Migrating from Bently Nevada 7200 and 3300 to 3300 XL: Replacing Legacy Sensors without Losing Protection

Many turbines and compressors in Kazakhstan still run Bently Nevada systems installed in the 1980s–2000s: 7200 racks, 3300 (non-XL) proximity systems, 7200 25 mm transducers for differential expansion. They are reliable, but the manufacturer long ago classed them as legacy. Spares get harder to find, and a failed module or sensor turns into downtime.

The good news: migrating does not have to mean replacing everything at once. Below is what is compatible, what is not, and how to plan the migration step by step.

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Sensors: what is compatible with 3300 XL

3300 (5 mm and 8 mm) → 3300 XL 8 mm

This is the simplest case. According to the Bently Nevada datasheet, 3300 XL 8 mm components (probe, extension cable and Proximitor) are electrically and physically interchangeable with non-XL 3300 5 mm and 8 mm system components. The 3300 XL Proximitor package looks different but fits the same four-hole mounting pattern.

In practice: when an old Proximitor or probe fails, it can be replaced with a 3300 XL component without changing the rest of the chain or reconfiguring the monitor. A full system replacement can be done gradually, as failures occur or during planned outages.

The 3300 XL 8 mm scale factor is 7.87 V/mm (200 mV/mil) with a 2 mm (80 mil) linear range. Details are on the 3300 XL 8 mm page.

7200 25 mm and 35 mm → 3300 XL 25 mm

For steam turbine differential expansion, older installations have 7200 25 mm, 7200 35 mm or 25 mm DE Integral systems. The 3300 XL 25 mm probe comes in many case configurations that physically replace these systems, including side and rear exit probes. The 3300 XL 25 mm Proximitor output is identical to the 7200 and 25 mm DE Integral systems, so the monitor does not need reconfiguring.

If rotor travel greater than 12.7 mm is needed, use the 3300 XL 50 mm system with a 27.9 mm range.

Other 7200 transducers

For other 7200 series transducers (for example 11 mm and 14 mm), compatibility with a specific monitor and the replacement path must be checked against the datasheets; there is no universal rule. Send us the nameplates and we will select the replacement.

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Monitors: 7200 → 3500 or Orbit 60

A 7200 rack cannot be replaced module for module; it is a platform change. Typical options:

Option	When it fits
3500	The API 670 protection standard, proven platform, wide module range, System 1 integration
Orbit 60	New projects and upgrades planned for a long lifecycle, extended diagnostics

The key question when choosing is compatibility of the new monitor's inputs with the sensors already installed. If the machine has 3300 or 3300 XL transducers, both 3500 and Orbit 60 support them and the sensors can stay. If it has old 7200 transducers, check support by the specific module or plan to replace the sensors together with the rack.

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Migration plan step by step

1. Audit. A list of all machines, measurement points, sensors (full codes from nameplates), monitors and their condition.
2. Risk assessment. Which machines are critical, where modules have already failed, which items are unavailable.
3. Quick wins. A stock of 3300 XL spare components to replace failed 3300 ones, as they are interchangeable.
4. Rack replacement project. Choosing between 3500 and Orbit 60, input compatibility, setpoint configuration, integration with the control system and System 1.
5. Implementation during a planned outage. Installation, configuration, checks of channels and protection setpoints.
6. Documentation. New drawings, order codes, configurations for the next repairs.

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Typical mistakes

• Waiting for failure. When a 7200 rack fails, finding a module will be hard and the outage unplanned.
• Replacing everything at once without an audit. Some 3300 sensors can stay, saving budget and installation time.
• Selecting by name rather than order code. Cable length, thread, armour and approval are set by options; one wrong option and the sensor does not fit or fails the zone requirement.

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Summary

Migrating from older Bently Nevada systems is simpler than it seems: 3300 XL 8 mm components are interchangeable with 3300 5 and 8 mm, and the 3300 XL 25 mm physically and electrically replaces 7200 25/35 mm systems. 7200 racks are replaced with 3500 or Orbit 60 by project, with input compatibility checks.

KEG TRK is an official business partner of Bently Nevada in Kazakhstan. We audit installed systems, select replacements by order code and carry out upgrades. More on working with an official partner is in the article on Bently Nevada in Kazakhstan.