Description
The Bently Nevada 21747-075-01 is a 7.5-meter armored extension cable designed for use within the legacy 7200 Series 5mm and 8mm Proximity Transducer Systems. This industrial-grade, non-contacting displacement measurement cable transmits high-frequency eddy-current signals from the probe tip to the Proximitor sensor, facilitating the monitoring of shaft vibration and dynamic position changes in rotating machinery.
Commercial Availability & Procurement
- Condition: New Original (New Surplus) or Refurbished (Fully Tested for Electrical Continuity and Shielding Integrity)
eBay
- Warranty: 12-Month Comprehensive Technical Warranty
NexAuto Technology Limited
- Lead Time: Ships within 1–2 business days from available legacy inventory
Quick Time Engineering Inc
- Pricing Note: Listed price is indicative and subject to vintage stock availability. Contact our sales office for a firm, up-to-date quote.
Part Number Breakdown
21747 - 075 - 01
│ │ │
│ │ └──── Armor Option: Stainless Steel Flexible Armor Protective Jacket
│ └────────── Cable Length: 7.5 meters (24.6 feet) nominal length
└───────────────── Base Model: 7200 Series Proximity Transducer Extension Cable Technical Specifications
| Parameter | Value |
|---|---|
| System Compatibility | Bently Nevada 7200 Series 5mm & 8mm Proximity Systems |
| Total Cable Length | 7.5 meters (approx. 24.6 feet) |
| Armor Material | 316L Stainless Steel interlocking flexible armor conduit |
| Core Conductor | Coaxial configuration, high-density fluoropolymer insulation |
| Linear Measuring Range | Up to 80 mils (2.0 mm) when combined with an 8mm 7200 probe |
| System Frequency Response | 0 to 10 kHz (0 to 600,000 cpm) |
| Operating Temperature | −40 to +177 °C (−40 to +350 °F) operating limits |
| Environmental Shielding | Resists degradation from lube oil, ammonia, and chemical solvents |
Field Experience & Engineering Insights
System Impedance and Matching Constraints
In field installations of eddy-current proximity systems, the total electrical length of the transducer system (probe plus extension cable) must accurately match the calibration parameters configured in the 7200 Proximitor sensor module.
- System Balancing: The 7200 system operates on a strictly balanced total network length profile (typically 5.0 meters or 9.0 meters total). When utilizing a 7.5-meter extension cable, ensure that it is mated exclusively to the corresponding 7200 probe variant designed for a matching total system loop profile.
- Mismatches: Mixing different system cables will alter the characteristic impedance of the coaxial connection loop, shifting the scale factor away from the standard 200 mV/mil (7.87 V/mm) calibration baseline and skewing SCADA/3500 rack telemetry.
Mechanical Armor Maintenance and Installation Routing
- Bend Radius Limits: The “01” suffix configuration features rugged stainless steel interlocking armor to shield the internal coaxial line from mechanical crushing, pinching, and flying debris. However, this armor adds mechanical rigidity. Do not exceed the minimum structural bend radius of 25 mm (1.0 inch) during conduit tray installation to avoid introducing micro-fissures in the internal copper shielding mesh.
- Connector Protection: The miniature gold-plated coaxial connectors (coaxial couplings) are susceptible to contamination. During machine outages or when pulling cables through protective junction boxes, apply self-fusing silicone tape or heat-shrink tubing over the mated connections to isolate the gold pins from water ingress, cutting fluids, and dirt.
System Integration & Compatibility Checklist
- API 670 Compliance: Meets standard API 670 guidelines for vibration monitoring loops when installed alongside matching 7200 components.
- Proximitor Interface: Connects to legacy Bently Nevada 7200 Proximitor sensors. Note: Not directly interchangeable with newer 3300 XL series Proximitor drivers unless an explicit system recalibration is carried out.
Moore Automation Limited+ 1
- Junction Boxes: Requires standard Bently Nevada terminal housings or aluminum conduit junction units to ground the system shielding properly.
Frequently Asked Questions
Can this extension cable be shorted or cut to a custom length if the run is too long?
No. Proximity sensor extension cables are precision-trimmed at the factory to meet specific electrical capacitance and inductance ratings. Splicing, cutting, or field-terminating the 21747-075-01 will destroy the system’s impedance matching, rendering the associated vibration monitor incapable of proper linear calibration. Always coil and secure any excess cable length inside a local junction box.
What should I check if the 3500 machinery monitor indicates a “Not OK” status after a swap?
First, verify the connection seating at the probe end and the Proximitor input terminal. The miniature connectors must click securely into place. Second, verify that the center conductor pin has not become bent or contaminated with dust during installation. Third, use a digital multimeter to verify the internal resistance metrics match factory specifications.
Is the 21747-075-01 certified for installation in hazardous environments?
Yes, when mounted within an approved Bently Nevada housing network and connected through a properly configured intrinsic safety barrier or galvanic isolator inside the machine rack enclosure, it conforms to industrial ATEX/IECEx Zone 2 requirements.
