330851-01-000-020-10-00-05 Bently Nevada 3300 XL 25mm Probe

Product Overview

The 330851-01-000-020-10-00-05 is a premium, heavy-duty 3300 XL 25 mm Proximity Probe manufactured in the United States by Bently Nevada. Engineered as a rugged eddy current sensor, this device is explicitly built to replace legacy 7200 25 mm, 7200 35 mm, and 25 mm Differential Expansion (DE) Integral transducer systems across harsh industrial applications. It features a standard fractional 1-1/4 - 12 threaded case with a 20 mm overall case length and zero unthreaded length. Outfitted with a 1.0-meter unarmored FluidLoc triaxial cable and rated with multiple global agency approvals (Option 05), this 0.23 kg (230 grams) sensor delivers sub-millisecond physical displacement tracking under intense steam turbine operating limits.

Core Technical Advantages

Premium FluidLoc Triaxial Moisture Seal

The probe utilizes a 75-ohm triaxial cable insulated with advanced perfluoroalkoxyethylene (PFA). Featuring Bently Nevada’s proprietary FluidLoc design, the internal cable layers are blocked to prevent high-pressure lubricating oils, process gases, and superheated steam from migrating along the wire path into clean instrumentation enclosures.

Rugged PEEK Thermoplastic Construction

The sensor tip is molded from high-performance Polyetheretherketone (PEEK). This advanced material provides exceptional dimensional stability and structural integrity under prolonged thermal stress. It protects the delicate internal driver coils from chemical corrosion, oil baths, and mechanical erosion inside turbine housings.

Extreme Thermal & Mechanical Performance

Enclosed in a durable AISI 304 stainless steel case, the probe operates continuously in environments spanning –35 °C to +200 °C. It can also withstand extreme short-term temperature peaks up to +250 °C for up to 24 hours. The robust mechanical design supports a massive structural torque rating up to 163 N·m (120 ft·lb).

Technical Specifications

Installation and Maintenance

Mechanical Threading and Torque Regulation

Clean the internal machine housing threads before installation. Thread the 1-1/4 - 12 probe body into the mounting bracket or casing by hand. Once the appropriate linear gap distance is set, tighten the primary locknuts with a calibrated torque wrench. While the device can withstand a maximum torque of 163 N·m (120 ft·lb), the manufacturer strongly recommends a installation torque of 68 N·m (50 ft·lb) to protect the stainless steel casing.

Voltage Gap Calibration and Proximitor Linkup

Connect the 1.0 m triaxial PFA cable lead to a 3300 XL 25mm Proximitor Sensor using a high-fidelity extension cable loop. Power the proximity system and monitor the DC output voltage. Adjust the mechanical depth of the 0.23 kg probe body until the sensor reads the target mid-range linear calibration voltage, then lock the outer hardware into place.

Hazardous Location Isolation Safety

When deploying the probe inside explosive atmospheres (EPL Ga/Gc), verify the installation matches Bently Nevada control drawings. For intrinsically safe "ia" Zone 0 loops, install appropriate zener barriers or galvanic isolators. For non-sparking "nA" or increased safety "ec" Zone 2 operations, ensure the wiring meets Class I, Division 2, Groups A, B, C, and D standards without any safety barrier bypasses.

Engineering Advantages

Universal Legacy System Retrofits

The 3300 XL 25mm series features an adaptable mechanical case configuration. It serves as a direct drop-in replacement for obsolete 7200 25mm, 7200 35mm, and older 25mm DE integral monitoring hardware, helping facilities upgrade their systems without costly casing modifications.

Maritime and Heavy Industry Approvals

Certified under the ABS (American Bureau of Shipping) 2009 Steel Vessels Rules, this probe is fully qualified for offshore rigs, marine propulsion shafts, and coastal processing infrastructure. It provides exceptional stability against high-vibration engine environments and harsh ambient marine salt air.

Extended Thermal Schedule Management

The probe is rated for flexible ambient temperature classes (T1 down to T5). This transparent temperature structure allows control engineers to quickly match ambient monitoring restrictions to hazardous location regulations, keeping operations safe even during thermal overloads up to 232 °C.

Technical FAQs

Q1: What are the consequences of exceeding the recommended installation torque of 68 N·m?
A1: Exceeding the recommended torque up toward the 163 N·m limit increases mechanical stress on the 1-1/4 - 12 threads. If over-torqued, the AISI 304 stainless steel case can warp or bind, which risks micro-fracturing the internal PEEK tip assembly or shifting the calibrated position of the inner coils.

Q2: Why is the unarmored version selected over the armored triaxial probe alternative?
A2: The unarmored version reduces the probe's weight to a light 230 grams and provides superior flexibility for routing through tight internal conduits. This makes it an ideal option for installations where external stainless steel armor is unnecessary, such as inside fully enclosed turbine housings or rigid outer pipe ducts.

Q3: How does the 25 mm probe tip cope with high-temperature spikes up to 250 °C?
A3: The PEEK tip and PFA insulation are rated to withstand intermittent spikes up to +250 °C for up to 24 hours without melting or losing calibration. If a thermal spike lasts longer than this window, it can lead to dielectric breakdown, signal drift, and potential loss of the internal fluid seal.