Configured for axial and radial position monitoring in industrial rotating machinery, the Bently Nevada 21000-28-05-00-105-04-02 (21000 Proximity Probe Housing Assemblies) provides a rigid physical interface for eddy-current transducer deployment.

Model Configuration Logic

• 21000: Base model for proximity probe housing assemblies.
• 28: Indicates the utilization of a 3300 XL 8 mm probe.
• 05: Specifies a 0.5 m (20 in) probe cable length.
• 00: Designates the omission of additional hazardous area approval accessories.
• 105: Defines a probe penetration depth of 10.5 in (266.7 mm).
• 04: Denotes the inclusion of one 3/4-14 NPT plug.
• 02: Specifies 3/4-14 NPT mounting threads.

Hardware Specifications

Rotor Dynamics and Transducer Scaling

The physical stability of this housing assembly is critical for maintaining consistent eddy-current probe scaling. When calibrating the transducer system, the target material must be verified for electrical conductivity consistent with 4140 steel to ensure linear voltage output. The assembly maintains a gap voltage validation target of -10 VDC at the mid-linear range. Cross-talk suppression is achieved through rigid physical isolation of the probe tip within the housing, preventing signal interference when multiple transducers monitor the same rotor target area. Proper seating of the 3/4-14 NPT threads is necessary to prevent mechanical vibration of the housing itself, which would otherwise manifest as noise in the radial vibration or thrust position waveform.

Ordering Info

1. 1 x 21000-28-05-00-105-04-02 Housing Assembly unit.
2. 1 x 3/4-14 NPT pipe plug.
3. 1 x Probe locking nut and associated O-ring seals.

Mechanical Installation Directives

• Thread Engagement: Ensure a minimum of 5 full thread turns engagement on the 3/4-14 NPT mounting port to maintain structural integrity.
• Grounding: The housing must be grounded to the machine casing to minimize electromagnetic interference on the coaxial signal path.
• Cable Routing: Avoid tight-radius bending of the 0.5 m coaxial cable to prevent impedance discontinuities.
• Gap Setting: Verify the cold-gap setting with a feeler gauge to ensure the probe tip does not contact the target during thermal expansion of the rotor.

Frequently Asked Questions

• Q: Can this housing be used for non-metallic targets?

  A: No, the eddy-current principle requires a conductive, metallic target to generate the necessary signal voltage.

• Q: What is the purpose of the O-ring provided in the assembly?

  A: The O-ring serves as a pressure seal to prevent oil leakage from the bearing housing or lubrication system.

• Q: Is the cable length adjustable in the field?

  A: No, the 0.5 m cable is factory-terminated and calibrated for specific system impedance; field shortening will alter signal characteristics.

• Q: How does thread contamination affect measurement?

  A: Debris or sealant in the threads can prevent the housing from seating squarely, leading to signal instability or incorrect gap readings.

• Q: Can this assembly be installed in a high-pressure environment?

  A: The 3/4-14 NPT configuration is rated for standard industrial pressures, but high-pressure applications require verification of O-ring material compatibility.

• Q: Does the probe require an external driver?

  A: Yes, this housing is designed to hold the probe, which must be connected to a compatible 3300 XL Proximitor sensor for signal conditioning.

• Q: Why is 4140 steel specified for calibration?

  A: Eddy-current probe linearity is highly sensitive to the metallurgical properties of the target; 4140 steel is the industry standard for consistent scaling.

• Q: What is the maximum operating temperature of the probe tip?

  A: The 3300 XL probe tip is rated for continuous operation up to 177 deg C, provided the housing is not exposed to thermal gradients exceeding specifications.