21504-04-12-05-02 | Bently Nevada 8 mm Proximity Probe Vibration

Introduction to the 21504-04-12-05-02 Proximity Probe

When machinery vibration threatens uptime, the 21504-04-12-05-02 from Bently Nevada provides accurate, real-time measurements. This 8 mm proximity probe is part of the Model 21504 7200 Proximity Transducer Systems, designed for continuous monitoring in harsh industrial environments. With a calibrated range of 80 mils (2.0 mm) and a scale factor of 200 mV/mil (7.87 V/mm), it delivers reliable data for predictive maintenance.

Key Features & Technical Specs of the 21504-04-12-05-02

• Power: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption.
• Calibrated Range: 80 mils (2.0 mm), beginning at approximately 10 mils (0.25 mm) from probe face.
• Scale Factor: 200 mV/mil (7.87 V/mm), ±4% when calibrated as a system.
• Linearity: Within 0.8 mils (0.02 mm) of a 200 mV/mil straight line if calibrated as a system.
• Frequency Response: 0 to 10 kHz (0 to 600,000 cpm); -5% at 10 kHz (600,000 cpm).
• Operating Temperature: Proximitor: -60°F to +212°F (-51°C to +100°C); Probe and Extension Cable: -30°F to +350°F (-34°C to +177°C).
• Relative Humidity: To 95%, noncondensing.
• System Weight: 1.3 lbs. (0.59 kg).

One standout spec is the frequency response of 0 to 10 kHz, which covers a wide range of machine speeds for early fault detection.

Applications & Use Cases

In rotating machinery like turbines, compressors, and pumps, the 21504-04-12-05-02 monitors shaft vibration and position. Its corrosion resistance (for 8 mm probes) allows operation in air, water, lube oil, and various chemicals, making it suitable for oil and gas, power generation, and manufacturing. For example, in a steam turbine application, this probe helps detect imbalance before catastrophic failure occurs.

Installation & Setup Guide

Install the probe with a 3/8-24 thread into a standard mounting hole. Ensure the unthreaded length (40 mm) and overall case length (120 mm) match your machine geometry. The total cable length is 0.5 metre (20 inches) with a miniature male coaxial connector. Secure the cable to avoid strain and maintain a consistent gap of approximately 10 mils (0.25 mm) from the target surface.

Maintenance & Reliability

Regularly inspect the probe and cable for physical damage or contamination. The system operates reliably in temperatures from -60°F to +212°F for the Proximitor and -30°F to +350°F for the probe. With a 12-month factory warranty from Bently Nevada, this probe delivers long-term performance when properly maintained.

Compatibility & Integration

The 21504-04-12-05-02 integrates with Bently Nevada 7200 series monitoring systems. It uses a standard coaxial connector for signal transmission. For system calibration, pair it with a compatible Proximitor to achieve ±4% scale factor accuracy.

FAQ about the 21504-04-12-05-02

What is the calibrated range of this probe?

The calibrated range is 80 mils (2.0 mm), beginning at approximately 10 mils (0.25 mm) from the probe face.

What is the scale factor and accuracy?

The scale factor is 200 mV/mil (7.87 V/mm), with ±4% accuracy when calibrated as a system.

What temperature range can the probe withstand?

The probe and extension cable operate from -30°F to +350°F (-34°C to +177°C).

Is this probe resistant to chemicals?

Yes, for 8 mm probes, operation is not affected by direct contact with air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, or DMF.

Product Support & Availability

The 21504-04-12-05-02 is available as a new, original Bently Nevada part in factory packaging. Contact Petro Auto Tech for current stock and ordering details.