The Sentry G3 machinery protection system

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The system is compliant to API 670 and meets IEC 61508 up to SIL-3 standards.

The Sentry G3 machinery protection system from Sensonics combines the flexibility of hardware in a single, easy-to-install and easy-to-use module type. The system is compliant to API 670– the most stringent protection requirement – and meets IEC 61508 up to SIL-3 standards.

The Sentry G3 system has been subject to ‘emphasis audits’ as part of its use in monitoring gas turbines in the UK. The emphasis method assesses a device’s compliance with IEC 61508 for functional safety standards, along with other requirements specific to the UK nuclear industry. It provides end-users with the confidence that both the hardware and software components in these protection systems meet the required high levels of design, testing and production which minimises the risk of systematic failures.

Advanced features include vibration, position and speed parameter trending facilities, including log and view of up to 60 days of data, ‘look back’ at trends and alarms, plus the ability to download data for further analysis in Excel. It is also now possible to directly view proximity probe gap and vibration transducer bias voltages, to verify correct transducer operation and calibration. The Sentry G3’s single module concept helps reduce ongoing maintenance costs whilst also lowering the risk in retrofitting applications.

The system is fully software programmable and upgradable. It’s also easy to expand, simply by adding additional G3 monitors. It offers excellent channel density with up to 24 measurement channels housed in a compact 3U x 19” rack mounted format which can halve the space needed on existing installations. Multiple outputs are available on the back of the rack for up to 3 alarm levels and 2 analogue outputs per channel. Dual redundant Modbus communications to a module level provide a robust communication system, while the in-built LCD display offers readings, sensor integrity voltages, trending and FFT, all of which confirm the accuracy of the installation.


In summary, Sentry G3 provides state-of-the-art, flexible, easy-to-install and maintains space-saving protection for the following modes:

Measurement - Absolute bearing and relative shaft vibration, shaft position and thrust wear, speed, phase and reverse rotation, differential and casing expansion, rod drop and temperature.

Turbine Specialist Measurement - Shaft eccentricity, order tracking, dynamic pressure and mark - space differential expansion.