Remaining Useful Life (RUL)
A subjective opinion of the years a component will continue to function before replacement is warranted; the field observer's judgment, not a guarantee.
By Nicolas Reimer, Founder, Baseline PCR · E2018-24 s3.2 · Published September 18, 2026
Remaining useful life is defined by E2018 as a subjective opinion of the years remaining before a component will need replacement, and the guide says explicitly that it is not a guarantee of performance. It is where the field observer's judgment enters the reserve table: a component's condition, its documented or reported age, its maintenance history and any warranty all inform the opinion, which may be longer or shorter than the arithmetic of expected life minus calendar age.
A reserve table should state the basis of each RUL (observer's opinion from condition, or expected life minus documented age, or an assumption pending confirmation) so a reader can tell judgment from arithmetic. Year due is the report year plus RUL; effective age is expected life minus RUL.
Related: expected useful life, effective age, long-term costs.
Sources
ASTM E2018-24 is copyrighted by ASTM International and is paraphrased here, never reproduced; buy the guide from ASTM to read the text. This page is general information for practitioners, not engineering, legal or lending advice.