Bently Nevada 31000 Series Modules - 31000-31-05-20-058-00-02

Technical Dossier

Product Details And Specifications

Bently Nevada 31000 Series Technical Notes

The Bently Nevada 31000 Series proximity probe system is one of the most widely deployed eddy-current sensing platforms in global heavy industry. Installed across petrochemical refineries, nuclear power stations, offshore platforms, LNG terminals, and rotating machinery monitoring systems, the 31000 Series provides continuous, non-contact measurement of shaft radial vibration, axial position, and differential expansion. Its field-proven architecture has made it the de facto standard for API 670-compliant machinery protection systems on critical rotating equipment including steam turbines, gas compressors, centrifugal pumps, and large induction motors. The system operates on the eddy-current principle: a high-frequency oscillator drives the probe tip, and any conductive target within range induces eddy currents that alter the oscillator's impedance — producing a DC voltage output linearly proportional to the gap distance. This measurement principle requires no physical contact with the rotating shaft, eliminating wear and enabling continuous online monitoring at speeds exceeding 100,000 RPM.

The Evolution of 31000 Series Architecture

The Bently Nevada 31000 Series was introduced as part of the broader 3300 XL machinery protection ecosystem, designed to replace earlier 7200 Series and 3300 Series probe systems while maintaining backward signal compatibility. Early 31000 configurations used a two-piece probe-and-extension-cable assembly with a separate proximitor (signal conditioning module) mounted in a junction box or rack. This architecture allowed field replacement of individual components without disturbing the entire measurement loop — a critical advantage in continuous-process industries where unplanned shutdowns carry multi-million-dollar cost implications.

Over successive generations, the 31000 Series incorporated armored extension cables with improved EMI shielding, high-temperature probe variants rated to 175°C for turbine bearing housings, and submersible configurations for subsea and wet-environment applications. The system's 5-meter and 9-meter standard cable lengths were supplemented by custom-length assemblies to accommodate large-frame machinery. Connector standardization (the BNC-to-TNC transition in later revisions) introduced compatibility challenges between early and late production runs — a key consideration when sourcing replacement parts for legacy installations. Current procurement must verify probe tip diameter (5 mm, 8 mm, 11 mm, 14 mm), cable length, temperature rating, and connector type to ensure drop-in compatibility.

31000 Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked components within the Bently Nevada 31000 Series proximity probe system. Each entry reflects a distinct mechanical or electrical configuration:

31000-00-05-10-02-00: 5 mm probe, 1 m armored extension, standard temperature, BNC connector
31000-00-05-10-05-00: 5 mm probe, 5 m armored extension, standard temperature, BNC connector
31000-00-08-10-02-00: 8 mm probe, 1 m armored extension, standard temperature, BNC connector
31000-00-08-10-05-00: 8 mm probe, 5 m armored extension, standard temperature, BNC connector
31000-00-08-10-09-00: 8 mm probe, 9 m armored extension, standard temperature, BNC connector
31000-00-11-10-05-00: 11 mm probe, 5 m armored extension, standard temperature, BNC connector
31000-00-11-10-09-00: 11 mm probe, 9 m armored extension, standard temperature, BNC connector
31000-00-14-10-05-00: 14 mm probe, 5 m armored extension, standard temperature, BNC connector
31000-25-05-10-05-00: 5 mm probe, 5 m extension, high-temperature rating (175°C), BNC connector
31000-25-08-10-05-00: 8 mm probe, 5 m extension, high-temperature rating (175°C), BNC connector
31000-25-08-10-09-00: 8 mm probe, 9 m extension, high-temperature rating (175°C), BNC connector
31000-25-11-10-05-00: 11 mm probe, 5 m extension, high-temperature rating (175°C), BNC connector
31000-31-05-20-058-00-02: Housing assembly for 5 mm probe, stainless steel body, standard mounting thread
31000-31-08-20-058-00-02: Housing assembly for 8 mm probe, stainless steel body, standard mounting thread
31000-31-11-20-058-00-02: Housing assembly for 11 mm probe, stainless steel body, standard mounting thread
31000-31-14-20-058-00-02: Housing assembly for 14 mm probe, stainless steel body, standard mounting thread
31000-50-00-01: Proximitor signal conditioner, -24 VDC supply, 200 mV/mil output scale factor
31000-50-00-02: Proximitor signal conditioner, -24 VDC supply, 100 mV/mil output scale factor

Sourcing Hard-to-Find & Obsolete 31000 Series Parts

The Bently Nevada 31000 Series has entered the mature-to-declining phase of its product lifecycle. Baker Hughes (the current owner of the Bently Nevada brand) has progressively shifted its active catalog toward the 3300 XL and Velomitor product lines. As a result, a significant portion of 31000 Series SKUs — particularly early-production housing assemblies, non-standard cable lengths, and high-temperature probe variants — are no longer available through standard OEM distribution channels.

Quality Control for the 31000 Series Range

The 31000 Series proximity probe system presents specific quality verification challenges due to its multi-component signal chain. A probe assembly that passes visual inspection may still exhibit degraded performance if the extension cable's characteristic impedance has drifted, the proximitor's oscillator frequency has shifted, or the connector interface has developed intermittent contact resistance. DriveKNMS applies a structured test protocol to all 31000 Series components prior to dispatch: