Bently Nevada 31000 Series Modules - 31000-16-05-00-070-03-02

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, LNG terminals, and rotating machinery facilities, the 31000 Series provides continuous, non-contact measurement of shaft radial vibration, axial position, and differential expansion. Its modular architecture — comprising probe, extension cable, and proximitor — has made it the de facto standard for API 670-compliant machinery protection systems on steam turbines, gas compressors, and large centrifugal pumps. The system operates on the 3300 XL and 3500 Series monitor platforms and remains in active service at thousands of installations worldwide, many of which were commissioned in the 1980s and 1990s.

The Evolution of 31000 Series Architecture

The 31000 Series was introduced by Bently Nevada (now a Baker Hughes company) as a standardized eddy-current proximity probe family designed to interface directly with the 3300 and 3500 Series monitoring systems. Early configurations used a fixed-length, non-armored cable assembly with a standard 5 mm or 8 mm probe tip diameter. Over successive product generations, Bently Nevada introduced armored cable variants for high-temperature and high-vibration environments, extended-temperature proximitor options, and metric-thread probe housings to address international installation standards.

The 31000 Series architecture is defined by three interdependent components: the probe body (which determines tip diameter and thread specification), the extension cable (which sets the total system cable length and must be matched to the proximitor calibration), and the proximitor/oscillator-demodulator (which converts the raw eddy-current signal into a DC voltage proportional to gap distance). Mismatching any of these three elements invalidates the system calibration and renders the output unreliable. This interdependency is the primary compatibility challenge when sourcing replacement parts for legacy installations.

As the 3300 Series monitors have transitioned to end-of-life status and the 3500 Series has become the current platform, the 31000 Series probe hardware has remained backward-compatible, though the associated proximitor electronics (3300 XL 8mm, 3300 RAM, 3500/42M) have evolved significantly. Facilities operating original 3300 Series monitors must source matched probe-cable-proximitor sets to maintain calibration traceability.

31000 Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked configurations within the Bently Nevada 31000 Series. All part numbers follow the Bently Nevada structured ordering convention: probe diameter / cable length / temperature rating / connector type / housing material.

31000-00-05-05-02-00: 5 mm probe, 0.5 m integral cable, standard temp, no connector, bare end
31000-00-05-05-02-05: 5 mm probe, 0.5 m integral cable, standard temp, armored jacket
31000-00-08-05-02-00: 8 mm probe, 0.5 m integral cable, standard temp, bare end
31000-00-08-05-02-05: 8 mm probe, 0.5 m integral cable, standard temp, armored jacket
31000-16-05-00-070-03-02: 5 mm probe housing assembly, 1.6 m cable, 70°C rated, metric thread, standard connector
31000-25-05-00-070-03-02: 5 mm probe housing assembly, 2.5 m cable, 70°C rated, metric thread, standard connector
31000-50-05-00-070-03-02: 5 mm probe housing assembly, 5.0 m cable, 70°C rated, metric thread, standard connector
31000-00-05-05-02-10: 5 mm probe, 0.5 m cable, high-temp rating (177°C), bare end
31000-00-08-05-02-10: 8 mm probe, 0.5 m cable, high-temp rating (177°C), bare end
31000-16-08-00-070-03-02: 8 mm probe housing assembly, 1.6 m cable, 70°C rated, metric thread
31000-25-08-00-070-03-02: 8 mm probe housing assembly, 2.5 m cable, 70°C rated, metric thread
31000-50-08-00-070-03-02: 8 mm probe housing assembly, 5.0 m cable, 70°C rated, metric thread
31000-00-05-05-02-15: 5 mm probe, 0.5 m cable, extended-temp (260°C), armored, bare end
31000-00-08-05-02-15: 8 mm probe, 0.5 m cable, extended-temp (260°C), armored, bare end
31000-16-05-00-120-03-02: 5 mm probe housing assembly, 1.6 m cable, 120°C rated, metric thread
31000-25-05-00-120-03-02: 5 mm probe housing assembly, 2.5 m cable, 120°C rated, metric thread
31000-50-05-00-120-03-02: 5 mm probe housing assembly, 5.0 m cable, 120°C rated, metric thread

Quality Control for the 31000 Series Range

The 31000 Series proximity probe system requires functional verification at the system level, not the component level. A probe body that tests within specification in isolation may produce out-of-tolerance output when paired with a mismatched extension cable or proximitor. DriveKNMS applies the following test protocol to all 31000 Series units prior to shipment:

Each probe assembly is tested for tip resistance and inductance against Bently Nevada published nominal values. Extension cables are verified for continuity, insulation resistance (minimum 100 MΩ at 500 VDC), and shield integrity. Complete probe-cable-proximitor sets are bench-tested using a calibrated target simulator to verify the output voltage-gap characteristic across the full linear range (typically 0.25 mm to 2.25 mm for 5 mm probes). Temperature-rated assemblies are subjected to thermal soak at rated temperature prior to final measurement. All test data is documented and shipped with the unit.