Sentry G3 machinery protection from Sensonics
The Sentry G3 machinery protection monitor is a high performance signal conditioning unit with a universal sensor interface developed by condition monitoring specialist Sensonics. The latest Sentry G3 systems are said to encompass vibration, position and speed measurements and 'best in class' channel hardware independence.
The four channel 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 is said to provide 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.
According to Sensonics, 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 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 of these factors, in combination with protection system channel redundancy, are used to calculate the overall safety integrity level.
