- June 28, 2025Diagnostic Test Interval (DTI) is the time between automatic diagnostic checks in a component. Often found in the safety manual,…
- June 28, 2025Mean Detection Time (MDT) refers to the average time diagnostics take to detect a failure in components. It’s a key…
- June 24, 2025Mean Repair Time (MRT) is the average time required to restore a failed safety instrumented function or device. Essential for…
- May 6, 2025STR is how often a SIF activates unintentionally, causing a false trip or shutdown. Low STR = high availability.
- May 5, 2025SFF is the ratio of safe and detected failures to all failures. Higher SFF means better reliability and often lower…
- May 5, 2025RRF is how much a SIF reduces risk—calculated as the inverse of PFDavg. Easier to interpret than small probability values.
- May 5, 2025Proof Test Coverage (Cpt) is the percentage of dangerous undetected failures a proof test can reveal. A Cpt of 100%…
- May 5, 2025The Proof Test Interval (TI) is the maximum time allowed between successive manual tests of a Safety Instrumented Function (SIF)…
- May 5, 2025PFH represents how frequently dangerous failures occur during continuous or high-demand operation. It’s used when PFD doesn’t apply.
- May 5, 2025PFD measures the chance a safety function will fail when needed. It’s the key metric for low-demand SIF performance.