C p 0.13 for integral flat circular heads
when the dimension d does not exceed 24 in. (600 mm),
the ratio of thickness of the head to the dimension d is not
less than 0.05 or greater than 0.25, the head thickness th
is not less than the shell thickness ts , the inside corner
radius is not less than 0.25t, and the construction is obtained
by special techniques of upsetting and spinning the end of
the shell, such as employed in closing header ends