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.

Definition

T-min combines pressure-design minimum thickness with structural-design minimum (e.g., to resist wind/seismic loads or to maintain shell stability). API 510/570/653 inspection programs continually measure t-actual versus t-min to determine remaining life.

Related terms

• 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.
• Minimum Required Thickness — Minimum required thickness is the wall thickness required to safely contain design pressure plus any required corrosion allowance, calculated per ASME Section VIII or B31.3 equations and used as the design-basis comparison for thickness measurements.
• Retirement Thickness — Retirement thickness is the wall thickness at which a pressure component must be removed from service, equal to the minimum-required thickness, sometimes increased by an additional safety margin to account for measurement uncertainty.
• 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.

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.