Product Overview

The Bently Nevada 26530-12-10-03-018-191-22-04-00 Dual Probe Transducer System combines a 3300 XL 8 mm proximity probe with a high-temperature, two-wire velocity transducer. The assembly is intended for rotating machinery installations where shaft movement and vibration of the supporting structure need to be measured together.

The two sensors serve different purposes. The proximity probe measures the distance between its sensing tip and the conductive shaft surface, providing shaft displacement relative to the probe mounting point. The velocity transducer measures vibration of the bearing housing or machine casing. When the supporting structure moves during operation, these separate measurements help engineers distinguish shaft-relative motion from structural vibration.

This distinction is important in large compressors, steam turbines, and other rotating equipment. During a startup or load change, the rotor may respond to changing operating forces while the bearing housing experiences its own vibration. A proximity measurement alone does not describe the complete motion of the shaft relative to a stationary reference when the housing is moving. The dual-transducer arrangement supplies complementary signals for a more comprehensive assessment.

The specified configuration incorporates a 1-meter probe lead, a 3/4-14 NPT adapter thread, an 018 adapter-length option, and a 191 probe-penetration option. It also uses the high-temperature, two-wire Seismoprobe configuration, a single 3/4-14 NPT plug fitting, and no optional probe support/oil seal. These options establish the mechanical and sensing arrangement of the assembly.

The 19.1-inch probe penetration is relevant when the intended measurement point is positioned deep within a machine casing or bearing structure. The installation must accommodate the required probe reach while maintaining the correct sensing gap and sufficient mechanical support. For extended installations, sleeve support and mounting rigidity deserve particular attention because mechanical resonance can affect measurement quality.

The system supports four related measurement functions: shaft relative radial position, shaft relative radial dynamic motion, machine-casing absolute vibration, and shaft absolute motion calculated from the relevant signals. The last function requires compatible monitoring equipment to process the seismic measurement and relative shaft displacement appropriately.

In practical maintenance work, the combined measurements can help engineers investigate changes in rotor behavior, bearing support vibration, and structural response. For example, an increase in casing vibration accompanied by a change in shaft-relative vibration provides different diagnostic information from a change in the proximity signal alone.

The assembly operates as part of a wider machinery monitoring system. Appropriate signal conditioning, wiring, mechanical installation, and monitoring-channel configuration are necessary for useful measurements. The selected sensors must be integrated with compatible instrumentation rather than treated as a standalone vibration protection device.

Technical Specifications

Product Features

• Combined sensing arrangement: Integrates a proximity probe and a velocity transducer in a common assembly.
• 3300 XL 8 mm proximity probe: Measures shaft displacement relative to the probe mounting point.
• High-temperature Seismoprobe: Measures vibration of the supporting structure using the specified two-wire configuration.
• Extended probe penetration: Uses the 19.1-inch penetration option for installations requiring an extended sensing reach.
• NPT mounting interface: Provides a 3/4-14 NPT adapter connection.
• Specified probe lead: Incorporates the 1-meter proximity probe lead configuration.
• Separate measurement signals: Allows shaft-relative movement and casing vibration to be evaluated independently.
• Combined motion assessment: Supports shaft absolute-motion calculations when the monitoring system processes both signals appropriately.
• Machinery monitoring integration: Supplies complementary measurements for compatible signal-conditioning and monitoring equipment.

Working Principle

The 26530 Dual Probe Transducer System uses two sensing methods to capture different aspects of rotating machinery movement.

The 3300 XL 8 mm proximity probe operates through eddy-current sensing. Its electromagnetic field interacts with the conductive shaft surface, and the electrical response changes as the gap between the probe tip and shaft changes. Compatible signal-conditioning equipment converts this response into a displacement measurement relative to the probe mounting point.

The high-temperature, two-wire Seismoprobe measures vibration of the supporting structure. Its output represents the movement of the bearing housing or casing rather than the shaft-to-probe gap. This measurement becomes particularly useful when the structure supporting the proximity probe also vibrates during machine operation.

Shaft Surface → 3300 XL 8 mm Probe → Relative Displacement Signal

Bearing Housing → High-Temperature Seismoprobe → Structural Vibration Signal

Compatible Monitoring Equipment → Signal Processing → Shaft Absolute-Motion Assessment

The proximity channel records changes in shaft-relative position and dynamic movement. The velocity transducer supplies information about casing vibration. When the monitoring system integrates the seismic signal into displacement and combines it appropriately with the relative shaft displacement, it can calculate shaft absolute motion.

Consider a compressor operating near a structural resonance. The shaft may move relative to the bearing housing while the housing itself vibrates. The proximity probe captures the relative shaft movement, and the Seismoprobe records the supporting structure’s vibration. Evaluating both measurements provides a clearer basis for investigating the machine’s response.

