Product Overview

The Bently Nevada 991-25-70-03-05 is a high-performance, loop-powered axial displacement transmitter designed to provide continuous monitoring of shaft thrust position. Engineered for integration with the 3300 NSv proximity probe series, this device translates eddy current sensor inputs into a standardized 4 to 20 mA analog signal. By providing a direct representation of axial shaft movement, it allows for seamless machinery protection within PLC or DCS architectures. This transmitter is particularly vital for detecting thrust bearing wear or potential rotor-to-stator contact, serving as a critical hardware layer for Turbine Supervisory Instrumentation (TSI) in space-constrained industrial environments.

Key Technical Characteristics

The 991-25-70-03-05 is optimized for field reliability, featuring integrated diagnostic ports and a robust, potted enclosure designed to survive extreme humidity.

• Model Identification 991-25-70-03-05

• Measurement Type Axial Thrust (Displacement)

• Full-Scale Range 25-0-25 mils (Option -25)

• System Length 7.0 Meters / 23.0 Feet (Option -70)

• Output Signal 4 to 20 mA DC (Proportional to shaft position)

• Input Voltage +12 to +35 Vdc (Two-wire, loop-powered)

• Mounting Interface 35 mm DIN rail clips and screw mount (Option -03)

• Hazardous Area Ratings ATEX, IECEx, and CSA certifications (Option -05)

• Diagnostic Outputs Buffered "PROX OUT" BNC and terminal for gap voltage/dynamic signal

• Environmental Protection Potted construction (resists 100% condensing humidity)

• Calibration Control Non-interacting zero and span potentiometers for loop adjustment

Industrial Applications

The 991 series transmitter is the preferred choice for Original Equipment Manufacturers (OEMs) and plant operators who require dedicated thrust monitoring without the footprint of a full rack system.

• Centrifugal Air Compressors Protecting against catastrophic thrust bearing failure by monitoring shaft axial movement in high-speed impellers.

• Small Pumps and Motors Providing cost-effective axial position trending for balance-of-plant (BoP) equipment.

• Maritime Machinery Utilizing its ABS maritime approvals for onboard monitoring of propulsion and auxiliary rotation assets.

• Hazardous Process Zones Safely deploying thrust protection in explosive atmospheres typical of oil, gas, and chemical refineries.

• Diagnostic Analysis Leveraging the buffered dynamic output to connect portable vibration analyzers for in-depth machinery health audits without interrupting the protection loop.

The inclusion of a "Power-up Inhibit" circuit ensures that transient voltages do not trigger false alarms during system startup, while the "Test Input" pin allows technicians to perform loop verification safely and efficiently.