Bently Nevada 21505 Series Modules - 21505-00-12-10-02

Technical Dossier

Product Details And Specifications

Bently Nevada 21505 Series Technical Notes

The Bently Nevada 21505 Series Standard Mount Proximity Probes are eddy-current, non-contact displacement sensing probes engineered for continuous vibration and position monitoring in rotating machinery. Deployed across global heavy industry — including petrochemical refineries, nuclear power stations, offshore platforms, and LNG processing facilities — the 21505 Series forms a core sensing layer within Bently Nevada's 3300 and 7200 Series monitoring systems. These probes conform to API 670 machinery protection standards and are rated for operation in hazardous area classifications including ATEX and FM. Their installation base spans decades of continuous service, making long-term parts availability a critical operational concern for plant reliability engineers worldwide.

The Evolution of 21505 Architecture

The 21505 Series was introduced as part of Bently Nevada's second-generation proximity probe platform, succeeding earlier 7000 Series probes. The architecture is built around a passive eddy-current coil embedded in a stainless steel housing, operating in conjunction with a dedicated extension cable and a proximitor (signal conditioning module). The three-component system — probe, extension cable, proximitor — must be matched as a calibrated set to maintain measurement accuracy within ±1% of full-scale output.

21505 Full Catalog & Functionalities (SKU List)

The following SKUs represent the documented 21505 Series product range, organized by configuration parameters (probe length, cable length, connector type, and temperature rating). Each model is a calibrated proximity probe assembly.

21505-00-12-10-02: 5mm probe, 5m extension cable, standard temperature, 2-pin connector, AISI 4140 target calibration.
21505-00-12-10-05: 5mm probe, 5m extension cable, standard temperature, 5-pin MIL-spec connector.
21505-00-12-10-08: 5mm probe, 5m extension cable, standard temperature, 8-pin connector configuration.
21505-00-12-05-02: 5mm probe, 2.5m short extension cable, standard temperature, 2-pin connector.
21505-00-12-15-02: 5mm probe, 7.5m extended cable, standard temperature, 2-pin connector.
21505-00-12-20-02: 5mm probe, 10m long extension cable, standard temperature, 2-pin connector.
21505-00-16-10-02: 8mm probe body, 5m extension cable, standard temperature, 2-pin connector.
21505-00-16-10-05: 8mm probe body, 5m extension cable, standard temperature, 5-pin MIL-spec connector.
21505-00-16-15-02: 8mm probe body, 7.5m extension cable, standard temperature, 2-pin connector.
21505-00-16-20-02: 8mm probe body, 10m extension cable, standard temperature, 2-pin connector.
21505-00-20-10-02: 11mm probe body, 5m extension cable, standard temperature, 2-pin connector.
21505-00-20-10-05: 11mm probe body, 5m extension cable, standard temperature, 5-pin MIL-spec connector.
21505-00-20-15-02: 11mm probe body, 7.5m extension cable, standard temperature, 2-pin connector.
21505-00-12-10-02-HT: High-temperature variant, 5mm probe, 5m cable, rated to 177°C tip, 2-pin connector.
21505-00-16-10-02-HT: High-temperature variant, 8mm probe, 5m cable, rated to 177°C tip, 2-pin connector.
21505-00-20-10-02-HT: High-temperature variant, 11mm probe, 5m cable, rated to 177°C tip, 2-pin connector.
21505-00-12-10-02-EX: ATEX/FM certified variant, 5mm probe, 5m cable, intrinsically safe, 2-pin connector.

Sourcing Hard-to-Find & Obsolete 21505 Series Parts

All sourced units are verified against original Bently Nevada calibration documentation where available. For sites requiring API 670 compliance, DriveKNMS can provide traceability records and calibration certificates issued by accredited third-party metrology laboratories. Customers operating legacy 3300 or 7200 Series monitoring systems who require matched probe-cable-proximitor sets for direct replacement are encouraged to submit their full bill of materials for cross-reference and availability confirmation.

Quality Control for the 21505 Range

The 21505 Series presents specific quality verification challenges due to its three-component calibrated system architecture. DriveKNMS applies the following test protocol to all 21505 units prior to dispatch:

Coil Impedance Verification: Each probe coil is measured for DC resistance and inductance at 1 MHz using a precision LCR meter. Values are compared against Bently Nevada factory specification sheets for the specific probe body diameter.
Gap Voltage Linearity Test: Probes are bench-tested against a certified AISI 4140 steel target across the full measurement range (0–2mm for 5mm probes, 0–4mm for 8mm probes). Output linearity must be within ±1% of the published sensitivity factor (200 mV/mil or 7.87 V/mm).
Cable Continuity and Insulation Resistance: Extension cables are tested for conductor continuity, shield integrity, and insulation resistance (minimum 100 MΩ at 500 VDC).
Connector Inspection: All MIL-spec and standard connectors are inspected for pin corrosion, thread integrity, and environmental sealing.
Matched Set Verification: Where a complete probe-cable-proximitor set is supplied, the full system output is verified against a reference proximitor to confirm calibrated sensitivity within specification.