Extended Range Machinery Protection

The Bently Nevada 128987-130-01-05 is a high-performance 3300 XL 25mm proximity probe designed for critical applications requiring an extended linear measurement range. This specialized sensor excels in monitoring large-scale rotating machinery where standard 8mm probes lack the necessary span, specifically for axial thrust position, differential expansion, and radial vibration on large diameter shafts. By providing a wider linear range of 12.7 mm (500 mils), it ensures that turbine operators receive accurate, non-contacting displacement data even during significant thermal growth or high-vibration events. As a primary component of a Turbine Supervisory Instrumentation (TSI) suite, this probe is essential for preventing catastrophic internal contact in steam turbines and large compressors.

Hardware Configuration and Option Breakdown

128987 - 3300 XL 25mm Probe

Identifies the core 25mm diameter eddy current probe, capable of a much larger linear range compared to the standard 8mm or 11mm series.

130 - Total Case Length

Specifies a 130 mm (approx. 5.12 inches) overall case length. This dimension ensures the probe can be mounted through thick bearing housings or specialized brackets while maintaining structural rigidity.

01 - Connector and Cable Option

Indicates a miniature coaxial connector with standard cable insulation. This configuration provides high-frequency signal integrity while maintaining a flexible lead for routing through conduit.

05 - Agency Approval Option

Designates the multiple approval version (ATEX, IECEx, CSA). This enables the sensor to be safely deployed in Zone 0, 1, or 2 hazardous areas when used with the appropriate intrinsically safe Proximitor and barriers.

Dimensional and Physical Specifications

Field Commissioning and Gap Strategy

The 25mm probe requires a specific gapping procedure due to its wide linear range. Engineers must target a center-gap voltage of -10.0 VDC at the Proximitor output for displacement measurements, or adjust based on the expected direction of thermal expansion for differential expansion tasks. Ensure a minimum side clearance of 50 mm (2 inches) from any surrounding metal to avoid "side-view" interference, which can distort the electromagnetic field and cause non-linear readings. When routing the coaxial lead, maintain a minimum bend radius of 25.4 mm (1 inch) and avoid over-tightening zip ties to prevent impedance changes in the cable.

Strategic Engineering Advantages

The 128987-130-01-05 provides a significant engineering edge in large-scale power generation. Its 25mm tip architecture is specifically hardened against the thermal cycles of steam turbines, offering industry-leading stability over a -51°C to +177°C range. Because it utilizes the 3300 XL system technology, it is fully compatible with the Bently Nevada 3500/42M Proximitor Monitor and easily integrates into Honeywell Experion PKS or Siemens S7-400H controllers. This compatibility ensures that critical "Danger" and "Alert" setpoints are triggered by high-fidelity signals, reducing the risk of false trips while guaranteeing protection during actual mechanical excursions.

Shipping and Logistics

Delivery time: 3-5 days when payment finish, BY DHL/FEDEX/UPS.

All sensors are shipped in anti-static industrial packaging with specialized tip-protection caps to ensure the ceramic-filled probe face arrives without micro-fractures or contamination.

Proximity System Technical FAQ

Q1: Can I use this probe with a standard 8mm Proximitor?

A1: No. The 25mm probe requires a dedicated 3300 XL 25mm Proximitor (e.g., 330850 series). Using an incorrect Proximitor will result in a scale factor error and unusable data.

Q2: What is the significance of the 130mm case length?

A2: This is the Dimension A of the probe. It represents the physical length of the threaded stainless steel body. You must ensure this length is sufficient to pass through your machine's casing to reach the target shaft.

Q3: How does the -05 approval impact installation?

A3: The -05 suffix means this probe is certified for worldwide hazardous areas. To maintain this certification, you must use a certified extension cable and ensure the Proximitor is installed within an appropriately rated enclosure or behind a safety barrier.