Bently Nevada 330851 Series Proximity Probes

Technical Dossier

Product Details And Specifications

Bently Nevada 330851 Series Technical Notes

The Bently Nevada 330851 Series comprises eddy-current proximity probes engineered for continuous, non-contact measurement of shaft radial vibration, axial position, and differential expansion in rotating machinery. These probes are integral components of the 3300 XL and legacy 3300 Series monitoring systems deployed across global heavy industry — including petrochemical refineries, nuclear power stations, LNG terminals, offshore platforms, and large-scale turbomachinery installations. The 330851 probe line is designed to operate within the Bently Nevada standard 5-meter and 9-meter extension cable systems, paired with compatible proximitor sensors (330180, 330130 series) to deliver a calibrated output of −200 mV/mil (−7.87 V/mm). Their field-proven reliability in high-temperature, high-vibration environments has made them a de facto standard in API 670-compliant machinery protection systems worldwide.

The Evolution of 330851 Architecture

The 330851 probe series traces its lineage to Bently Nevada's original 3300 Series eddy-current system, introduced in the 1970s as the industry's first standardized proximity measurement platform. Early-generation probes used a fixed 5-meter integral cable design with a 7.87 mm (5/16 in) tip diameter, calibrated exclusively for AISI 4140 steel targets. As turbomachinery OEMs demanded greater installation flexibility, Bently Nevada introduced the modular cable architecture — separating the probe body from the extension cable — enabling field replacement without recalibration of the full loop.

The 330851 designation encodes a structured configuration matrix: probe tip diameter (8 mm standard), cable length (ranging from 0.5 m to 9 m), connector type (standard or reverse mount), and target material calibration (carbon steel default, with stainless and Inconel variants). The transition from the 330851 to the current 330900 and 330980 Series reflects a shift toward ATEX/IECEx Zone 0 intrinsic safety ratings and extended temperature ranges (−40°C to +177°C), while the 330851 remains the dominant installed base in pre-2005 machinery trains. Compatibility between 330851 probes and 3500 Series rack monitors requires verification of proximitor output range and gap voltage calibration — a critical consideration during system upgrades or partial retrofits.

330851 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified configurations within the Bently Nevada 330851 proximity probe series, organized by cable length and connector configuration:

330851-00-000-050-10-00-CN: 8 mm probe, 0.5 m integral cable, standard connector, carbon steel calibration
330851-01-000-050-10-00-CN: 8 mm probe, 1.0 m integral cable, standard connector, carbon steel calibration
330851-02-000-050-10-00-CN: 8 mm probe, 2.0 m integral cable, standard connector, carbon steel calibration
330851-03-000-050-10-00-CN: 8 mm probe, 3.0 m integral cable, standard connector, carbon steel calibration
330851-04-000-050-10-00-CN: 8 mm probe, 4.0 m integral cable, standard connector, carbon steel calibration
330851-05-000-050-10-00-CN: 8 mm probe, 5.0 m integral cable, standard connector, carbon steel calibration
330851-06-000-050-10-00-CN: 8 mm probe, 6.0 m integral cable, standard connector, carbon steel calibration
330851-07-000-050-10-00-CN: 8 mm probe, 7.0 m integral cable, standard connector, carbon steel calibration
330851-08-000-050-10-00-CN: 8 mm probe, 8.0 m integral cable, standard connector, carbon steel calibration
330851-09-000-050-10-00-CN: 8 mm probe, 9.0 m integral cable, standard connector, carbon steel calibration
330851-02-000-050-10-00-02: 8 mm probe, 2.0 m cable, reverse-mount connector, carbon steel calibration
330851-05-000-050-10-00-02: 8 mm probe, 5.0 m cable, reverse-mount connector, carbon steel calibration
330851-02-000-050-10-00-SS: 8 mm probe, 2.0 m cable, standard connector, stainless steel target calibration
330851-05-000-050-10-00-SS: 8 mm probe, 5.0 m cable, standard connector, stainless steel target calibration
330851-02-000-050-10-00-IN: 8 mm probe, 2.0 m cable, standard connector, Inconel target calibration
330851-05-000-050-10-00-IN: 8 mm probe, 5.0 m cable, standard connector, Inconel target calibration
330851-02-000-050-10-00-TI: 8 mm probe, 2.0 m cable, standard connector, titanium target calibration

Quality Control for the 330851 Range

Each 330851 proximity probe processed by DriveKNMS undergoes a structured verification protocol prior to dispatch. Probe tip coil resistance is measured against OEM specification (nominally 9.3 Ω ± 5%) using a calibrated LCR meter. Cable continuity and insulation resistance are verified across the full cable length at 500 VDC. The probe is then installed in a standardized test fixture replicating the Bently Nevada 3300 XL proximitor circuit, with gap voltage swept from −2 VDC to −18 VDC to confirm linear output response (−200 mV/mil ± 1%). Connector integrity — including thread engagement torque and O-ring sealing — is inspected per IEC 60529 IP67 requirements. All test results are logged against the probe serial number and supplied with the shipment documentation. Probes that fail any parameter are quarantined and not returned to inventory.