Bently Nevada 128240-01 3500/42M Prox/Seismic I/O Module

External-termination I/O for the 3500/42M Proximitor Seismic Monitor

The 128240-01 is the Prox/Seismic I/O Module with External Terminations for the Bently Nevada 3500/42M Proximitor Seismic Monitor. It sits in the rear slot behind the monitor and carries the four transducer channels out on one multi-pin TRANSDUCERS connector to an external termination block, with a separate RECORDER OUTPUTS connector for the 4 to 20 mA recorder signals.

In the 3500/42M ordering code it is I/O module type 02. Bently Nevada lists it for Seismoprobe velocity transducers and notes that Prox/Accel and Velomitor inputs are supported but not recommended on this module; for those transducers the Prox/Velom I/O modules (140471-01, 140482-01) are listed.

Technical specifications

What else to order with 128240-01

Because the terminations are external, the termination blocks and cables are separate line items for each I/O module. The transducer side uses a Proximitor ET block, 125808-02 with Euro style connectors or 128015-02 with terminal strip connectors, with a 129525 cable. The recorder outputs use a recorder ET block, 128702-01 or 128710-01, with a 129529 cable. Both cables are coded by length from 5 to 100 ft and by assembly option.

The internal-termination equivalent is 128229-01. Match the module already fitted in the rack, because the monitor configuration depends on the I/O type.

Documents and quotation

The 3500/42M Proximitor Seismic Monitor datasheet (143694) is attached. See the 3500/42M Proximitor Seismic Monitor page for the monitor.

For a quotation, send the part number, quantity and any ET blocks and cables required with their lengths.

How the 128240-01 I/O Module Fits into the 3500/42M Monitor

Every 3500 monitor is made of two cards: a main module in the front of the rack, which processes the signals, raises alarms and drives the displays and relays, and an I/O module in the rear slot directly behind it, which handles the field wiring. The 128240-01 is the rear card for the 3500/42M Proximitor Seismic Monitor. It supplies power to the connected transducers, receives their signals and passes them to the main module, and it brings out the recorder outputs.

The 3500/42M is a four-channel monitor that can be configured for radial vibration and position with proximity probes, or for casing (seismic) vibration with velocity and acceleration transducers. Seismoprobe velocity transducers are self-generating moving-coil sensors, so the supply they need is very small compared with the powered transducers listed in the specification table. That difference is why this I/O module is recommended for Seismoprobe inputs and why the Prox/Velom I/O modules are listed for the other transducer types.

External versus internal terminations

With internal terminations, the field wires land directly on terminals on the I/O module at the back of the rack. With external terminations, as on the 128240-01, the I/O module has multi-pin connectors, and prefabricated cables run to an external termination (ET) block mounted elsewhere in the cabinet. External terminations are often chosen when the rack sits in a crowded cabinet, when field wiring is marshalled on separate terminal rails, or when a monitor needs to be replaced without disturbing individual field cores. The trade-off is the extra ET block and cables that must be ordered and kept as spares.

128240-01 Replacement & Maintenance Notes

• Record the existing rack configuration with the 3500 configuration software before work starts, because the monitor configuration is tied to the I/O module type.
• Replace a rear I/O card with the same part number unless the change has been engineered and the configuration updated accordingly.
• Observe electrostatic discharge precautions and follow the 3500 manual for module removal and insertion.
• Check the ET block cables and connectors when channels show faults; a damaged cable or loose connector can look like a faulty transducer.
• After replacement, check that each channel reads correctly, that the OK status is restored and that recorder outputs reach the DCS or recorder as expected.

Typical Applications in Oman & the GCC

3500/42M monitors with velocity transducers are used for casing vibration on gas turbines, pumps, fans, cooling towers and other rotating equipment in oil and gas, power, petrochemical and water plants. Plants that standardised on external terminations years ago need matching I/O modules, ET blocks and cables for maintenance and expansion of existing racks.

Seven Star LLC supplies Bently Nevada 3500 modules and accessories across Oman and the GCC. Send the part number, the installed monitor type and any ET blocks and cables required, and our team can help confirm the correct ordering codes.

Planning spares for a 3500/42M channel

For critical machines, many plants keep one spare main module and one spare I/O module of each type installed in their racks. With external terminations, a spare transducer cable and recorder cable of the installed length are also worth holding, because a damaged cable takes the whole module’s channels out of service. Label each ET block and cable with the rack, slot and channel numbers so replacements can be made quickly during an outage, and keep the configuration file for each rack in the plant document system.