T-Actual (Measured Thickness)
T-actual is the actual measured wall thickness at a Condition Monitoring Location (CML), recorded periodically by ultrasonic thickness measurement and trended to determine corrosion rate and remaining life.
Definition
T-actual is typically the average of multiple readings at a CML, or the minimum thickness from a UT scan, depending on the inspection procedure. The lowest t-actual on a circuit governs the remaining-life calculation.
Related terms
- T-min (Minimum Thickness) — T-min is the minimum acceptable in-service wall thickness, equal to the larger of the pressure-design minimum and the structural-stability minimum, used as the threshold below which equipment must be repaired or retired.
- Corrosion Rate — Corrosion rate is the rate of wall-thickness loss in mm/year (or mils/year) calculated from successive thickness measurements, used to determine remaining life and inspection intervals under API inspection codes.
- Remaining Life — Remaining life is the calculated time until equipment reaches its retirement thickness or minimum required thickness at the current measured corrosion rate, used by API 510/570/653 to set the next inspection interval.
Further reading
ultrasonic thickness measurement corrosion monitoring guide
More data terms
A-Scan · B-Scan · C-Scan · D-Scan · S-Scan · L-Scan · Distance-Amplitude Correction · Distance-Gain-Size · Time-Corrected Gain · Gating
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.