Effective monitoring of turbines, including overspeed protection in the power generation industry, is critical to ensure smooth running and trouble-free operation. Failure of the turbine or pump speed governing system can lead to rotor damage with expensive consequences. Independent speed monitoring and protection are essential to minimise these risks.
Sensonics deployed its technology at the National Gas Transmission (Previously National Grid) site at Huntingdon Compressor Station, part of the UK’s National Transmission System (NTS). This is one site within a network of pipelines that supplies gas from natural gas terminals situated on UK coastlines to around 40 UK power stations and other large industrial users as well as commercial and domestic customers. The compressors at the Huntingdon site help to maintain and boost gas pressures flows to the South and South West of the UK. The site currently has three operational gas compression units covering the Power Turbine System and Gas Turbine Starter System.
Sensonics supplied two Sentry G3 Overspeed Protection Systems with two out of three voting capability, with certification to IEC 61508 functional safety level SIL 3, to the Huntingdon Compressor Station. These were installed in January 2023, replacing existing obsolete equipment which had been deemed to be ‘end of life’ and in ‘fault condition’.
After 10 months of operation, Ray Woolmer, control & instrumentation engineer, part of the rotating machinery support team, said: “The new Sentry G3 rack was an available and fully compliant solution with the same footprint as the original equipment, removing the need for additional modifications”.
“The Sentry G3 units were fully compliant systems, providing reliability and simplicity of use and features such as local channel status displays on each module provides us with quick and easy status checks”.
Looking ahead, Woolmer appreciates that Sentry G3 units have the ability to be repurposed for the ongoing research and development of a future grid Hydrogen Network and so assists them in ensuring compliance for the additional safety requirements of a Hydrogen network.
Since its introduction over 20 years ago, the design of the Sentry G3 system and its features have been developed and enhanced in conjunction with customers’s needs in both the conventional and nuclear power industries, resulting in a reliable hardware configuration with online test facilities. For example, the provision of gas turbine specific measurements such as first order vibration tracking and dynamic pressure which are both requirements recommended by gas turbine manufacturers. In addition, the speed algorithm has also been optimised to accept a wider range of speed probes and now offers a sensitivity performance over a wide speed range, ensuring the turbine interlocks can be integrated effectively into the G3 system over a range of operational conditions.
The new measurement algorithms can be downloaded into the common hardware module and complement the other established measurements such as broadband vibration, temperature and speed. The flexibility of the G3 system sensor interface also permits a range of sensor types to be utilised providing both the necessary drive power supplies and fault detection.
The system is said to offer channel density with up to 24 measurement channels in a 3U x 19” racking format. The diverse system architecture separates functions across the independent modules, providing a channel reliability suitable for safety instrumented systems.
In summary, Sentry G3 provides protection for the following modes:
Measurement - Absolute bearing and relative shaft vibration, displacement and thrust position, 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.
The additional features incorporated into the latest Sentry G3 system ensures more than just machine protection, it provides a set of tools to assist plant engineers to optimise the control and overspeed management of turbines and other rotating plant.