The extended probe penetration also affects the mechanical installation. The probe must reach the intended conductive target while maintaining an appropriate gap throughout expected shaft movement. The mounting must remain sufficiently rigid, and extended probe or sleeve arrangements may require additional support to avoid mechanical resonance.

The velocity transducer’s orientation and frequency characteristics must suit the application. The specified configuration has an orientation range of 0° ± 100° and a minimum operating frequency of 600 cpm. These characteristics should be considered when selecting the measurement point and interpreting operating data.

The assembly does not independently diagnose a mechanical fault or initiate a shutdown. Those functions depend on the connected monitoring equipment, signal processing, configured alarm limits, and the protection logic implemented in the wider system.

Role in a Rotating Machinery Monitoring System

The Bently Nevada 26530-12-10-03-018-191-22-04-00 supplies complementary signals for machinery condition monitoring. Its proximity channel tracks shaft movement relative to the mounting point, while its velocity channel measures vibration of the supporting structure.

Shaft Movement → Proximity Measurement

Casing Vibration → Seismic Measurement

Monitoring Channels → Signal Processing → Operator Display and Alarm Logic

For radial-bearing diagnostics, two suitable assemblies can be positioned along perpendicular X-Y axes. When the monitoring equipment is configured to process the corresponding signals, this arrangement supports shaft orbit analysis and shaft centerline evaluation.

Industrial Applications

Installation and Maintenance

1. Confirm the measurement location: Select a mounting point that provides access to the intended shaft target and a suitable mechanical reference on the bearing housing or casing.
2. Check the adapter interface: Confirm that the mounting provision matches the specified 3/4-14 NPT adapter connection.
3. Review the penetration arrangement: Account for the 1.8-inch adapter-length option and 19.1-inch probe-penetration option when checking the installation geometry and available clearance.
4. Inspect the target surface: Ensure the shaft surface is suitable for eddy-current measurement and that the probe faces the intended measurement area.
5. Set the probe gap: Establish the initial clearance according to the applicable 3300 XL 8 mm installation procedure and the connected signal-conditioning requirements.
6. Secure the assembly: Tighten the mounting hardware according to the installation requirements to prevent movement of the sensor housing during machine operation.
7. Inspect the probe lead: Check the 1-meter lead for cuts, crushing, abrasion, and excessive strain before connecting the electrical circuit.
8. Connect the velocity transducer: Follow the wiring requirements for the high-temperature, two-wire Seismoprobe and its compatible receiving input.
9. Check sensor orientation: Position the velocity transducer within its specified orientation range and ensure that the measurement axis suits the intended monitoring function.
10. Verify signal conditioning: Confirm that the proximity and velocity signals are connected to suitable inputs with the correct scaling and measurement configuration.
11. Assess mechanical support: For the extended probe arrangement, check that the mounting and sleeve support are adequate to limit unwanted vibration or resonance.
12. Establish baseline readings: Record shaft-relative displacement and casing vibration under known operating conditions, then compare subsequent trends against those baseline measurements.

During maintenance, inspect the probe gap, mounting security, lead condition, and electrical connections. If the proximity and velocity signals show different trends, investigate the two measurement paths separately before attributing the change to rotor behavior or structural vibration.

Related Components

Recommended Related Models

Key Advantages

• Combines shaft-relative displacement and casing-vibration measurements.
• Helps distinguish rotor movement from motion of the supporting structure.
• Uses a 3300 XL 8 mm proximity probe and a high-temperature, two-wire Seismoprobe.
• Supports shaft absolute-motion assessment through compatible signal processing.
• Accommodates the specified extended probe-penetration configuration.
• Supplies complementary measurement data for rotating machinery diagnostics.

Technical FAQs

How does the dual-transducer system help when the bearing housing is vibrating?

The proximity probe measures shaft movement relative to its mounting point, while the Seismoprobe measures vibration of the supporting structure. Comparing these signals helps compatible monitoring equipment distinguish relative shaft movement from casing motion and calculate shaft absolute motion where supported.

What installation considerations apply to the 19.1-inch probe penetration?

The extended penetration must suit the distance between the mounting interface and the intended shaft target. The installation needs adequate clearance, correct probe-gap adjustment, and sufficient mechanical rigidity. Extended probe arrangements should also be assessed for sleeve support and potential resonance.

Why is the high-temperature, two-wire Seismoprobe used with the proximity probe?

The Seismoprobe provides a structural vibration measurement that complements the proximity probe’s shaft-displacement signal. The high-temperature option suits the specified temperature range, while the two-wire configuration must be connected to compatible receiving instrumentation.

Can the 26530 assembly independently provide complete shaft orbit measurements?

A single assembly provides measurements from its installed sensing arrangement. Radial shaft orbit analysis generally requires two suitable assemblies positioned along perpendicular X-Y axes, together with monitoring equipment configured to process the corresponding signals.