Product Overview

The Bently Nevada 138700-01 is a specialized Shaft Absolute Input/Output (I/O) module designed for integration with the 3500/42M Proximitor Seismic Monitor. This module is engineered to facilitate the "Shaft Absolute" vibration measurement, which combines shaft relative vibration (from proximity probes) and bearing housing absolute vibration (from seismic transducers). By performing this vector summation, the 138700-01 provides a comprehensive view of the shaft's motion relative to free space, rather than just the bearing clearance. This data is vital for high-precision monitoring of large turbomachinery where the casing itself may be subject to significant motion.

Hardware Architecture and Engineering Specifications

The 138700-01 serves as the rear-mount termination point for field wiring, providing the necessary signal conditioning and galvanic isolation for complex vibration loops.

• Module Identification: 138700-01

• Module Function: Shaft Absolute Vibration I/O

• Transducer Interface: Supports simultaneous input from Proximitor sensors and Accelerometers/Velocity sensors

• Channel Density: 4-channel capacity when paired with the 3500/42 monitor

• Signal Processing: Real-time vector addition of relative and seismic signals

• I/O Type: Internal Terminations (standard)

• Unit Weight: 0.84 kg

• Physical Dimensions: 2.6 cm x 24.2 cm x 24.1 cm

• Operating Temperature: -30°C to +65°C (-22°F to +149°F)

• Compliance: API 670 Standard for Machinery Protection

• Manufacturing Origin: USA

Strategic Industrial Deployment

• Heavy-Duty Gas Turbines: Essential for monitoring shaft behavior in gas turbines where casing vibration must be compensated for to understand true rotor dynamics.

• Hydroelectric Generators: Used to track absolute shaft displacement in large-scale vertical and horizontal hydro units where structural vibration is prevalent.

• Nuclear Steam Turbines: Provides high-integrity data for safety-critical monitoring, ensuring that shaft excursions are detected independently of bearing pedestal movement.

• Large Pump Trains: Ideal for high-energy pumps in water transmission or oil transport where absolute motion detection prevents seal and coupling failures.

• Predictive Maintenance Programs: Feeds accurate waveform data to diagnostic software for identifying resonance, unbalance, and misalignment in rotating assets.

FAQ

Q: What is the primary purpose of the "Shaft Absolute" measurement facilitated by the 138700-01?

A: It provides the "true" vibration of the shaft by subtracting or adding the vibration of the bearing housing. This ensures that if the entire machine is shaking, you can still distinguish how the shaft is moving relative to a fixed point in space.

Q: Can this I/O module work as a standalone unit?

A: No, the 138700-01 is an I/O interface. It must be installed in the rear of a 3500 rack directly behind a 3500/42 or 3500/42M monitor module to function.

Q: Does this module support 3300 XL Proximitor sensors?

A: Yes, it is fully compatible with the 3300 XL transducer series as well as standard velocity and acceleration transducers used for seismic measurements.

Q: Is the 138700-01 module hot-swappable?

A: While the 3500 rack supports the physical removal of I/O modules while powered, doing so will disconnect the field sensors from the monitor, which will likely trigger a "Rack Not OK" status and potentially trip the machinery if interlocks are active.

Q: How does this differ from a standard 3500/42 I/O module?

A: Standard I/O modules typically process either proximity OR seismic signals. The 138700-01 is specifically wired and circuited to handle both signal types simultaneously for the Shaft Absolute calculation.