Bently Nevada 330780-50-00 Proximity Sensor – 3300 XL Series

Bently Nevada 330780-50-00 — 8 mm Eddy-Current Proximity Probe in the 3300 XL Transducer System

The Bently Nevada 330780-50-00 is an 8 mm eddy-current proximity probe with a 5.0 m integral armored cable, manufactured as part of the 3300 XL Proximity Transducer System. Within a machinery protection loop, this probe functions as the primary sensing element: it generates a high-frequency electromagnetic field (nominally 1.0 MHz) that induces eddy currents in the conductive target shaft. The resulting impedance change is converted by the matched Proximitor into a DC voltage proportional to the air gap between probe tip and shaft surface. This voltage signal — spanning −1 VDC to −17 VDC across a linear measurement range of 0.25 mm to 2.25 mm — feeds directly into Bently Nevada 3500 Series monitors or compatible third-party DCS/PLC inputs for real-time radial vibration, axial position, and differential expansion measurement.

The probe is factory-calibrated as a matched set with its extension cable and Proximitor, delivering a certified scale factor of 7.87 V/mm (200 mV/mil) against AISI 4140 steel targets. This calibration traceability is a mandatory requirement under API 670 Fourth Edition for machinery protection systems in oil & gas, power generation, and petrochemical facilities. The “-50” suffix designates the 5.0 m probe cable length; the “-00” suffix indicates the standard connector configuration with no special options.

Physically, the probe body is constructed from 316 stainless steel with an M8 × 1.0 threaded housing, allowing direct installation into standard probe holders and brackets without adapter hardware. The integral cable is armored with a stainless steel braid jacket, providing mechanical protection against abrasion and fluid ingress in turbine bearing pedestals and compressor casings. The connector terminates in a MIL-spec coaxial interface compatible with Bently Nevada 330130-series extension cables.

Intrinsic safety certifications — ATEX, IECEx, FM, and CSA — permit installation in Zone 1/Zone 2 hazardous areas without additional Zener barriers in most configurations, reducing installation hardware cost and simplifying loop documentation for regulated facilities.

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Technical Parameters

Hardware Logical Analysis

The 330780-50-00 operates on the eddy-current (inductive) sensing principle. The probe tip contains a wound coil driven by the Proximitor oscillator at approximately 1.0 MHz. When the probe tip approaches a conductive target, the alternating magnetic field penetrates the target surface to a depth governed by the skin-effect formula: δ = √(2ρ / ωμ), where ρ is target resistivity, ω is angular frequency, and μ is magnetic permeability. For AISI 4140 steel at 1.0 MHz, the effective penetration depth is approximately 8–12 µm — meaning the sensor responds to the surface layer of the shaft, not bulk material properties. This makes the output highly sensitive to surface finish and material consistency, which is why API 670 mandates target material verification and calibration curve adjustment for non-standard shaft materials such as 17-4 PH stainless or titanium alloys.

The impedance change in the probe coil — caused by eddy-current loading — is demodulated by the Proximitor into a DC voltage with a linearity error of less than ±0.5% of full-scale across the specified measurement range. The three-component matched-set architecture (probe + extension cable + Proximitor) is critical: the extension cable’s distributed capacitance and inductance are factored into the Proximitor’s oscillator tuning. Substituting an unmatched cable length or a cable from a different series (e.g., 3300 RAM) shifts the resonant frequency of the LC circuit, degrading scale factor accuracy by up to 3–5% and invalidating the factory calibration certificate.

EMC performance is achieved through the armored cable construction: the stainless steel braid provides a continuous Faraday shield from probe tip to Proximitor input, attenuating radiated interference from variable-frequency drives, high-voltage bus bars, and RF sources common in turbine halls. The shield is grounded at the Proximitor end only (single-point grounding) to prevent ground-loop currents from introducing low-frequency noise into the DC output signal. This design maintains signal integrity in environments with common-mode noise levels up to 50 V peak.

The M8 × 1.0 threaded housing allows precise gap adjustment during installation: one full rotation of the probe body changes the air gap by exactly 1.0 mm, enabling field technicians to set the initial gap to the midpoint of the linear range (nominally 1.0–1.5 mm) without measurement instruments. The stainless steel body resists corrosion from turbine lube oil, seal gas condensate, and process fluid mist, maintaining dimensional stability across the full operating temperature range.

System Integration Benefits

• Deterministic real-time response: The Proximitor outputs a continuous DC voltage with no sampling latency — the 3500 Series monitor reads shaft position at its full A/D conversion rate (up to 65,536 samples/revolution at high shaft speeds), enabling sub-millisecond detection of vibration transients.
• API 670 compliance out of the box: Factory calibration as a matched set satisfies the mandatory scale factor verification requirement, eliminating the need for field calibration before commissioning and reducing pre-startup testing time.
• Hazardous area installation without barriers: ATEX/IECEx/FM/CSA intrinsic safety approvals allow direct installation in Zone 1 classified areas in most configurations, removing the cost and wiring complexity of Zener barrier or galvanic isolator assemblies.
• Diagnostic transparency via gap voltage: The DC bias voltage at the Proximitor output provides a continuous, readable indicator of probe-to-shaft gap. Technicians can verify probe installation gap, detect probe fouling (gap voltage drift), and identify shaft centerline migration without removing the probe from service.
• Broad DCS/PLC compatibility: The −1 VDC to −17 VDC output is accepted by Bently Nevada 3500/3300 monitors, Emerson DeltaV, Honeywell Experion, ABB 800xA, and any third-party system with a high-impedance (≥10 kΩ) voltage input and −24 VDC supply capability.
• Multi-measurement capability from a single probe: One 330780-50-00 installation can simultaneously provide radial vibration (AC component), shaft average centerline position (DC component), and — when used as a Keyphasor — once-per-revolution phase reference, reducing the total probe count per bearing location.
• Long-term spare parts availability: The 3300 XL series has been in continuous production since the 1990s. Component interchangeability across the series ensures that replacement probes, extension cables, and Proximitors remain available for the full lifecycle of installed machinery — typically 20–30 years for large turbomachinery.
• Reduced commissioning risk: The matched-set calibration certificate provides a documented baseline for acceptance testing. Any deviation from the certified scale factor during loop check immediately identifies a wiring or component error before the machine enters service.

Quality Assurance & Global Logistics

Every Bently Nevada 330780-50-00 unit supplied by siemensplc.com is sourced as genuine OEM hardware — no rebranded, counterfeit, or reverse-engineered substitutes. Each unit undergoes a pre-shipment inspection protocol covering: physical integrity of the probe body and tip, continuity and insulation resistance of the integral cable, connector pin condition and seating, and verification of the part number label against the purchase documentation.

Certificates of Conformance (CoC) and original manufacturer documentation are available upon request. For regulated industries — oil & gas, nuclear, power generation — full traceability documentation including batch records and inspection reports can be provided at the time of quotation.

Shipments originate from our warehouse in Xiamen, China. Xiamen is a designated free-trade port with direct access to major international freight carriers including DHL Express, FedEx International Priority, UPS Worldwide Express, and consolidated sea-air freight services. In-stock units are dispatched within 1–3 business days of order confirmation. Express air freight to Europe, North America, Southeast Asia, and the Middle East typically achieves door-to-door delivery in 3–7 business days. For project quantities or time-critical shutdowns, dedicated air charter and hand-carry options are available upon request.

All shipments are packed in anti-static, moisture-barrier packaging with foam cushioning to protect the probe tip and cable connector during transit. Export documentation — commercial invoice, packing list, certificate of origin, and HS code classification — is prepared in compliance with destination country import requirements to minimize customs clearance delays.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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