3500/25 Keyphasor® Module

Overview

The Bently Nevada 3500/25 Keyphasor® Module provides the precise once-per-revolution phase and speed reference that unlocks advanced diagnostics in a Bently Nevada 3500 rack. By conditioning proximity-probe or magnetic-pickup tach signals into a clean Keyphasor reference, the 3500/25 enables order tracking, orbit/polar plots, startup/coast-down analysis, and accurate correlation of alarms across the rack—without interfering with protection logic. Deployed alongside vibration monitors such as 3500/40M (Proximitor) or 3500/42M (Velocity/Accel), and streamed via a 3500/22M TDI to System 1, the Keyphasor module turns raw vibration into actionable, phase-aware insight for compressors, turbines, large motors/generators, pumps and fans.

Why a Keyphasor Matters

A machinery protection rack can alarm on overall levels, but fault identification (unbalance, misalignment, rubs, looseness, fluid-induced instabilities, blade-pass, gear mesh) often requires knowing phase vs. speed. The 3500/25 Keyphasor Module delivers a stable one-per-rev (or scaled) reference so you can:

• Track phase angle of shaft vibration, create orbits and polar plots, and separate synchronous from asynchronous content.

• Run order-based diagnostics during startups, coast-downs and variable-speed operation.

• Align alarms and events from multiple monitors in time and rotational position for fast root-cause analysis.

How the 3500/25 Works

• Inputs & Transducers: Accepts eddy-current proximity (tach) or magnetic pickup signals. Each input is validated, shaped and converted to a Keyphasor pulse train.

• Dual Independent Channels: Two channels can be configured redundant (two sensors on one machine), diverse (two different machines), or gear-scaled (tooth count) for multi-target applications.

• Scaling & Validation: Supports once-per-rev (keyway/notch) or gear-ratio scaling to derive true RPM. Signal validation maintains clean triggering across low and high speeds.

• Rack Integration: The Keyphasor reference is distributed to other 3500 monitors for protection and to System 1 (via 3500/22M TDI) for trends, waveforms, orbits and order plots. Protection remains in the monitors; the 3500/25 supplies the reference only.

Integration with System 1 (Data & Diagnostics)

When your rack includes a 3500/22M TDI, the 3500/25 provides synchronized phase/speed data so System 1 can store phase-referenced waveforms, build Bode/Cascade/Waterfall plots, and correlate temperature, process and vibration events by rotational position. This gives maintenance teams higher confidence during balancing, alignment checks, and post-trip investigations.

Typical Channel Architectures

• Single Train (Redundant Tach): CH-A once-per-rev proximity on keyway; CH-B magnetic pickup on gear tooth—redundancy plus cross-validation.

• Twin-Train Machine: CH-A on Compressor-1; CH-B on Compressor-2—single module serving two shafts.

• High-Tooth Gears: Gear with N teeth; configure pulses/rev to 1 using scaling so monitors and System 1 see accurate RPM.

• Keyphasor + Keyphasor (Dual Bearings): Use two once-per-rev targets for complex trains needing multiple phase references.

Setup & Configuration Checklist (Practical)

1. Transducer data: type (prox/mpu), gap, sensitivity, cable length.

2. Targeting method: once-per-rev notch/keyway or gear tooth count (N).

3. Speed range: min/max RPM for reliable triggering and anti-bounce filtering.

4. Channel use: redundant vs. separate machines; assign scaling per channel.

5. Rack map: confirm slot, monitor dependencies (e.g., 40M/42M), and System 1/TDI versions.

6. Validation: live check RPM stability vs. DCS/PLC tach; verify phase coherence with radial probes.

Applications & Fault Coverage

• Turbomachinery: gas/steam turbines, expanders—order plots, Bode during run-ups; phase-based rub/misalignment detection.

• Compressors & Blowers: unbalance, looseness, aerodynamic instabilities, surge event timing.

• Large Motors/Generators: soft-foot/misalignment identification with phase tracking.

• Pumps/Fans: phase-referenced trend correlation for cavitation/rub.

Commissioning & Maintenance Best Practices

• Place the once-per-rev mark at a clear mechanical reference (keyway or precision notch).

• For gears, document exact tooth count and desired pulses/rev; apply gear scaling accordingly.

• Route tach leads away from high-noise power cabling; check grounding/shielding.

• After configuration, run a startup test: verify stable RPM, correct phase lock, and expected order amplitudes in System 1.

• Keep a spare 3500/25 for fleets where run-up data are critical to outage planning.

Compatibility & Ordering Notes

Share your transducer type/model, gap and cable length, tooth count or notch details, machine speed range, rack BOM/slot map, and System 1/TDI versions. We’ll confirm firmware compatibility, channel assignments, and the right scaling so your 3500/25 Keyphasor Module delivers a clean, reliable reference across the rack.

Included / Not Included

Included: 3500/25 Keyphasor® Module (card only).

Not included: transducers, I/O modules, rack hardware, cables—quoted as required.

Internal Links (helpful)

• Vibration category: https://omansevenstar.com/product-category/automation/vibration/

• 3500/22M TDI: /product/bently-nevada-3500-22m-tdi/

• 3500/40M Proximitor: /product/bently-nevada-3500-40m-proximitor-monitor/

• 3500/60 Temperature: /product/bently-nevada-3500-60-temperature-monitor/

Call to Action

Need help setting once-per-rev or gear scaling? Send your tach probe details, tooth count and rack BOM. Seven Star LLC will validate configuration, confirm availability/lead time, and offer the best regional pricing for Bently Nevada 3500/25 Keyphasor® Module spares and upgrades.