical safety data remains accurate even during peak thermal cycles.