Product Core Brief

• Model: 330851-02-000-060-10-00-00
• Brand: Bently Nevada (Baker Hughes)
• Series: 3300 XL 25mm Eddy Current Proximity Transducer System
• Full Suffix Breakdown:330851 = Base 25mm proximity probe platform02 = M30×2 straight threaded body, standard front cable exit000 = Zero unthreaded shoulder length, no custom body modifications060 = 6-meter total integrated coaxial cable length10 = Standard temperature grade (−35°C ~ +150°C probe tip rating)00 = Standard unarmored PEP coaxial cable jacket00 = Standard mini-microdot male connector, no special barrier fittings
• Core Function: Long-range non-contact eddy current sensor for differential expansion, axial thrust, large shaft radial displacement and Keyphasor speed reference on heavy steam/gas turbines
• Product Type: Complete integrated 25mm proximity probe assembly (probe body + 6m factory-attached coaxial cable)
• Key Specs: 25mm sensing tip / 12.7mm (500 mil) linear range | 6m integrated cable | −35°C to +150°C tip operating temperature
• Condition: New Original Factory Sealed; refurbished fully calibrated surplus inventory available with 5-day dispatch lead time

Key Technical Specifications

• Sensing Tip Diameter: 25 mm (1 inch)
• Linear Measurement Range: 0.635 mm to 13.33 mm (25–525 mils); recommended installation gap = 6.35 mm (250 mils)
• Body Thread Standard: M30 × 2 stainless steel threaded housing (AISI 304)
• Total Cable Length: 6 meters factory-molded integrated coaxial cable
• Cable Insulation: FEP fluoropolymer, standard unarmored construction
• Tip Temperature Rating: −35 °C to +150 °C continuous operation
• Max allowable process pressure at tip: 5 bar (72.5 psi)
• Connector Type: Standard mini-microdot male plug at cable end
• System Compatibility: Matches 3300 XL Proximitor drivers, fully interoperable with 3500/45 position monitor rack cards
• Frequency Response: DC to 10 kHz for slow thermal displacement and low-frequency shaft vibration capture
• Calibration Accuracy: ±0.25% full linear range across operating temperature band
• Compliance: Fully meets API 670 rotating machinery protection standards for differential expansion monitoring
• Physical Weight: 0.82 kg full assembly (probe + 6m cable)

Product Introduction

Standard 8mm proximity probes lack the measurement stroke required to track large thermal differential expansion between turbine rotors and casings, and this assembly solves that gap with a 25mm wide linear range designed exclusively for heavy power generation turbomachinery. It outputs a linear negative voltage proportional to metal target gap for continuous axial position trending and trip logic.Its integrated 6m factory cable eliminates field splices that introduce signal noise and drift, cutting calibration rework during turbine overhaul by over 70%. This component cannot be paired with standard 8mm Proximitor signal conditioners; it requires dedicated 25mm-range Proximitor drivers. Not recommended for small compressor bearing vibration monitoring, as the large tip diameter creates insufficient target coverage on small-diameter shafts below 150mm.

Key Selling Points & Differentiators

1. 12.7mm full linear range captures extreme thermal rotor-casing growth during turbine cold startup, eliminating false high-gap alarms common with smaller 8/11mm probes.
2. Factory-molded one-piece probe + 6m cable removes field splice points, reducing EMI interference from VFD cabinet wiring in power plant layouts.
3. −35°C to +150°C tip temperature rating withstands sustained turbine exhaust and casing heat without signal drift or insulation degradation.
4. Direct compatibility with the 3500/45 position monitor card enables redundant differential expansion safety voting per API 670 single-failure elimination rules.
5. 12-month factory calibration warranty covers linearity and temperature stability for surplus calibrated stock; factory-new assemblies ship with a full 36-month OEM performance warranty.
6. M30×2 standard thread matches all OEM turbine probe mounting bosses on GE, Siemens, and Alstom steam/gas turbine frames, no custom adapter machining required.

Quality Transparency SOP

1. Incoming Verification: Cross-reference serial numbers against OEM production calibration archives to filter counterfeit assemblies. Complete visual audit of stainless thread body, molded cable strain relief, mini-microdot connector pins, and FEP jacket; timestamp photos of jacket cracking, thread galling, or connector pin tarnish.
2. Live Bench Calibration Test: Mount the unit in a precision micrometer gap test fixture paired with a matched 3300 XL 25mm Proximitor driver. Run continuous 24-hour thermal soak test across −35°C to +150°C to record linear voltage output at 0.5mm gap increments across full measurement range.
3. Electrical Insulation Tests: 500V megohmmeter test confirms cable core-to-shield insulation resistance >1000 MΩ; validate no leakage across full temperature cycling.
4. Calibration Record Backup: All test gap voltage readings logged and stored with unit serial number; calibration curve data provided to buyers on formal request. No user-configurable firmware exists on this passive transducer assembly.
5. Final QC & Packaging: Perform end-to-end continuity and linearity spot check as final validation. Wrap the full assembly in anti-static bubble wrap, attach serialized calibrated QC Passed tag with full gap voltage test data, ship inside rigid shock-resistant cardboard crates to prevent cable kinking during transit. Bench calibration photos and raw linearity logs are available upon written buyer request.

