The established Sentry G3 machinery protection monitor is a high performance signal conditioning unit with a universal sensor interface developed by condition monitoring specialists SENSONICS. The latest Sentry G3 systems encompass vibration, position and speed measurements, the hardware fault tolerance of which has recently been independently verified through a recent study.
Channel hardware independence is important for machinery protection applications where a failure of any hardware assembly should have a minimal effect on the overall system measurement integrity and in this respect Sentry G3 offers the 'best-in-class'.
The four channel G3 module has been specifically designed with an independent digital signal processor (DSP) for each channel of measurement. The DSP can be loaded with the specific measurement algorithm which not only controls the sensor selection, but also the protection relay status and analogue output levels. This provides complete hardware autonomy from sensor through to the protection relay combined with high channel density (24 channels in a 3U format).
The rack based system operates on a dual +24V power supply backplane which can be connected externally or derived from the optional G3 dual redundant rack based power supplies. When a high integrity protection function is required, the IEC61508 international standard for functional safety can be applied to ensure that sufficient integrity is designed into the electrical / electronic systems employed for the safety function. A failure mode and effects analysis is carried out on the overall measurement control loop, from sensor to shutdown actuator. This determines not only the Mean Time between Failure (MTBF) of the protection equipment but also the diagnostic coverage and the safe failure fraction (SFF). The diagnostic coverage illustrates the percentage of failure modes of the equipment that are detectable from an operator perspective and the SFF determines the percentage of failures which result in a safe process condition.
All these factors, in combination with protection system channel redundancy, are used to calculate the overall SIL (Safety Integrity Level). A recent SIL analysis has demonstrated a single Sentry G3 measurement channel is suitable for use in a SIL-2 low demand safety function and when combined in a suitable voted redundant channel arrangement the system could be utilised for SIL-3 applications.
Sentry G3 provides state-of-the-art protection for vibration, position and speed measurements, turbine specialist algorithms to cover shaft eccentricity and large differential expansion measurements are also included within the equipment scope.
Further details on Sentry G3 are available from: Russell King, Sensonics Ltd,
Berkhamsted, Hertfordshire, UK.
Tel: +44 (0) 1442 876833. Fax: +44 (0) 1442 876477
Email: email@example.com www.sensonics.co.uk