Bently Nevada 991-25-70-01-00 991 Thrust Transmitter

Description

The Bently Nevada 991-25-70-01-00 is a two-wire, loop-powered thrust transmitter designed primarily for original equipment manufacturers (OEMs) of centrifugal air compressors, small pumps, motors, or fans. It accepts input signals from a 3300 NSv proximity probe and matching extension cable, transforming displacement data into a simple 4 to 20 mA proportional axial displacement (thrust) signal. This configuration enables seamless integration directly into a machinery control system, PLC, or DCS without requiring an external Proximitor sensor unit.

The device features non-isolated "PROX OUT" and "COM" terminals alongside a coaxial connector, providing a dynamic vibration and gap voltage signal output for machinery diagnostics and maintenance verification.

Features

• Integrated Proximitor sensor functionality eliminates the need for a separate signal conditioning unit.
• Direct 4 to 20 mA current loop output matches standard machinery control system inputs.
• Dynamic diagnostic signal output via non-isolated coaxial connector for convenient troubleshooting.
• Designed for compatibility with 3300 NSv proximity probe systems.
• Robust design tailored for mounting near monitored machinery.

Applications

• Centrifugal air compressors axial displacement monitoring
• Industrial pumps and fans machinery protection systems
• Small electric motors thrust bearing wear detection
• Balance drum monitoring on high-pressure fluid machinery
• Balance piston position tracking in rotating equipment

Ordering Information

991-25-70-01-00

• 991: Thrust Transmitter
• 25: Full-scale option: 25-0-25 mils
• 70: System length option: 7.0 metres (23.0 feet)
• 01: Mounting option: 35 mm DIN-rail clips
• 00: Agency approval option: Not required / Standard approvals

Technical Specifications

Connections/Interfaces

Installation Guidelines

DIN Rail Installation

Mount the transmitter using the pre-installed 35 mm DIN-rail clips. Ensure the rail is properly grounded and located in an area with minimal physical exposure to falling debris or direct process fluid leaks.

Shielding and Grounding

Always employ twisted, shielded pair cabling for the 4 to 20 mA loop connections. Connect the cable shield to the instrumentation ground at the control system or DCS side only. Do not ground the shield at both ends to avoid ground loop current errors.

Cable Routing

Run the signal cables away from high-voltage AC power lines, electric motor feed cables, or switching relays to minimize EMI/RFI noise interference on the low-voltage 4 to 20 mA loop signal.

Probe Gap Adjustment

Set the initial probe gap using the "PROX OUT" and "COM" terminals to monitor the initial DC gap voltage. Verify that the physical distance between the probe tip and the target material places the output safely within the linear operation range of 10 to 65 mils.

FAQ

What is the primary function of the Bently Nevada 991?

It converts raw proximity probe data into a standard 4 to 20 mA loop signal representing axial shaft displacement or thrust.

Which proximity probe family is compatible with this model?

This model is designed specifically to interface with the Bently Nevada 3300 NSv proximity probe series and matching extension cables.

What power supply is required to drive the transmitter loop?

The transmitter operates on a standard loop power supply ranging between 12 Vdc and 35 Vdc.

Can I read raw dynamic signals while the transmitter is running?

Yes, the transmitter includes a non-isolated BNC coaxial connector and PROX OUT terminals to capture dynamic gap and vibration signals for diagnostic analysis.

What mounting option does the 991-25-70-01-00 feature?

This configuration includes integrated 01-option mounting hardware suited for standard 35 mm DIN rails.