174985-00-12-10 Underwater Sensor Bently Nevada 3300 XL 25mm

Executive Summary

The 174985-00-12-10 is an extended-range eddy current sensor engineered for critical machinery protection under continuous fluid submersion. Part of the Bently Nevada 3300 XL 25mm Series, this transducer delivers non-contact shaft displacement data across long gaps where standard 8mm probes lack sufficient measuring margin.

Constructed with a 1.25-12 UNF threaded 304 Stainless Steel casing and a protective Tefzel armor tube, the 174985 probe shields signal conductors against non-corrosive process liquids and pressurized lubricants.

Core Architecture & Operating Principles

The 3300 XL 25mm Probe operates on high-frequency electromagnetic induction principles. Radio frequency excitation generated by a matching Proximitor driving circuit creates a magnetic field at the coil tip. Dynamic movements of conductive target metals induce eddy currents, altering RF field amplitude and yielding a linear DC voltage output proportional to target distance.

Because of its larger 25mm tip diameter, the 174985-00-12-10 maintains an extended linear range, making it ideal for large-diameter shafts, high differential expansion zones, or structural locations where generous mechanical installation clearances are required.

Technical Specifications

Part Number Configuration Breakdown

The 174985-00-12-10 code defines precise mechanical geometry and electrical cable lengths for specialized vessel entry:

• 174985 - Sealed Case 25mm Submerged Probe (1.25-12 UNF thread, Tefzel Armor Sheath)
  • 00 [Option A - Unthreaded Length]: 0.0 inches (Fully threaded case profile; configurable from 0.0 to 8.9 in in 0.1 in steps)
  • 12 [Option B - Overall Case Length]: 1.2 inches (Minimum case body length; configurable from 1.2 to 9.9 in in 0.1 in steps)
  • 10 [Option C - Total Length]: 1.0 meter (3.3 feet) system cable length

Installation Guidelines & Engineering Best Practices

Proper physical setup guarantees linear response and guards against mechanical damage in submerged environments.

• Target Side Clearance: Because 25mm sensing heads emit wide RF fields, maintain a minimum target diameter equal to or greater than 67 mm (2.63 in). Ensure side wall clearance of at least 75 mm (3.0 in) to prevent field distortion from adjacent structural metal.
• Mechanical Thread Engagement: Torque the 1.25-12 UNF stainless steel threads to spec using appropriate anti-seize compound verified for process fluid compatibility.
• Conduit Termination: Secure the Tefzel protective sheath so that physical movement or fluid turbulence does not chafe the tubing against machine walls.
• Connector Dry Zone Isolation: Run the cable end out of the wet chamber. Terminate the coaxial connector in an IP66/NEMA 4X dry junction enclosure. Never submerge the cable connector.

Target Machinery, Applications & Diagnostic Capabilities

Engineers specify the 174985-00-12-10 transducer for high-load heavy rotating machinery under severe environmental conditions.

Target Equipment & Scenarios:

• Large hydro-turbine generator shaft guide bearings operating flooded.
• Heavy multi-stage submerged boiler feed water pumps.
• Marine propulsion shafting and submerged gear line assemblies.
• Subsea pumping stations and wet-gas compressor housings.

Diagnostic Capabilities:

• Differential Expansion Monitoring: Tracks thermal growth differences between heavy rotor shafts and outer machine casings during start-up cycles.
• Axial Thrust Position Tracking: Detects severe thrust bearing wear before rotor-to-stator mechanical contact occurs.
• Low-Frequency Peak-to-Peak Displacement: Measures large dynamic shaft excursions on slow-speed heavy industrial shafts.

System Integration & Compatibility

The 174985-00-12-10 probe integrates into standard machine monitoring architectures:

• Bently Nevada 3300 XL 25mm Proximitor Sensors (e.g., matched 1.0m total system calibration units).
• Bently Nevada 3500 Machinery Protection Racks utilizing 3500/42M or 3500/22M monitoring modules.
• Legacy Bently Nevada 3300 monitoring hardware configured for 20 mV/mil scale factor input.

Global PLC Spare HUB's Insight

When selecting the 174985-00-12-10 probe for submerged duty, pay close attention to two critical mechanical factors:

1. Chloride Stress Corrosion Avoidance: The case of the 174985 uses 304 Stainless Steel. While highly resilient in hydraulic oil, raw freshwater, and boiler fluids, 304 SS susceptible to rapid pitting corrosion and stress cracking in brackish or marine saltwater environments. For ocean or high-salinity applications, specialized titanium or high-nickel alloy modifications are required.

2. Target Area Miscalculations: Site technicians upgrading from an 8mm probe to a 25mm probe often forget that the 25mm head requires a significantly larger metal target surface. If the shaft collar or flat target area is smaller than 67 mm in diameter, the probe's scale factor will deviate from the nominal 20 mV/mil rating, introducing measurement error into your 3500 system configuration.

Logistics, Packaging & Warranty Terms

• Product Guarantee: Supplied with comprehensive 12 Months Warranty protection covering manufacturing defects.
• Dispatch Lead Time: In-stock units process quickly with guaranteed shipment within 24-48 hours.
• Global Express Courier Delivery: Expedited global air freight handling via FedEx, UPS, or DHL directly to job sites.
• Packaging Integrity: Ships in heavy-duty ESD shielding containers with rigid thread caps protecting target tips.

Selection Guide & Technical FAQ

Selection Guide: When should I choose the 25mm probe over an 8mm version?

Choose a 25mm probe like the 174985 when your displacement measuring span exceeds 2.0 mm (80 mils), up to 12.7 mm (500 mils). It is ideal for differential expansion or heavy shaft thrust applications where target position moves over a wide mechanical range.

How does total system length affect Proximitor matching for the 174985-00-12-10?

This transducer option has a 1.0-meter integrated cable. You must pair it with the appropriate extension cable and 25mm Proximitor driver tuned specifically for a total system length of either 5.0 meters or 9.0 meters. Mismatched cable lengths compromise signal linearity.

Can the Tefzel protection tubing be cut or shortened during installation?

No. The Tefzel armor tubing is factory sealed to the 304 Stainless Steel case body to maintain the 34 Bar pressure boundary. Cutting or altering the tubing destroys the fluid seal and voids warranty coverage.

What zero-gap voltage setting is recommended during baseline installation?

Because the 25mm system features a 20 mV/mil sensitivity scale across 500 mils, the mid-scale gap point typically corresponds to -7.0 to -9.0 VDC output at the Proximitor test points. Always consult your specific machine calibration curve prior to final lock-nut torquing.

How do I handle probe replacement if process fluid pressure exceeds 34 Bar (500 psi)?

The standard 174985 rating seals static pressures up to 34 Bar Nitrogen equivalent. For high-pressure casing penetrations exceeding 500 psi, specialized high-pressure sealing gland modifications or external thermowell style pressure sleeves must be ordered.

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