Machine condition monitoring installed in Chinese turbine

Sensonics has completed a project for the Chongqing steel company in China. The contract to supply and install Sentry G3 Protection Monitors and Proximity Probes was successfully completed in conjunction with Sensonics' Shanghai-based partners, Star Royal Industry & Engineering Co Ltd.

The four new systems provide online monitoring and shutdown protection of a new turbine installation delivered through the Chinese-based OEM Qingdao turbine. Commenting on the project, Joe Chin, the Managing Director of Star Royal, said: "The Sentry G3 concept of a universal platform to cover all machine measurements and protection functions is very good and we are pleased to see the installations functioning reliably. The Sentry G3 installation went smoothly and the system has now been up and running for over eight months. The reliability of the system has been excellent and the end user is very happy with the system performance and the user-friendly features."

Two of the systems are installed in the combined-cycle power plant where waste heat from the blast furnace is utilised to drive two 25MW thermal recovery turbines manufactured by Hangzhou Steam Turbine (HTC). The other two G3 racks are installed on Qingdao turbine machines, which form part of the Coke Dry Quenching Technology used at the plant. This advanced closed system circulates gas to extract energy from the spent fuel, which, in turn, is used to generate steam to drive the turbines.

Monitoring system

The turbine supervisory system comprises: eight channels of shaft relative vibration (X and Y position on four sleeve bearings); two channels of thrust position at the HP end of the turbine; two channels of rotor-to-case differential expansion; and two channels of turbine speed measurement. Standard 8mm diameter (2.5mm range) proximity probes were utilised for the vibration measurements and for the differential expansion points. Sensonics PRD08 disk probes were used to provide 8mm of differential expansion range against a shaft collar.

Extended-range probes were implemented at the thrust position locations to allow for easy calibration. These 4mm range probes in an 8mm diameter package are said to be unique to Sensonics and are suitable for measurement ranges that are close to 2mm, but still need to allow for a minimum gap set-up as well as any possible float. The complete measurement chain is contained within a single Sentry G3 3Ux19inch rack system. This also includes spare slots for up to eight additional channels to be added at a later date if required (absolute bearing vibration, for example may be considered in the future).

Only one type of Sentry G3 module is required to cover all the measurement modes and each channel has the capacity to be programmed to any of the required turbine supervisory regimes. This not only permits efficient usage of hardware (note that the first module in the rack is programmed for two channels of thrust position and two channels of speed) but also minimises the requirement to hold spares. The hot-swappable modules can be replaced online and the previous settings are simply uploaded through the user interface software.

Display

The Sentry G3 system offers an integral LCD display that can operate in several modes; this obviates the requirement for additional hardware and the need for a separate panel-mounted LCD for local viewing of readings and events. Through the G3 display, each channel measured (value and alarm status) can be rapidly understood, while further analysis of dynamic channels can also be performed through the inherent FFT (vibration frequency analysis) facility available for each channel. An event log in each module permits the recall of up to 100 events to enable the user to determine past performance and capture fleeting channel alarms. Regarding the FFT facility, the site engineer commented: "This is the first time I have seen and utilised such a tool within this type of monitoring system and it has proved to be very useful with the Sentry G3 diagnostics."

The completion of the Chongqing project is another example of continued success for Sensonics in the Far East and underlines the company's commitment to developing the most effective systems for vibration, position and speed monitoring for critical machine condition monitoring applications.

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