Description
Bently Nevada 126623-01 Aero GT Vibration I/O Module
Product Introduction
The Bently Nevada 126623-01 is an Aero GT Vibration I/O Module designed for the 3500/44M Aeroderivative GT Vibration Monitor. The 3500/44M is a four-channel machinery monitoring platform developed for aeroderivative gas turbine applications, and the Aero GT I/O assembly provides the signal interface between the turbine vibration sensors or interface modules and the monitor electronics. Bently Nevada documentation specifically identifies 126623-01 as the Aero GT I/O Module with external terminations.
The Bently Nevada 126623-01 accepts one to four applicable vibration signals from interface modules such as 86517 and 86497 and supports the signal-processing functions required by the 3500/44M architecture. These include signal integration, 1X vibration tracking, and band-pass filtering. The documented Aero GT input impedance is greater than 95 kΩ, while the transducer supply is specified at −23 VDC nominal with a maximum current of 43 mA. Typical module power consumption is approximately 7.7 W.
The Bently Nevada 126623-01 uses external terminations rather than the internal-termination arrangement found on other 3500/44M I/O variants. That distinction is important when replacing an installed module because the termination method affects the associated terminal hardware and field wiring. The module occupies one full-height rear slot in the 3500 rack and is specified for operation from −30°C to +65°C.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Model | 126623-01 |
| Manufacturer | Bently Nevada |
| Product Type | Aero GT Vibration I/O Module |
| System Series | 3500 |
| Compatible Monitor | 3500/44M Aeroderivative GT Vibration Monitor |
| Termination Type | External Termination |
| Input Channels | 1–4 signals, depending on configuration |
| Input Impedance | >95 kΩ |
| Compatible Signal Sources | Interface modules 86517/86497; applicable Velomitor and accelerometer configurations |
| Signal Processing | Integration, 1X tracking, band-pass filtering |
| Tracking Range | 60–240,000 cpm |
| Direct Signal Frequency Range | Approx. 4 Hz–30 kHz, −3 dB |
| Low-Pass Corner | 200 Hz, −3 dB |
| High-Pass Options | 25, 75, or 100 Hz, −3 dB |
| Typical Signal Accuracy | ±0.33% of full scale, typical; ±1% maximum, excluding filters |
| Alarm Setpoints | Alert and Danger |
| Alarm Accuracy | ±0.13% |
| Transducer Supply | −23 VDC nominal |
| Maximum Transducer Supply Current | 43 mA |
| Typical Power Consumption | 7.7 W |
| Operating Temperature | −30°C to +65°C |
| Storage Temperature | −40°C to +85°C |
| Humidity | 95%, non-condensing |
| Dimensions | 241.3 × 24.4 × 99.1 mm |
| Weight | Approx. 0.45 kg |
| Rack Space | 1 full-height rear slot |
| Communication | 3500 rack/internal monitor architecture |
| Standalone Ethernet | No |
| Standalone Modbus Interface | No |
| Protection Rating | Not applicable as a standalone field enclosure |
The signal-processing and environmental values above are from documentation describing the 3500/44M Aero GT I/O family and 126623-01 external-termination configuration.
126623-01
Main Features and Engineering Considerations
1. Dedicated Aero GT interface
The 126623-01 is not a general-purpose analog input card. It is specifically designed around the 3500/44M Aero GT vibration-monitoring architecture. Its input characteristics, filtering, tracking functions, and sensor interface must therefore be evaluated together with the 3500/44M monitor configuration.
2. External termination architecture
The “-01” part number is specifically associated with the external-termination Aero GT I/O configuration. Bently Nevada documentation lists 126623-01 alongside the internal-termination and TMR variants.
This matters during replacement. A module with the same general Aero GT function but a different termination arrangement may require different field wiring hardware.
3. Four-channel monitoring architecture
The 3500/44M is documented as a four-channel monitor, with the Aero GT I/O capable of accepting one to four applicable vibration signals.
Before commissioning a replacement, verify which channels are actually configured in the existing rack. A spare module may be physically correct but still require the correct rack configuration and channel parameters.
4. Signal conditioning and tracking
The module supports signal integration, 1X vibration tracking, and band-pass filtering. The documented tracking range extends from 60 to 240,000 cpm, allowing the monitor to accommodate a broad range of aeroderivative turbine operating speeds.
This processing is part of the measurement chain. Incorrect filter or tracking parameters can produce apparently plausible readings that are not directly comparable with the original system configuration.
5. Interface modules are part of the measurement chain
The Aero GT architecture can use Bently Nevada interface modules such as 86517 and 86497 between field velocity transducers and the monitor.
