21505-20-48-05-02 | Bently Nevada 8mm Probe Proximity Vibration

Introduction to the Bently Nevada 21505-20-48-05-02

When rotating machinery fails unexpectedly, the consequences can be costly. The 21505-20-48-05-02 from Bently Nevada provides early warning of vibration issues, helping you avoid unplanned downtime. This 8 mm proximity probe is part of the 7200 series and is designed for continuous monitoring in demanding industrial environments.

With a calibrated range of 80 mils (2.0 mm), the probe detects shaft vibration and displacement with high accuracy. Its 200 mV/mil scale factor ensures clear, measurable output for your monitoring system. Whether you are protecting turbines, compressors, or pumps, this probe delivers the data you need.

Key Features and Technical Specifications

The 21505-20-48-05-02 offers several features that make it a reliable choice for vibration monitoring. Here are the core specifications:

• Total length option: 0.5 metre (20 inches) – fits standard installations.
• Power requirement: -17.5 Vdc to -26 Vdc at 12 mA maximum consumption – low power draw.
• Calibrated range: 80 mils (2.0 mm), beginning at approximately 10 mils (0.25 mm) from the probe face – wide measurement window.
• Scale factor: 200 mV/mil (7.87 V/mm), ±4% when calibrated as a system – precise output.
• Linearity: Within 0.8 mils (0.02 mm) of a 200 mV/mil straight line when calibrated as a system – excellent accuracy.
• Frequency response: 0 to 10 kHz (0 to 600,000 cpm) – captures a broad range of vibration frequencies.
• Temperature sensitivity: Typically -3% change in scale factor at +150°F (+65°C) at 50 mils gap (1.27 mm) – stable performance across temperatures.
• Operating temperature for Proximitor: -60°F to +212°F (-51°C to +100°C) – suitable for extreme environments.
• Probe and extension cable temperature: -30°F to +350°F (-34°C to +177°C) – robust thermal tolerance.
• Relative humidity: Up to 95%, noncondensing – withstands humid conditions.
• System weight: 1.3 lbs (0.59 kg) – lightweight and easy to handle.

One standout feature is the 200 mV/mil scale factor. This high sensitivity means even small vibration changes produce a clear signal, allowing your monitoring system to react quickly to potential issues.

Real-World Applications

The 21505-20-48-05-02 is ideal for monitoring rotating equipment in industries such as power generation, oil and gas, and manufacturing. For example, in a steam turbine, the probe can detect shaft vibration that indicates bearing wear or misalignment. By catching these problems early, you can schedule maintenance before a catastrophic failure occurs.

Additionally, the probe's corrosion resistance for 8 mm probes means it can operate in environments with exposure to air, water, lube oil, ammonium hydroxide, sulfuric acid (10%), MEK, or DMF. This makes it suitable for harsh chemical processing plants.

Installation and Setup

Proper installation is critical for accurate vibration readings. The probe should be mounted so that the sensing tip is positioned within the calibrated range, typically starting at 10 mils (0.25 mm) from the target surface. Use the 3/8-24 thread configuration to secure the probe in place.

Ensure the lead armor (stainless steel) is properly routed to protect the cable from damage. The miniature male coaxial connector provides a secure connection to your extension cable. Always follow the manufacturer's guidelines for gap setting and initial calibration to achieve optimal performance.

Maintenance and Reliability

Regular inspection of the probe and its connections helps maintain reliable operation. Check the probe face for any buildup of contaminants that could affect measurement. Although the probe is corrosion-resistant, it is still wise to keep the sensing area clean.

Verify that the cable and connector remain intact and free from wear. Periodically test the system's output against a known vibration source to confirm accuracy. Following these simple steps can extend the service life of your 21505-20-48-05-02 and prevent unexpected failures.

Compatibility and Integration

The 21505-20-48-05-02 is designed to work with Bently Nevada 7200 series monitoring systems. It connects via a miniature male coaxial connector, ensuring a secure and reliable signal path. The probe's output is a voltage signal proportional to vibration, which can be fed into compatible monitors or data acquisition systems.

For detailed integration guidance, refer to the official Bently Nevada documentation or contact Petro Auto Tech for support.

Troubleshooting Common Issues

If you encounter erratic readings, first check the probe gap. The calibrated range begins at approximately 10 mils (0.25 mm) from the probe face; if the gap is outside this range, readings may be inaccurate. Also, inspect the cable for damage or loose connections.

Temperature extremes can affect scale factor. The temperature sensitivity is typically -3% change at +150°F (+65°C) at a 50 mils gap. If your environment approaches these limits, consider compensating for temperature effects in your monitoring system.

Frequently Asked Questions

Q: What is the calibrated range of the 21505-20-48-05-02?

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

Q: What is the scale factor of this probe?

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

Q: What power supply does the 21505-20-48-05-02 require?

A: It requires -17.5 Vdc to -26 Vdc at 12 mA maximum consumption.

Q: What is the operating temperature range for the probe?

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

Q: Is the probe resistant to corrosive substances?

A: 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 and Availability

The 21505-20-48-05-02 is available from Petro Auto Tech, an industrial automation parts supplier. It comes new and in original factory packing with a 12-month warranty. Contact Petro Auto Tech to check current availability and lifecycle status before ordering.