SIL2/SIL 3 RATED VIBRONIC POINT LEVEL MEASUREMENT DEVICES FOR OVERFILL PROTECTION

摘要

Safety instrumented systems (SIS) that are rated according the Safety Integrity Levels (SIL) are gaining importance in the process industries. In this presentation vibronic point level measurement devices are used in highly reliable overfill protection system will be discussed. Starting from the basics of how these tuning fork system work, the construction principle will be illustrated. With regard to a high functional safety, a focus will be put on the self monitoring capability of vibronic systems and the PFM (pulse frequency modulation) technology that is used for signal transmission from the sensor to the switching amplifier. The combination of these capabilities has led to a SIL2/SIL3 rating of these sensors for overfill protection systems according to the international standard IEC 61508/61511. The probability of failure on demand (PFD) requirements according EEC 61508 fulfilled by these systems are identical to the corresponding American standard ANSI/ISA-S84.01.