(1) Where steels with specified Charpy V notch impact
properties at low temperature are used, the thickness
above which post-weld heat treatment is to be applied
may be increased, subject to the special agreement of
the Society.
(2) For 2,25Cr 1Mo and 0,5Cr 0,5Mo V grade steels, heat
treatment may be omitted for pipes having thickness
lower than 8 mm, diameter not exceeding 100 mm and
service temperature not exceeding 450°C.
(3) For C and C-Mn steels, stress relieving heat treatment
may be omitted up to 30 mm thickness, subject to the
special agreement of the Society.