In the previous edition of ASME VIII-1, the hydrotest pressure was specified as Pt = 1.3 x MAWP x LSR with the caveat of footnote [34]. Normally, the MAWP should be calculated and it should be higher than the design pressure. The footnote [34] however, allowed in given circumstances to select the MAWP equal to design pressure. Accordingly, per footnote [34], the minimum hydrotest pressure may be Pt = 1.3 x Pd x LSR. Nevertheless, the minimum hydrotest pressure could be higher than that if it was based on the calculated MAWP, presumably higher than the Pd. A higher hydrotest pressure increases the rating of the finished equipment and is recorded accordingly on the nameplate.
