Bently Nevada 3500/25 (125792-01) – Keyphasor Reference Module | 3500 Series Machinery Protection System
Engineering Background: The Keyphasor signal is the cornerstone of rotating machinery diagnostics. It provides a once-per-revolution phase reference pulse derived from a notch, keyway, or reflective target on the rotating shaft. Without a reliable Keyphasor signal, vector-based vibration analysis, balancing, and phase-referenced waveform acquisition are impossible. Bently Nevada pioneered this technology and the 3500/25 module represents its most refined rack-mount implementation.
Product Positioning: The 3500/25 Keyphasor Module is a dedicated signal conditioning and distribution card within the Bently Nevada 3500 Series Machinery Protection System (MPS). It accepts raw proximity probe or magnetic pickup signals and conditions them into clean, logic-level Keyphasor pulses distributed to up to four monitoring modules within the same rack. It is the authoritative phase reference for turbines, compressors, pumps, motors, and all critical rotating assets in API 670-compliant installations.
Complete Technical Specifications
- Part Number: 125792-01
- Model: 3500/25
- Module Type: Keyphasor Module
- Platform: Bently Nevada 3500 Series MPS
- Input Channels: 2 independent Keyphasor inputs
- Input Signal Types: Eddy-current proximity probes (200 mV/mil standard), magnetic pickups
- Input Voltage Range: –24 VDC bias (proximity probe), AC magnetic pickup
- Output Distribution: Up to 4 Keyphasor outputs per input channel (rack-distributed)
- Output Signal: TTL-compatible logic pulse, once-per-revolution
- Speed Range: 1 RPM to 100,000 RPM (application dependent)
- Power Supply: Supplied via 3500 rack backplane (±24 VDC, +5 VDC)
- Rack Slot: Dedicated Keyphasor slot (Slot 2 or Slot 3 per rack configuration)
- Form Factor: Single-width 3500 Series rack card
- Weight: 340 g (approx.)
- Operating Temperature: 0°C to +65°C
- Storage Temperature: –40°C to +85°C
- Humidity: 5% to 95% RH, non-condensing
- Certifications: CE, FM, CSA (per system configuration)
- Standards Compliance: API 670 (4th & 5th Edition)
- Country of Origin: USA
Proven Application Environments
- Steam and gas turbine trains (power generation, petrochemical)
- Centrifugal and axial compressors (upstream/downstream oil & gas)
- Large centrifugal pumps and motor-driven equipment
- Gearboxes requiring phase-referenced mesh frequency analysis
- Expanders and turboexpanders in LNG and refinery service
- Any API 670-compliant machinery protection installation requiring vector vibration, balancing, or phase waveform data
Engineering Advantages
- Dual-channel independence: Two fully isolated Keyphasor inputs allow simultaneous monitoring of two separate shaft sections or machines from a single module slot.
- Multi-module distribution: A single Keyphasor signal is conditioned and fanned out to up to four downstream monitor modules via the rack backplane — eliminating external signal splitters and associated noise injection.
- Noise immunity: Onboard signal conditioning filters EMI/RFI interference common in heavy industrial environments, ensuring pulse integrity at high shaft speeds.
- Hot-swap compatibility: Designed for live rack insertion/removal in conjunction with 3500 rack architecture, minimizing planned maintenance downtime.
- Backward compatibility: Fully interoperable with legacy 3500 racks and current-generation 3500/22M, 3500/40M, 3500/42M, 3500/45, and 3500/46M monitor modules.
System Architecture & Signal Flow
The 3500/25 occupies a dedicated Keyphasor slot in the 3500 rack. Proximity probe or magnetic pickup field wiring terminates at the I/O module connected to the 3500/25 via the rack backplane. The module conditions the raw analog signal — applying gap voltage, threshold detection, and pulse shaping — and outputs a clean TTL reference pulse. This pulse is distributed across the backplane to all configured monitor modules (e.g., 3500/40M radial vibration, 3500/42M axial position) that require phase reference for vector calculations, 1X/2X amplitude and phase trending, and Bode/polar plot generation in System 1 or GE Orbit software.
Sourcing & Quality Verification
- All units sourced from verified industrial decommission, OEM-authorized distributors, or certified repair facilities.
- Each module undergoes visual inspection, label/firmware revision verification, and functional bench test prior to listing.
- Revision suffix (-01) confirmed: 125792-01 is the standard production revision for this module.
- Packaging: ESD-safe anti-static bag, foam-lined carton, with inspection checklist included.
- Traceability documentation available upon request for regulated industries.
Procurement Process
- Lead Time: In-stock units ship within 1–3 business days (DHL Express / FedEx International Priority available).
- MOQ: 1 unit. Volume pricing available for 3+ units — contact us for a formal quotation.
- Payment: T/T (wire transfer), PayPal, credit card via Shopify Payments.
- Export: Worldwide shipping. Export documentation (commercial invoice, packing list, COO) provided. HS Code: 9032.89.
- Returns: 30-day return window for DOA units with prior RMA authorization.
- Technical Support: Pre-sale engineering consultation available — describe your rack configuration and we will confirm compatibility.
Technical FAQ
Q: Can the 3500/25 accept a magnetic pickup (MPU) input instead of a proximity probe?
A: Yes. The module supports both eddy-current proximity probes and passive magnetic pickups. Confirm input type when ordering to ensure correct I/O module pairing.
Q: How many monitor modules can one 3500/25 channel drive?
A: Each Keyphasor input channel distributes to up to four monitor modules via the rack backplane. No external splitter is required.
Q: Is the 125792-01 revision compatible with my existing 3500 rack?
A: The -01 revision is the standard production variant and is compatible with all standard 3500 rack frames (3500/05, 3500/15, 3500/20). Confirm rack firmware revision if using with 3500/20 Enhanced Rack Interface Module.
Q: Can this module be used with System 1 software?
A: Yes. The Keyphasor signal distributed by the 3500/25 is fully compatible with Bently Nevada System 1 (Evolution and legacy) for vector trending, Bode plots, and polar plots.
Q: Do you provide a warranty?
A: Yes — 90-day functional warranty on all tested units. Extended warranty options available upon request.
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