TL;DR: The Bently Nevada 3500/22M Transient Data Interface (TDI) is the module every 3500 rack needs in order to be configured, read and networked. Baker Hughes describes it as combining “the function of a 3500/20 Rack Interface Module (RIM) with the data collection capability of a communication processor such as TDXnet”. It occupies slot 1 – the reserved position beside the power supplies – takes one full-height front slot plus one full-height rear I/O slot, draws 10.5 W, and stores the rack’s RAK configuration file. If you are specifying a new rack, you specify a TDI; if you are repairing a rack that has a 3500/20 RIM, the TDI is the upgrade path.
What is the 3500/22M TDI?
Think of the TDI as the rack’s front door and its memory at the same time. Three jobs sit in it. It holds the configuration: the RAK file that defines every setpoint in the rack lives in the interface module, which is why a rack with a dead interface module is a rack you cannot read or re-configure. It moves data: static values from each monitor channel plus transient waveform data, which is what lets you capture a vibration spectrum or an orbit rather than only a 4-20 mA reading. And it presents rack health: the Rack OK relay contacts and the remote Trip Multiply, Alarm Inhibit and Rack Reset inputs are all in the TDI’s I/O module.
One boundary matters when you are troubleshooting: field wiring never touches the TDI. Proximity probes, temperature inputs and the rest land on the I/O module belonging to their own monitor. A TDI fault costs you visibility, configuration access and waveform capture – not the protection logic.
3500/22M specifications
Values from Baker Hughes datasheet 161581 (Transient Data Interface Module).
| Role | Rack interface, configuration store and transient data acquisition |
|---|---|
| Requirement | Every 3500 rack requires one TDI or RIM; the TDI is the current part |
| Slot position | Slot 1 – right of the two power supply positions, at the left-hand end of the rack |
| Hardware footprint | 1 full-height front slot + 1 full-height rear I/O slot |
| Size / weight | 241.3 x 24.4 x 241.8 mm / 0.91 kg |
| Power draw | 10.5 W |
| Indicators | OK, TX/RX, TM, CONFIG OK |
| Networking | Proprietary TDI protocol plus Ethernet TCP/IP, 10/100Base-TX and 100Base-FX fibre |
| Cable limits | Shielded Cat5 with RJ-45 up to 100 m; MT-RJ fibre up to 2000 m; USB up to 5 m (3 m lead supplied with the rack) |
| Rack OK relay | SPDT, normally energised, 5 A at 24 Vdc / 120 Vac; gold-plated contacts rated down to 1 mA at 1 Vdc |
| Remote inputs | Dry-contact Trip Multiply, Alarm Inhibit and Rack Reset, each under 1 mA dc |
| Event memory | Rack-level records of 2000 alarm events plus 1000 system events, time-stamped |
| Operating temperature | -30 to +65 °C |
| Storage temperature | -40 to +85 °C |
| Humidity | 95% non-condensing |
| Hazardous-area rating | cNRTLus and ATEX II 3G Ex nA nC ic IIC T4 Gc at Ta = -20 to +65 °C, installed per drawing 149243 or 149244 |
Compatible racks and slots
The TDI fits the same reserved position as the RIM it replaced, so it drops into standard full-size 19-inch racks and mini racks alike. The left-hand end of a 3500/05 rack is dedicated: two half-height power supplies and the interface module. Everything else – monitor, relay, Keyphasor, display and gateway modules – goes in the 14 remaining slots of a full-size rack, or the 7 of a mini rack. A 3500/06 weatherproof housing encloses the same rack and does not change slot assignments.
Waveform capture has one licence-like detail worth knowing before you specify: transient data collection is enabled by a Channel Enabling Disk. Without it the TDI still stores configuration and passes static values, but you do not get the dynamic records you are probably buying a 3500 for.
Installation and configuration
Two mechanical rules dominate the job. Main modules are hot-swappable; rear I/O modules are not, so the TDI I/O work is a de-energised task. And when you move a rack from RIM to TDI, the order is fixed: remove the RIM, remove the RIM I/O module, install the TDI I/O module, then install the TDI. Leaving RIM I/O in place while inserting a TDI damages the new module.
For configuration, you connect a laptop either to the TDI’s front USB port or over the plant network. Use the specified USB lead (123M4610) – it exists to preserve the isolation between chassis and signal ground, and a substitute lead can defeat it. Feed the laptop from its own battery rather than a mains adapter for the same reason: a mains-referenced laptop through USB creates a ground loop that presents as intermittent communications loss.
Configuration is edited in 3500 System Configuration Software (document 141527) and written to the TDI as a RAK file. Access is guarded by a keylock plus a two-level password scheme. If a rack is running modules that need a newer interface – the 3500/32M relay module, for example, requires configuration software at 4.5 or later and TDI firmware at 1.71 or later – update the TDI as part of the same visit.
