Bently Nevada 125808-01 Proximitor External Termination Block

Bently Nevada 125808-01 Proximitor external termination block

The Bently Nevada 125808-01 is the Proximitor External Termination (ET) Block with Euro style connectors for the Bently Nevada 3500/40M Proximitor Monitor. It moves the transducer field wiring from the back of the 3500 rack to a separate termination point, typically in a marshalling cabinet, and connects to the monitor’s external-termination I/O module through a multi-conductor cable. The 125808-01 is listed in the 3500/40M datasheet as an accessory of the monitor; it is not a monitor in itself.

Overview

A 3500/40M monitor accepts signals from up to four proximity transducers and is supplied with one of three I/O module types: internal terminations, external terminations, or internal barriers with internal terminations. When the external-termination I/O module is chosen, the field wires do not land on the I/O module. They land on an ET block, and a pre-made cable links the ET block to the I/O module at the rear of the rack. This keeps large cable bundles away from the rack and lets field wiring be terminated before the rack is installed.

Seven Star LLC supplies the Bently Nevada 125808-01 on request for machinery protection systems in Oman and the GCC. Availability, condition and lead time are confirmed at quotation, and we provide technical support with selection and cross-checking of the reference against your rack configuration.

Key features

• External termination block for 3500/40M Proximitor Monitor channels.
• Euro style plug-in connectors for field wiring.
• Used only with external-termination I/O modules.
• Connects through the 129525 transducer signal to ET block cable, available in standard lengths from 1.5 to 30.5 m.
• Allows field wiring to be marshalled away from the rack.

Technical specifications

Operating principle

The ET block is a passive wiring interface. Proximitor sensor power, signal and common for each channel are landed on its Euro style connectors, and the 129525 cable carries them to the external-termination I/O module of the 3500/40M. The monitor then performs the measurement and alarm functions. The 3500/40M input impedance is 10 kΩ, and the monitor accepts transducer scale factors of 3.94 mV/µm (100 mV/mil) or 7.87 mV/µm (200 mV/mil), so the ET block must preserve wiring integrity and shielding all the way to the transducer.

Because 3500/40M channels are configured in pairs (channels 1 and 2, channels 3 and 4), the wiring on the ET block should follow the same pairing: for example, two X–Y radial probes on one bearing are normally landed on one channel pair, and two axial thrust probes on the other. The monitor itself draws 7.7 W typical; the ET block adds no measurement function, so channel behaviour, alarm setpoints and OK limits are all set in the 3500 rack configuration, not at the block.

Typical applications

The 3500/40M channels, programmed in pairs, provide radial vibration, eccentricity, REBAM, thrust position and differential expansion measurements. This ET block is therefore found on protection systems for:

• steam and gas turbines in power plants and desalination facilities;
• centrifugal compressors on gas processing, LNG and refinery units;
• large pumps, fans and gearboxes with fluid-film bearings;
• projects where field wiring is terminated in separate marshalling cabinets.

Selection and ordering notes for the Bently Nevada 125808-01

The 3500/40M ordering code is 3500/40M-AA-BB. Option A01 is the internal-termination I/O module, A02 is external terminations and A03 is internal barriers with internal terminations; the B options define the hazardous-area approval. Order rules from the datasheet:

• ET blocks cannot be used with internal-termination I/O modules; the monitor must have option A02 (external-termination I/O, spare part 126615-01) or the TMR external-termination I/O 149716-01.
• ET blocks and cables are ordered separately, one set for each I/O module.
• For TMR systems, Bently Nevada lists bussed TMR ET blocks: 132242-01 (Euro style) and 132234-01 (terminal strip). The bussed blocks are for TMR I/O only.
• Choose 125808-01 for Euro style connectors or 128015-01 for terminal strip connectors.

Related 3500/40M spares are the monitor 176449-01, internal-termination I/O 125680-01, barrier I/O 135489-04 and the user guide 143488. Do not confuse 125808-01 with the 125808-02 and 125808-08 blocks listed for the 3500/42M Proximitor/Seismic Monitor; they use the same 129525 cable but serve a different monitor.

Installation and commissioning

• Mount the ET block in the marshalling cabinet using the mounting method given in the 3500 installation documentation.
• Route the 129525 cable from the ET block to the external-termination I/O module and secure the connectors.
• Land each Proximitor channel on the correct terminals, keeping shields continuous and grounded at one point only.
• Check the Proximitor supply and gap voltage at each channel with the 3500 configuration software before putting alarms into service.

Maintenance and troubleshooting

A channel reporting “not OK” after work in the cabinet often points to a loose connector, a reversed signal/common pair or a damaged cable between the ET block and I/O module. Measure the transducer gap voltage at the ET block and compare it with the value seen by the monitor; a difference indicates a wiring or cable fault. Check that connector screws are tight and that shields are not grounded twice, which can introduce noise.

Quotation enquiries for Oman and the GCC

Seven Star LLC supplies the 125808-01 ET block on request; availability, condition and lead time are confirmed at quotation. Please send:

• the exact part number 125808-01 and the required 129525 cable code, including length and assembly option;
• quantity;
• a photo of the ET block label or of the 3500/40M I/O module;
• the application and machine, for example compressor radial vibration or turbine thrust.