Bently Nevada 31000 Series Modules - 31000-28-05-00-061-01-02

Technical Dossier

Product Details And Specifications

Bently Nevada 31000 Series Technical Notes

The 31000 Series operates on the fundamental eddy-current principle: a high-frequency oscillator drives a coil in the probe tip, generating an electromagnetic field. When a conductive target (shaft) enters this field, eddy currents are induced, loading the oscillator and producing a DC output voltage linearly proportional to the gap between probe tip and target surface. This output feeds directly into Bently Nevada 3300, 3500, and ADAPT.wind monitoring systems, as well as legacy 7200 Series monitors, making the 31000 Series a cross-platform sensing element with a service life spanning multiple monitor generations.

The Evolution of 31000 Series Architecture

The 31000 Series was introduced as a standardized replacement and extension of earlier Bently Nevada probe families, consolidating probe tip diameters, cable lengths, and connector configurations into a rationalized catalog. Early variants used a two-piece probe-and-armored-cable assembly with a separate proximitor module (typically the 3300 XL 8mm or 5mm Proximitor). The housing assembly—the component designated by part numbers such as 31000-28-05-00-061-01-02—encapsulates the probe coil, tip geometry, and integral cable in a single field-replaceable unit, reducing installation variables and improving measurement repeatability.

Over successive revisions, Bently Nevada refined the 31000 Series to address three primary field failure modes: connector corrosion in high-humidity environments, cable jacket degradation under continuous vibration, and probe tip wear in applications with intermittent contact. The current generation uses a hermetically sealed tip assembly and a reinforced armored cable jacket rated for continuous operation from -35°C to +177°C. Compatibility with the 3500 Series monitoring rack was maintained through standardized output sensitivity of -7.87 V/mm (-200 mV/mil), ensuring that 31000 Series probes can replace earlier 7200 Series probes in most installations without recalibration of the monitor.

31000 Series Full Catalog & Functionalities (SKU List)

The following SKUs represent the core of the 31000 Series proximity probe housing assembly catalog, organized by probe tip diameter and cable/connector configuration. Each entry reflects a distinct mechanical and electrical specification.

31000-28-05-00-061-01-02: 8mm probe, 5m armored cable, standard connector, -7.87 V/mm sensitivity, API 670 compliant housing assembly.
31000-28-08-00-061-01-02: 8mm probe, 8m armored cable, extended reach for large bearing housings, standard output sensitivity.
31000-28-10-00-061-01-02: 8mm probe, 10m armored cable, used in installations requiring long cable runs between probe and proximitor.
31000-28-05-00-061-00-00: 8mm probe, 5m cable, non-armored jacket variant for low-vibration indoor installations.
31000-25-05-00-061-01-02: 5mm probe tip, 5m armored cable, for small-diameter shaft applications and tight bearing clearances.
31000-25-08-00-061-01-02: 5mm probe, 8m armored cable, extended cable for 5mm tip geometry in deep-access installations.
31000-28-05-00-025-01-02: 8mm probe, 5m cable, high-temperature tip rated to +177°C for turbine exhaust-side mounting.
31000-28-05-00-025-00-00: 8mm probe, 5m cable, high-temperature, non-armored, for controlled-environment turbine enclosures.
31000-28-03-00-061-01-02: 8mm probe, 3m short-cable assembly for compact machinery frames with proximitor mounted adjacent to bearing.
31000-25-03-00-061-01-02: 5mm probe, 3m cable, compact assembly for small turbomachinery and compressor applications.
31000-28-05-00-061-02-02: 8mm probe, 5m cable, reverse-mount thread configuration for installations with limited front-access clearance.
31000-28-05-00-061-01-05: 8mm probe, 5m cable, stainless steel housing variant for corrosive or wash-down environments.
31000-28-05-00-061-01-03: 8mm probe, 5m cable, ATEX/IECEx certified variant for Zone 1 hazardous area classification.
31000-25-05-00-025-01-02: 5mm probe, 5m cable, high-temperature tip, for small-shaft high-temperature applications in steam turbines.
31000-28-05-00-061-01-04: 8mm probe, 5m cable, CSA/FM certified variant for North American hazardous location compliance.
31000-28-05-00-061-01-06: 8mm probe, 5m cable, dual-probe assembly for X-Y radial vibration measurement at a single bearing plane.

Sourcing Hard-to-Find & Obsolete 31000 Series Parts

A substantial portion of the 31000 Series catalog has transitioned to limited-availability or extended lead-time status through the OEM channel. Facilities operating legacy 3300 Series monitors—which remain in service at hundreds of sites globally due to the capital cost of full system replacement—depend on the aftermarket for probe assemblies that are no longer stocked at regional distributors.

Quality Control for the 31000 Series Range

The 31000 Series proximity probe housing assembly presents specific quality verification requirements that differ from standard electronic component testing. The critical performance parameters—output sensitivity (V/mm), linearity across the measurement range, and gap voltage at reference distance—must be verified against the probe's integral cable and the target proximitor module, as sensitivity is a system-level characteristic, not a standalone probe specification.

DriveKNMS applies the following test protocol to all 31000 Series assemblies prior to shipment: (1) DC resistance measurement of the probe coil to verify coil integrity and detect open or shorted windings; (2) insulation resistance test between the coil circuit and the probe housing to confirm hermetic seal integrity; (3) functional gap-voltage test using a calibrated 3300 XL Proximitor and a certified target material (AISI 4140 steel) to verify output sensitivity within ±1% of the -7.87 V/mm nominal; (4) linearity sweep across the full measurement range (0–2.54mm for 8mm probes) to confirm linear output with less than ±0.5% deviation; (5) cable continuity and shield integrity test for the full cable length; (6) visual inspection of the probe tip, housing threads, and connector for mechanical damage, corrosion, or contamination.