Bently Nevada 21000-28-05-00-047-04-02 Proximity Probe Housing Assembly

Product Overview

The Bently Nevada 21000-28-05-00-047-04-02 is an external mounting Proximity Probe Housing Assembly designed to facilitate the installation of proximity transducers through machine casings. It is a primary component for Turbine Supervisory Instrumentation (TSI) systems, allowing for the adjustment or replacement of probes without disassembling the machine. The assembly provides environmental protection for the probe and maintains a seal against machine internal pressure.

This specific 21000 series configuration includes an integrated 3300 XL 8 mm proximity probe with multiple agency approvals and a 0.5-metre (20 in) integral cable. The housing is specified with a 4.7-inch probe penetration depth and a 3/4-14 NPT mounting thread. It is commonly utilized in power generation and petrochemical industries for monitoring radial vibration and axial thrust on steam turbines, compressors, and large gearboxes where external accessibility to the transducer is required.

Technical Configuration

Ordering Information

This assembly is configured based on specific application requirements. Ensure the penetration depth and mounting threads match the machine casing specifications.

Engineering & Installation Guide

Mechanical Alignment and Gapping:

The 21000 housing allows for the probe to be gapped externally. During installation, the probe is threaded into the sleeve until it reaches the target. It must then be backed off to achieve the desired DC gap voltage (typically -10.0 Vdc for 3300 XL systems). Once gapped, the locknut must be secured to prevent the probe from moving due to machine vibration.

Pressure Sealing:

The 3/4-14 NPT mounting thread must be treated with a high-quality thread sealant to ensure a leak-proof connection with the machine casing. If the machine utilizes high-pressure lubricants or is under vacuum, verify the integrity of the O-rings within the housing assembly during routine maintenance intervals.

Cable Protection:

The 0.5-metre integral cable is terminated with a miniature coaxial ClickLoc connector. This connector should be housed within the terminal head of the 21000 assembly. Ensure the cable is not pinched when closing the housing cover. Use the provided 3/4-14 NPT plug for unused conduit entries to maintain the environmental rating of the enclosure.

Replacement Precautions:

When replacing a probe within the 21000 housing, ensure the replacement probe matches the "Total Length" of the original system (typically 5m or 9m total). This 0.5m probe requires a specific extension cable to reach the Proximitor sensor. Using mismatched lengths will lead to calibration errors in the vibration monitor.

Troubleshooting FAQ

Q: Can I change the penetration depth in the field?

A: No. The penetration depth (047 = 4.7 inches) is factory-set based on the internal sleeve and probe length. Attempting to modify this will compromise the mechanical limits and gapping capability.

Q: What if oil is leaking from the housing head?

A: This indicates a failure of the internal seal or O-ring between the probe sleeve and the housing body. Inspect the O-rings for degradation or hardening and replace them with authentic Bently Nevada seal kits.

Q: How do I identify a grounding issue with the 21000 housing?

A: If the vibration signal shows 50/60 Hz interference, verify that the housing is electrically bonded to the machine casing and that the cable shield is only grounded at the Proximitor/Rack end to avoid ground loops.

Q: Is the 3300 XL probe inside the housing replaceable?

A: Yes. The probe is a discrete component (-28 option). However, it is highly recommended to replace the probe with the exact same option code to maintain the hazardous area certifications associated with the assembly.