Counting Hidden Failures: IEC 61508 Part II, Hardware, Fault Tolerance, Safe Failure Fraction and the Arithmetic of PFD

Deep End Era. Engineering with Sankalp · Oct 28, 2026 · 57m

The new export pipeline at Al Sahil is rated for less than the wellhead shut-in pressure, so it needs a high integrity pressure protection system: SIL 3, three transmitters, two fast valves and no relief. Tomas Novak and Aisha Rahman have to prove the hardware can do it. Along the way: what diagnostic coverage really buys, why safe failure fraction is not a safety measure, why two valves are only as good as the test that proves they close, and the arithmetic that turns a datasheet into a probability of failure on demand.

Chapters

00:00:00 Cold open: a pipeline with no relief

00:02:37 Three…