Unavailability assessment of redundant safety instrumented systems subject to process demand

A contribution to reliability assessment of safety-instrumented systems

Simplified formulas are popular for reliability analysis of safety instrumented systems (SISs). Both the IEC 61508 standard and the PDS-method provide such formulas for calculation of the average frequency of dangerous failures per hour (PFH). These formulas give reasonably accurate values for the PFH, but both of them also have significant weaknesses. The IEC-formulas can only be applied to sy...

Safety Instrumented Systems - Health Monitoring

The unique SIS-Health Monitoring solution is a set of tools and services that enable industry practitioners to measure the status and health of their safety instruments, analyze their reliability and safety integrity, optimize test intervals, and reduce spurious process trips. In addition, the SISHealth Monitoring solution enables the detection of unexpected trends, the maintenance of test freq...

Testing Strategies of Redundant Safety Instrumented Systems with Dangerous Detected Failures

Proof testings are regularly conducted on safety instrumented systems (SISs) to reveal dangerous undetected (DU) failures so as to reduce process risks. Sometimes, self-diagnostic tests of SISs can find dangerous detected (DD) failures which will be fixed as soon as possible. If such detections of failures also activate further tests for all components in the SIS in order to discover hidden fai...

Spurious activations of safety-instrumented systems

Selecting Transmitters for Safety Instrumented Systems

Users design safety systems to mitigate the risk of identified process hazards within tolerable levels, using application-specific risk models, defined user inspection schedules, and safety data for the devices under consideration. Some suppliers provide safety data for their devices. However, supplier data, even when validated by a third party, reflects laboratory results, and can be an order ...