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Technical notes for safety engineers

Standards, regulation and field practice in functional safety and OT cybersecurity — explained for the engineers who apply them.

Pressure transmitter and shutdown valve on a refinery pipework skidFunctional safety11 Nov 2026 · 6 min read

IEC 61511 70% Confidence Level Failure Rate Explained

A failure rate that looks acceptable in a SIL calculation may not be the 70% upper confidence limit IEC 61511 expects. Here is what the figure means and how to test it.Read article →
Pressure transmitter and shutdown valve actuator on a process plant pipe runFunctional safety9 Nov 2026 · 6 min read

Generic, Vendor or Plant Data? IEC 61511 Prior Use Failure Data

IEC 61511 asks for reliability data that is credible, traceable, documented and justified. Here is how to judge generic, vendor and plant data against that test, and what to write down.Read article →Actuated emergency shutdown valve with positioner and solenoid mounted on the actuator in a process plantFunctional safety13 Oct 2026 · 6 min read

Partial Stroke Test Proof Test Coverage: What Can You Claim?

A partial stroke test covers only some valve failure modes, and the full proof test after it is rarely perfect either. Here is how to credit both honestly in SIL verification.Read article →Actuated shutdown valve and pressure transmitter on a process pipe in an industrial plantFunctional safety12 Oct 2026 · 5 min read

Proof Test Interval Calculation: Don't Inherit the Default

Many proof test intervals come from a vendor default or an SRS template. Here is how to derive one from the SIF's PFDavg target and λDU, and how to document the basis so it survives an audit.Read article →