Offering channel hardware independence, the Sentry G3 machinery protection monitor high performance signal conditioning unit with a universal sensor interface. Developed by SENSONICS, it encompasses vibration, position and speed measurements, the hardware fault tolerance of which has recently been independently verified. The four channel G3 module has been designed with an independent DSP, for each channel of measurement, which can be loaded with the specific measurement algorithm to control the sensor selection, the protection relay status and analogue output levels. This provides complete hardware autonomy from sensor through to the protection relay combined with 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 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. Suitable for use in a SIL-2 low demand safety function, a single Sentry G3 measurement channel can be utilised for SIL-3 applications if combined in an appropriate voted redundant channel arrangement the system. The machinery protection monitor provides protection for vibration, position and speed measurements, turbine specialist algorithms to cover shaft eccentricity and large differential expansion measurements are also included within its scope.
Edited by: Teoman Tugsuz
