Bently Nevada 3500/50M-01-00 Tachometer Monitor – Reliable Speed & Keyphasor Monitoring for 3500 Racks

The Bently Nevada 3500/50M-01-00 is a two-channel tachometer monitor designed for speed, phase reference, and direction-of-rotation monitoring in the 3500 machinery protection system. From my experience, it’s the default choice when you need dependable speed measurements from proximity probes or magnetic pickups, along with configurable Alert/Danger alarms that integrate cleanly with your existing 3500 rack logic and relays. You might notice that it fits seamlessly with standard 3300 XL proximity systems and Keyphasor setups, which keeps commissioning straightforward.

Order Placement Process and Guarantees

• Warranty: 365 days
• Delivery: 1 week if in stock; no more than one month at the latest
• Payment: 50% advance payment; full payment before delivery
• Express options: FedEx, UPS, DHL

Key Features

• Two independent tachometer channels: Each channel measures speed/frequency with separate Alert and Danger setpoints for flexible protection strategies.
• Wide input compatibility: Accepts proximity probes (e.g., 3300 XL) or magnetic pickups via the matched I/O module, which simplifies retrofit projects.
• Direction and zero-speed detection: Useful for coastdown logging, reverse rotation detection, and safe startup checks.
• Buffered transducer outputs: Front/rear buffered outputs on the I/O module aid diagnostics and portable data collection without disturbing the signal.
• Backplane integration with TDI: Communicates over the 3500 backplane to the 3500/22M TDI for configuration and data transfer to System 1 software.
• Rack-based alarming: Configurable Alert/Danger logic; relay actions handled by dedicated 3500 relay modules (e.g., 3500/32M).
• Hot-swappable front module: Typically allows service with minimal downtime when paired with the correct rear I/O.
• Model variant -01-00: Common option set for general-purpose tach monitoring; it seems to be the go-to for turbines, compressors, and critical pumps.

Technical Specifications

Application Fields

This module is typically used on:

• Steam and gas turbines for speed and turning-gear checks
• Compressors and expanders tracking coastdown profiles and zero speed
• Pumps and blowers with reverse rotation detection to protect seals and bearings
• Gearboxes, generators, and machine trains needing Keyphasor reference and speed alarming

A maintenance lead at a power plant told us the 3500/50M “cleaned up the speed dropout we had with an older tach card,” especially after switching to a proximity-based Keyphasor on the main shaft.

Advantages & Value

• Reliability: Mature design and proven stability in harsh industrial environments; fewer nuisance trips in many cases when properly grounded.
• Compatibility: Integrates with existing 3500 racks, 3300 XL probes, and 3500 relays—no surprises during upgrade work.
• Lower lifecycle cost: Standardized spares and quick swap of front modules reduce downtime and maintenance labor.
• Data visibility: Seamless data path to System 1 through the TDI, enabling trending, audit trails, and alarm rationalization.
• Flexible alarming: Independent setpoints per channel with logic handled at the rack-level for consistent plant standards.

Installation & Maintenance

• Cabinet & environment: Install in a 3500 rack within a clean, ventilated enclosure. Avoid high EMI sources; keep proper clearance for airflow.
• Wiring practices: Use shielded cable for proximity or magnetic pickup signals; ground shields at the rack end. Maintain proper probe gap and scale factor.
• Module pairing: Match the 3500/50M front card with its correct rear I/O module; verify terminal identification before landing wires.
• Configuration: Set speed range, teeth/pulses-per-rev, and Alert/Danger limits via the 3500 configuration software. Confirm rotation direction and zero-speed logic.
• Safety note: 3500/50M provides monitoring and alarming; for SIL-rated overspeed trip, use dedicated overspeed protection (e.g., 3500 overspeed module) as per your safety case.
• Routine maintenance: Periodically check probe gaps, clean connectors, validate buffered output signal quality, and review firmware compatibility notes on the TDI.

Quality & Certifications

• CE compliant; typically UL/cUL for North America (module and rack series)
• RoHS conformity for most current production variants
• Manufactured under ISO 9001 quality systems
• Manufacturer’s warranty is typically 1 year through authorized channels; our supply supports a 365-day warranty as stated above

Related/Supporting Components

• 3500/22M TDI – Transient Data Interface for configuration and data to System 1
• 3500/32M – 4-Channel Relay Module for Alert/Danger actions
• 3300 XL Proximitor sensors and probes – Common speed/Keyphasor pickups
• Keyphasor probes and wheels – For accurate phase reference and tach pulses