Product Overview

The Bently Nevada 3500/50 is a high-precision, 2-channel tachometer module designed for the 3500 Machinery Protection System. This module is engineered to process signals from proximity probes or magnetic pickups to determine shaft rotative speed, rotor acceleration, and direction of rotation. Unlike standard I/O, the "Discrete Internal Barrier" version incorporates integrated safety barriers, allowing for direct connection to transducers located in hazardous areas without requiring external galvanic isolators. By providing real-time speed data and critical alarm logic, the 3500/50 ensures that rotating assets operate within safe design limits, preventing overspeed conditions and mechanical damage.

Hardware Parameters and Technical Characteristics

The 3500/50 module is built for high-speed signal processing and reliability in safety-critical applications. It features a robust architecture that supports various transducer types and complex monitoring logic.

• Module Type Tachometer with Discrete Internal Barrier I/O

• Channel Capacity 2 independent channels per module

• Input Compatibility Proximity Probes, Magnetic Pickups (Passive), and Passive Transducers

• Internal Barriers Integrated Zener barriers for intrinsically safe (IS) field connections

• Speed Range Supports measurements from 1 rpm to 99,999 rpm

• Accuracy Within ±0.01% of the measured value (static speed)

• Signal Output Buffered transducer outputs available via the I/O module

• Alarming Logic Programmable for Zero Speed, Reverse Rotation, and Speed Band alarms

• Power Consumption 5.8 Watts typical

Industrial Applications

The 3500/50 Tachometer Module is a fundamental component of Turbine Supervisory Instrumentation (TSI) in power generation and petrochemical sectors. Its primary use cases include:

• Overspeed Protection Providing rapid alarm and trip signals to prevent catastrophic rotor failure.

• Rotation Direction Detection Ensuring compressors or pumps do not rotate in reverse, which could cause immediate bearing or seal failure.

• Zero Speed Monitoring Verifying that a machine has come to a complete stop before engaging turning gears or performing maintenance.

• Acceleration Trending Monitoring the rate of speed change during turbine startup to ensure thermal stresses remain within acceptable limits.

By integrating the 3500/50 into a broader 3500 Series rack, plant operators can consolidate speed monitoring with vibration and thrust measurements, creating a unified machinery protection environment that complies with API 670 standards.