Technical Risk Avoidance Section

❗ Proximitor Driver Mismatch Risk: Pairing this 25mm probe with an 8mm-range Proximitor driver results in severely compressed linear output and uncalibrated gap readings. Prevention: Deploy only dedicated 25mm 3300 XL Proximitor signal conditioners matching the transducer series. Field anecdote: A coal-fired power plant installed this probe to an 8mm driver and received unreadable DE signals during turbine startup, requiring full rework of signal cabinet wiring.❗ Dual-End Cable Shield Ground Loop Risk: Grounding the coaxial cable shield at both the Proximitor terminal block and turbine probe mounting boss creates circulating low-frequency ground loop current that distorts gap voltage output and triggers persistent nuisance high-gap alarms. Prevention: Terminate cable shield at only the Proximitor rack side of the wiring run; leave probe-side shield floating.❗ Excessive Probe Thread Torque Risk: Tightening the M30×2 mounting nut beyond OEM 12 N·m torque gallsthe stainless thread housing and cracks internal probe tip insulation, causing permanent signal short circuits. Prevention: Use calibrated torque wrenches set to 10–12 N·m for all mounting boss installation.❗ Cable Sharp Bend Damage Risk: Routing the 6m coaxial cable around tight cabinet corners with bend radius below 50mm fractures internal center conductors, creating intermittent gap signal dropouts during turbine thermal expansion cycles. Prevention: Maintain minimum 50mm bend radius for all cable routing paths.❗ ESD Tip Damage Risk: Ungrounded maintenance tools touching the exposed 25mm sensing tip discharge static and crack delicate internal coil windings inside the probe body, rendering the assembly uncalibratable. Prevention: Mandate grounded ESD wrist straps for all probe removal, installation, and calibration service work on energized turbine systems.

Quick summary: Match with 25mm Proximitor drivers only, single-point shield grounding, controlled mounting torque, minimum cable bend radius, and ESD protection to eliminate nearly all field calibration and signal failure modes for this long-range displacement transducer.

FAQ

Q: Can this 25mm probe be used to measure radial shaft vibration on a 100mm diameter auxiliary pump shaft?A: Not recommended. The large 25mm tip diameter creates averaging across too much shaft surface area, blurring small radial vibration fault signatures. Smaller 8mm probes are the OEM standard for bearing vibration monitoring on shafts below 150mm diameter.Q: Does this assembly work with legacy 3300 rack monitor cards and modern 3500 series TSI racks?A: Yes, the analog voltage output is fully cross-compatible with both legacy 3300 position cards and current-generation 3500/45 monitor hardware, provided a matching 25mm Proximitor driver is installed between the probe and rack input channel.Q: What warranty coverage applies to refurbished calibrated surplus inventory of this transducer?A: Refurbished assemblies carry a 12-month calibration warranty covering linear measurement performance, cable insulation integrity, and connector continuity. Cosmetic thread scuffs and minor surface jacket discoloration are excluded from claim eligibility. Factory-new OEM probe assemblies ship with a full 36-month manufacturer performance warranty.Q: Will high-temperature steam spray contacting the probe tip damage the transducer permanently?A: Short-duration steam exposure within the −35°C to +150°C rating causes no permanent damage; continuous exposure above 160°C degrades the PPS tip insulator and shifts calibration permanently. Shield the probe boss from direct steam impingement during turbine design layout.Q: Can I cut and splice the 6m integrated factory cable to shorten the assembly for compact cabinet layouts?A: Splicing the coaxial cable breaks the factory matched electrical length required for linear calibration, introducing permanent gap voltage drift across temperature ranges. For shorter cable requirements, order alternate suffix variants with factory shorter cable lengths instead of field splicing.Q: Does this probe store displacement measurement data locally on the assembly?A: No, this is a passive analog eddy current sensor with no on-board memory or data logging capability. All position trending and fault waveform capture is handled by the rack’s position monitor card and Slot1 TDI communication gateway module.Q: Can multiple 25mm probes be wired in parallel to a single Proximitor driver channel for redundant differential expansion measurement?A: No, parallel wiring distorts the driver oscillator frequency and invalidates linear gap output. Redundant DE monitoring requires separate independent probe-Proximitor-rack channel signal chains for SIL/API 670 compliant 2oo3 voting schemes.