LEDs and what they mean
| OK | Module self-test passed and the module is operating normally |
|---|---|
| TX/RX | Communicating with the rest of the rack over the backplane |
| TM | Trip Multiply condition active |
| CONFIG OK | Stored configuration matches the hardware present |
| CONFIG OK not lit | A module is unconfigured or misconfigured, stored configuration does not match the hardware fitted, or a security option is not satisfied |
The TDI has no published fault-code list, so treat CONFIG OK as the summary indicator and work from there. The failure mode we see most often after maintenance is an I/O module replaced without a matching firmware update: the rack reports an I/O module mismatch, and channels can be suppressed rather than reading wrongly. If you have swapped an I/O module and the rack suddenly looks worse, check firmware before you check the sensor.
Ordering codes
TDIs are ordered as 3500/22-AXX-BXX-CC. Published option positions are A = 01 (standard), B = 01, 02, 03 or 04 and C = 00, 01 or 02. The A and C positions follow the convention used across the current 3500 module range – C = 00 no hazardous-area approval, C = 01 cNRTLus for Class I Division 2, C = 02 ATEX / IECEx / CSA for Class I Zone 2 – but the datasheet does not spell out each B sub-code in the material we can cite. Confirm the B position against the ordering page of datasheet 161581 or send us the label from an existing module, and we will match it.
3500/22M parts we can supply
Part number
| 3500/22M-01-01-00 | 3500/22M-01-01-00 Monitoring Module · In stock · View |
|---|---|
| 145988-01 | 3500/22M Transient Data Interface (TDI) · Special order · View |
Frequently asked questions
Is the 3500/22M the same thing as a TDI?
Yes. 3500/22M is the ordering designation and TDI – Transient Data Interface – is the module’s name. Both refer to the full-height interface module that every 3500 rack needs in slot 1.
Does every 3500 rack need a 3500/22M?
Every rack needs an interface module, and on current systems that is the TDI. The wording in datasheet 161581 is that every 3500 rack requires one TDI or RIM, always in slot 1 – so a legacy rack with a 3500/20 RIM is compliant, and a rack with neither simply will not configure or report.
What does the CONFIG OK light mean on a 3500/22M?
It means the configuration stored in the TDI matches the hardware actually fitted. The light goes off when a module is unconfigured or misconfigured, when the stored configuration does not match what is in the rack, or when a security option has not been satisfied. It is the first thing to look at after any module change.
Can I use the Rack OK relay for an emergency shutdown?
No. The Rack OK relay lives in the TDI’s I/O module, is single-pole double-throw and normally energised, and Baker Hughes specifies that it should not be part of a machinery automatic shutdown circuit. It is a general rack-health indication. Protection trips go to relay modules – 3500/32M or 3500/33 – driven by the monitors’ alarm logic.
How far can I run cable to a 3500/22M?
Shielded Category 5 twisted pair on RJ-45 is limited to 100 m. Fibre on MT-RJ connectors runs to 2000 m, which is what makes the TDI usable on large turbine islands where the control room is far away. The front USB port is limited to 5 m, and a 3 m lead ships with the rack.
Can I fit a TDI into a rack that had a 3500/20 RIM?
Yes, following the fixed sequence: remove the RIM, remove the RIM’s I/O module, install the TDI I/O module, then install the TDI. Skipping the I/O change will damage the TDI. Before you order, also check your monitor list – the TDI manual warns that some M-series monitors, for example 3500/40M, may not be compatible with a 3500/22 upgrade.
Do I get waveform data without extra hardware?
Static measurements, yes; transient waveform capture needs the channel enabling option. The TDI collects both static and transient data, but dynamic capture is enabled through a Channel Enabling Disk, so specify the number of enabled channels when you order rather than assuming all of them are live by default.
Why does my rack report an I/O module mismatch after a swap?
Usually because the replacement I/O module is at a different firmware level from the rack’s expectation. Rear I/O modules are not hot-swappable and a newer I/O piece often needs a TDI or monitor firmware update to be recognised. Until it is reconciled the affected channels are suppressed rather than mis-read, so the safe response is to match firmware, not to start replacing sensors.
Specify or replace a TDI
Send us the label from slot 1, or the module list if you are planning a RIM-to-TDI upgrade, and we will confirm availability, the matching I/O module and the firmware level you need. We quote per enquiry – prices are not published on this site – and we state the datasheet revision each part was checked against.
Keep reading: the 3500 system complete guide covers how the TDI, power supplies, monitors and relay modules combine into a compliant protection train.