Understanding API ICP653 Reading 7-Worksheet-04 Part1

3.21 as-built standard: The standard (such as API standard or UL5 standard)
used for the construction of the tank component in question. If this standard is
not known, the as-built standard is the standard that was in effect at the date
of the installation of the component. If the date of the installation of the
component is unknown, then the current applicable standard shall be
considered to be the as-built standard. See Appendix A for a list of API
welded storage tank standards. The standard used for repairs or alterations
made after original construction is the as-built standard only for those repairs
or alterations, so there may be more than one as-built standard for a tank.
3.22 current applicable standard: The current edition of the standard (such
as API standard or UL standard) that applies if the tank were built today.
Charlie Chong/ Fion Zhang