A failed interface module, cable, or sensor can therefore mimic an I/O-module problem. Check the complete signal path before condemning the 126623-01.
6. Machinery-protection application
The module participates in a machinery-monitoring system that provides configurable Alert and Danger setpoints. The documented alarm accuracy is ±0.13%.
For a protection application, alarm values should be verified against the approved machine-protection configuration after replacement rather than assuming that the replacement card retains the required parameters.
Application Scenarios
Aeroderivative Gas Turbines
The primary application is vibration monitoring on aeroderivative gas turbines using the Bently Nevada 3500/44M platform.
Gas Turbine Compressor Drives
The 3500/44M system can be applied to gas-turbine-driven compressor equipment where vibration information is required for machinery protection and condition monitoring.
Power Generation
Aeroderivative turbines used for power generation can use the Aero GT monitoring architecture to monitor vibration-related machine condition and alarm states.
Oil & Gas and Process Plants
The module is relevant to rotating equipment installations in oil and gas, LNG, petrochemical, and other process facilities where aeroderivative turbines are used as mechanical drivers or generators.
Engineer’s Guide: Field Pitfalls
Pitfall 1 — Confusing 126623-01 with a generic vibration input card
This is an Aero GT-specific I/O module for the 3500/44M. Do not substitute a standard 3500 Proximitor I/O module simply because both appear in the same rack family.
Pitfall 2 — Ignoring external termination
126623-01 is the external-termination configuration. Confirm the installed terminal hardware and field cables before approving a replacement.
Pitfall 3 — Replacing the module without checking the sensor interface
The 3500/44M Aero GT architecture uses specific interface modules for applicable velocity-transducer signals. Check the sensor, interface module, cable, and I/O card as one signal chain.
Pitfall 4 — Treating the transducer supply as a general 24 V supply
The documented transducer supply is approximately −23 VDC nominal, with a 43 mA maximum. It should not be confused with a conventional +24 VDC instrument supply.
Pitfall 5 — Losing the original filter configuration
The module supports integration, 1X tracking, and band-pass functions. Record the existing configuration before replacement so that the new module is evaluated under equivalent measurement conditions.
Pitfall 6 — Assuming the module itself provides plant communications
The 126623-01 is an I/O assembly inside the 3500/44M architecture. It is not a standalone Modbus, Ethernet, or Profinet communication gateway.
Pitfall 7 — Ignoring rack power during replacement
The module should be removed or installed according to the applicable 3500 maintenance procedure. Field documentation specifically warns against removing/installing this type of module with rack power applied.
Frequently Asked Questions
What is Bently Nevada 126623-01?
It is an Aero GT Vibration I/O Module with external terminations for the Bently Nevada 3500/44M Aeroderivative GT Vibration Monitor.
How many channels does 126623-01 support?
The 3500/44M Aero GT architecture is a four-channel system, and the Aero GT I/O accepts one to four applicable signals, depending on configuration.
What sensors can be used with it?
The architecture supports signals from Bently Nevada interface modules such as 86517 and 86497, as well as applicable Velomitor and accelerometer configurations.
What is the operating temperature?
The documented operating range is −30°C to +65°C, with storage from −40°C to +85°C and 95% non-condensing humidity.
What is the power consumption?
Typical power consumption is approximately 7.7 W.
What is the input impedance?
For the Aero GT I/O, the documented input impedance is greater than 95 kΩ.
Does 126623-01 have Ethernet?
No. It is an I/O module within the 3500/44M rack architecture, not a standalone Ethernet communication module.
What is the difference between internal and external termination?
The external-termination version routes field connections through external termination hardware rather than terminating the field wiring directly at the I/O module. Bently Nevada identifies 126623-01 specifically as the external-termination Aero GT I/O option.
Procurement Note
For purchasing, specify the complete identifier:
Bently Nevada 126623-01 — Aero GT Vibration I/O Module, External Terminations, for 3500/44M
Do not substitute based solely on the description “3500/44M I/O module.” Confirm 126623-01, external termination architecture, rack compatibility, and the installed sensor/interface configuration.
For used or refurbished equipment, request photographs of the actual part-number label, connector/termination side, and PCB revision. Before returning a replacement to a protection service, verify the 3500/44M configuration, sensor chain, channel assignments, filter settings, Alert/Danger setpoints, and signal response.
One important correction for procurement records: some online listings describe 126623-01 with generic signal ranges, Profinet, IP67, or other specifications that conflict with the documented 3500/44M architecture. Those claims should not be used as engineering specifications. The reliable identification is the Bently Nevada 3500/44M Aero GT I/O, external-termination configuration, with the technical values above taken from the 3500/44M documentation.
